2022-12-14: How Can Matter Be BOTH Liquid AND Gas?
- 01:06: The reason solids melt and liquids boil is that rising heat energy allows the bonds between atoms and molecules to break.
- 01:14: But high pressure helps to keep particles together so that it takes more heat energy to break bonds.
- 10:39: ... bean and a fine powder of caffeine molecules - I guess for the energy drink that you need after your decaffeinated coffee didn’t ...
- 12:08: ... great at moving heat energy around due to their high density and corresponding heat capacity, so we ...
- 18:29: These neutrinos would now have energies 10 billion times smaller than regular neutrinos, say from the Sun.
- 19:09: Quasars or “active galactic nuclei” glow from the heat energy of matter being ripped to shreds as it spirals towards a supermassive black hole.
2022-12-08: How Are Quasiparticles Different From Particles?
- 01:38: These electrons are locked in place in the now-full valence energy level.
- 01:44: ... they can still get bumped up to a higher energy state - say, by thermal vibrations or in the case of solar cells by a ...
- 05:10: We have one quasiparticle from making a gap in one spot in the electron energy level.
- 05:16: And we can make another one by making a very different tweak to the local energy in the crystal.
- 05:24: Another way energy can be stored in the lattice is in the vibrational modes of the atoms.
- 05:39: In this way vibrational energy can move around the lattice.
- 05:55: Those vibrational modes in the crystal are quantized, similar to electron energy levels.
- 06:01: In this case, the crystal lattice can vibrate at any frequency, but the amount of energy at each vibrational mode can only go up in discrete chunks.
- 06:11: That means vibrational energy also gets transferred in discrete packets.
- 06:16: So now we have something like a particle - a quantum of vibrational energy moving around the lattice.
- 06:47: They have energy equal to the planck constant times their frequency.
- 07:45: ... Energy is often transferred between phonons and other particles - quasi- and ...
- 08:09: In doing so they can dump its energy into a vibrational mode and create a phonon.
- 11:15: ... take a little of the original electron’s energy in a vibration that’s part of a phonon, mixed up and indistinguishable ...
- 12:54: In fact at very low temperatures all of the pairs in an enormous network of flowing electrons can all occupy the lowest energy state.
- 13:03: They don’t have the energy to excite new phonons, and so … they don’t.
- 14:39: And it turns out that any field, elementary or not, will give rise to particles as long as that field has quantized energy states.
2022-11-23: How To See Black Holes By Catching Neutrinos
- 01:43: ... at very close to the speed of light, just because it doesn’t take much energy to get them close to the cosmic speed ...
- 09:26: ... powerful magnetic fields because in many of them we see jets of high energy particles blasted out from the vicinity of the black hole, and these ...
- 10:02: In 2017 a single very high energy neutrino was detected by IceCube coming from the direction of a known blazar.
- 10:29: ... active phase, so there’s a good chance it was spitting out high energy neutrinos at an enhanced ...
2022-11-16: Are there Undiscovered Elements Beyond The Periodic Table?
- 08:39: We have to think of these nucleons as having energy levels, just like electrons do.
2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations?
- 20:06: ... standard model lagrangian episode, Schrodinger’s half-dead cat, phantom energy, Maxwell’s demon, or Laplaces ...
2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
- 06:33: ... light excited electrons in calcium atoms to higher energy level and they would then drop down again, with the lost energy ...
2022-10-19: The Equation That Explains (Nearly) Everything!
- 03:36: ... quantum states. For classical physics it simplifies to just Kinetic Energy minus Potential ...
- 04:05: ... symmetry will reveal the existence of a conserved quantity like energy or momentum. And this is Noether's Theorem, and we also have an episode ...
- 06:02: ... Meanwhile particles with integer spin are called bosons. They transmit energy and momentum according to the symmetries of each force. Some parts of ...
- 06:57: ... made of the derivatives of the A field. In other words, this is like the energy of the photons as they change in space and time, and this is true for ...
- 07:27: ... is where these mu/nu symbols come from. The kinetic energy of the field in one direction may depend on what is happening in the ...
- 07:51: ... for the fields of the other two forces, we also need their kinetic energy in every possible direction. Except if two photons come close they'll ...
- 08:23: ... need an extra term to describe the potential energy of that interaction, which we add to the kinetic term. Here we see a ...
- 09:03: ... multiplication because that turns them into the appropriate units of energy - or something close to energy - because that’s what the Lagrangian ...
- 09:45: ... of two parts. We have a derivative, which as we mentioned tells us the energy of the field as it changes, but we also have this part with the field of ...
- 14:00: ... structure constant we discussed recently. And it doesn't explain dark energy or the matter-antimatter imbalance, among other things. And it is a bit ...
2022-10-12: The REAL Possibility of Mapping Alien Planets!
- 15:45: ... was essentially as it is today. Radoslaw Garbacz ask What does exactly "energy of interaction" ...
- 18:29: ... this is just the amount of energy available in a particle interaction for the creation of the ...
2022-09-28: Why Is 1/137 One of the Greatest Unsolved Problems In Physics?
- 01:34: As with much of quantum mechanics, it started with us watching the light produced as electrons flicked between energy levels in atoms.
- 01:43: ... process results in the emission of photons of specific energies that we observe as spectral lines - sharp peaks in the light observed ...
- 01:58: Hydrogen atoms only emit light with these specific energies.
- 02:22: ... to be composed of two lines at almost but not quite identical energies. ...
- 02:36: ... effects of Einstein’s still-new relativity, as well as the fact that the energy levels of electrons with opposite spins are separated slightly by their ...
- 02:55: ... found something peculiar: that the difference in energy between the fine lines was always a multiple of one particular ...
- 04:05: ... example, the repulsive energy between two electrons is 137 smaller than a photon with wavelength equal ...
- 04:26: And the energy of that ground state electron is smaller than the rest mass energy of the electron by a factor of 137 squared.
- 07:10: It changes with the energy of the interaction.
- 07:13: The higher the energy, the larger the constant.
- 07:16: ... the insane energies right after the Big Bang, the coupling constant for the EM field - which ...
- 07:30: We’re now at the bottom of the energy scale, and the fine structure constant has bottomed out at 1/137.035999.
- 11:20: ... time in relativity; it’s also the relationship between mass and energy in Einstein’s famous ...
2022-09-21: Science of the James Webb Telescope Explained!
- 17:21: ... get on with business and discover the big bang, dark matter and dark energy, and figure out how the universe is going to ...
2022-08-24: What Makes The Strong Force Strong?
- 00:00: Quantum mechanics gets weirder as you go to smaller sizes and higher energies.
- 03:33: One consequence of this is that no two electrons can occupy the same energy level in an atom.
- 03:58: ... quarks - in reality, 3 valence strange quarks - three quarks in the top energy level. There's a lot happening under the hood. Now, there must be ...
- 07:16: The flux tube has a tension, and just like a stretched elastic band, the more you stretch the flux tube the more energy it holds.
- 07:25: At a certain point the tube will snap - but only when exactly enough energy has been built up to create a new pair of quarks.
- 07:46: If you want to break them apart you just end up forming new particles, so quarks never end up alone except in the most extreme energies.
- 07:55: ... enough energy, like in the very early universe or at impact point in a large particle ...
- 16:44: And then the one on quintessence, one of the leading ideas for how dark energy might behave.
- 17:41: There’s also weird stuff, like the fact that there’s enough kinetic energy in this matter to cause spontaneous particle-antiparticle creation.
- 19:07: Yes, they very much would. So changing quintessence means changing strength of dark energy, which means changing rate of accelerating expansion!
- 19:18: The current age estimate of 13.7 billion years assumes a constant dark energy.
- 19:24: If dark energy has gotten stronger then the universe would be older, because it would have been expanding slower in the past than expected.
- 19:32: On the other hand if dark energy has weakened then the universe might be older than expected.
- 20:07: For example, apparently you can do this eliminate the so-called Higgs instability, which blows up the Higgs field at high energies.
- 20:15: Others use this coupling to explain dark energy AND dark matter.
2022-08-17: What If Dark Energy is a New Quantum Field?
- 00:00: ... at an ever-increasing rate. We call this mysterious influence dark energy, but while we’ve talked a lot about how it behaves, we’ve never really ...
- 00:28: So, what is dark energy, really?
- 00:36: ... mainstream physical explanation for dark energy is that the vacuum of space has a constant energy density. Empty space ...
- 01:25: ... default model for dark energy is that it can be described with a so-called cosmological constant. This ...
- 01:41: ... the fabric of space has energy - dark energy - then the expansion of the universe creates the stuff. ...
- 02:31: ... slightly counter-intuitive thing about dark energy is that, on top of the anti-gravitational effect of its negative ...
- 03:22: Standard “cosmological constant” dark energy has omega -1. This is just what you get when you say that the vacuum has a constant energy density.
- 03:33: ... we assume this is true we can figure out what energy density would be needed to cause the acceleration we observe. That ...
- 04:41: If we can measure the energy density, can’t we also measure omega, the equation of state?
- 05:18: ... mentioned that there are problems with the explanation where dark energy is due to quantum fluctuations. For example, it’s actually very ...
- 05:50: ... naive calculation for the energy of the vacuum gives you a number something like 120 orders of magnitude ...
- 06:25: ... into the late universe. The Planck measurement assumes a constant dark energy and an unchanging omega of -1. But if dark energy has changed over time, ...
- 07:31: ... rather than all quantum fields fluctuating a teensy bit above their energy minima. So if a specific field was responsible for inflation, couldn’t ...
- 09:13: ... The equation of state depends on this field strength and the kinetic energy of the particles of the field. The field strength can also change over ...
- 09:51: ... coincidences that seem necessary with a cosmological constant dark energy. Currently around 70% of the energy in the universe is dark energy with ...
- 10:08: ... As the universe expands, matter dilutes away while most versions of dark energy stay constant or relatively constant, or even increase in some models. ...
- 10:55: ... starts to thin out. That provides a natural explanation for why dark energy kicked in at around the same time as stars and planets were able to ...
- 11:51: ... look at how it actually behaves. As I mentioned, the behavior of dark energy is driven by its equation of state. Any value of omega less than -⅓ ...
- 13:04: ... only way to get omega less than -1 is for the kinetic energy of the field to be negative. These sorts of negative energy scenarios ...
- 13:27: ... us much. If we could actually confirm a change in the density of dark energy then it would be strong support for quintessence, because that would ...
- 14:41: ... constant problem is coincidental with a quintessentially consistent dark energy, or scalar quantum fields shift in a quintessence-saturated space ...
- 15:05: ... the fifth element. of the alchemists, the aether. In that you give us energy in the vacuum of the YouTube funding models. Helping us exponentially ...
2022-08-03: What Happens Inside a Proton?
- 06:02: ... than the fine structure constant, of order 1, though it depends on energy scale. That’s what makes the strong force strong, ...
- 07:07: ... are sustained oscillations in a quantum field that have real energy and consistent properties. Virtual particles are just a handy ...
- 15:29: ... temperature. We said that it is defined as zero kinetic energy in the particles, but actually this doesn’t account ...
2022-07-27: How Many States Of Matter Are There?
- 03:20: ... doesn’t really have a temperature, it has a velocity - but the average energy of motion of all water molecules is its ...
- 05:28: Although we’re going to need it fairly hot - around 7 trillion Kelvin, due to the extremely high binding energies of nucleons.
- 07:16: Here it's temperature versus baryonic potential instead of pressure, which is basically how much energy quarks can absorb or emit.
- 08:26: These are configurations of entangled particles that oscillate between states even when they have no energy.
- 08:32: In regular thermodynamics, the lowest energy corresponds to absolute zero temperature, which in turn means zero motion of particles.
- 08:40: ... lowest energy state of a time crystal involves real motion, which makes them ...
2022-07-20: What If We Live in a Superdeterministic Universe?
- 16:49: There are certain fundamental lengths, distances, energies, etc. that aliens could use to translate their units.
- 16:56: For example, Planck units, or the energies or masses or decay timescales of common particles and elements.
2022-06-30: Could We Decode Alien Physics?
- 15:41: ... and that’s stopping, because the ship itself needs to carry all the energy that it needs to stop. Where as the energy to accelerate can be ...
- 16:39: ... So this concern is very valid. Slowing down takes as much energy as speeding up. If your destination isn’t already set ...
2022-06-22: Is Interstellar Travel Impossible?
- 04:59: Well, At 0.2 c, an encounter with a grain of dust around a millimeter wide delivers a few hundred million joules of kinetic energy.
- 07:50: ... the speed of impact with every air molecule, and so a lot of kinetic energy gets dumped into the falling object, usually destroying them before they ...
- 08:19: The kinetic energy deposited by each particles is 1/2 times mass times velocity squared.
- 12:22: Interstellar space is flooded with high energy particles, from simple protons to massive iron nuclei.
- 17:20: ... should recombine inside a black hole, given that they do so in the high energies of particle ...
- 17:31: ... of a black hole matter should reach arbitrarily high densities and energies - as high as is possible before physics stops behaving as we know ...
2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?
- 00:26: ... when we try to describe the tiniest scales and the highest energies. This drives our quest for theories of everything. A quest ...
2022-05-25: The Evolution of the Modern Milky Way Galaxy
- 17:21: ... Yes and no. First, assuming no cosmological constant and dark energy, the expansion of the universe does not continue to tug ...
- 18:10: ... Cleland responded to that comment to address the dark energy issue. He rightly points out that the Schwarzschild metric ...
2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life?
- 03:40: ... nuclear fusion. The outward flow of fusion-generated energy supports the Sun against gravitational collapse. It’s been ...
2022-05-04: Space DOES NOT Expand Everywhere
- 07:12: ... then the expansion slows under the influence of gravity, then dark energy takes over and expansion accelerates ...
- 11:59: ... that’s even true if empty space contains something. Like dark energy. Empty space has a very weak energy density, even in the absence of ...
- 13:50: ... measure its mass “directly”, but you can measure the masses and kinetic energies of its decay products and determine the mass of the ...
2022-04-27: How the Higgs Mechanism Give Things Mass
- 01:48: ... wiggles are quantized - they come in discrete packets of energy that can move around - and those are the particles of a ...
- 07:01: ... The “walls” of the valley are just the potential energy - the energy stored when the field value moves away from the ...
- 07:52: ... It’s really just the difference between the kinetic energy and the potential energy in the field. Our plot was of ...
- 08:09: ... strength of the field everywhere in space. The potential energy part is the “shape” of the field, and is made of various powers of ...
- 09:59: ... angle twirling around freely, and it doesn’t need any minimum energy to oscillate, so the gauge boson is ...
- 10:15: ... the particle of the original field needs a rest mass energy to be able to oscillate up and down the potential ...
- 11:56: ... original for two reasons. The first is that the lowest energy state - the vacuum state - isn’t where the field strength is zero. ...
- 12:26: ... and it’s massless because the valley is flat - there’s no energy differential. However it isn’t a gauge boson because ...
- 16:02: ... could have a ghostly presence as virtual particles in the energy field of the boson. The fact that FermiLab measured a ...
2022-04-20: Does the Universe Create Itself?
- 15:24: ... answer is absolutely yes in the good old days when we didn’t have dark energy. If you just consider the positive effect of gravity, then the spatial ...
- 16:10: ... detectable without a universe-sized camera. It would also have such low energy that it wouldn’t have any effect on any sane ...
- 17:39: ... mass density to avoid recollapse. At least in the absence of dark energy. Thanks dark energy. That “coincidence” itself may require some ...
2022-03-30: Could The Universe Be Inside A Black Hole?
- 07:37: ... our universe appears to be highly homogeneous - matter and energy are very evenly spread out, and it was even more evenly spread out in ...
2022-03-23: Where Is The Center of The Universe?
- 02:57: His general theory of relativity explains gravity as the warping of space and time due to the presence of mass and energy.
- 03:03: Explains gravity as the warping of space and time due to the presence of mass and energy.
- 04:14: ... The exact shape is determined by the relative amounts of matter and dark energy in the ...
- 04:30: The presence of matter increases the curvature and the presence of dark energy decreases the curvature.
- 11:18: ... his solution for the shape of the universe by assuming that matter and energy are evenly spread out ...
2022-03-08: Is the Proxima System Our Best Hope For Another Earth?
- 06:29: That sounds perilous, until you realize that Proxima’s energy output is nearly 600 times lower than the Sun’s.
- 11:22: ... can cause the star to have powerful outbursts - flares - that blast high energy particles and radiation through the planetary ...
- 11:36: During flares, Proxima B is blasted with X-rays and ultraviolet light and high energy particles.
2022-02-23: Are Cosmic Strings Cracks in the Universe?
- 00:58: ... has cracks in it. Universe-spanning filaments of ancient Big Bang energy, formed from topological defects in the quantum fields, aka cosmic ...
- 04:51: ... everywhere in the universe found itself sitting at a higher energy than it needed. It was momentarily stable at that ...
- 05:59: ... with different phase angles then sometimes the lowest energy approach to lining up the phase angles is for them to vary ...
- 07:33: ... defect tighten as much as they can. The filament of high vacuum energy is squeezed it down to one-ten-trillionth the width of ...
- 10:09: ... gravitational waves. In this way cosmic strings shed energy, and so they slowly decay away. Eventually they vanish as the ...
2022-02-16: Is The Wave Function The Building Block of Reality?
- 14:52: ... wave will get deflected and partially absorbed. The absorbed energy can go into changing the black hole’s velocity, but also can be added to ...
- 17:28: ... the surface from which light is infinitely redshifted - sapped of all energy - before it reaches that infinite ...
2022-02-10: The Nature of Space and Time AMA
- 00:03: ... space in a sense um in this that that new space has the same vacuum energy density the old one has the same kind of behavior of virtual particles ...
2022-01-27: How Does Gravity Escape A Black Hole?
- 09:39: It appears to freeze at the event horizon, and the light it emits becomes stretched out and sapped of energy.
- 11:27: ... in general relativity in part because the gravitational field itself has energy, and so is a source of ...
2022-01-12: How To Simulate The Universe With DFT
- 00:54: ... to learn the probability distribution of the electron locations, or the energy levels of the system, or ...
- 01:48: ... the particle is in some environment described by a sum of potential energies - that’s the V. V could result from the electromagnetic field inside the ...
- 02:08: And this E is just the total energy of the system.
- 02:10: ... possible values of E that form solutions to this equation define the energy levels of the ...
- 10:29: ... map from this charge density to the interesting observables - like the energy of the system, without having to go through the impossibly complex ...
- 11:23: Solving those equations becomes possible, and it gets you the ground state energy for your guess at the charge density.
- 11:30: Then iterate until everything is consistent - when the ground state energy, the potential, and the charge density converge.
- 11:54: The secret sauce that makes this work is something called the energy functional - it’s the functional in density functional theory.
- 12:02: When given a ground state density, it let’s us construct this fictitious non-interacting “Kohn-Sham” system and figure out its total energy.
- 12:10: DFT is all about finding the energy functional.
- 17:33: The black hole could never deposit enough energy on its passage through the moon to break it apart.
- 17:38: It would need to grant the entire moon enough energy to overcome its own self-gravity.
- 18:04: Energy becomes useful when it’s moved between a low entropy to a high entropy configuration.
- 18:10: ... sun’s visible light into infrared, ultimately releasing exactly as much energy as it absorbed, but in a much higher entropy ...
- 18:21: ... it weren’t releasing as much energy as it absorbsd then the interior of the sphere would have to heat up ...
- 18:43: Such a beam has a lower entropy than isotropic thermal radiation, and so less energy is made available for the aliens.
- 18:51: ... scary to imagine an alien civilization that would need the amount of energy generated by a Dyson ...
- 19:04: ... followed several people speculating on what they might need all that energy ...
- 19:16: Phudlow may have hit on the biggest potential energy sink - FTL travel, if possible, will certainly take a ridiculous amount of energy.
- 19:44: And actually there’s a way to shed your excess energy, and you have an escape route when the Reapers arrive.
- 19:50: Another potential energy need is matrioskha brain.
- 20:03: And that would presumably take quite a bit of energy, depending on the frame rate.
2021-12-29: How to Find ALIEN Dyson Spheres
- 00:14: Any energy-hungry civilization more advanced than our own may leave an indisputable technological mark on the galaxy.
- 00:34: Humanity is an energy-hungry species, and that hunger grows exponentially.
- 00:44: ... could satisfy humanity’s current energy needs by covering a tiny fraction of Earth’s surface with solar cells. ...
- 01:38: ... radius of its planet of origin, for the purpose of both habitation and energy ...
- 02:49: It doesn’t reflect nearly as much of the Sun’s light as you’d expect for a globe of water and rock - it's as though that energy is being sucked up.
- 02:58: But if you shifted your gaze from visible light to infrared, you’d find all of the missing energy.
- 03:24: ... in the process they warm up, shedding all of that energy as a new thermal spectrum, now at 300 or so Kelvin, with its peak at ...
- 06:37: ... into an equilibrium state in which the outward flow of fusion-generated energy balances the inward crush of its own ...
- 12:12: ... home galaxy and built a huge number of Dyson spheres, or similarly energy-hungry ...
- 13:04: No very energy-hungry ones at any rate.
2021-12-10: 2021 End of Year AMA!
- 00:02: ... i end up as the host of pbs space time well if any of you have the energy to scroll all the way down to the bottom of our videos page on pbs ...
2021-11-17: Are Black Holes Actually Fuzzballs?
- 10:50: Light trying to escape would still be massively redshifted - sapped of energy by the gravitational field - rendering the object effectively black.
2021-11-10: What If Our Understanding of Gravity Is Wrong?
- 06:06: It doesn’t respect conservation of energy or momentum or angular momentum.
2021-11-02: Is ACTION The Most Fundamental Property in Physics?
- 00:02: ... an obscure concept in physics that may be more fundamental than energy and entropy and perhaps time itself. Ready? Action. In order to wrench ...
- 01:22: ... - for example Euler considered properties involving momentum and kinetic energy - but to no avail. In the meantime Isaac Newton came up with his laws of ...
- 02:11: ... air. We can describe that motion without the painful vectors if we use energy. ...
- 02:21: ... ball starts out moving fast - it has a lot of kinetic energy, which it trades for potential energy as it rises, and then back to ...
- 02:50: ... realized that a particular combination of kinetic and potential energy had the same minimizing property as does time for the path of light. He ...
- 03:17: ... Formally, it’s the integral over time of the kinetic minus potential energies. ...
- 03:33: ... that difference in energies itself got the name Lagrangian, which itself turns out to be an ...
- 05:00: ... can dispense with forces and vectors in general, and only consider the energies. ...
- 05:52: ... Mercury’s orbit. After all, planets trade between potential and kinetic energy as they move around their orbits, just like the ...
- 07:09: ... think about that. Before Action was a somewhat vague notion of change in energy, but working with a more precise model of the universe we see Action is ...
- 08:06: ... that in the classical limit proper time becomes kinetic minus potential energy for objects with mass, but for objects without mass, like light, proper ...
- 10:26: ... the quantum action doesn’t come from adding up kinetic minus potential energy nor the proper time. Instead, it effectively calculates the phase shift ...
- 12:16: ... the places the ball could reach with its current Potential and Kinetic Energies. When we take this to relativity we see the configuration space becomes ...
2021-10-20: Will Constructor Theory REWRITE Physics?
- 05:44: Again, this task is impossible, since it’s ruled out by the laws of quantum mechanics and the principle of conservation of energy.
- 06:06: David Deustch gives the example of the perpetual motion machine of the first kind - a device from which infinite energy can be extracted.
- 06:43: ... law of conservation of energy says that it’s impossible to create energy from nothing, and the second ...
- 10:51: ... stripping away all but the bare facts about the nature of electron energy levels - including abandoning any pre-existing dynamical ...
- 12:30: ... tunneling. The presence of a barrier changes the potential energy in that region. If that potential barrier is too high for the ...
2021-10-13: New Results in Quantum Tunneling vs. The Speed of Light
- 01:32: You can still make it over the hill if you have enough speed - enough kinetic energy to see you to the top.
- 02:11: If one of these particles had enough energy it could punch through that barrier.
- 02:22: In radioactive decay, particles that should never have enough energy to escape the nucleus are found to leak out.
- 14:33: They ask — if these can’t be removed by smooth variation in the vectors then how come they're created in high energy events?
- 14:43: ... answer is that at very high energies, the direction of the Higgs field becomes free to vary wildly and ...
2021-10-05: Why Magnetic Monopoles SHOULD Exist
- 13:13: ... not so surprising given that the LHC reaches energies about 100 billion times lower than is needed to produce the monopoles ...
- 15:08: We represented very distinctly separated electron energy levels in our explanation of how fermion’s can’t occupy identical quantum states.
- 15:16: ... notes that energy levels in atoms can actually hold 2 electrons, not one, because it’s ...
- 15:29: ... have said that we were trying to represent separate quantum states, not energy levels in an ...
- 16:57: In the case of the collapsing star, densities and energies become high enough for electrons to be captured by protons, converting them to neutrons.
2021-09-21: How Electron Spin Makes Matter Possible
- 01:44: ... the same quantum state, which is why electrons can’t occupy the same energy states in atoms. Without this, electrons in multi-electron atoms would ...
- 14:00: ... the energy level spectrum becomes unbounded from below, meaning you can continually ...
2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe
- 02:00: ... matter-antimatter pairs are created out of the extreme energy photons in the magnetic field. That field then becomes a ...
- 05:48: ... more energetic these electrons become - and soon those energies are high enough to drive some very exotic nuclear reactions. ...
- 06:38: ... by the incredible pressures and extreme electron energies in the neutron ...
- 07:06: ... here - we’re beyond the point where we can duplicate these energies and these neutron-rich nuclei in particle ...
- 11:29: ... can do things like sustain vortices with enormous amounts of energy. Some physicists think that the dissipation of these vortices ...
2021-09-07: First Detection of Light from Behind a Black Hole
- 04:37: ... gravitational field of the black hole and the continuous blaze of high energy radiation from the inner accretion ...
- 04:57: This gas starts to glow in a different way - not from heat, but from the motion of electrons between their atomic energy levels.
- 10:01: As light from the accretion disk passes through this haze it gains energy from the electrons, boosting it all the way up to X-ray energies.
- 15:42: ... didn’t know the full answer - but he tells us that it depends on the energy difference between the false and true vacuum - presumably the bigger the ...
- 15:54: ... I would also imagine that the bigger the energy difference, the less probability of the field tunneling to the true ...
2021-08-18: How Vacuum Decay Would Destroy The Universe
- 02:18: ... position. That position is the field value where the energy is minimized. Physicists like to represent this by plotting the ...
- 02:52: ... most quantum fields, the minimum energy is where the field value is zero. For example, for an ...
- 03:11: ... field that breaks these rules. That’s the Higgs field. The minimum energy state of the Higgs field is not where the field strength is zero. ...
- 04:00: ... This would look like multiple dips in our graph of energy versus field strength. A quantum field with multiple ...
- 05:03: ... has at least two minima, and those minima should have different energy values. There’s a true minimum - the true lowest energy, or ...
- 08:08: ... from vacuum decay. First up, everything gets fried. The energy released in the decay of the Higgs field fills the expanding ...
- 08:30: ... particles their masses. Those masses depend on the energy in the field - the so-called vacuum expectation value. ...
- 10:54: ... remember there’s another way to hop between energy minima. If enough energy can be pumped into a patch of space, the ...
2021-08-10: How to Communicate Across the Quantum Multiverse
- 06:09: ... creep in which can do things like damp the waves - cause them to lose energy. ...
- 16:27: ... And that is exactly it. The supernova shock front is a mixture of high energy particles and magnetic fields. Those magnetic fields do lots of things - ...
2021-08-03: How An Extreme New Star Could Change All Cosmology
- 03:58: ... brightly. You also need to know how efficiently it’s shining - how much energy for every unit of surface area - but that’s just a function of its ...
- 06:21: ... its electrons would start to overlap - they’d have to occupy the same energy states. But that’s forbidden by quantum mechanics - specifically, by the ...
- 06:51: ... attraction to the nucleus. And those electrons can occupy discrete energy levels, where the higher the energy, the closer the electron is to ...
- 09:18: ... because they emit gravitational radiation that saps away their orbital energy. We’ve seen the result of this with black holes and neutron stars when ...
- 11:36: ... of type 1a supernovae were how we first discovered the existence of dark energy, and we’ve talked about how that was done ...
- 11:52: ... white dwarfs then perhaps our calculations of the amount of dark energy are wrong. And in case you haven’t been paying attention, there does ...
- 12:16: ... get me wrong, this issue with the supernovae would not make dark energy go away - there’s too much independent evidence - but it’s probably ...
- 15:19: ... electrons in atoms can’t be shoved into each other to occupy the same energy levels. Now we’ll actually be coming back to this when we get into the ...
- 17:08: ... - can magnetic fields be used to explain dark matter or to explain dark energy? Or could magnetic fields be used to power spacecraft? So the answer is ...
2021-07-21: How Magnetism Shapes The Universe
- 04:16: Magnetic field lines cross each other, and enormous magnetic energy densities pile up.
- 04:29: ... spray that magnetic field out into the solar system - carrying high energy particles with ...
- 11:08: Electrons and atomic nuclei can be accelerated in this magnetic field to high energies - into what we call cosmic rays.
- 11:47: Those fields grab particles of matter and accelerate them to incredible energies, flinging cosmic rays out into the universe.
2021-07-07: Electrons DO NOT Spin
- 02:25: ... the specific wavelengths of photons emitted when electrons jump between energy levels in atoms. Peiter Zeeman, working under the great Hendrik ...
- 03:20: ... anomalous Zeeman effect. In some cases, the magnetic field causes energy levels to split even further - for reasons that were, at the time, ...
- 11:34: ... electron spin angular momentum and magnetic moment by looking at the energy and charge currents in the so called Dirac ...
- 13:00: ... for us having a periodic table, for electrons living in their own energy levels and for matter actually having structure. It’s the ...
- 15:31: ... meant that the entropy associated with matter was extremely high. Energy was as spread out as it could get between all of the particles and the ...
2021-06-23: How Quantum Entanglement Creates Entropy
- 01:02: ... of air has a temperature, which is a measure of the average energy of motion of all the individual air molecules. But a ...
- 02:48: ... amount of useful work that could be extracted by moving heat energy around. If heat energy is perfectly mixed inside and out of ...
2021-06-16: Can Space Be Infinitely Divided?
- 01:16: ... blackbody, or thermal radiation - by requiring that the energy of light in this heat-glow was not infinitely divisible. ...
- 05:45: ... now adding two key ideas from Einstein: first that mass and energy are equivalent, as expressed by the most famous equation ever, ...
- 06:02: ... also increases the photon’s energy and momentum. As we crank up the energy even further we start to notice something. The photon is starting ...
- 06:39: ... Let’s replace the mass with the effective mass of our photon - its energy over c^2, and the energy of a photon is Planck’s ...
- 07:10: ... this is where, I hope, it gets interesting. As you pump up the energy of your photon, reducing its wavelength also reduces the ...
- 08:37: ... also means increasing the uncertainty in energy density in that volume. By the time we localize the electron to ...
2021-06-09: Are We Running Out of Space Above Earth?
- 01:45: ... that scary on earth, at orbital speeds of 7 km/s they can carry as much energy as a ...
- 04:31: ... change - in particular, during times of high solar activity when more energy is pumped into the atmosphere, causing it to puff up and cause increased ...
2021-05-25: What If (Tiny) Black Holes Are Everywhere?
- 02:28: The distribution of particle energies should follow a blackbody spectrum, as though the black hole has a real temperature.
- 03:08: ... waves with kilometers-long wavelengths, so really, really low energy radio ...
- 03:20: Such a black hole would appear very cold, and would leak away its energy very slowly.
- 03:25: But as the black hole shrinks in mass and in size, its Hawking radiation also decreases in wavelength - but it increases in energy.
- 05:05: A red hot poker glows because it has an enormous number of iron atoms, vibrating with every possible energy.
- 05:23: It jiggles in its little crystal lattice cage with very specific vibrational modes, producing photons of specific energies.
- 05:39: The black hole loses energy one photon at a time, but the process seems smooth and continuous.
- 06:11: If it happens at all, it’ll be when the average energy of the Hawking radiation is close to the entire rest-mass energy of the remaining black hole.
- 06:37: It doesn’t sound like much but that’s around 2 billion Joules of energy.
- 08:03: ... the extreme energies and densities near the Big Bang, there are a few different ways to ...
- 13:57: ... when an incoming photon causes an electron in a crystal to drop in energy to produce an identical photon matched in phase and direction of the ...
- 14:09: In certain materials known as non-linear crystals, the incoming photon is absorbed and the energy is instantly emitted as two photons.
2021-05-19: Breaking The Heisenberg Uncertainty Principle
- 01:36: Exact measurement of its energy means its location in time is blurred.
- 02:47: ... to measure the position more precisely, you would need a higher energy photon, which would kick the object even harder, causing an even greater ...
- 09:34: And that introduces its own type of noise - radiation pressure noise as these photons transfer energy to the mirrors in the interferometer.
2021-05-11: How To Know If It's Aliens
- 15:39: ... would be released in the forward direction. This would have so much energy on release that even just the space dust from a short interstellar trip ...
2021-04-21: The NEW Warp Drive Possibilities
- 02:30: His special theory of relativity just says that it takes infinite energy to accelerate anything with positive mass all the way to light speed.
- 04:01: ... these equations we input a physically possible distribution of mass, energy, on the right side and it spits out the spacetime geometry on the ...
- 04:11: ... backwards through the equations to see what distribution of matter and energy would be ...
- 04:31: ... combat this, we have a set of energy conditions that go alongside the Einstein field equations that are meant ...
- 04:48: We can summarize this by saying that it requires a negative energy density, which should be impossible except perhaps on the tiniest, quantum scales.
- 05:11: ... other minor hiccup is that Alcubierre’s original field required more energy than is contained in all the matter in the visible universe to move a ...
- 05:21: ... studies improved on Alcubierre’s warp design and brought down the energy requirement to less insane levels - although they typically remained ...
- 05:30: ... studies demonstrated that any superluminal warp drive MUST use negative energy ...
- 06:58: ... Warp drives are inertially moving shells of positive or negative energy material which enclose a `passenger' region with a flat ...
- 08:44: ... even a subluminal reaction-less warp drive would still require negative energy and an enormous amount of it for any decent sized ...
- 09:11: Lentz claims to have found an actual superluminal warp field solution that does NOT require the impossible negative energy densities.
- 09:54: When you calculate the total energy with only this component than it’s alway negative.
- 10:01: ... direction of motion he could build a superluminal soliton in which the energy came out positive ...
- 10:19: Energy is distributed along these tracks, potentially as a plasma, in some places at some pretty insane temperatures.
- 10:39: The energy required to carry a 100-meter diameter bubble is about the rest-mass energy of a tenth of our Sun.
- 11:36: ... deal-breaker can be resolved - that of requiring a non-existent type of energy. ...
- 11:47: ... other possibly-impossible hurdles remain - can the required energy densities be created without creating black holes for any useful sized ...
- 13:16: These guys define a type-1 warp field as a surface of positive energy density enclosing a flat metric.
- 15:01: ... example, the energy distribution of those decays products are sensitive to the complex ...
2021-04-07: Why the Muon g-2 Results Are So Exciting!
- 10:02: The frequency of the precession also governs the energy of the particles that these muons decay into.
- 10:08: ... by measuring the energies of those particles, positrons in particular, the researchers can ...
- 10:19: ... they detected a new particle based on a slight bump at a particular energy of the decay ...
2021-03-23: Zeno's Paradox & The Quantum Zeno Effect
- 01:27: ... that certain quantum events - like the electrons moving between atomic energy levels, or the decay of atomic nuclei, can be frozen through the simple ...
- 01:50: ... specific, discrete values - like how an electron can only occupy certain energy states in an ...
- 05:37: ... claimed to have demonstrated it in an experiment by halting electron energy ...
- 06:00: A constant radio-frequency field is tuned to cause electrons to oscillate smoothly between two energy levels - call them 1 and 2.
- 06:18: Next they flash the atoms with a laser whose frequency matches the energy difference between state 1 and a new state, state 3.
- 06:25: ... and jumps to 3, and then immediately drop back down to 1, releasing the energy as a new photon that the researchers can detect - so the atoms glow ...
- 07:47: ... of the quantum Zeno effect, including various studies of atomic energy levels, as well as the freezing of quantum tunneling - the same ...
- 14:09: For example, based on the amount of matter and dark energy, we can figure out now much the expansion should have slowed or sped up.
- 14:38: In might, for example, tell us that dark energy has changed over time - which might help us figure out what dark energy actually is.
2021-03-16: The NEW Crisis in Cosmology
- 03:13: ... universe expanding, but that expansion is accelerating. And so dark energy was discovered - a mysterious and ubiquitous energy that ...
- 03:55: ... energy very likely holds deep, deep clues about the fundamentals of ...
- 05:31: ... Adam Reiss, one of the Nobel-winning discoverers of dark energy has doubled down on the supernova method. A couple of years ago ...
- 05:52: ... possible explanation for the difference is that the nature of dark energy has changed over time. The Planck team’s ...
- 06:05: ... what you expect for the simplest models of what dark energy might be, But if dark energy has HAS changed over time it ...
2021-03-09: How Does Gravity Affect Light?
- 03:18: Wavelength increases, which means frequency and energy drop.
- 04:27: ... body is large enough, light emerging from it can be sapped of ALL energy - redshifted so the wavelength is effectively ...
2021-02-24: Does Time Cause Gravity?
- 02:33: We know that the presence of mass and energy warp spacetime - and the most intense part of that warping is in time - our gravitational time dilation.
- 06:29: ... see the same favorable exchange when we try to convert mass into energy via Einstein’s most famous equation, E=mc^2 - the speed of light is the ...
2021-02-17: Gravitational Wave Background Discovered?
- 00:00: ... only by weird quantum forces neutron stars tend to channel jets of high energy particles due to their intense magnetic fields they also rotate rapidly ...
2021-02-10: How Does Gravity Warp the Flow of Time?
- 01:37: Mass and energy change the lengths of rulers and the speeds of clocks - and somehow those changes lead to objects being attracted to each other.
2021-01-26: Is Dark Matter Made of Particles?
- 04:15: If it did, then giant regions of dark matter would lose energy in those collisions and contract.
- 08:25: ... in our particle accelerators - perhaps we just haven’t produced enough energy to make one ...
- 10:33: ... would have been popping into existence constantly, borrowing energy from the crazy radiation of that ...
- 10:46: And then when the particle bumps into its antiparticle they both annihilate, releasing that energy again.
- 10:53: As the universe cooled and energy dropped, that process ceased.
2021-01-19: Can We Break the Universe?
- 13:48: The energy levels are represented by a very small number of photons in a cavity - 0 to 5 - so quite quantum.
2021-01-12: What Happens During a Quantum Jump?
- 00:36: ... electrons in atoms jump randomly and instantaneously from one orbit or energy level to another, without ever occupying the intervening ...
- 01:22: ... spectrum - by assuming that light is made up of irreducible packets of energy that we now call ...
- 01:37: ... placed a similar restriction on atoms - he required that electron energy levels were quantized - could only have very specific energies that ...
- 01:49: Electrons would then jump between energy levels by emitting or absorbing a photon that corresponded to the difference in energy.
- 02:50: The electron goes from one energy level to the other without moving in between.
- 05:01: ... rejected the idea of the “photon” as an irreducible energy packet, and even dismissed the notion that electrons transitioned ...
- 06:28: ... barium - is bathed in a laser beam with a frequency exactly tuned to the energy difference between two of its electron levels - call them 1 and ...
- 06:52: For the right choice of energy levels, this should happen extremely quickly - the electron should become locked between the two levels.
- 07:14: ... jumps - that required an extra level of cleverness, as well as an extra energy level - we’ll call this level ...
- 08:48: The 3 different energy levels of this artificial atom corresponded to the number of electromagnetic quanta of energy stored in the circuits.
2020-12-15: The Supernova At The End of Time
- 02:39: ... as a bright ball of hydrogen, bathing a young planetary system in the energy produced by its fusion ...
- 04:48: Once its nuclear fuel supply runs out, there would be no outward flow of energy to resist the gravitational crush.
- 06:54: They start out hot and bright, but with no capacity to generate new energy, they slowly radiate away the heat of their youth.
2020-12-08: Why Do You Remember The Past But Not The Future?
- 04:23: ... rocks for just a second, let’s go as simple as possible - in the crazy energy of the early universe, a positron and a neutral pion particle combine to ...
- 09:41: ... over time as they interact with each other - for example, by sharing energy - which is another way to think about the rise in ...
- 11:09: Just as our bodies expend entropy by using and redistributing energy.
- 12:23: ... a real mystery with the big bang theory The distribution of matter and energy in the early universe does appear to have been random - which we ...
2020-11-18: The Arrow of Time and How to Reverse It
- 03:12: ... about entropy. Today we’ll talk about it in terms of distribution of energy. Energy can take many forms, and can be transferred between forms and ...
- 03:47: Over time, energy tends to get shared out as evenly as possible due to, say, collisions.
- 03:53: ... you had many ele ctrons in a box, and half of them had a lot of kinetic energy - were moving fast, while the others had none - pretty quick energy ...
- 04:13: ... if you start from a situation where energy is not perfectly randomly spread out, then over time it’ll become more ...
- 05:10: ... directions, the cluster will inevitably disperse. Entropy increases as energy spreads out to all possible states - in this case towards all possible ...
- 06:57: ... scales due to random alignments of particle trajectories or however else energy is moving around. Entropy can decrease, reach a minimum, and then will ...
- 10:34: ... yes, at least to some degree. The Higgs field sits at a non-zero vacuum energy so could potentially decay to zero, or even to a lower non-zero state ...
2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces
- 02:19: But Fermi’s model only worked at low energies, and neither it nor its successors explain why the weak interaction violates charge-parity symmetry.
- 03:48: ... of forces with massive force carriers is usually attributed to the energy-time uncertainty relation, and we’ve presented it that way ...
- 04:02: Anyway, this new gauge theory of the weak interaction seemed to be okay with parity violation, and it wasn’t only accurate at low energies.
- 05:36: When we quantize that field - when we let it oscillate with discrete packets of energy - we get the photon.
- 10:03: ... high enough temperatures - above the Curie temperature - thermal energy causes the particles to rotate randomly so the overall magnetization of ...
2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time
- 05:01: ... of gravitational fields is called the weak energy condition of general relativity, and it almost certainly holds in ...
- 11:10: ... of pure general relativity, and assume the various energy conditions. We know that general relativity is not the ...
2020-09-28: Solving Quantum Cryptography
- 17:05: ... would not apply ... so like, yeah, "we’re creatures made of light and energy and are at the center of the universe, and we're orbited by specks of ...
2020-09-21: Could Life Evolve Inside Stars?
- 01:13: ... idea was just published in Letters High Energy Physics Letters by physicists Luis Anchordoqui and Eugene Chudnovsky, ...
- 04:02: ... the universe with different properties - for example, different vacuum energies. ...
- 05:21: And 3) a source of free energy.
- 07:53: And finally, life condition number 3: do we have a source of free energy?
- 07:58: By free energy, I don’t mean energy that you don’t have to pay for.
- 08:01: I mean energy that is available for use, in a thermodynamic sense.
- 08:05: Energy can only be used to do work if there exists differences in the amount of energy in different possible states.
- 08:12: If energy is concentrated in certain places we would call that an ordered, low entropy situation.
- 08:20: Energy likes to spread itself out as evenly as possible, moving towards disordered, high-entropy states.
- 08:28: It’s possible to use energy as it flows between different states in this process, like putting a water wheel in a flowing river.
- 08:35: For example, life uses the energy flowing from the high energy-density of the Sun to the lower energy density of the Earth.
- 08:47: We saw that these temporary increases in order, represented by life, actually speed up the process of smoothing out all of the energy.
- 09:02: OK, so inside a star there’s definitely free energy.
- 09:06: Energy flows from the fusion engine in the core to the surface.
- 09:14: Well, it would have to hasten the spreading out of energy.
- 09:18: Energy could be spread more evenly across the electromagnetic spectrum, which would look like cooling - the star might appear cooler than it should.
- 09:27: Or perhaps the nuclear reactions in the core proceed faster, hastening the dissipation of the star’s energy through space.
2020-09-08: The Truth About Beauty in Physics
- 08:35: ... allowed the electron to have states with negative energy levels - not technically possible, but we now understand these as ...
- 13:58: Shouldn't those same electrons then drop back down in energy level, emitting the same wavelengths they absorbed?
- 14:22: ... absorption - that's because although those atoms to reemit the absorbed energy, they do so in random directions AND potentially through a cascade of ...
- 15:49: To detect these you need more collisions, not higher energies.
2020-09-01: How Do We Know What Stars Are Made Of?
- 00:51: We didn’t know what stars were made of nor where their energy came from.
- 03:06: ... at different colors - or in other words, from photons of different energies of ...
- 03:44: Those are where photons of very specific energies have been plucked out of this thermal light.
- 04:54: An atom can absorb a photon if doing so would cause one of its electrons to jump up to a higher energy level.
- 05:02: The energy of the photon and the energy of the electron jump have to be exactly the same.
- 05:07: So any photons trying to escape the Sun that happen to have one of these particular energies are going to get sucked up on its way out.
- 05:19: Each element on the periodic table produces a different set of lines corresponding to its unique energy levels.
- 06:45: ... changes the energy levels of the electrons that remain, resulting in a different set of ...
2020-08-24: Can Future Colliders Break the Standard Model?
- 00:38: ... be capable of colliding particle beams with 8 times the current LHC energy. ...
- 01:47: Some particles would collide with enough energy to be destroyed, and their energy would be released in the form of new particles.
- 02:03: There’s a serious limit to the energy you can muster by colliding particles into a stationary object.
- 02:10: To be precise, collision energy with a fixed target goes up with the square root of accelerator energy.
- 02:17: Which means you’re wasting lots of energy.
- 02:19: ... WITH each other then you get the full oomph of the impact - twice the energy in the individual ...
- 03:19: The Americans soon followed up with a 12 meter electron-electron collider with a similar luminosity to VEP-1 but higher energies than even the AdA.
- 03:29: Finally we’d reached collision energies needed to test predictions of the still relatively new quantum electrodynamics.
- 03:54: Since then, colliders have only grown in size and energy.
- 04:33: The beams cross in four locations, where they collide with energies of several terra-electron volts.
- 04:38: Which is, for reference, a lot of energy.
- 06:26: The Large Hadron Collider reaches energy a few times higher than the top of that range, so it should have seen such particles by now.
- 07:07: ... motley zoo of particles and forces, we probably need to achieve higher energies - energies even closer to the instant of the Big Bang, when the forces ...
- 07:25: ... are other clever ways to probe these energies - for example using natural particle accelerators like the sun or ...
- 07:41: ... these ultra-high energy cosmic rays are rare, and to reliably detect a new particle we need to ...
- 08:37: ... point of this upgrade isn’t primarily to access higher energies where new particles might exist, but rather to make the LHC much better ...
- 08:47: IF either SUSY or other very high-mass particles do exist, then they may be actually a good way beyond the energy range of the LHC.
- 09:03: If it goes ahead, it’ll hit energies of 100 TeV - 8 times the current LHC energy.
- 09:33: It’s easier to achieve the energies and luminosities to produce, for example, large numbers of Higgs particles in relatively clean collisions.
- 09:50: ... example, at our current energies, we don’t know how often it interacts with the superheavy top quark, a ...
- 10:24: However there’s no guarantee that any new particles exist in the expanded energy range that the FCC will probe.
2020-08-17: How Stars Destroy Each Other
- 06:16: ... powerful magnetic field channels high energy particles into a jet that traces a circle across the sky - and often ...
- 07:09: ... to know that when you look at our galaxy in gamma rays - the highest energy light there is - the brightest points you see are pulsars, and those ...
- 07:58: ... dwarf, which is a star not quite massive enough to generate its own energy by nuclear ...
2020-08-10: Theory of Everything Controversies: Livestream
- 00:00: ... they wouldn't unify with those new particles differently if you up the energy scale i would say to you um why is it that everybody talks about ...
2020-07-28: What is a Theory of Everything: Livestream
- 00:00: ... that something has gone horribly wrong you know things like infinite energies or probabilities greater than one these kinds of things indicate that ...
2020-07-20: The Boundary Between Black Holes & Neutron Stars
- 03:34: ... to an explosion observed across the electromagnetic spectrum - energy released as the neutron stars tore themselves apart in their collision ...
- 12:52: However it never actually becomes impossible to keep charging up a black hole if you can put enough energy behind your electron beam.
- 13:34: ... smeared out at the event horizon - and then yes, they would see your energy exit again as the black hole shrank - but it would itslef be as ...
2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing?
- 00:22: ... other out completely, and leaving only two photons to carry away the energy. And it works in reverse too. Particle and anti-particle pairs can be ...
- 04:48: ... understanding of the universe is incomplete. It doesn’t explain dark energy, dark matter, or this baryon asymmetry problem. So, if there exists some ...
- 05:19: ... the charge and spin thing — it must have the same mass, the same quantum energy levels, and the same interactions with its ...
- 07:21: ... accelerates protons to 10’s to 100’s of G-electron Volts of kinetic energy, corresponding to over 99% of the speed of light. These high-energy ...
- 09:19: ... anti-hydrogen securely in the trap, scientists measure the difference in energies between the various positron orbitals in the anti-atoms using laser ...
2020-06-30: Dissolving an Event Horizon
- 05:45: In very massive black holes the Hawking radiation has trouble mustering the energy for anything but weak photons.
- 10:12: As Einstein taught us, mass and energy are equivalent.
- 10:15: And there’s an enormous amount of energy in the electric field of all those electrons that you smooshed together into the black hole.
2020-06-22: Building Black Holes in a Lab
- 05:25: ... separated - one escapes and one falls in, somehow converting to negative energy and so decreasing the mass of the black hole. A more technical ...
- 06:33: ... happens inside the black hole itself. The standard picture is that energy gets sapped from the black hole because the infalling ...
- 07:24: ... field” in a vortex black hole analog. In fact, both the analog of energy and angular momentum seems to be sapped by this Hawking-like ...
- 08:04: ... we saw was that rotating black holes can donate some of their rotational energy to particles or waves that pass close by. This is the Penrose process, ...
- 10:04: Here, the edge of the laser acts as the event horizon—the rubidium atoms don’t have enough energy to jump back up over the waterfall.
2020-06-15: What Happens After the Universe Ends?
- 08:24: Two ways to think about this: A particle's energy is a combination of its kinetic energy and rest mass energy.
- 08:31: Kinetic energies were so high at the big bang that rest mass energy was completely negligible - all particles behaved like light-speed particles.
- 08:57: ... a change in the nature of the Higgs field - if it decayed to a lower energy - could eliminate elementary particle masses in the late universe ...
- 10:55: That means it needs dark energy.
- 12:20: In CCC, all of the energy - and, importantly, the gravitational field - is smoothed out over infinite time between aeons.
- 12:28: ... of the previous universe, where exponential expansion was fueled by dark energy. ...
2020-06-08: Can Viruses Travel Between Planets?
- 02:25: ... cells, viruses do not metabolize - so they don’t produce their own energy, and they can’t reproduce without coopting the reproduction machinery of ...
- 15:22: ... the Casimir effect is thought to be due to an alteration in the vacuum energy between a pair of conducting surfaces, which leads to those surfaces ...
- 15:49: ... with so-called lifshitz theory, which is based on this altered vacuum energy ...
2020-05-27: Does Gravity Require Extra Dimensions?
- 06:48: We can also think about it as gravity producing excitations within those extra dimensions that sap its energy.
2020-05-18: Mapping the Multiverse
- 12:06: ... black hole then the forward flow of time carries a current of positive energy, while the backwards carries negative ...
- 12:34: So if you do get to the inner horizon you are in a bath of energy on par with the Big Bang.
2020-05-11: How Luminiferous Aether Led to Relativity
- 03:25: ... we’ll call classical waves - are a chain reaction that propagates an energy pattern through some medium. So if light is a wave, surely it also needs ...
2020-05-04: How We Know The Universe is Ancient
- 09:39: ... the universe of around 13 billion years, assuming no gravity and no dark energy. But that’s remarkably close to the currently accepted value. Sandage ...
- 11:07: ... slowing down expansion through its gravity and also the effect of dark energy speeding it up. Those can be put into the Friedman equations and a bit ...
- 12:09: ... story short, the accelerating effect of Dark Energy counters the slowing effect of gravity to ultimately give us an age of ...
- 12:25: ... the age of the universe is to get the matter content, and the dark energy content, and the expansion rate, and more all from the one source - the ...
- 12:59: ... by the Planck satellite we get the relative amounts of matter and dark energy and a number of other quantities. Quantities important for plugging into ...
- 14:36: ... does not have an event horizon, but you need the non-existent negative energy to do so and keep it open long enough to traverse. The reality is that, ...
2020-04-28: Space Time Livestream: Ask Matt Anything
- 00:00: ... so Michael from the community tab asks if I can describe how dark energy and evaporating black holes with virtual particles do not violate ...
2020-04-22: Will Wormholes Allow Fast Interstellar Travel?
- 07:52: ... and any topology. The only limitation is the nature of the matter and energy that spacetime contains. In fact by defining the geometry you want - eg ...
- 08:42: ... common way to think of exotic matter is anything with negative energy density. Something with negative mass could produce the required ...
- 09:11: In general, exotic matter violates the so-called energy conditions of general relativity.
- 09:17: ... are constraints that are placed on allowable distributions of mass and energy in Einstein’s equation in order for those equations to make physical ...
- 09:44: ... in that region. The gap between the plates will then have a negative energy density relative to surroundings. Unfortunately, the Casimir effect is ...
- 10:15: ... if you could create a Casimir negative energy wall in the center of a wormhole that should keep it open. Unfortunately ...
2020-04-14: Was the Milky Way a Quasar?
- 02:42: We have of course covered dark matter and dark energy in detail previously.
- 03:56: It goes like this: atomic nuclei - mostly lone protons - can get accelerated to extreme energies, typically in supernovae or other cataclysmic events.
- 04:49: The gamma rays produced by neutral pion decay from these cosmic ray collisions tend to drop off in intensity towards higher energies.
- 04:57: So, fewer very high energy gamma rays.
- 05:00: On the other hand, the Fermi Bubbles produce a lot more gamma rays at higher energies.
- 05:05: The difference in energy distributions - or in their gamma ray spectra, means that the diffuse gamma ray background can be cleanly subtracted.
- 05:36: And so that’s what we’re seeing here - light bounced off extremely high energy electrons within the vast bubbles.
- 05:42: It’s estimated that the energy contained in this ocean of electrons is equivalent to that released by 100,000 supernova explosions.
- 05:52: So the questions become - where the bleep did that energy come from, and when was it released?
- 06:21: I mentioned an energy of 100,000 supernovae - well that’s actually a serious option.
- 08:25: ... of that mass goes into the black hole, but 10% or more is converted into energy in the form of light before it hits the black hole, which is why quasars ...
- 08:37: Sagittarius A* would have converted matter to energy with much less efficiency.
- 09:10: That all sound good in terms of our energy budget.
- 10:17: This starburst and the subsequent supernova barrage smooths out the energy in the bubbles.
- 10:34: The energy from those outflows will eventually shut down the star formation, but in the early phase it can help kick it off.
- 11:41: ... the energy required to power these radio bubbles is several thousand times lower ...
2020-04-07: How We Know The Earth Is Ancient
- 06:47: ... Rutherford, discovered that certain elements released energy from radioactive decay at an ever-decreasing rate. And that some of ...
2020-03-31: What’s On The Other Side Of A Black Hole?
- 13:31: ... But how big is the bomb? Well the limit is as much rotational energy as the black hole contains. for a maximally rotating black hole that's ...
2020-03-24: How Black Holes Spin Space Time
- 07:50: ... is to say it’s impossible. That same switch also allows us to extract energy from the ergosphere, as we’ll ...
- 09:17: ... from the ergosphere and escapes. In fact it escapes with more kinetic energy than it had coming in - up to 20% of the energy than was bound up in the ...
- 09:37: ... energy is extracted from the rotational energy in the ergosphere, slowing the ...
- 10:00: ... hole, blow them apart at the right instant, and then catch the kinetic energy of the pieces that get ...
- 10:11: ... the ergosphere in the direction of rotation will also extract rotational energy and emerge amplified in a process called ...
- 10:27: ... way the rotational energy can be extracted with, in principle, 100% efficiency. Oh, and you can ...
- 10:51: ... those magnetic field and can radiate intense light. Ultimately, the energy of that light is extracted from the rotational energy of the black hole. ...
2020-03-16: How Do Quantum States Manifest In The Classical World?
- 04:28: ... This is the so-called Einstein-Podolsky-Rosen, or EPR paradox. A high energy photon decays into an electron and a positron. These particles both have ...
- 07:15: ... two states doesn’t matter as long as it doesn’t change the spin or sap energy from the electron. One possibility would be that the spin of one of the ...
2020-02-24: How Decoherence Splits The Quantum Multiverse
- 10:20: The electrons in the detector and in the circuits will be at different locations and will have different energies.
2020-02-18: Does Consciousness Influence Quantum Mechanics?
- 14:05: The idea is when that event occurred and axions became massive, they may have experienced a sort of friction that robbed them of their kinetic energy.
- 15:28: ... theta field yields particles because it has a lowest energy state - a value for theta where potential energy is lowest, and on ...
- 15:37: ... it's a dip in energy, the field can oscillate within that dip - and that oscillation is our ...
- 15:46: You wouldn't get the same sort of energy structure by varying all of the other constants.
2020-02-11: Are Axions Dark Matter?
- 03:59: ... isn’t really nothing. “Vacuum” is the word we use to describe the lowest energy state of a field - which is what you’ll find when there are no actual ...
- 04:33: ... can hop between these different states. But because they're all the same energy, quantum weirdness allows the QCD vacuum to sort of simultaneously occupy ...
- 05:16: ... will then naturally fall to zero - because that reduces the overall energy of the vacuum, and the universe always seeks the lowest energy ...
2020-02-03: Are there Infinite Versions of You?
- 00:26: ... not; it could turn out that the universe contains enough matter and energy to close in on itself and be finite, or perhaps the simplest ...
- 07:19: The constants of nature or the energy of the vacuum may well be different between regions.
- 08:10: It IS technically possible for the energy of the vacuum itself to have any value, even enormously large.
- 08:17: But universes with large vacuum energies will exponentially expand, until that vacuum energy decays to lower values in smaller regions within.
2020-01-27: Hacking the Nature of Reality
- 07:12: ... conditions include things like conservation of energy and momentum, the behavior of quantum properties like spin, and the ...
- 14:29: ... some places it gives up angular momentum - it's orbital energy - to the gas, causing it to migrate inwards, while in other places it ...
2020-01-20: Solving the Three Body Problem
- 10:30: ... possible configurations consistent with some basic properties like the energy and angular momentum of the system. The system explores what we call a ...
2020-01-13: How To Capture Black Holes
- 00:59: ... space into expanding ripples - gravitational waves - which saps orbital energy from the system. The black holes spiral closer and closer together. In ...
- 05:58: ... pair gets captured by the disk, the surrounding gas saps their orbital energy much more quickly than by gravitational radiation alone. This means they ...
2020-01-06: How To Detect a Neutrino
- 04:24: ... 𝘦𝘭𝘦𝘤𝘵𝘳𝘪𝘤 𝘱𝘪𝘢𝘯𝘰 𝘴𝘰𝘧𝘵𝘭𝘺 𝘢𝘳𝘱𝘦𝘨𝘨𝘪𝘢𝘵𝘦𝘴) ♪ just long enough to exchange energy between the neutrino and, say the nucleus of an ...
- 04:37: ♪ ♪ just long enough to exchange energy between the neutrino and, say the nucleus of an atom.
- 04:41: ♪ ♪ It borrows the energy it needs to exist from, well, nowhere, really.
- 04:46: ... ♪ It's sort of cheats energy conservation by taking advantage of the Heisenberg uncertainty ...
- 04:59: ♪ ♪ ♪ ♪ So: the briefer the lifetime of this virtual boson, the more energy it's allowed to borrow.
- 05:15: ♪ ♪ In order to exist, they need to borrow a lot of energy to cover their rest mass.
2019-12-17: Do Black Holes Create New Universes?
- 04:14: ... constants can change at all then surely it’s in the highest possible energy environments, which is exactly the end of a black hole ...
- 07:47: That favours lots of dark energy generating rapid expansion.
2019-12-09: The Doomsday Argument
- 01:48: ... a quick refresher: the cosmological constant defines the amount of dark energy, which is the stuff causing the expansion of the universe to ...
- 03:03: He got a value that was a factor of 10 higher than what would be observed 10 years later when dark energy was discovered.
- 03:48: Weinberg calculated that the density of dark energy should most typically be observed to be around 5-10 times the density of matter.
- 03:57: That was in the early to mid 90s, right before dark energy was actually discovered and found to be around three times that of matter.
- 04:05: ... by a factor of 2 - which considering the method, and the fact that dark energy could potentially have spanned many, many orders of magnitude, is pretty ...
- 14:29: ... a universe like ours where matter and energy is evenly distributed on the largest scales the curvature does changes ...
2019-12-02: Is The Universe Finite?
- 01:38: ... by the influences of dark matter and a constant density of dark energy. ...
- 02:19: And that's even accounting for accelerating effect of a constant dark energy.
- 04:04: The geometry of the universe is determined by two things: 1) the mass and energy it contains.
- 04:10: ... stuff in the universe - a higher energy density - means more gravity, which tends to pull a universe in on ...
- 06:45: More lensing suggests the universe has a higher energy density than previously thought.
- 06:51: Remember that more energy density tends to introduce positive curvature.
- 07:14: ... of inflation, the amount and behavior of all different types of mass and energy, ...
- 08:50: The four-point correlation function found an amount of lensing consistent with the old result of less energy density and a flat universe.
- 10:59: ... of the universe really has evolved it may mean that the behavior of dark energy is changing - and that could reveal the true nature of dark ...
- 12:01: ... identifying any errors, perhaps discovering the nature of dark energy, and perhaps verifying the positively curved, finite geometry of space ...
- 13:58: ... Weinberg's prediction of the cosmological constant years before dark energy was ever ...
2019-11-18: Can You Observe a Typical Universe?
- 14:56: ... needs to last a reasonable amount of time, have stable regions and energy sources for those structures to form, and have some building blocks - ...
2019-11-11: Does Life Need a Multiverse to Exist?
- 05:10: ... the carbon-12 nucleus formed in this process has a natural internal energy state that allows it to quickly radiate away the excess energy it had on ...
- 05:23: Without that convenient way to shed energy it would quickly tear itself apart again.
- 08:43: It represents the action of dark energy.
- 08:45: ... existence of dark energy was discovered in the 90s as astronomers tried to measure the expansion ...
- 08:59: Physicists knew that empty space itself could have its own energy.
- 09:04: ... of matter or radiation, were expected to have a so-called zero-point energy. ...
- 09:16: ... even when there are no particles around, resulting in a quantum buzz of energy everywhere in the universe that would accelerate its ...
- 09:29: ... problem is, when we try to calculate the strength of this vacuum energy from our theory we get an enormous number - 10^60 to 10^120 larger than ...
- 09:49: If fact, that’s true if the strength of vacuum energy were only a little larger than is observed.
- 10:02: One possibility is that the zero-point energies of unknown quantum fields cancel out the known contributions.
- 10:25: ... there are other theoretical ways to get the vacuum energy to take on different values in different regions of the universe - or in ...
- 11:24: ... that the values of the fundamental constants, including the vacuum energy, are set by the particular configuration of the extra coiled dimensions ...
- 12:04: ... and in each bubble the constants of nature - and especially the vacuum energy - taking on different ...
2019-11-04: Why We Might Be Alone in the Universe
- 10:55: ... absorbed cell became mitochondria, an energy power house that allowed the new chimerical cell to massively increase ...
- 12:39: The strings of string theory have a somewhat physical interpretation - the fact that they can hold energy and vibrate and exist in space.
2019-10-21: Is Time Travel Impossible?
- 02:15: In order for any object with regular mass to even reach light speed it would need infinite energy – which can never be obtained.
- 03:16: ... of curvature in the fabric of spacetime due to the presence of mass and energy. ...
- 05:37: Really what we need to open the wormhole is a negative energy density.
- 05:42: ... argued that we already produce this in the Casimir effect, in which the energy of the vacuum is lowered between two nearby conducting ...
- 05:51: However there’s no clear path to translating this to a large-scale negative energy distribution that could keep a wormhole open.
- 05:59: And in fact we'd need entire planets – perhaps entire stars converted to negative energy to do this.
- 06:05: Some other time travel options also involve using negative energy densities - for example the Alcubierre warp drive, which we already covered.
- 06:33: These are the so-called energy conditions.
- 06:36: They’re a set of requirements that do things like prevent negative energies and enforce energy conservation.
- 06:42: But the energy conditions don’t have a really fundamental basis, and they're seen to be violated in some cases – like with the Casimir effect.
- 06:51: We can’t completely rule out wormhole or warp drive time machines based just on the energy conditions.
- 07:55: Stephen Hawking showed that unless the cylinder is infinitely long this doesn’t work – unless you also modify the spacetime with negative energy.
- 08:20: His involved an entire universe, rotating about a central axis and with matter and dark energy perfectly balancing it against collapse or expansion.
2019-10-15: Loop Quantum Gravity Explained
- 02:31: They describe how the presence of mass and energy warp the fabric of spacetime.
- 03:33: ... classical physics, we have variables like position, time, momentum, energy - mathematical expressions that represent the observable properties of ...
- 12:41: ... to predict that the speed of light should depend very slightly on the energy of the photon, with, for example, high-energy gamma rays travelling a ...
- 16:29: ... the amount stretching of spacetime is proportional to the mass and and energy contained by that ...
- 16:47: The smaller the number, the more energy is needed to stretch spacetime.
2019-10-07: Black Hole Harmonics
- 02:48: As those vibrations give up their energy – in this case to sound waves – the vibrations fade. The bell rings down.
2019-09-30: How Many Universes Are There?
- 01:14: ... due to the vacuum of space itself having a large and constant energy ...
- 01:27: Energy locked into something called the inflaton field.
- 01:31: ... tiny patches stop inflating – the inflaton field in that patch loses its energy and so accelerating expansion stops ...
- 05:53: For example the cosmological constant – the strength of dark energy – could be different.
- 05:59: Remember that it was the high energy density of the inflaton field that drove inflation, and the loss of that energy density that ended it.
- 06:09: But what if the inflaton field retained just a tiny bit of energy after its decay?
- 06:15: That residual field might be what we observe as dark energy.
- 06:19: ... an open and contentious question why the current energy density of the vacuum should be so low without being exactly zero given ...
- 06:31: ... awfully lucky – if dark energy were much stronger then our universe would have restarted its ...
- 06:43: Here’s a possible explanation: what different bubble universes can end up with different vacuum energies?
- 06:51: ... low vacuum energies like ours might be extremely rare, but there are so many bubble ...
2019-09-16: Could We Terraform Mars?
- 08:24: The energy cost in both cases is similar, though – several septillion joules.
- 08:31: Several thousand times the total annual energy consumption of the entire Earth.
- 09:04: There’s really no other viable energy source.
- 09:06: ... need to channel this energy deep into the crust to power vast hoards of robotic ...
- 13:27: The resources and energy needed to build this is insane – but hey, we just built an atmosphere, so why not?
- 16:37: Give such a field a constant energy density and you get exponential expansion.
- 16:59: Joshua Kahky asks whether the Inflaton Field could also explain Dark Energy.
- 17:08: Inflation supposedly happened because the inflaton field had a very high energy density, and it stopped when that energy dropped to a very low value.
- 17:20: ... the inflaton field was left with a very tiny but positive energy density, then it's possible that it could now be powering the current ...
- 17:32: ... two stable or semi-stable states that are a factor of 10^27 different in energy. ...
2019-09-03: Is Earth's Magnetic Field Reversing?
- 11:54: ... may be higher incidents of cancer and other mutation from more high energy particles reaching the ground, and probably we’ll have to get much ...
2019-08-19: What Happened Before the Big Bang?
- 00:50: The idea is that the energy trapped in the so-called "Inflaton field" caused exponential expansion of space.
- 01:36: ... inflaton field, which had the bizarre property of containing a ton of energy even in the absence of ...
- 01:47: It had a nonzero vacuum energy.
- 02:50: I mentioned last time that quantum fields can hold energy without actually having particles.
- 03:11: This self interaction gives the field some potential energy.
- 03:15: ... potential energy because the field would much rather reconfigure itself into a lower ...
- 03:27: Although scalar fields are the simplest, they can exhibit complicated relationships between this potential energy and the field strength.
- 03:43: Guth's idea is that there's a local minimum in potential energy that allows the inflaton field to get stuck in a false vacuum state.
- 03:54: When that state decays, potential energy is released as real particles, ending inflation, and re-heating the universe in an expanding bubble.
- 04:52: As it did, the energy would drop very very slowly.
- 04:57: ... would still give us our near constant energy density needed to power inflation and then, as the roll sped up towards ...
- 05:41: Before we get to that, I want a quick word on why the Inflaton field should have one potential energy curve over any other.
- 06:23: Very flat potential energy slopes are also possible in these theories, enabling slow roll inflation or a combination of both.
- 06:54: As the inflaton field rolls down the potential energy hill, the field strength should fluctuate slightly.
- 08:06: ... strong fluctuation would force the inflaton field back up the potential energy slope, causing inflation to last a lot longer in that ...
- 09:23: A fraction of the Planck energy within a Planck volume.
- 12:02: That energy would then end up in the cosmic background radiation photons, but not for a while.
- 12:39: ... inflation doesn't explain where the very first speck of space-time and energy came from but it does give a potential explanation for the 'bang' part ...
2019-08-06: What Caused the Big Bang?
- 00:43: ... of the biggest questions in cosmology, those being: why is matter and energy so smoothly spread out across the entire observable ...
- 02:37: They describe how its expansion or contraction depend on the matter and energy it contains.
- 02:50: But there's one type of energy that can have an anti gravitational effect.
- 02:54: Anything that causes the fabric of space itself to have energy - anything that has a constant energy density pushes rather than pulls.
- 03:04: Now, we know that something like this exists because we've observed it in the accelerating expansion produced by dark energy.
- 03:13: We've covered how this works for dark energy in a lot of detail. Check out the playlist if you want to get an insight into the actual math.
- 03:23: ... the upshot is that if the vacuum of space has a constant energy density, then Einstein's equations end up having a term that we call the ...
- 03:42: The speed of that exponential expansion depends on the strength of the vacuum energy density.
- 03:48: ... dark energy, that number is incredibly small and so dark energy only works because it ...
- 04:13: ... do this, the energy density of the vacuum during inflation would need to be vastly stronger ...
- 04:32: So, the vacuum energy would need to drop from a very high value to basically zero.
- 04:48: QFT can explain how a vacuum can have energy, which - surprise surprise - we also covered in a playlist.
- 05:22: ... is just an oscillation in this field strength - a little packet of energy held by the field. If a quantum field has energy in the form of ...
- 05:41: Particles get dispersed and so the energy density goes down.
- 05:45: ... quantum field can contain an intrinsic energy even without particles. In that case, it will always try to drop to the ...
- 06:05: Now, a field doesn't just jump to the lowest energy state, it makes its way there by changing the field strength one step at a time.
- 06:14: ... we graph a quantum field potential energy versus field strength, it might look something like this: If the field ...
- 06:29: And by the way, the lowest energy state of a field is called its vacuum state.
- 06:35: But sometimes, the energy contained by a field has a more complex relationship with the field strength.
- 06:42: I'm gonna have to save the how and why of these potential energy curves for another video.
- 06:47: For now, let's just go with it. One possibility is that the field could have what we call a local energy minimum.
- 07:02: It would have a lot of energy but no particles.
- 07:06: We would call this a false vacuum and it gives us exactly the constant vacuum energy density needed for inflation.
- 07:13: There are other ways for a field to end up with a positive vacuum energy density and I'll come back to these.
- 07:26: ... of that time. As the universe cools the field loses strength and energy. ...
- 07:46: But then, it gets stuck in this local energy minima.
- 07:54: It would have to get over this potential energy barrier to do that.
- 07:59: ... at a constant very high energy density, inflation takes hold; the exponential nature of inflation ...
- 08:51: ... minimum - perhaps the true vacuum state - and suddenly starts to lose energy again racing towards that ...
- 09:07: ... the true vacuum and so the entire inflaton field would cascade down in energy. ...
- 10:04: The energy that existed in the inflaton field doesn't just go away, it remains in that field very briefly, but now in the form of inflaton particles.
- 10:26: ... particles are unstable and they very quickly disperse their energy into the other quantum fields. The inflatons decay into the familiar ...
- 10:50: In fact, this process would reheat the universe to the extreme energies that we expect existed right after the Big Bang.
- 11:26: ... when these non inflating bubbles form, all of the energy gets released at their boundaries; their expanding spherical fire walls ...
2019-07-18: Did Time Start at the Big Bang?
- 00:25: ... to Einstein's equations, it seems inevitable that all space and mass and energy should once have been compacted into an infinitesimally small point - a ...
2019-07-15: The Quantum Internet
- 11:32: In a recent episode we talked about Thorium and the future of Nuclear Energy!
- 12:15: ... it decays to protactinium isotope that itself decays to emit a very high energy gamma ray, and that gamma radiation can fry bomb electronics and is ...
- 14:55: Funnies aside, you can't run an energy-hungry compact vehicle on solar or batteries for very long.
2019-07-01: Thorium and the Future of Nuclear Energy
- 00:00: ... Energy too cheap to meter That was the promise of nuclear power in the 1950s at ...
- 00:17: The question is "should it?" Energy isn't scarce. It's everywhere. Seriously, literally all mass is energy The trick is getting at it.
- 00:33: ... coal and you liberate a tiny bit of the energy locked in its chemical bonds That's easy and cheap to do but the energy ...
- 02:49: ... when hit by a single neutron When these nuclei split, they release energy and fast-moving neutrons Those new neutrons can smash into nearby nuclei ...
- 16:59: ... when such a jet is first launched It tends to balloon out and spread its energy through a good fraction of the galaxy So orientation isn't so important. ...
2019-06-20: The Quasar from The Beginning of Time
- 04:53: ... its component wavelengths, similar to a prism, and it records how much energy is received at each wavelength. We called that a ...
- 05:12: ... traveling through the expanding universe sapped energy and stretched the wavelength of that light so that it was infrared by ...
2019-06-17: How Black Holes Kill Galaxies
- 02:54: ... of Physics of the Universe especially the nature of Dark Matter and Dark Energy we expect 'Bottom up Galaxy formation' this is what we see in our ...
- 06:33: ... Black Hole the gas forms a whirlpool-like accretion disk heated by the energy that's long formed it gets so hot that around 10% the mass of the ...
- 07:21: ... and its powerful winds and jets can dump an enormous amount of energy into the gas through the surrounding galaxy that can do two things It ...
2019-06-06: The Alchemy of Neutron Star Collisions
- 02:47: ... towards each other as a gravitational radiation saps their orbital energy in the last minute before merger that radiation is so strong that it'll ...
2019-05-16: The Cosmic Dark Ages
- 05:13: ... but it did block some very particular types of light. Any photon whose energy happened to exactly match an electron energy transition in the hydrogen ...
2019-05-01: The Real Science of the EHT Black Hole
- 05:21: In this case it’s the energy released by matter falling into the black hole.
2019-04-10: The Holographic Universe Explained
- 08:05: A nice feature is that the changing the length of the strand – which defines the energy in the bond – doesn’t change the basic physics.
- 08:36: Which is ridiculous given the puny energy scale of a meson - gravitons shouldn’t exist there.
- 09:27: These arose from the way string size and energy scales could be rescaled.
- 10:15: The strings connected to these branes are scale invariant, so their length and energy can vary without changing the physics.
- 10:57: This quality fcame from the energy-scale-invariance of the strings embedded in the construction of this space.
2019-04-03: The Edge of an Infinite Universe
- 15:16: ... itself to shreds on subatomic scales due to runaway increase in dark energy. ...
- 16:18: Chris Hanline wisely notes that dark energy appears to break the conservation of energy.
- 16:25: ... sort of true - except that the law of conservation of energy has a very clear range of validity - it's valid in systems that are time ...
- 16:39: In fact conservation of energy comes from this symmetry, as revealed by Noether's theorem.
- 16:53: In its most familiar form, conservation of energy doesn't apply and so dark energy CAN be created from nothing.
- 17:01: ... have argued that energy is conserved and that dark energy is created from the increasing ...
2019-03-28: Could the Universe End by Tearing Apart Every Atom?
- 00:25: ... stopped us from giving it a name we call this unknown influence dark energy. the observed acceleration is for the most part nicely described with a ...
- 01:55: ... see each other let alone fill each other's gravity but as long as dark energy doesn't increase there'll be no expansion inside those lonely galaxies ...
- 03:05: ... is Einstein's gravity not Newton's, gravity is influenced by mass and energy density but also by pressure. Both mass energy density and any positive ...
- 04:25: ... let's add dark energy in the form of a cosmological constant it usually hangs out outside the ...
- 04:32: ... and get rid of regular massive pressure, after all, in the future dark energy will completely dominate the expansion so we have the energy density of ...
- 05:32: ... acceleration is therefore positive which means dark energy is pushing outwards to increase the expansion rate. In fact, any ...
- 05:51: ... than -1, that's still accelerating expansion but in that case the dark energy is decreasing over ...
- 06:20: ... time offhand, that doesn't sound so much crazier than regular old dark energy except that it is much crazier. As the rate of expansion increases and ...
- 07:47: ... not the case if dark energy increases. After our galaxy is disrupted by the increasing dark energy ...
- 08:25: ... doesn't stop us from giving it a name, we call any dark energy that increases in strength - so with an equation of state less than -1, ...
- 09:26: ... is quite inside the Milky Way just yet, just that the effect of phantom energy is stronger than the gravity binding the stars ...
- 10:03: ... the last 30 minutes phantom energy is strong enough to overcome Earth's own gravitational binding energy ...
- 10:45: Our efforts to understand the nature of dark energy are focused on measuring the value of this 'equation of state parameter thing'.
- 10:53: We can do that by combining all of the clues to dark energy's behavior.
- 11:08: Combined with a few other measures these tell us that the equation of state of dark energy is very very close to -1.
- 11:16: ... plunk science team calculate -1.028, plus or minus, 0.032 - Phantom energy is still a faint possibility but even at its most extreme from the ...
- 11:35: ... affairs in order. But more likely is that W is exactly -1, meaning dark energy is constant for three reasons: first, it seems too much of a coincidence ...
- 11:54: ... there's a plausible physical explanation for a constant dark energy that the vacuum has a set amount of energy per volume. There are at ...
- 12:06: As far as I know, there aren't serious ideas for an increasing dark energy.
- 12:11: ... the final reason to hate on phantom energy: it violates energy conservation in a way far worse than regular dark ...
- 12:27: ... hate let's finally get to the one significant result that suggests dark energy may be increasing after all. In fact, we've already covered it in our ...
- 13:18: ... journal Club on that paper that actually presented evidence that dark energy may be increasing in strength based on measurements of distant ...
- 13:28: ... when you try to separate composite quark particles - hadrons, the energy put into breaking the bond just generates new quarks - so you just get ...
- 14:00: Depends on whether the splitting hadrons can keep up with the exponentially increasing dark energy.
- 14:05: ... that Dot found is the most fun - that the exponentially increasing dark energy leads to exponential particle production, which ends up looking like a ...
- 14:34: ... Stark asks, "if dark energy changed in the past, can it also change in the future?" In fact, if it ...
- 15:06: The amount of mass and energy it contains just doesn't provide enough gravity.
- 15:10: On the other hand, if dark energy evolved into an attractive rather than repulsive force, who knows!
- 15:16: There's no good reason to believe that it will but we also don't know what dark energy even is - so, live in hope.
- 15:23: ... Pick notes that dark energy backs up their hypothesis that massive dinosaur fossils were actually ...
2019-03-20: Is Dark Energy Getting Stronger?
- 00:04: ... the Lambda CDM Model and is built on the idea about the behavior of Dark Energy and Dark ...
- 00:29: Subtle clues are emerging that the accepted model for the nature of dark energy and dark matter may not be all that.
- 01:34: Back in the late 90s two teams of astronomers accidentally discovered dark energy.
- 01:51: It was revolutionary and radical at the time, but a few Nobel prizes later and dark energy is now textbook cosmology.
- 01:59: ... accelerating expansion is what you expect if empty space has a constant energy density – so that more space means more dark ...
- 02:13: Mathematically we represent a constant vacuum energy with Einstein’s cosmological constant – or Lambda.
- 03:02: Constant dark energy, cold dark matter – or the Lambda-CDM model.
- 03:19: ... reveal the starting conditions of the universe – the balance of dark energy, dark matter, and everything else at the earliest of times when the CMB ...
- 03:54: The expansion history of the universe is typically measured using the same type of supernova observations that first discovered dark energy.
- 04:09: These explode in very predictable ways, releasing a predictable amount of energy.
- 04:14: ... comparing that expected energy output with the amount that actually reaches our telescope, we can ...
- 06:09: That early period is extremely important for understanding the true behavior of dark energy.
- 07:07: They can have a huge range of energy output, depending on the mass of the black hole and how much fuel it’s getting.
- 07:25: It’s not just the accretion disk – the energy produced in that disk powers all sorts of crazy energetic activity.
- 07:51: The new study uses the brightness X-ray corona to figure out the true energy output of quasars.
- 08:09: In that encounter they can get boosted to even higher energies – right up to X-rays – in a process called Compton up-scattering.
- 08:32: If UV and X-ray light track each other perfectly, there would be no way to differentiate the effects of distance and intrinsic energy output.
- 09:12: See, the ratio between the amounts of X-ray versus ultraviolet light depends on true ultraviolet energy output of the quasar.
- 10:52: And that dashed line – that reflects the expansion history expected in a universe with constant dark energy – a Lambda-CDM, concordance universe.
- 11:22: ... line is a model of the expansion history of the universe in which dark energy is NOT constant, but instead is getting stronger as the universe ...
- 11:51: Is dark energy getting stronger?
- 12:00: At the moment, dark energy is only strong enough to accelerate the expansion of space on the largest scales.
- 12:15: ... if dark energy is getting stronger, then eventually it could cause the universe to ...
- 12:34: It’s a potential end of the universe in which space-time rips itself to shreds at subatomic scales due to the increasing strength of dark energy.
- 12:53: 2) if dark energy has changed in the past that doesn’t mean that it’s steadily increasing.
- 13:07: ... example, there’s the idea that dark energy that started out much stronger dropped off rapidly, or even that it ...
- 14:06: Perhaps this is the clue we need to finally better understand this stuff we call dark energy.
- 14:13: ... even if the Concordance model ends up reigning supreme– even if dark energy proves to be constant after all – which I suspect it will – we’ll have a ...
- 14:27: One way or another I guess it’d be nice to know whether dark energy will one day rip to shreds the subatomic fabric of space time.
2019-03-13: Will You Travel to Space?
- 07:28: ... than rockets at low altitude. As well as a combustible fuel as an energy source, rockets need to carry an oxidant to burn that fuel and a ...
- 07:51: ... only need to carry the energy supply which is usually a combustible fuel, but could also eventually be ...
- 13:44: The type that can keep on ticking without energy input or output.
- 15:44: So you can't get energy from nothing.
- 15:47: You'll always lose energy as entropy increases. And you can never not have some entropy.
- 16:00: ... then at the expense of other players. Like by stealing their aces aka energy, and giving them your 2's aka entropy, and Yeah, this is where we leave ...
2019-03-06: The Impossibility of Perpetual Motion Machines
- 00:30: We have perpetual motion machines of the first kind - they violate energy conservation - they pump more energy out than they need to keep running.
- 00:43: ... wrongness because break the second law of thermodynamics - extracting energy by reversing ...
- 02:29: Losses due to friction mean that water or wind driving a mill could never produce enough energy to fully complete the cycle.
- 02:41: Now to be fair to the people working during the middle ages and Renaissance, the law of conservation of energy hadn’t been discovered yet.
- 02:48: Thus the proliferation of first-type machines that could generate more energy than they used.
- 03:07: ... law states that entropy can never decrease over time – in other words, energy will tend to spread itself out as evenly as possible – to a state of ...
- 03:20: All machines work by riding this flow of energy as it redistributes itself.
- 03:26: Machines of the second kind claim to be able to tap reservoirs of energy that are already evenly spread – effectively reversing the growth of entropy.
- 04:39: With no energy or temperature gradient, no energy can be extracted.
- 04:43: In fact there’s an absolute limit to the amount of energy that can be extracted based on a difference in temperature.
- 05:01: ... of gas in a piston chamber that will provide the maximum possible energy as heat flows between reservoirs of different ...
- 05:23: Drive the piston in reverse with exactly the same amount of energy, and it’ll transfer energy from cold to hot.
- 05:30: ... principle a Carnot engine could extract energy from a temperature gradient and then pump it back in again, making it a ...
- 05:40: But even in this most ideal case the ratio of energy in to energy out is exactly unity.
- 05:49: No extra energy is extracted.
- 06:06: These are perpetual motion machines that do not attempt to generate energy – they just keep themselves running forever.
- 06:21: So remove all outside forces – remove all friction, all energy losses of any kind, and surely any machine can tick on forever.
- 06:44: Just eliminate ANY leakage of energy.
- 07:08: Even if that heat is recaptured, the outer walls of even the most carefully isolated system must radiate, slowly leaking energy.
- 07:42: ... lots of magnets, somehow powering their own motion and producing extra energy ...
- 07:52: These are often referred to as over-unity devices – the ratio of energy out to energy in is greater than one.
- 08:00: ... Academy of Science refuses to even review devices claiming over-unity energy ...
- 08:23: They have various explanations for how they don’t violate conservation of energy.
- 08:29: ... motion: they violate the 2nd law of thermodynamics by extracting energy where there is no energy ...
- 08:41: One popular source of free energy is the zero-point energy of the quantum vacuum, and it’s the most fun to debunk.
- 08:48: ... the quantum vacuum for the physics, but the important point is that any energy of the vacuum is exactly the same ...
- 09:00: It has no energy gradient, so isn’t accessible as an energy source.
- 09:05: ... it may be possible to create an energy gradient, for example with the Casimir effect in which plates are pulled ...
- 09:15: But doing so repeatedly in an engine cycle takes at least as much energy as it produces.
- 09:37: ... vibrations sound fancy, but are typically less good at generating free energy than they are at directing you to their donate button or selling you a ...
- 10:15: The result is that a positive and negative mass should accelerate indefinitely, potentially powering an infinite energy device.
- 11:06: This post-it will be framed in the Smithsonian after the Romeo-engine solves humanity’s energy crisis.
2019-02-20: Secrets of the Cosmic Microwave Background
- 07:42: ... of a triangle add up to 180 degrees However the presence of matter and energy as well as cosmic expansion cause geometry to be curved which would mess ...
- 11:14: ... tell use that that baryons constitute only about 5% of the total energy of the Universe And finally we get to the other peaks which represent ...
- 12:34: ... size of the spots in the first peak tells you the total amount of dark energy dark energy, and baryons The second peak gives you just the amount of ...
2019-02-07: Sound Waves from the Beginning of Time
- 00:22: These are the Baryon Acoustic Oscillations (BAO), and they may hold the key to understanding the nature of dark energy.
- 04:52: ... diffused, and the photons themselves were stretched, redshifted to ower energies, themselves were stretched, redshifted to ower energies, the universe ...
- 05:26: ... are restricted to only those specific frequencies corresponding to the energy level transitions of that ...
- 10:57: It was to confirm dark energy.
- 11:00: Dark energy was first discovered by using distant supernovae as distance measurements- to track the rate of expansion of the universe.
- 11:08: Those observations revealed that the expansion rate is accelerating due to an unknown influence what we call dark energy.
- 12:17: They confirm the existence of dark energy.
- 12:20: They also confirm the dark energy behaves just as is predicted by Einsteins cosmological constant.
- 12:26: It appears unchanging over time, just as we'd expect if dark energy is the energy of the vacuum itself.
- 12:34: Frankly, dark energy aside, just being able to see these patterns is cool enough for me.
- 16:40: It can also be used to explain dark energy and dark matter.
2019-01-30: Perpetual Motion From Negative Mass?
- 00:59: And we also recently covered a very new use for negative mass: as “dark fluid”, a proposed explanation for both dark matter and dark energy.
- 06:36: ... presence of active gravitational mass, and of energy, momentum, pressure, and more, change the geometry of spacetime and that ...
- 09:00: At first glance that sounds like it breaks conservation of momentum and energy.
- 09:06: ... positive mass apple gains positive momentum and energy as it speeds up, while the negative mass apple balances that with ...
- 09:16: In fact the energies are completely unbounded – they can go to plus and minus infinity.
- 09:32: It also violates the energy conditions of general relativity.
- 09:37: They are a set of conditions against negative energies that seem necessary in order for general relativity to describe a sensible universe.
- 09:46: ... fact the mere existence of negative mass breaks certain energy conditions, but the prospect of a bottomless well of infinite negative ...
- 10:03: In particular, with the idea of negative and positive masses accelerating each other to infinite energies?
- 11:52: ... matter, and it also means flipping the sign of its kinetic and potential energy. ...
- 12:04: Push exotic matter and it simultaneously accelerates towards you and loses kinetic energy.
- 13:32: I want a device that provides a continuous energy source.
2019-01-24: The Crisis in Cosmology
- 01:45: ...of the matter and energy it contains,...
- 05:08: ...revealing the existence of dark energy.
- 11:38: Insufficient numbers could skew the energy balance of the early universe, and mess up the calculation.
- 12:05: Three: Dark energy isn't constant.
- 12:08: The current calculations assume that dark energy is described by the cosmological constant,...
- 12:16: But if dark energy increases,...
- 13:02: ...to investigate the mysterious physics of dark energy, dark matter,...
- 13:29: ...as a unifying explanation of both dark matter and dark energy.
- 16:14: And I guess you're referring to the idea that time-reversed energy has its sign flipped.
- 17:46: He reveals to us that dark energy equals dark matter,...
2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe
- 13:52: ... be right and that supersymmetry hasn't yet been detected at the expected energy scale that's the energy scale expected if supersymmetry is to also ...
- 15:29: ... to help with the hierarchy problem because it was at far too high an energy scale. But then as I did mention in the video the current Large Hadron ...
- 16:49: ... is that the untestability of string theory is connected to the extreme energy scale of quantum gravity and that problem is not unique to string ...
- 17:15: ... is not science. String theory may be currently untestable due to the energy scales involved but the universe has no obligation to make itself ...
2019-01-09: Are Dark Matter And Dark Energy The Same?
- 00:07: Dark energy AND dark matter?
- 00:22: ... at Oxford just published a paper suggesting that both dark energy and dark matter may result from the same ...
- 00:58: Farnes 2018, “A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified Lambda-CDM framework”.
- 01:08: As with any new theory combining dark matter and dark energy, probably it helps to know what they are first.
- 01:47: Dark energy is completely different – or so the standard story goes.
- 01:57: That acceleration matches the effect you would get if empty space itself had a tiny bit of energy.
- 02:03: As more space comes into existence because of that expansion thing the more“dark energy” you get, which causes more acceleration.
- 02:11: Actually, we gotta think a bit harder about why dark energy causes accelerated expansion, it’s important for the new paper.
- 02:18: The standard picture of dark energy is that it’s an actual greater-than-zero energy of the vacuum of space.
- 02:25: According to Einstein’s general theory of relativity, any such positive energy produces an inward-pulling gravity.
- 02:31: That’s true of dark energy.
- 02:53: But here’s the punchline: if empty space has a constant, positive energy density then it also has a negative pressure.
- 03:10: ... dark energy has competing effects – its positive energy density gives it a positive ...
- 03:20: In the case of dark energy the latter wins, and so the expansion of the universe accelerates.
- 03:27: An important part of this is that the energy density of dark energy is constant, so it doesn’t dilute as the universe expands.
- 03:34: In Einstein’s equations and the Friedmann equations, that constant energy density is represented by the cosmological constant, or Lambda.
- 03:50: Jamie Farnes was looking for a way to get an anti-gravitational effect that explained both dark energy AND dark matter.
- 04:06: Forgetting that pressure stuff for a moment, positive masses and energies always have a positive gravitational effect.
- 05:53: This is supposed to give the outward push to replace dark energy.
- 06:59: To make the same negative mass stuff also emulate dark energy requires an extra gigantic assumption.
- 07:43: But that’s cool – the physical justification behind dark energy is pretty tenuous too.
- 07:49: So, you remember I said that a constant POSITIVE energy density can be expressed as a cosmological constant?
- 08:02: Well a constant NEGATIVE energy density – like the one proposed by Farnes, gives a negative cosmological constant.
- 08:18: ... cosmological constant – has the same competing effects as regular dark energy, but in the opposite ...
- 08:50: ... some contradiction because he also suggests that it’s a good dark energy replacement because it acts like a cosmological ...
- 10:16: Does a universe with a constant negative energy density fit the observations?
- 10:23: First, does it predict an expansion history that fits the supernova observations that originally discovered dark energy?
- 10:40: But then that deceleration turned around as dark energy kicked in, resulting in the current accelerating expansion.
- 11:00: ... age for his universe of 13.8 billion years assuming a very low negative energy density, but that really just corresponds to the very first straight ...
- 11:19: We already know that a constant expansion rate happens to give a similar age to the standard dark energy age.
- 11:47: ... energy, with its positive energy density, when added to the energy of both ...
- 11:57: If you replace both dark energy and dark matter with negative-energy stuff, then the universe becomes negatively curved.
2018-12-20: Why String Theory is Wrong
- 08:01: ... around this compactified dimension is called its winding number. The energy of such a string depends on the winding number times the radius of the ...
- 08:17: These strings are vibrating with standing waves like guitar strings, and their energy also depends on the frequency of that vibration.
- 11:49: ... number for super gravity dimensions. Super gravity should be the low energy, large-scale limit to super string theory. So it was incredibly exciting ...
2018-12-12: Quantum Physics in a Mirror Universe
- 00:02: ... that don't change under reflections are called even things like the energy of the ball its mass the time on its clock and as we'll see angular ...
2018-11-21: 'Oumuamua Is Not Aliens
- 14:00: ... said that extremely high energy neutrinos aren't expected to make it all the way through the planet, ...
- 14:15: Neutrinos have no trouble passing through the planet whatever their energy.
2018-11-14: Supersymmetric Particle Found?
- 02:41: To solve the hierarchy problem perfectly, those particles would need to have masses at around what we call the electroweak energy.
- 02:49: That's the energy at which the electromagnetic and weak nuclear forces merge into the same force.
- 02:54: ... together hard enough in the Large Hadron Collider, there'd be enough energy in those collisions to produce a supersymmetric ...
- 03:27: To detect more massive supersymmetric particles, you need higher energy particle collisions.
- 03:42: Actually, there is a way to probe energies far higher than is possible with the Large Hadron Collider.
- 03:52: ... ray bursts, black hole magnetic fields are all expected to blast high energy particles like electrons and atomic nuclei into the ...
- 04:05: The highest energy cosmic rays can have energies around a billion times that of the LHC.
- 04:11: Unfortunately, for particle physics experiments cosmic rays at these energies are extremely rare.
- 04:50: When ultra high energy cosmic rays travel through space, they bump into the photons of the cosmic microwave background.
- 05:01: Those cosmic rays lose energy to the CMB, which is partly why the most energetic cosmic rays are so rare here on earth.
- 05:09: But in those interactions, cosmic rays can create extremely high energy neutrinos.
- 05:20: So detecting the highest energy neutrinos allows us to learn about the cosmic rays that produced them.
- 05:32: Lower energy neutrinos can flow right through the Earth as though it isn't there.
- 06:08: ... works in a similar way, but it's focused on catching the very highest energy neutrinos, the ones that are produced by cosmic ray interactions with ...
- 06:37: ... an ultra high energy neutrino decays in the ice anywhere within 700 kilometers of ANITA, the ...
- 07:19: That's because the most energetic neutrinos actually do lose energy passing through the earth.
- 07:29: ... scientists were a little confused when they spotted two extremely high energy radio bursts that could only have been produced by a high energy ...
- 08:13: But seeing these very high energy tau events from directly below doesn't make sense.
- 08:19: ... on our understanding of the normal background rate of high energy neutrinos, it's estimated that there is around a 1 in 3 trillion chance ...
- 09:07: A stau particle was produced on the opposite side of the planet by an incoming ultra high energy neutrino plowing into the earth.
- 09:23: This then causes a high energy radio flash coming from directly below.
- 09:56: ... the Earth with enough high energy neutrinos, for example from a supernova explosion, and at least some of ...
- 10:21: On the other hand, the supernova in question wasn't nearly bright enough to make even one earth penetrating ultra high energy neutrino likely.
- 11:09: ... back into the IceCube archive and actually did find some possible high energy tau lepton events that may have come from directly ...
- 13:47: Eddie Galtech asks why you can't get meaningful energy from the Casimir effect.
- 13:51: Well, it's the same reason you can't get continuous energy for a ball falling off a roof.
- 13:56: You get the kinetic energy once, but then you have to expend at least as much energy raising the ball back to the top of the roof.
- 14:05: The Casimir plates pull together, giving you a very tiny amount of energy.
- 14:09: But to get more energy, you have to pull them apart again, which takes just as much energy as you got when they fell together.
2018-11-07: Why String Theory is Right
- 04:02: The energy density at that point becomes infinite.
- 15:14: ... if the Casimir effect really is due to a change in the zero-point energy-- and there are those who say it isn't-- but if it is, then it's still ...
- 16:03: David Ratliff asks if a quantum tree falls in a vacuum and nobody is around to measure it, does it still have energy?
2018-10-31: Are Virtual Particles A New Layer of Reality?
- 00:14: They borrow the energy for their existence so briefly that they cheat the watch fly of the universe.
- 02:12: In particle interactions, packets of energy are exchanged between these fields.
- 02:18: For example, two electrons-- excitations in the electron field-- will repel each other by exchanging energy through the electromagnetic field.
- 03:25: ... electron interacts once with the EM field, transferring between them energy momentum and one photon worth of quantum properties in a single packet ...
- 05:18: ... and spin, but they don't need to obey Einstein's relationship between energy mass and ...
- 07:09: ... one of these infinite possible virtual particles represents a quantum of energy in a single possible vibrational mode of the underlying quantum ...
- 09:20: ... mode should have 0 energy in a vacuum, but in quantum mechanics, nothing can be so exact-- thanks, ...
- 09:31: In order to remain "uncertain," there has to be a slight chance that when you look at a vacuum, any given mode will have non-zero energy.
- 09:41: This leads to a non-zero average energy called, confusingly, the zero point energy.
- 09:48: So there's a chance that when measured the vacuum will appear to have energy and so have particles.
- 10:19: It has a constant zero point energy.
2018-10-18: What are the Strings in String Theory?
- 06:14: The result is that for a given string, only certain frequencies corresponding to certain energies are possible.
- 06:38: But this sort of behavior, where only specific, discrete energy modes are allowed, sounds very quantum-like.
- 07:14: Tension is, after all, just energy per unit length.
- 08:13: ... answers include pure mass energy, fundamental irreducible existence, topological irregularities in the ...
- 08:45: They can hold energy.
- 09:10: ... try to describe gravitational interactions on the smaller scales, the energies required to interact on that scale produce black ...
2018-10-10: Computing a Universe Simulation
- 06:46: ... states in quantum jargon-- the radius proportional to the average energy of the ...
- 07:04: The more energy in the system, the quicker it's quantum states can evolve.
- 08:04: ... the energy of the system, we use the mass of the observable universe, around 10 to ...
- 08:52: The number is based on its energy content, and it has to spread that computational power over its particles.
2018-10-03: How to Detect Extra Dimensions
- 02:26: ... between gravity and the other forces of nature to the nature of dark energy. ...
- 05:22: That means gravity has to look just like the other forces at very high energies.
- 07:26: It can also be used to explain another mysterious phenomenon, dark energy.
- 07:39: This is usually thought of as coming from the action of the energy of the vacuum.
- 08:32: It would look like dark energy.
- 08:41: ... extra spatial dimension, then gravitational waves should lose energy to that extra dimension as they travel through ...
- 10:49: There was no observable leakage of gravity into extra spatial dimensions, pretty much ruling this out as an explanation for dark energy.
2018-09-20: Quantum Gravity and the Hardest Problem in Physics
- 01:45: In it, the presence of mass and energy warp the fabric of space and time.
- 05:32: The more precisely you want to measure position, the higher the energy of that interaction.
- 05:50: The Heisenberg uncertainty principle tells us the minimum energy of our beam for a given precision.
- 05:57: ... length around 10 to the power of negative 35 of a meter, the amount of energy you would need to put into that region of space would make a tiny black ...
- 06:16: Try to measure more precisely, and you need more energy.
- 06:34: But large momentum also means large energy.
- 06:37: The uncertainty principle also defines the precision trade-off between time and energy.
- 07:30: That means ridiculously high kinetic energies.
- 08:52: In general relativity, the presence of mass or energy warps the gravitational field.
- 08:59: Any energy must cause space-time curvature.
- 09:14: The energy of those excitations should themselves precipitate more space-time curvature, represented as further excitations.
- 13:30: When two black holes merge, a lot of energy is pumped into gravitational waves.
- 13:35: There's only one place for that energy to come from, the mass of the black holes.
- 14:03: It's possible to extract energy from a rotating black hole by throwing in objects on near-miss trajectories.
- 14:12: And the incoming object absorbs some of that rotational energy and get flung out at a higher speed.
- 14:18: The loss of rotational energy by the black hole also means a loss of mass.
- 15:27: No real quantum states means no information except, perhaps, whatever information you need to track the bulk properties, like vacuum energy.
- 16:02: The more fundamental formula is in terms of radius and contained energy.
2018-09-12: How Much Information is in the Universe?
- 00:25: ... not to mention space itself, with its fluctuating quantum fields, dark energy, blah blah, stuff ...
- 13:50: ... useful to be able to ignore insignificant amounts of space, or time, or energy in the presence of much larger ...
2018-09-05: The Black Hole Entropy Enigma
- 03:35: One, it's a measure of how evenly energy is spread out.
- 03:41: So energy is very evenly distributed and can't be extracted in a useful way.
- 04:12: ... that entropy of an isolated system must always increase, which means energy tends to spread out evenly and particles tend to randomize, reducing our ...
- 06:22: If you merge two black holes, some of their mass gets converted to the energy radiated away in gravitational waves.
- 06:29: There's also the Penrose process in which you can extract rotational energy of a spinning black hole.
- 07:21: Just replace change in entropy and internal thermal energy with change in black-hole surface area and black-hole mass, respectively.
- 07:29: ... can also add the work done when you extract energy from the black hole, and it looks the same as the equation for the work ...
- 09:18: Good old-fashioned thermodynamic entropy tells us that change in entropy is change in internal thermal energy divided by temperature.
- 09:26: ... temperature into that equation along with black-hole mass for internal energy and figured out the total entropy contained in a black ...
2018-08-23: How Will the Universe End?
- 01:19: ... or, scientifically, many ways for the universe to cool down, dissipate energy, and gain ...
- 08:07: During the long Black Hole Era, there is still energy to be had for an enterprising, super-advanced civilization.
- 08:25: If life manages to master this energy source, then its future history could be as ridiculously long as the Black Hole Era.
- 09:48: By a process called quantum tunneling, everything eventually reaches the lowest possible energy state.
- 11:49: At this point, there's really no hope for extracting useful energy from the universe.
- 11:54: ... approaches heat death in which all energy is perfectly distributed, entropy has peaked, and there's nothing for ...
- 12:19: Dark energy may tear space to shreds in the Big Rip.
- 12:23: Vacuum decay may drop the universe to an even lower energy state, wiping out the laws of physics as we know them.
2018-08-15: Quantum Theory's Most Incredible Prediction
- 04:33: ... results in a subtle torque on these electrons, changing their energy states, and resulting in the fine structure splitting of electron energy ...
- 14:48: It's pretty firmly established that energy must be pumped into the corona by magnetic fields.
- 15:05: ... break and reconnect into different forms, they can dump huge amounts of energy into the plasma of the ...
2018-08-01: How Close To The Sun Can Humanity Get?
- 01:05: ... energy it pumps out equivalent to a few hundred quadrillion nuclear power ...
- 01:15: But that energy doesn't only come as life-giving light.
- 01:22: Magnetic storms driving a constant stream of energy and potentially, destructive particles.
- 03:31: ... of the Parker Solar Probe-- as stated by NASA-- is to trace the flow of energy and understand the heating of the solar ...
- 04:38: It will follow the flow of energy from the solar corona into the accelerating solar wind and connect the solar wind to its source.
- 04:51: ... particles like electrons, protons, and heavier nuclei, measuring their energies and mapping them back to their origin in the ...
- 07:17: Venus will end up traveling infinitesimally faster as it absorbs Parker's orbital energy.
- 09:51: ... in which the particles in two halves of a box are sorted without using energy. ...
- 11:40: Surely, when you open and close the gate to admit the particle, you use energy.
- 11:45: And if energy is coming in from the outside, then it's OK for entropy to decrease.
- 12:02: It has to be the act of telling the gate to open and close again that expends energy.
- 12:41: That latch can be thought of as a very tiny activation energy that needs to be overcome to set the gate moving.
- 12:48: That energy can come from the incoming particle.
- 12:57: So an incoming particle is detected and the latch releases, the gate opens, closes, and the particle passes through without losing any energy.
- 13:10: That also requires a tiny bit of energy.
2018-07-25: Reversing Entropy with Maxwell's Demon
- 00:38: Ultimately, entropy is a measure of the availability of free energy, of energy that isn't hopelessly mixed into thermal equilibrium.
- 00:46: Pump energy into a small system and complexity can thrive.
- 01:06: Know a system perfectly and you can return it to order, or you can extract its energy.
- 03:06: ... on one side could represent particles that all have high or all have low energies, or particles that are all on one side of a ...
- 03:20: The particles would quickly flow to fill the available space, and you could extract energy from that flow.
- 03:49: How are you going to extract energy?
- 04:06: ... from thermal equilibrium, and it also defines the availability of free energy, energy that can be extracted as the system moves back to ...
- 06:20: But all of this appears to have been done without exchanging energy or entropy with the outside universe.
- 06:26: ... which demands entropy remain constant or increase, unless energy is exchanged with the outside ...
- 07:58: That's a physical process that reduces the demon's internal entropy, and that takes an irreversible transfer of energy.
2018-07-18: The Misunderstood Nature of Entropy
- 01:54: Heat engines, which in Carnot's day, were the new-fangled steam engines, worked by turning the flow of heat energy into mechanical energy.
- 02:06: A perfectly efficient engine, one undergoing the Carnot cycle, converts all transferred heat energy into useful work.
- 02:28: Around a half century after Carnot, Rudolf Clausius was inspired to quantify this tendency of heat energies to decay over time, enter entropy.
- 02:37: Clausius defined entropy as the internal property that changes as heat energy moves around within a system.
- 02:44: Specifically, the change in entropy of each reservoir is the heat energy going into or out of that reservoir divided by its temperature.
- 03:10: Carnot and Clausius' work revealed entropy as a measure of how evenly spread out a system's energy is.
- 03:17: ... more evenly spread, the less useful the energy is, and for an isolated system, the best you can hope for is that the ...
- 03:27: In reality, it will almost always increase unless energy comes in from the outside to reestablish the temperature differential.
- 06:49: And instead of particles being distributed through position space, a microstate is really defined by how energy is distributed through phase space.
- 07:13: So if you leave a system alone long enough, its particles and its energy will find its way into all the different forms that are possible.
- 07:20: ... vast majority of possible distributions of energy leave the system very close to a single macrostate, that's the state of ...
- 09:30: But to do so, you must introduce an external source of energy.
- 09:52: It comes from counting the ways that energy can be distributed.
2018-07-11: Quantum Invariance & The Origin of The Standard Model
- 00:38: Previously, we've talked a bit about the symmetries of these equations and how they lead us to conserved quantities like energy and momentum.
- 09:13: ... quantum principles to our field, like considering its internal or self energy and allowing quantized oscillations in the field ...
2018-07-04: Will A New Neutrino Change The Standard Model?
- 09:21: Forgive the particle-physics energy units for mass.
2018-06-20: The Black Hole Information Paradox
- 00:34: But matter and energy aren't erased from existence.
- 03:06: And the energy to create those particles must come from the mass of the black hole itself.
- 03:13: According to Hawking's calculation, those particles should come out with energies that follow the black-body spectrum.
2018-06-13: What Survives Inside A Black Hole?
- 04:58: ... up over an enclosed surface is proportional to the amount of mass and energy contained by that ...
- 12:47: It's encoded in the energy, phase, polarization, et cetera of the two gamma-ray photons that are created.
2018-05-23: Why Quantum Information is Never Destroyed
- 01:43: For example, if the equations stay the same from one point in time to the next, then energy is conserved.
- 11:11: Merissan has plans to use the loss of energy in cosmological redshift as a refutation of conservation of energy arguments.
- 11:22: Conservation of energy is completely valid and always applies on the scales of systems that humans deal with.
- 11:29: In a related question, AFastidiousCuber asks why free energy and perpetual motion machines are impossible?
- 11:42: Space is not globally expanding or contracting on those scales and so energy is absolutely conserved.
- 11:49: Pepsi could extract some free energy if you could build a device that spans several million light years or, I don't know, install some solar panels.
- 11:59: Could the energy lost to cosmological redshift actually become dark energy?
- 12:05: The energy density of photons is much, much lower than the energy density of dark energy.
- 12:11: Dark energy now comprises 70% of the energy density of the universe and is getting larger.
- 12:17: Radiation, including photons and neutrinos, dominated the energy density until around 50,000 years after the Big Bang.
- 12:26: Today, the contribution is minuscule and they can't be powering the increase in dark energy.
- 12:39: It's worth noting that you didn't really step in to tackle the energy problem that was dogging early general relativity.
2018-05-16: Noether's Theorem and The Symmetries of Reality
- 01:09: Among them is the fact that energy is not always conserved in general relativity.
- 01:24: And so the energy of each photon drops.
- 01:27: Where does the energy from red-shifted photons go?
- 01:34: But the failure of energy conservation was still clear from the math of general relativity.
- 01:49: She discovered why the law of conservation of energy broke down in general relativity.
- 04:01: Noether's theorem reveals that this time translation symmetry gives us energy conservation.
- 04:31: That includes the apparent breaking of conservation of energy in general relativity.
- 04:52: Energy can be lost in the case of cosmological redshift, and it can be created from nowhere in the case of dark energy.
- 05:00: The law of conservation of energy is fundamental in Newtonian mechanics, in which space and time are unvarying and eternal.
- 05:08: But in Einstein's universe, energy conservation is only valid as a special case.
- 05:33: ... saves energy conservation by incorporating the entire universe's gravitational ...
2018-05-09: How Gaia Changed Astronomy Forever
- 09:37: Many of you point out that there will be useful sources of energy in the universe long after the last red dwarf fades away.
2018-05-02: The Star at the End of Time
- 01:05: ... absolute requirement for the continued existence of life is energy or, more accurately, a persistent energy gradient, as we've also ...
- 01:15: For life to stave off rising entropy and decay, energy must flow.
- 01:20: And the deepest wells of accessible energy in the universe are stars.
- 01:51: Stars generate energy, fusing hydrogen into helium in their cores.
- 01:55: ... every second, generating 4 by 10 to the power of 26 watts or around the energy equivalent of 20 million times the Earth's entire nuclear arsenal every ...
- 03:09: The layer above the Sun's core is what we call "radiative." All of the energy travels in the form of photons bouncing their way upwards.
- 03:20: Energy is transported in giant convection flows rising to the surface and sinking again.
- 03:40: Rivers of plasma flow from the core to the surface, carrying both energy and the helium produced in the fusion reactions.
- 04:43: If you increase the energy output but keep the size of the star the same, then you necessarily increase the surface temperature of the star.
2018-04-25: Black Hole Swarms
- 06:54: ... high temperature, while X-ray binaries glow at both high and low energies, due to the large temperature range of the accretion ...
- 10:22: There may be more efficient ways to gather energy at that scale, like a good old fashioned Dyson sphere.
- 11:00: We now know that they can lose energy to matter, but you would need a lot of matter.
2018-04-18: Using Stars to See Gravitational Waves
- 07:18: That heat energy comes from the gravitational wave.
- 07:21: ... circumstances gravitational waves should be able to dump some of their energy into matter, for example, into ...
- 12:20: Sometimes the conditions for a given path to low energy or to high entropy are unusual.
2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)
- 01:24: ... arrangements, like thermal energy being concentrated in your cup of coffee or all the matter in the ...
- 03:43: So a system's unable to exchange energy with the outside environment.
- 03:51: Both receive energy from outside.
- 03:54: Ultimately, that source of energy is the sun.
- 04:42: The type of order that life feeds on can be thought of as free energy.
- 04:46: By free energy, I mean the special out-of-equilibrium energy sources like a cup of coffee or the sun.
- 04:54: Another way to say this is that life feeds on energy gradients.
- 04:58: When two systems with very different energy densities come into contact, energy must flow.
- 05:05: In fact, the importance of energy gradients to life can help us understand the actual origin of life and its precursors.
- 05:55: They sit at persistent energy gradients.
- 06:20: These systems are doing their best to obey the second law of thermodynamics by redistributing their energy as evenly and randomly as they can.
- 06:29: ... energy flows from hot to cold, seeking a uniform temperature, but energy is ...
- 06:39: ... of that energy gets distributed into chemical bonds as simple molecules form via every ...
- 06:50: As those molecules form, new channels open up for distributing energy into the chemical bonds of increasingly complex molecules.
- 06:58: ... complexity would all cease when the system reaches thermal equilibrium, energy is perfectly evenly distributed and new molecules break apart exactly as ...
- 07:11: But when our energy source is flowing into a much larger reservoir, why, the ocean, for example, then equilibrium is never reached.
- 07:20: Complexity can increase indefinitely as a byproduct of the system striving to redistribute the endless gradient in energy.
- 07:46: But even life and self-replication might be a very natural part of the same thermodynamic drive to dissipate energy.
- 08:01: The most random possible form for energy is thermal radiation, and the lower the energy of its component photons, the higher the entropy.
- 08:20: ... density packets of matter called food and convert it to lower energy density waste as well as that same infrared heat ...
- 08:30: Life is great at dissipating energy, and more generally, it may be that self-replicating systems are the best possible energy dissipators of all.
- 10:10: ... the process of redistributing energy into the most random possible state, little eddies of order, like ...
- 12:13: The accelerating observer must expend more energy to produce the same acceleration.
- 12:18: Ultimately, that's the source of energy for whatever effects those Unruh particles cause, whether or not you actually see the Unruh particles.
2018-04-04: The Unruh Effect
- 04:28: In reality, eternal constant acceleration would take infinite energy.
- 04:33: So after draining all of the energy in the universe, they'd finally have to stop accelerating, and my message would overtake them.
- 07:33: Where does that energy appear to come from if not from particles?
- 08:02: This particle is coupled to the quantum field of interest, meaning it can exchange energy with that field.
- 08:08: That means the particle can be excited into a higher energy quantum state when it encounters a particle associated with that field.
- 08:51: That causes energy to be dumped into the detector particle.
- 08:55: The source of that energy is the acceleration itself.
- 09:13: An inertial observer sees the charged particle itself radiating, its energy extracted from the magnetic field.
- 09:27: The Rindler and inertial observers disagree on the source of the energy even if they agree on the final result.
2018-03-28: The Andromeda-Milky Way Collision
- 02:36: He observed Cepheid variables, which have a pulsation rate that depends on their energy output.
- 06:20: When those black holes are around a light year apart, they'll start losing orbital energy to gravitational waves.
2018-03-21: Scientists Have Detected the First Stars
- 06:06: And I asked you to use energy methods to figure some stuff out.
- 06:33: My question was, which shot was the most damaging, assuming damage only depends on the kinetic energy of the projectile at impact?
- 06:41: To answer this, we need to know how much of the counterweights starting potential energy ends up in the projectile.
- 06:58: It has no kinetic energy, and so, all of its energy is in potential energy.
- 07:03: So the energy it lost to the projectile, is just the difference between these potential energies.
- 07:08: That's the same for both shots so both gave the projectile the same total energy.
- 07:15: ... don't know anything about the kinetical potential energies at the moment of release, but we do know that the final potential ...
- 07:27: That means the projectiles kinetic energies at the point of impact must also be the same.
- 07:54: This is the power of using energy in calculations.
- 08:01: Like I just explained, we can equate the energy lost by the counterweight with the energy gained by the projectile.
- 08:07: Then, subtract the potential energy of the projectile at its point of impact, and we have its kinetic energy.
- 08:18: The kinetic energy of a 90 kilogram stone at that speed is about that of a third of a stick of dynamite.
2018-03-15: Hawking Radiation
- 01:54: ... spontaneously appear and then annihilate each other, briefly borrowing energy from the vacuum ...
- 02:03: ... event horizon, leaving the other free to escape and taking its stolen energy with ...
- 02:14: That energy can't come from nothing.
- 03:14: They fluctuate in energy due to quantum uncertainty.
- 09:44: To produce particles with mass, the energy of the radiation has to be high enough to cover the rest mass of the particle.
- 10:43: Alternatively, uncertainty in energy can lead to particle creation.
2018-02-28: The Trebuchet Challenge
- 00:00: [JINGLE PLAYING] Energy is a powerful tool for predicting the behavior of our universe, from quantum to cosmological scales.
- 00:24: We asked, what is energy?
- 00:41: In physics, energy is still intangible.
- 00:47: But the energy of physics is anything but vague.
- 01:56: We named that quantity kinetic energy.
- 01:59: ... we know the exact amount of kinetic energy that will be gained or lost by traveling between two points, then we can ...
- 02:11: We do this by defining this thing called potential energy.
- 02:14: ... the right way, the sum of kinetic and potential energy, or motion and potential for motion, remains constant, and not just for ...
- 02:35: Kinetic and potential energy are defined as combinations of more basic quantities, for example, position, velocity, and mass.
- 02:59: But today, I want to highlight the power of energy as a tool in calculation.
- 03:37: ... trebuchet is incredibly efficient at converting the potential energy of a massive counterweight into the castle-destroying kinetic energy of ...
- 05:02: This is where energy comes in.
- 05:04: The law of conservation of energy tells us that the sum of kinetic and potential energies of the projectile and the counterweight are conserved.
- 05:12: You should be able to use simple energy arguments to calculate for your enemy's destruction.
- 05:25: No energy is transferred to the structure of the trebuchet through friction or other motion.
- 05:29: All energy stays in the projectile and the counterweight.
- 05:38: But in a real energy calculation, losses due to non-conservative effects like friction and air resistance can be accounted for.
- 07:45: That's the power of energy.
2018-02-21: The Death of the Sun
- 01:31: ... life, I mean the period of core hydrogen fusion, when the steady flow of energy from the core provides consistent support against the gravitational ...
- 02:22: ... last gasp, it'll be less than 20 million K. So with no outward flow of energy to fight against gravity, that core begins to collapse, dragging the ...
- 03:09: That incredible outward flow energy does counteract gravity for the outer layers of the sun, and those layers expand.
- 03:33: But that energy output is spread over an increasing surface area, and so the surface cools down.
- 04:05: That means that all energy states are occupied.
- 05:25: The energy output is insane, and the sun swells to a red giant once more.
- 09:38: Last week we asked the question, what is energy?
- 09:44: ... are close together versus when they're far apart due to the potential energy between them being ...
- 09:57: ... property of mass is just a measure of the energy bound into the system, whether the system be an atomic nucleus or a ...
- 10:06: ... than far apart, because close together they have a lot of potential energy, a lot of potential to repel each ...
- 10:28: And they lose an enormous amount of potential energy when that happens.
- 10:40: Does this mean that the combined system of the Earth plus you gains mass every time you jump, because you gain potential energy?
- 10:55: Well, that's a great question, because potential energy is relative.
- 10:59: It represents the energy exchange that would result from a particle or system moving between two points under the action of a conservative force.
- 11:07: It tells you the kinetic energy that will be gained or lost in motion between two points due to the work done by that force.
- 11:21: But potential energy doesn't have an absolute zero point.
- 11:36: The difference in potential energy due to any fall would still be the same.
2018-02-14: What is Energy?
- 00:17: We all know what it feels like to be energetic to have energy it's this something that allows us to move, be active, get out of bed in the morning.
- 00:33: Energy seems near tangible to us.
- 00:49: In physics, energy is not a substance nor is it mystical energy, it's a number, a quantity.
- 01:05: It was 17th century polymath Gottfried Leibniz who first figured out the mathematical form of what we call kinetic energy, the energy of motion.
- 01:32: Leibniz called this early incarnation of energy vis viva, the living force.
- 02:08: It took another genius, Emilie du Chatelet to show that vis viva, or energy, as Thomas Young eventually named it, is conserved.
- 02:20: When she introduced the idea of gravitational potential energy, she put the laws of conservation of energy and momentum on equal footing.
- 02:28: The brilliant experiments of James Prescott Joule and others extended the idea to include heat energy.
- 02:35: Energy is always conserved but only if you account for all types of energy.
- 02:40: The law of conservation of energy is an incredibly powerful tool.
- 02:47: ... example, du Chatelet's gravitational potential energy, mass times the gravitational acceleration times height, is just a ...
- 03:22: It starts moving up with the same speed and kinetic energy it landed with.
- 03:40: Gravitational potential energy gets converted to kinetic energy in the fall and then back to exactly the same amount of potential energy in the rise.
- 03:49: Sure, energy is conserved but only if we define kinetic and potential energy in the right way.
- 04:00: The concept of energy is incredibly powerful.
- 04:03: And the key is this reversibility in the conversion between kinetic and potential energy.
- 04:28: ... and then retraces its path, the conversion between kinetic and potential energy will happen in ...
- 04:42: As long as the ball ends up back where it started, it will always have the same combination of kinetic and potential energy as when it left.
- 04:53: ... will always experience the same conversion between potential and kinetic energy, no matter what path it ...
- 05:07: ... the same amount of work, the same shift between kinetic and potential energy. ...
- 05:22: Energy is the currency of that trade.
- 05:25: Of course, anything that saps energy from the ball as it moves will mess with this transaction.
- 05:30: It may strike other bulls and grant them some of its kinetic energy.
- 05:34: Any impacts may remove energy if they aren't perfectly elastic.
- 05:37: It may encounter energy sapping effects, like friction or air resistance, so-called dissipative or non-conservative forces.
- 05:57: They exchange kinetic energy with perfect efficiency with the particles comprising the ball.
- 06:02: If we account for every particle and field involved, then the transaction between kinetic and potential energy is a zero sum game.
- 06:09: The energy ledger is always balanced.
- 06:12: Energy calculations are about balancing the books and accounting for all of the places energy can be stored.
- 06:20: In the case of air resistance, the kinetic energy transfer to the air particles ends up as heat.
- 06:25: ... the entire ball-Earth system when we add in gravitational potential energy, because that energy is stored in the Earth's gravitational ...
- 06:35: ... we even need to account for the potential energy in the forces that bind subatomic particles together, the energy of ...
- 06:47: Tracking the shift between different forms of energy allows us to predict the behavior of the universe in ways that would otherwise be impossible.
- 06:55: Just adding conservation of energy to Newton's mechanics gives an extra constraint that allows us to solve problems we couldn't otherwise.
- 07:32: Energy doesn't care what the individual particles are doing.
- 07:35: Instead, the concept of energy allows us to write down equations describing the evolution of the entire system.
- 07:42: ... of fluids by demanding the conservation of the kinetic and potential energy of the fluid and also of the internal energy due to fluid ...
- 07:56: ... the concept of energy and its conservation has led to new types of mechanics that have ...
- 08:20: Then there's Hamiltonian mechanics, which traces the evolution of the total energy of the system.
- 08:43: The concept of energy is so versatile that Hamilton's approach was even adapted to quantum mechanics.
- 08:50: ... quantum Hamiltonian operator describes the total energy of a quantum system and allows us to describe anything from the motion ...
- 09:09: The way it uses energy is inherently consistent with special relativity, unlike Hamiltonian mechanics.
- 09:32: So what is energy?
- 09:45: See, the law of conservation of energy arises because of symmetry, in particular time translational symmetry.
- 09:53: Energy is conserved if the physics of a system, for example, the nature of a force field, stays the same over time.
- 10:44: And in fact, energy is not conserved on those scales.
- 10:48: This leads to effects like dark energy and the accelerating expansion of the universe.
- 10:53: ... actually, conservation of energy is generally invalid in the context of Einstein's general theory of ...
- 11:15: Energy is not fundamental.
2018-01-31: Kronos: Devourer Of Worlds
- 08:34: ... change the chemistry of the atmosphere, and B, we get unlimited free energy. ...
2018-01-24: The End of the Habitable Zone
- 00:27: Hydrogen is fused into helium in the sun's core, producing energy that keeps it shining and keeps the earth warm and hospitable to life.
- 01:09: ... of fiery hydrogen due to a delicate balance between the outer flow of energy produced by fusion in the core and the gravitational crush of its ...
- 01:28: ... core became dense enough, dense enough for fusion to produce exactly the energy to balance that gravitational ...
- 01:53: But as soon as that starts to happen, the drop in energy production disrupts the delicate balance between outward pressure and gravity.
- 02:06: ... once again re-establishing equilibrium between gravitational crush and energy ...
- 02:24: That means it needs to increase its energy output to resist the increased crush.
- 02:35: This increased energy output actually causes its outer layers to expand slightly even as the core shrinks.
- 02:45: It's been calculated that the sun should currently be increasing in energy output by close to 1% every 100 million years.
- 03:15: But how much more energy will be too much?
- 11:20: ... the thermal bath of particles should include all particles and their energy distribution should be the Planck distribution, the same distribution as ...
- 11:31: Actually, now that I think about it, that might mean that you would only see particles whose rest masses are less than the allowed energy.
- 12:38: In order for the two states to be consistent, the after vacuum state has an excess of positive energy modes.
- 12:48: And conservation of energy demands that the black hole give up mass.
2018-01-17: Horizon Radiation
- 02:40: If the field vibrates with a single quantum of energy, we see a particle.
- 04:42: That oscillator can increase in energy in discrete chunks-- in quanta.
- 04:47: And we interpret each quantum of energy as representing a single particle.
- 11:39: Now we've already seen how this effect reduces the energy of the vacuum between conducting plates.
- 12:46: Neutron stars certainly seem to experience star quakes-- massive releases of energy, as the star's ion crust cracks.
2018-01-10: What Do Stars Sound Like?
- 00:38: ... the balance between the gravitational crush and the outward flow of energy from the fusion reactions in the ...
- 00:49: ... calculate things like the density and temperature of the core, the way energy flows to the surface, and even the life span of ...
- 03:45: ... tap can set an entire bell ringing, a single traveling wave feeds its energy into standing pressure waves that cause the entire star to ...
- 13:05: ... photons, perhaps synchrotron photons, and scatter them to higher energies, and preferentially in the direction of the ...
2017-12-20: Extinction by Gamma-Ray Burst
- 04:22: And nitrogen dioxide absorbs visible light, reducing the energy received from the sun.
- 11:21: So its kinetic energy, half mv squared, was around 3 by 10 to the power of 17 joules, or 70 megatons of TNT.
- 11:36: ... it might actually reach the ground before disintegrating to deliver that energy. ...
2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series
- 13:58: ... was once in that galaxy, so the cloud of gas ionized by the last burp of energy from an active supermassive black hole in the middle of a spiral galaxy ...
2017-11-29: Citizen Science + Zero-Point Challenge Answer
- 06:00: There were two, both quizzing you on the zero-point energy of the quantum vacuum.
- 06:57: ... a simplistic theoretical estimate of the vacuum energy density comes from assuming that there are no virtual photons above a ...
- 07:06: ... that to be the frequency corresponding to a photon with the Planck energy, you get a vacuum energy density of a ridiculously high 10 to the power ...
- 07:18: In this theoretical estimate, vacuum energy density is proportional to the fourth power of cutoff frequency.
- 07:25: So my question was what cutoff frequency is needed for this theoretical estimate to give you the energy density implied by dark energy?
- 07:34: OK, so the energy density implied by dark energy is around 10 to the power of minus 8 ergs per centimeter cubed, or one joule per cubic kilometer.
- 07:49: The frequency of a photon with the Planck energy is the Planck energy divided by the Planck constant, or an insane 3 by 10 to the power of 42 hertz.
- 07:59: And if vacuum energy is proportional to the fourth power of cutoff frequency, then this equation gives the relationship we need.
- 08:07: There are a bunch of constants in the cutoff frequency vacuum energy relation, but they cancel out.
- 08:13: That ratio of vacuum energies is 10 to the power of 120.
- 08:17: So we get a cutoff frequency for dark energy of 3 by 10 to the power of 12 hertz.
- 08:32: ... maximum virtual photon frequency definitely can't give us the vacuum energy that we see as dark ...
2017-11-22: Suicide Space Robots
- 07:21: ... per second, delivering nearly five tons of TNT in kinetic impact energy and forming a crater 30 meters ...
- 10:42: ... episodes have continued discussion of the quantum vacuum and zero-point energy, including some discussion of the pseudoscience behind these ...
- 12:00: You say that quantum field theory makes no prediction about the energy of the vacuum.
- 12:12: QFT may not make a prediction about the zero-point energy, but it does predict the existence of a fluctuating quantum vacuum.
- 12:20: ... model theory, has a lot of trouble explaining why it produces the tiny energy density observed as dark energy, as opposed to either 0 or very high ...
- 12:46: Hawking radiation is related to this whole vacuum energy virtual particle thing.
- 13:41: ... raised-- the idea that rejecting ideas like the EmDrive or zero-point energy generators is an example of scientists being stuck in the dogma of the ...
- 14:57: Those false powers sometimes sound pretty cool because they imply things like infinite free energy or fast space travel.
2017-11-08: Zero-Point Energy Demystified
- 00:00: ... PLAYING] The mysterious zero-point energy, the quantum vacuum, has been a misrepresented subject of science fiction ...
- 00:14: Let's talk about what vacuum energy really can and really can't do.
- 00:19: [MUSIC PLAYING] It seems pretty crazy that space itself might contain a higher density of energy than the nucleus of the atom.
- 00:32: ... is the prediction of quantum field theory, that there exists an energy of the vacuum resulting from the non-zero zero-point energies of the ...
- 00:43: ... the electromagnetic field alone, this energy density has been estimated to be up to a crazily high 10 to the power of ...
- 00:53: ... of the accelerating expansion of the universe suggest a vacuum energy density of only 10 to the power of minus 8 ergs per centimeter ...
- 01:05: ... this mismatch between the measured and theoretical values of vacuum energy is one of the greatest unsolved problems in ...
- 01:26: This means we should take the idea of zero-point energy seriously and are justifiably perplexed at the mismatch between theory and measurements.
- 01:35: ... the scientific validity of zero-point energy has also encouraged some pretty terrible pseudoscience and outright ...
- 02:02: If the vacuum has an energy density of 10 to the power of ridiculous ergs per centimeter cubed, where is it?
- 02:10: Why can't we pull infinite free energy out of nothing?
- 02:40: We harness that decay of order whenever we draw energy from a system.
- 03:02: In its return to high-entropy equilibrium, energy is extracted, and your car accelerates.
- 03:24: So even if a system contains a lot of energy, that energy may be inaccessible.
- 03:40: Energy is extracted in the movement towards equilibrium in the increase of entropy.
- 03:45: No such movement is possible for the vacuum, and so the vacuum contains no useful energy.
- 03:51: This is why so-called zero-point energy machines are baloney.
- 03:56: They claim to access an inexhaustible source of energy, but no such source exists.
- 04:02: In order to access vacuum energy, we need to introduce a disequilibrium.
- 04:08: In fact, we need to reduce the vacuum energy in one region of space.
- 04:12: The universe would then try to fill that energy hole, and we could harness that to extract energy.
- 04:31: By cutting off certain frequency modes between the plates, you lower the vacuum energy in that region.
- 04:50: While that initial pull between the plates may seem like a free lunch, to extract continuous energy, you need to pull the plates apart again.
- 04:58: This takes as much energy as you originally gained.
- 05:02: ... popular notion is that the reduction of energy between Casimir plates can be considered negative energy and so could be ...
- 05:18: Well, if we define the average vacuum energy as 0, then the Casimir Effect produces negative energy.
- 05:26: Unfortunately, the vacuum energy between Casimir plates is very much positive in an absolute sense.
- 05:32: The gravitational effect of energy depends on its absolute value.
- 05:36: That means the vacuum energy between Casimir plates still produces positive spatial curvature, not the negative curvature required for warp drives.
- 06:59: Vacuum energy is real, and it's part of the fundamental clockwork of the universe.
- 07:09: And regardless of its strength, it's not accessible to us as an energy source or as a miracle resource for far space travel.
- 07:56: Geckos literally manipulate quantum vacuum energy to climb walls.
- 08:35: ... as we saw last week, the theoretical density of the vacuum energy due to the electromagnetic field is estimated by integrating the energy ...
- 08:48: You get that the vacuum energy density is proportional to the fourth power of that cutoff frequency.
- 08:55: Based on the vacuum energy density, as we've already talked about, answer me this.
- 09:00: What cutoff frequency is needed for this theoretical estimate to give the energy density implied by dark energy.
2017-11-02: The Vacuum Catastrophe
- 00:15: There's a massive disagreement between the theoretical and the measured values of the energy of the vacuum.
- 00:35: Virtual particles appear and vanish from nowhere in seeming violation of our intuitions about the conservation of mass and energy.
- 00:51: ... tells us that there's a quantum fuzziness in the amount of energy contained at every point in space-- a non-zero zero point energy in the ...
- 01:06: This suggests that space itself contains energy, but how much energy?
- 01:13: Quantum field theory predicts that the energy of the vacuum should be up to 120 orders of magnitude greater than the measured value.
- 01:26: Let's talk about vacuum energy from a theoretical standpoint.
- 01:40: Higher energy oscillations represent the presence of real particles.
- 01:45: However, even the lowest possible energy oscillation, the one corresponding to the absence of particles, the so-called vacuum state, has some energy.
- 02:09: ... that's a minuscule amount of energy, except to properly describe a perfect vacuum, every single possible ...
- 02:23: To calculate the density of energy of the vacuum, we should add this tiny energy over an infinite range of frequency modes for all fields.
- 02:33: Now, multiply a finite energy density no matter how small by infinity, and you get infinite energy density.
- 02:42: We'll get back to whether the idea of an infinite vacuum energy is actually possible.
- 03:12: It's where photon energy is equal to the Planck energy, or 10 to the power of 19 giga electron volts.
- 03:24: Until we develop a theory of quantum gravity, we can't say whether the photons above this energy are possible.
- 03:31: ... if we add up the vacuum energy, including virtual photons, all the way up to the Planck energy, we get a ...
- 03:42: The energy density would be 10 to the power of 112 ergs per centimeter cube.
- 03:49: ... and Richard Feynman, who noted that one teacup of space with this energy density would contain enough energy to boil all of the oceans on the ...
- 04:12: In fact, in both quantum mechanics and classical mechanics, a particle's equations of motion depend only on changes in energy.
- 04:20: The zero point of the energy scale is irrelevant.
- 04:23: As long as the vacuum energy is the same everywhere, then it's inaccessible to us as an energy source.
- 04:31: ... upcoming episode, so you'll be able to knowledgeably scoff at zero point energy perpetual motion ...
- 04:39: Long story short-- a crazily high, even infinite, vacuum energy doesn't affect the predictions of quantum field theory.
- 04:57: Einstein's theory tells us that any form of energy produces gravity, and what matters is the absolute amount of energy, not relative deviations.
- 05:07: Vacuum energy should produce a gravitational effect, and a huge vacuum energy should produce a huge gravitational effect.
- 05:18: An energy of space itself should cause exponential expansion, at least in the case of an already expanding universe.
- 05:37: ... rabbit hole if you haven't already, but the upshot is that, if vacuum energy really did have the enormous value predicted by theory, then our gently ...
- 06:07: ... some fields can have extremely large positive zero point energies, then perhaps others have extremely large negative zero point energies ...
- 06:25: It gives particles a supersymmetric counterpart that may precisely cancel out their vacuum energy.
- 06:32: ... only allows us to cancel out photons down to the so-called electroweak energy, which brings the predicted vacuum energy down to a mere 10 to the 47 ...
- 06:52: For a while, theorists assumed that something like this must be happening, meaning the vacuum energy was really 0.
- 07:05: That is, until we discovered dark energy.
- 07:09: ... fact, accelerating in exactly the way we'd expect from a non-zero vacuum energy. ...
- 07:20: ... expansion allows us to measure the absolute density of vacuum energy. ...
- 07:31: Assuming vacuum energy is to blame, dark energy weighs in at 10 to the power of negative 8 ergs per centimeter cubed.
- 07:43: ... between the two, or 55 orders of magnitude if we use the electroweak energy cutoff instead of the Planck energy ...
- 07:59: ... can give us an extremely high vacuum energy or a vacuum energy of exactly 0 if we assume symmetry of positive and ...
- 08:19: Gigantic positive and gigantic negative zero point energies would need to cancel each other out down to a very tiny non-zero value.
- 08:38: ... rare universe whose fundamental fields canceled out their zero point energies, at least enough of them to allow life and astronomers to ...
- 08:50: That would imply countless other universes with different, less comfortable vacuum energies.
- 09:54: However, usually the dark sector term is used to describe the actual sources of dark matter and dark energy.
- 10:23: This means it doesn't take much energy to accelerate the particles to very high speeds.
- 10:28: Temperature is just a measure of the average kinetic energy per particle, so a little bit of energy leads to very high temperatures.
- 10:36: That energy comes from shocks that develop as the material flows in the gravitational field of surrounding clusters.
- 10:55: ... X asked whether it's possible to tap into the zero point energy or dark energy, like with the zero point modules in "Stargate." The ...
- 11:05: Vacuum energy can't be used as a power source.
2017-10-25: The Missing Mass Mystery
- 00:49: However, we've known for some time that around 95% of the energy content of the universe is in dark matter and dark energy.
- 01:39: First, a quick refresher on dark matter and dark energy.
- 01:52: It comprises 80% of the mass of the universe or around 25% of its total energy content.
- 02:08: Now where dark matter pools, dark energy pushes.
- 02:19: This energy of the vacuum comprises 70% of the universe's energy content.
- 08:32: As photons from the CMB pass through a giant filament, the hot plasma in the filament grants it a little energy boost.
- 08:41: In fact, the electrons in that plasma scatter CMB photons to higher energies.
- 11:02: Last week, we talked about virtual particles, zero point energies and the nature of nothing.
- 11:10: Michael asks whether the space containing an intrinsic energy also means that it has intrinsic mass?
- 11:21: A non-zero vacuum energy would have a gravitational effect.
- 11:34: So enough vacuum energy could result in a closed, rather than infinite, universe.
- 11:39: And rather differently to regular matter, vacuum energy doesn't dilute in an expanding universe.
- 11:53: Check out our dark energy [INAUDIBLE] for details.
- 11:59: ... the annihilation of virtual matter anti-matter particles would introduce energy into the universe and therefore violate the law of conservation of ...
- 12:09: The energy is borrowed from the energy of the vacuum for the minuscule time allowed by the uncertainty principle.
2017-10-19: The Nature of Nothing
- 01:30: This results in a real minimum average kinetic energy called a zero-point energy.
- 02:15: ... fields oscillate, vibrate with different energies, and those oscillations are the electrons, quarks, neutrinos, photons, ...
- 02:28: Now these fields are quantum fields, which means their oscillations can't just have any old energy.
- 02:35: They can only be excited in quantized chunks, integer multiples of some baseline energy.
- 02:41: In each quantum state, so each combination of particle properties, there is a ladder of energy levels, a bit like electron orbitals in an atom.
- 03:12: ... bottom of this energy ladder corresponds to these quantum oscillators having no energy, which ...
- 03:25: Inside a perfect vacuum, all of the field at all locations should be in the vacuum state, exactly zero energy at all times.
- 03:45: Well, it's also impossible to simultaneously perfectly define time and energy.
- 03:51: ... the behavior of a quantum oscillator, the less certain we can be of its energy state in that time ...
- 04:00: On extremely short time scales, a quantum field exists as a blur of many energy states.
- 04:07: In a vacuum, the most likely state in that blur is the zero energy vacuum state.
- 04:13: But sometimes the field finds itself with enough energy to create a particle, seemingly out of nothing.
- 05:41: And the higher the energy of the particle, the less time it can exist.
- 05:50: For example, the massless photon can have the tiniest of possible energies.
- 06:03: On the other hand, it always takes a baseline chunk of energy to create a gluon, the carrier of the strong nuclear force, because gluons have mass.
- 07:10: ... came in 1947, when Willis Lamb and Robert Rutherford noticed a tiny energy difference between the two electron orbitals that comprise the second ...
- 07:26: According to the best existing theory of the time, those orbitals should have had exactly the same energy.
- 07:40: ... Hans Bethe successfully explained it in terms of a fluctuating vacuum energy. ...
- 08:20: ... popping into and out of existence, then the so-called zero point energy of those fields should not be ...
- 08:30: Completely empty space should have some real energy.
- 08:34: It should have vacuum energy.
- 08:51: ... any non-resonant virtual photon would be excluded, reducing the vacuum energy between the ...
- 09:11: The higher vacuum energy outside, compared to the inside of the plates, should result in a pressure differential that pushes the plates together.
- 09:42: Now while there are potentially other explanations for the observed force, this has been taken as strong evidence that vacuum energy is real.
- 09:51: Neither the Casimir effect nor the Lamb shift allow measurement of the absolute strength of vacuum energy.
- 10:05: So how much vacuum energy is there?
- 10:18: Dark energy itself may be vacuum energy.
- 10:22: ... so, then the amount of vacuum energy needed to produce the observed acceleration is tiny, around one one ...
- 10:33: And the theoretical calculation of the strength of the vacuum energy is a little higher than that.
- 10:53: ... in all of science, and yet it's prediction of the strength of the vacuum energy seems to be wildly ...
- 14:26: ... normal positive temperatures, particle kinetic energies span a large range, but always have a distribution characterized by the ...
- 14:38: But at negative temperatures, most particles are excited towards the highest possible energy states.
- 14:44: This means that a negative-temperature substance can only lose thermal energy to a positive-temperature substance, not gain it.
- 14:57: Temperature can be defined as the rate of change of thermal energy divided by the rate of change of entropy.
- 15:11: But when you stack particles towards the highest energy states, that's a special arrangement, making it low entropy.
- 15:20: Add more energy, and more particles reach the highest energy state, which decreases entropy further.
- 15:29: So if temperature is change in thermal energy over entropy, then temperature is negative.
2017-10-11: Absolute Cold
- 00:28: Temperature is just a measure of internal kinetic energy.
- 00:32: So then, the feeling of cold is the relative absence of internal kinetic energy.
- 01:32: Pumping more energy in all liquids will vaporize into gas.
- 01:45: In these states of matter, particles have an enormous range of individual energies, some moving or vibrating fast, some slow.
- 01:52: Temperature just represents the average kinetic energy of the countless particles.
- 02:07: They can only occupy certain energy levels of vibration or motion, much like the discrete electron orbitals in an atom.
- 02:15: This quantum nature is revealed when we look at the spectrum of light produced as those particles hop between energy levels.
- 02:46: As we sap energy out of certain substances, its particles drop into the lowest possible energy state.
- 04:40: In theory, absolute zero temperature means no thermal energy so no internal motion of particles whatsoever.
- 05:44: This translates to a very real minimum in average energy and to a minimum temperature.
- 05:55: We call the lowest possible energy of a quantum system it's zero-point energy.
- 06:00: For a group of particles that make up any form of matter, that zero-point energy isn't actually zero.
- 06:07: There's always a little bit of kinetic energy remaining, and so it's impossible to reach absolute zero in temperature.
- 06:21: For example, the quantum fields that fill our universe also fluctuate due to the Uncertainty Principle resulting in what we know as vacuum energy.
- 06:39: This leads to the famous Higgs mechanism and possibly also the phenomena of inflation and dark energy.
2017-10-04: When Quasars Collide STJC
- 06:09: Typically, knots and lumps in a jet have a pretty even energy distribution.
- 06:14: Spiraling electrons produce radio waves a lots of frequencies all the way down to very low energies.
- 06:21: ... the jet begins, we think the matter should be so dense that the lowest energy radio waves have trouble escaping the ...
- 06:41: Both knots have the classic energy distribution of a completely independent jet launching point.
- 06:47: The extreme energy densities observed are also what you'd expect from the bases of two distinct jets.
- 07:35: Each time they do that they lose a bit of orbital energy or angular momentum, causing them to fall deeper into the gravitational well.
- 09:38: Longer exposure radio observations will pin down the energy distribution to confirm whether these really are jets produced by two black holes.
2017-09-28: Are the Fundamental Constants Changing?
- 04:18: ... parameter was through its effect on the fine grain structure of atomic energy levels, which is where the constant gets its ...
- 04:34: Electron energy levels-- or orbitals in atoms-- are quantized, meaning only certain levels are allowed.
- 04:41: When electrons move between levels, they emit or absorb photons with energies equal to that lost or gained by the electron.
- 04:59: And if you look at their fine grained structure, you'll see that some lines are split in two, corresponding to very slightly different energies.
- 05:08: This splitting is due to the fact that each atomic energy level can host two electrons.
- 05:59: It has a slightly lower energy than the opposite alignment.
- 06:02: So when electrons jump between orbitals, the energy they absorb or emit depends on their spin alignment.
2017-09-13: Neutron Stars Collide in New LIGO Signal?
- 03:17: And that gravitational radiation sucks energy from the orbiting system, causing the neutron stars to spiral inwards.
- 03:30: The rate of loss of orbital energy exactly matches the expected rate of emission of gravitational radiation.
- 06:38: ... Fermi satellite had spotted a flash of gamma radiation-- so the highest energy light-- from a galaxy 130 million light years ...
- 13:14: At any rate, by simple energy arguments, it just doesn't work for any weapon we now possess.
2017-08-30: White Holes
- 09:58: However, it would immediately explode in a burst of energy as soon as entropy and time resumed their normal flow upwards and forwards.
- 10:32: It's an expanding outpouring of space time containing a vast amount of energy, and the bang itself can never be entered.
- 11:04: Energy entering the black hole exits the white hole.
2017-08-24: First Detection of Life
- 05:26: Water has a high dielectric constant, which means it's good at storing electrical energy.
- 05:46: It takes a lot of energy to cause it to change temperature.
2017-08-16: Extraterrestrial Superstorms
- 01:45: In the case of earth storms, the energy powering that convection comes from the sun-warmed ocean.
- 02:42: These storms can persist as long as the warm ocean provides energy to drive the convection cycle.
- 04:37: As they contract, gas giants convert gravitational potential energy into heat, which in turn powers the largest storms in the solar system.
- 06:46: ... that the beast frequently cannibalizes small storms, absorbing their energy, and that it is sandwiched between a pair of 300 to 400-mile-an-hour jet ...
- 09:54: Turbulent flow acts like friction, sapping energy away from the bulk rotation.
2017-08-10: The One-Electron Universe
- 12:24: M. Paulson poked fun at astronomers for using "dark" to describe anything they don't understand-- dark matter, dark energy, dark flow.
- 12:35: To be fair, we did workshop lots of other words, but huh matter, discombobulating energy, and WTF flow just didn't do as well in the focus group.
2017-08-02: Dark Flow
- 03:55: As the photons of the CMB pass through that plasma, they steal a little bit of its energy.
- 04:01: As a result, when we look at the cosmic microwave background through one of these clusters, we see that its energy is boosted just slightly.
- 10:30: Incoming and outgoing particles must obey energy and momentum conservation.
2017-07-26: The Secrets of Feynman Diagrams
- 03:56: ... again, and the picture is of a photon coming in and giving up its energy to produce an electron-positron pair, a process we call pair ...
- 04:35: ... because of conservation laws-- energy and momentum conservation requires that particles not just vanish or ...
- 05:37: We know their properties-- for example, their energy and momentum.
- 05:51: They sit on the shell structure you get when you plot Einstein's equation of energy, momentum, and mass.
- 08:01: For any particle besides the going and outgoing on shell particles, any energy, speed, and even direction in time is possible.
2017-07-19: The Real Star Wars
- 04:56: Then, by passing electromagnetic radiation at a wavelength tuned to an energy level transition in that substance, stimulated emission can occur.
- 05:05: The excited electron releases its energy is a photon that exactly matches the phase and direction of the seed photon.
- 13:19: It covers nuclear energy and weaponry, as well as satellites, but I think I had the most fun with the episode on the invention of the crossbow.
- 15:06: ... is so relevant that physicists call the infinities resulting from high energy loops "ultraviolet divergences," in reference to the ultraviolet ...
- 15:20: Nicholas Aiello asks if it's possible that electrons have no fundamental mass and are made up entirely of self energy.
- 15:36: ... not the same as the self energy interaction, but it's analogous in some ways the Higgs field exchange is ...
- 15:51: It's a very different interaction to the self energy interaction, but the result is the same.
- 15:56: ... Higgs field for the bare mass, or the electromagnetic field for the self energy correction to that ...
2017-07-12: Solving the Impossible in Quantum Field Theory
- 09:07: ... one of these self-energy loops, you need to add up all possible photon energies, but those energies can be arbitrarily large, sending the self-energy-- ...
- 09:21: In reality, something must limit the maximum energy of these photons.
2017-07-07: Feynman's Infinite Quantum Paths
- 04:51: It's proportional to both the transfer between kinetic and potential energy over a path and the travel time.
- 10:10: ... the photon, but it also includes the probability amplitude of a photon's energy moving from the electromagnetic field into, say, the electron field, ...
2017-06-28: The First Quantum Field Theory
- 02:17: A larger amplitude and/or larger frequency means the vibration carries more energy.
- 04:43: The smallest possible oscillation above zero is an indivisible little packet of energy that we call a photon.
- 09:40: ... with incredible precision, the tiny difference in atomic electron energy levels due to electron spins-- spins interacting with magnetic fields in ...
- 13:44: In fact, Schrodinger followed the same approach, starting with Einstein's mass energy momentum equation.
- 13:50: ... Diagrams points out, the resulting Klein Gordon equation gives negative energy solutions just like the Dirac equation does, but Schrodinger didn't know ...
- 14:02: ... electrons because it failed to predict the fine structure emission line energies in hydrogen due to not accounting for electron ...
2017-06-21: Anti-Matter and Quantum Relativity
- 03:06: Pauli realized that to explain electron energy levels in atoms, those electrons must obey a rule that we call the Pauli exclusion principle.
- 03:53: ... two separate electrons, one up, one down, to occupy the same atomic energy level, without occupying the same quantum state and therefore violating ...
- 05:02: He then used quantum mechanical expressions for energy and momentum.
- 06:22: The answer came from trying to calculate the energy of the electron using this equation.
- 06:30: It allowed electrons to exist in states of negative energy.
- 06:38: ... a lone electron moving in an electromagnetic field could keep releasing energy as light infinitely, and sink lower and lower, to infinite negative ...
- 06:50: There was no bottom to the energy well.
- 07:06: These electrons occupy all of the negative energy states, all the way from negative infinity, up to zero.
- 07:14: The only time we can actually interact with an electron is when one has a positive energy, which would leave it sitting on top of the sea.
- 07:26: If the energy states of this imaginary ocean are all completely full, then that one extra electron can't lose any more energy.
- 08:03: ... if a positive energy electron found one of these holes, it would fall in, annihilating both, ...
- 08:49: They have a very definite energy, usually zero.
- 08:53: And the elementary particles that we know and love are just regions where a field has a bit more energy.
- 08:59: That energy manifests as vibrations in the field.
- 09:13: Paul Dirac's negative energy solutions describe anti-matter, not holes in the Dirac sea.
- 10:06: They are two sides of the same coin, positive and negative energy solutions of the same type of vibration in the electron field.
- 10:37: It's not negative mass despite this negative energy description.
- 10:41: When matter, anti-matter counterparts find each other, they annihilate, releasing an awful lot of very real energy.
- 13:50: Galdo145 asks whether bubble universes with different vacuum energies would convert to the lower energy state after colliding?
- 14:02: ... vacuum field can have one or more local minima, where the vacuum energy can come to a rest in an eternally inflating spacetime, halting ...
- 14:14: The vacuum energy may come to a rest at different minima in different bubbles or it can be a false vacuum in one and the true vacuum in the other.
- 14:23: If two bubbles with different vacuum energies collide, then the one with the higher energy should convert to the lower energy.
- 14:30: ... the lower energy bubble, that's bad, at least in the region of the collision, because a ...
- 14:38: ... the high energy bubble, it's much worse because that change in the vacuum energy state ...
2017-06-07: Supervoids vs Colliding Universes!
- 03:54: The ISW effect is dark energy in action.
- 04:00: Gravity pulls things in while dark energy pushes things out.
- 04:05: A photon entering a matter-rich galaxy cluster gets an energy boost as it falls into the cluster's gravitational well.
- 04:27: The photon exits with a net energy gain, which would register as a higher temperature on our CMB map.
- 04:39: It loses energy going in, because it's being pulled backwards by the higher density universe behind it.
- 04:53: The ISW effect would be tiny, in fact negligible, in a universe without dark energy.
- 05:07: ... around 4 billion years ago, dark energy caused the expansion of our universe to begin accelerating, whereas ...
- 05:25: So if there are giant voids in the direction of the cold spot, then these could have sapped energy from the CMB photons as they passed through.
- 06:03: ... the direction of the cold spot all the way out to the point where dark energy started to dominate the ...
- 09:13: In particular, its vacuum energy takes on a stable value.
- 09:48: Well, they merge and exchange an enormous amount of energy.
2017-05-31: The Fate of the First Stars
- 04:52: But that results in a dramatic increase in fusion rate, and therefore, energy output.
- 06:05: Warm clouds have more internal energy, helping them to stay puffed up against their own gravity.
- 06:22: As these metals get jostled in a warm cloud, their electrons absorb energy, jumping up in energy levels.
- 06:29: Those electrons then lose that energy by emitting light at specific wavelengths-- signature photons that are different for every element or molecule.
- 06:39: Those photons quickly escape the cloud, taking energy with them, and helping to cool things down.
- 06:45: ... that begins to contract under its own gravity, it can shed its thermal energy quickly, and that includes the extra heat that builds up due to its ...
2017-05-10: The Great American Eclipse
- 04:40: Every year, the moon steals a little bit of Earth's rotational kinetic energy and drifts about 3.8 centimeters away from us.
2017-04-26: Are You a Boltzmann Brain?
- 00:55: Prior to Boltzmann, entropy was only understood as a measure of the proportion of energy in a system that can be used for useful work.
- 01:13: The energy in that burning gasoline does the useful work of driving your car down the street.
- 01:25: The gas in the piston still contains the same amount of energy, but it's useless energy.
2017-04-19: The Oh My God Particle
- 00:13: These ultra-high energy cosmic rays still perplex scientists.
- 00:51: ... was an early experiment by the University of Utah to spot the highest energy cosmic rays in the ...
- 01:03: ... cosmic ray responsible for this particular flash must have had a kinetic energy of 300 exaelectron ...
- 01:14: That's 48 joules, an amount of energy we associate with macroscopic, not subatomic objects.
- 01:21: That single atomic nucleus carried as much kinetic energy as a good sized stone thrown at your head at 50 miles an hour.
- 01:35: In fact, cosmic rays of that energy was supposed to be impossible.
- 01:48: High energy particles, electrons, and small atomic nuclei, as well as gamma rays, are ejected when heavier radioactive elements decay.
- 02:02: ... to weaken with height above the ground, because the radiation loses energy to air ...
- 03:03: For lower energy cosmic rays, one approach is to look for their Cherenkov radiation.
- 03:31: Higher energy cosmic rays tend to obliterate themselves several kilometers above the ground in massive collisions with nuclei of air molecules.
- 04:02: ... analyzing the energies and trajectories of the debris, the collision that produced them and the ...
- 05:19: ... come in at all energies, from a sickly billion electron volts at the low end to the crazy 10 to ...
- 05:31: The higher the energy, the rarer they are.
- 05:33: At the lowest energies, the cosmos flings one particle every second per square meter of the Earth's surface.
- 05:39: At energies up near that of the OMG particle, they are incredibly rare.
- 05:54: To accelerate a particle to the energies of cosmic rays, you need a particle accelerator.
- 06:10: For lower energy cosmic rays, it's believed that many, and perhaps most, come from supernova explosions within our galaxy.
- 06:29: The higher the energy of the cosmic ray, though, the more likely it is to have originated from outside our galaxy.
- 06:53: See, the universe is basically opaque to particles with such high energies.
- 07:11: ... rays with energies over 5 times 10 to the power of 19 electron volts, about 8 joules, can't ...
- 07:36: Only a very small number of these extreme energy cosmic rays have been seen since the OMG particle.
- 09:20: ... highest energy cosmic rays, like the Oh-My-God particle, generate collisions far more ...
2017-04-05: Telescopes on the Moon
- 10:41: Feinstein 100 asks whether energy could be extracted from the flowing space time inside a black hole.
- 10:52: You could transform the gravitational potential energy of things falling towards the event horizon into usable energy.
- 11:09: ... converts gravitational potential energy into kinetic energy but that kinetic energy is only positive relative to ...
- 11:33: ... negative pressure, in a way that's mathematically similar to dark energy. ...
- 12:02: So I mean you could try to use that energy for something, like being instantly fried.
2017-03-29: How Time Becomes Space Inside a Black Hole
- 13:20: So in Frank Wilczek's initial idea, his hypothetical time crystals didn't require any input energy to keep them oscillating.
- 13:33: And the oscillations were supposed to go on forever without any energy inputs.
- 13:50: To keep them oscillating, you need to keep putting in energy.
2017-03-15: Time Crystals!
- 03:07: More, he imagined a substance for which oscillations were the most fundamental lowest energy or ground states.
- 03:48: No energy in, no energy out.
- 03:51: ... a way to make time crystals by using some sort of external input of energy to force the oscillating ...
- 04:19: Either direct alignment or opposite alignment are both a lower energy state than random alignment.
- 04:48: That laser is what takes the system out of equilibrium, because you are basically pumping in energy.
2017-03-01: The Treasures of Trappist-1
- 11:07: But the gene's mass could also be derived by a simple energy balance.
2017-02-22: The Eye of Sauron Reveals a Forming Solar System!
- 02:47: And outflowing energy resists any further collapse.
- 05:31: Infused with extra energy, that dust orbit shifts outwards.
- 05:43: Having lost energy, that dust spirals closer towards the star.
2017-02-15: Telescopes of Tomorrow
- 08:58: It will be easier to find new supernovae, the explosive deaths of stars which, among other things, will improve our understanding of dark energy.
- 11:39: ... on the space-time diagram and the geometry that comes from mass and energy-curving ...
- 11:53: There's no mass or energy warping it.
2017-02-02: The Geometry of Causality
- 07:03: This transformation allows you to calculate how properties, like distance, time, velocity, even mass and energy, shift between reference frames.
- 09:23: I can change that path by expanding energy to change my velocity, although doing so realigns the contours so I always slide down the steepest path.
2017-01-25: Why Quasars are so Awesome
- 04:24: It is swept up into a raging whirlpool around the black hole that we call an accretion disk, where its energy of motion is turned into heat.
- 04:46: Some is converted directly into energy and radiated as light.
- 06:07: ... when a supermassive black hole feeds and blasts energy into the universe, what we see depends on its orientation, whether or ...
2017-01-19: The Phantom Singularity
- 13:28: A scientist who decided to look into this has to divert grant money, lab space, personnel, and most critically a lot of their own time and energy.
2017-01-11: The EM Drive: Fact or Fantasy?
- 02:19: ... fundamentally limited by the fact that they have to carry not just an energy source, but propellant, a bunch of mass to shoot out the back end to ...
- 07:36: Photons would need to give up their energy, producing particle anti-particle pairs.
- 08:05: ... that such a medium can reproduce certain quantum observables, like the energy levels of the hydrogen ...
2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer
- 05:12: It has enough energy to produce a black hole with a mass of 100,000 suns and an event horizon that almost reaches the moon's orbit.
- 07:25: ... all of the energy of that shell is concentrated in a volume smaller than its own ...
- 09:23: The Dyson sphere absorbs all of the energy from the shell, so it immediately gains the entire mass equivalence, 100,000 suns worth.
- 10:41: ... strong Dyson sphere and charged it with an impossible amount of energy. ...
2016-12-21: Have They Seen Us?
- 15:35: The probably impossible technology of the warp drive allows you to cause a patch of space to move at really any speed you have the energy to reach.
2016-12-14: Escape The Kugelblitz Challenge
- 04:42: Now, light has energy and so has a gravitational effect.
- 05:22: ... us that the entire inside of a spherically symmetric shell of mass or energy feels no gravitational force from that ...
- 06:04: It would completely absorb the incoming pulse, storing it as a ridiculous amount of electrical energy and the accompanying increase in mass.
- 06:14: Maybe that energy can then power a super weapon to fight the aliens.
2016-11-30: Pilot Wave Theory and Quantum Realism
- 13:18: In that case, having one strange for every one up and one down quark is a very low energy state and so is very stable.
- 16:05: A five centimeter tube of neutronium would explode with the equivalent energy of around a trillion hydrogen bombs.
2016-11-16: Strange Stars
- 05:40: It has three quark types instead of two, and that means more particles can occupy the lowest quantum energy states.
- 05:58: ... lower energy state means that strange matter may be the most stable form of matter in ...
- 07:04: The outflowing energy is almost all in neutrinos.
- 08:32: As down quarks flip into the more massive strange quarks, they have to absorb energy from somewhere to provide for that extra mass.
- 08:41: That energy would be the heat energy of the neutron star.
- 10:29: So last week we talked about a new study that suggested that dark energy may not be all that we thought it was.
- 10:35: Turns out dark energy probably is still real.
- 11:19: I referenced a previous video when I made that statement in last week's dark energy episode.
- 12:57: ... and the possibility that it might explain both dark matter and dark energy. ...
2016-11-09: Did Dark Energy Just Disappear?
- 00:06: Did all of dark energy just vanish?
- 01:11: ... outward pressure that has come to be known as "dark energy." The finding led to a shared Nobel Prize for the leaders of the supernova ...
- 01:24: For a deep dive into the mysteries of dark energy, we actually already made this entire playlist on the topic.
- 01:36: So why are we talking about dark energy again?
- 01:46: They claim the data are consistent with there being no dark energy; no accelerating expansion.
- 02:02: ... claim is just as controversial as the original discovery of dark energy because dark energy is now the "industry standard." Of course, the media ...
- 02:16: ... figure out whether we should throw away nearly 20 years of work on dark energy, and delete our playlist based on this ...
- 02:43: As with the initial discovery of dark energy, these scientists used Type 1-A supernovae to track the expansion history of the universe.
- 03:19: So, did dark energy just go away?
- 03:22: Actually not at all, and here's why: the new study actually agrees with the old dark energy result... mostly.
- 03:31: It finds that an accelerating universe containing dark energy still fits the data best.
- 04:14: ... of general relativity to give the anti-gravitational effect of dark energy. ...
- 04:26: If the cosmological constant exists, and is larger than zero, then dark energy is a real thing.
- 04:32: ... so the messiness in the data, would cause a universe with no dark energy to just happen to look like one with dark ...
- 05:14: So for a really big scientific claim like the existence of dark energy, 3-sigma just doesn't cut it.
- 06:09: If we include other stuff about the universe, our confidence in the existence of dark energy rockets well above 5-sigma for all of these studies.
- 06:19: We can't yet observe dark energy directly; we can only infer its existence based on how it affects the expansion of the universe.
- 06:27: But that means we have to consider all off the things affecting that expansion when we decide whether dark energy is part of that equation.
- 06:35: ... there are things that tend to accelerate expansion, which we call dark energy, and there are things that slow expansion, which is just the ...
- 07:00: This graph is how we like to show the balance of these energy types: dark energy on the Y-axis, and normal energy (so, matter) on the X.
- 07:11: ... numbers, Omega Lambda and Omega m, represent the fraction of the total energy in the universe that these two types would comprise, assuming that the ...
- 07:28: Those blue ovals represent the ranges of combinations of matter and dark energy that are consistent with the new supernova measurements.
- 08:07: ... a small chance that we lie on this part of the graph: little or no dark energy. ...
- 08:52: That alone rules out the region of the supernova results that suggests there's no dark energy.
- 10:24: That little region where the supernova and CMB results overlap represents the most likely combination of dark energy and matter.
- 10:42: ... the "no dark energy" region down there is so far from the combined likely region that we can ...
- 11:23: ... So this is a thing that seems to happen in our universe. Dark energy, whatever it is, is still a ...
- 12:07: ... will be taking a long and careful look at the evidence for dark energy, and its effect on the expansion of ...
2016-10-19: The First Humans on Mars
- 05:25: Of course, all of this requires energy, and this may be the simplest part.
2016-10-12: Black Holes from the Dawn of Time
- 00:35: As long as a volume of space contains a high enough density of mass or energy, general relativity tells us that a black hole will form.
- 12:39: In addition, water has an extremely high specific heat, meaning it takes a lot of energy to change its temperature.
2016-09-29: Life on Europa?
- 02:37: Well, in general, it's because life needs energy.
- 02:42: We know that the tidal squeezing from Jupiter's gravitational field provides the energy that keeps Europa's ocean liquid.
- 03:49: The foundation of these are the single-celled organisms that extract energy from the hydrogen sulfide spewing from the vents.
- 04:32: It's believed that an energy source and a rich mineral content in liquid water are the main ingredients needed for abiogenesis.
- 04:46: ... may have driven a series of peculiar chemical processes, enabled by the energy differential and abundant minerals produced by deep sea black ...
- 06:20: And the process of melting and refreezing produces an energy gradient that can power metabolisms.
- 07:05: Ultimately, their energy and nutrients come from sunlight-powered microorganisms, like algae and plankton, at the ocean's surface.
- 07:13: Europa's ocean roof doesn't have an abundant energy source, and certainly not one that could power a 100-kilometer deep biosphere.
- 07:23: ... may be that the ocean floor vents are blasting enough energy and nutrients upwards to support all those alien whale things and ...
2016-09-14: Self-Replicating Robots and Galactic Domination
- 10:44: In a recent episode, we asked whether it's even possible, or a good idea, to build a Dyson swarm to capture all of our sun's energy.
- 11:33: ... "Firefly." Cobra60six would maybe like us to talk about more doable energy solutions like thorium power ...
- 11:52: Dyson swarms will not solve the current energy crisis.
- 12:03: But even solar power stations at Earth's surface will soon be a viable solution for most of our current energy needs.
2016-09-07: Is There a Fifth Fundamental Force? + Quantum Eraser Answer
- 00:37: Atomic nuclei have energy levels, just like their electron shells do.
- 00:41: Protons and neutrons can occupy excited states, contain excess energy.
- 00:45: And when they settle down again, they give off that energy as photons, but also sometimes as a particle or a particle-antiparticle pair.
- 01:00: They can pop out at a lot of different energies.
- 01:03: Researchers noticed a slight excess in their energies at 17 megaelectron volts.
- 01:09: It's as though something with a mass energy equivalence of 17 MEV was decaying into those particles.
- 02:06: That transition meant a difference in energy, but also a difference in some of the quantum stuff, spin parity and isospin.
- 02:49: Well, the standard wisdom for finding new particles is to create higher and higher energies; hence, the Large Hadron Collider.
- 02:56: Any particle capable of existing at lower energies should have been spotted.
- 03:11: ... that's the case, it could be produced at much lower energies than the gigaelectronvolt energies produced in the LHC, like the ...
2016-08-24: Should We Build a Dyson Sphere?
- 00:37: ... advanced civilization would have such extreme real estate and energy requirements that they might build artificial habitats in the form of ...
- 01:06: We don't really know how the energy requirements of advanced civilizations evolve.
- 01:16: On the other hand, securing access to an entire star's energy output officially elevates a civilization to type 2 on the Kardashev scale.
- 03:03: Build enough of these, and you can read the entire sun in all directions, absorbing its entire energy output.
- 04:13: It would reflect light into a small solar power plant that would then beam energy somewhere useful, perhaps with a laser or a maser.
- 04:40: Energy supply is the big limiting factor at the start, so it takes about 10 years to build the first collector.
- 05:04: Every new collector increases the energy available to build more collectors.
- 06:06: Once complete, the Dyson swarm would harvest a good fraction of the sun's energy, so trillions of times the current energy output of the planet.
- 06:14: What we then do with that energy is another matter.
- 06:39: Only 0.7% of the rest mass of the ingoing hydrogen fuel at the sun's core is converted to energy.
- 07:00: What if instead of converting 0.7% of fuel rest mass into energy we could achieve 100% efficiency?
- 07:10: But currently it takes more energy to create the anti-matter fuel than we get back out.
- 07:22: ... Energy can be harvested from a black hole, either from the Hawking radiation, ...
- 07:54: ... is really 100% efficient conversion of mass into energy, assuming we can find a way to pump new matter into the proton-sized ...
- 08:30: The Dyson sphere/swarm can absorb at most the entire energy output of the sun.
- 08:50: ... million kilogram Kugelblitz, it takes something like 10% of the sun's energy output each second, focused into a single attometer at a single ...
- 09:08: So there's something to do with the swarm's energy.
- 09:13: Then use that partial Dyson swarm's energy to build Kugelblitzes, in orbit, say, around Jupiter.
- 09:26: Aliens build partial swarms to provide the energy to build more efficient engines, which would be essentially undetectable.
- 10:35: I learned a ton about energy production and use from Professor Wysession.
2016-08-10: How the Quantum Eraser Rewrites the Past
- 04:32: ... an incoming photon, and creates two new photons, each with half the energy of the ...
- 14:15: ... to produce efficient stable and healthy societies that actually have the energy and collective intelligence to progress ...
2016-07-27: The Quantum Experiment that Broke Reality
- 02:13: ... know that light comes in indivisible little bundles of electromagnetic energy called "photons." Einstein demonstrated this through the photoelectric ...
- 03:25: ... second, third, and fourth photons, also-- they deliver their energy at a single spot and so they appear to be acting like particles of ...
- 03:56: This pattern has nothing to do with how each photon's energy gets spread out, as was the case with the water wave.
- 04:03: Each photon dumps all of its energy at a single point.
- 05:52: In fact, several quantum properties, like momentum, energy, and spin, all display similar waviness in different situations.
- 06:24: ... put the laser or electron gun or buckyball trebuchet and it releases its energy at a well-defined spot on the ...
2016-07-20: The Future of Gravitational Waves
- 06:32: ... get the alpha particle velocity from its kinetic energy, which I gave you, and you get the size of the polonium nucleus from the ...
- 07:03: ... reaches the 8.78 mega electron volts of the alpha particle's kinetic energy. ...
2016-06-29: Nuclear Physics Challenge
- 02:49: The alpha particle ejected in the decay of polonium 212 has a kinetic energy of 8.78 MEV.
- 02:56: And you can calculate the velocity using the equation for kinetic energy and the mass of the alpha particle.
- 03:28: To successfully tunnel, the alpha particle needs to reach a lower energy state.
- 03:34: That happens when the potential energy of the cooling force trying to drive it away from the nucleus is equal to the kinetic energy of the particle.
2016-06-22: Planck's Constant and The Origin of Quantum Mechanics
- 02:12: ... and the de Broglie wavelength, but also the Schrodinger equation, the energy levels of electron orbits, and importantly, the relationship between the ...
- 03:10: Heat is just the energy in the random motion of particles comprising an object.
- 05:12: It states that an object's heat energy will end up juggling all of its particles in all the ways that they can be jiggled.
- 05:20: In physics speak-- at equilibrium, energy is evenly spread between all possible energy states.
- 05:58: It paints the crazy picture of a universe full of infinite extreme energy gamma radiation.
- 06:28: The Rayleigh-Jeans calculation allows particles to vibrate with any amount of energy, all the way down to infinitesimally tiny wiggles.
- 06:37: ... they tried to mathematically distribute heat energy to equipartitionates across possible energy states, way too much energy ...
- 06:51: ... were chasing Zeno's tortoise, infinitely dividing the smallest remaining energy states, and so never ever finding an end to ...
- 07:09: ... he needed some sort of math trick to count the supposedly infinite energy ...
- 07:26: He decided that those particles could only vibrate with energies that were a multiple of some minimum energy.
- 07:35: He quantized the energy states.
- 07:38: He set this minimum energy to be the frequency of a particle's vibration times a very, very small number, a number that had yet to be measured.
- 07:58: It allowed Planck to equipartition energy in a way that solved the ultraviolet catastrophe.
- 08:05: Because it limited how much energy those high frequency vibrations could hold.
- 08:21: Now Max Planck didn't originally think that these quantized energy levels were real.
- 08:29: He expected his new constant to turn out to be 0, which would mean no interval between energy states, no quantization, no minimum energy.
- 08:52: Energy quantization is real.
- 09:36: ... little vibrating particles do have quantized energies, but it's because they can only gain or lose energy by absorbing or ...
- 09:48: And that light comes in indivisible energy packets.
- 09:52: ... of the photon-- part wave, part particle, carrying a quantum of energy equal to the now familiar frequency of the wave times the Planck ...
2016-06-15: The Strange Universe of Gravitational Lensing
- 01:27: ... resembles our mind's eye Euclidean lattice in the absence of mass and energy. ...
- 10:05: ... yourself at a point in your wave function that has an equal or lower energy state than your starting ...
- 10:18: Think about that alpha particle trying to tunnel through the potential energy wall of the strong nuclear force.
- 10:41: To escape, it needs to tunnel all the way to the other side, where it finds itself in a lower energy state.
- 10:51: You'd be tunneling to a higher energy state, which is impossible.
2016-06-08: New Fundamental Particle Discovered?? + Challenge Winners!
- 01:34: Their energy is released and reshapes itself into new particles.
- 01:42: And some are so hopelessly unstable that they decay into high energy light-- gamma rays-- before they ever reach a detector.
- 01:51: We only know they ever existed because the resulting gamma radiation has an energy corresponding to the mass of the decayed particle.
- 02:00: ... 125 gigaelectron volts above the otherwise smooth spectrum of gamma ray energies. ...
- 03:14: There are theoretical ideas of particles that could cause a bump at this energy, and would also make pretty decent dark matter candidates.
- 03:40: So, a higher energy vibration in the Higgs field.
- 04:39: OK Time for the solution to the dark energy challenge question.
- 04:46: He's about to go full nerd with the dark energy challenge answer.
- 08:58: Back to [INAUDIBLE] Matt for the dark energy challenge answer.
- 09:03: For the main question, I asked you to figure out how many times the universe doubled in size after dark energy first started to show its influence.
- 09:20: More precisely, for how many past and future doublings of the scale factor are they both at least 10% of the energy content of the universe?
- 09:37: To start with, let's ask how large this volume was when dark energy only comprised 10% of its total energy.
- 09:50: Right now, 70% of the energy in any volume in the universe is in the form of dark energy.
- 09:55: So 70 parts dark energy and 30 parts matter.
- 10:02: Back in the day, it was whatever the sum of dark energy and matter was back then.
- 10:08: The overall amount of energy in the form of matter doesn't change, because matter is spreading out with the expanding volume.
- 10:21: But the amount of energy in the form of dark energy is proportional to the volume.
- 10:30: We can scale past dark energy according to the current dark energy content like this.
- 10:52: So our total energy becomes this.
- 11:05: ... in our current 70 units of dark energy and 30 units of matter, and we get that the universe was 36% of its ...
- 11:27: You can take exactly the same approach to ask when in the future matter will only have a 10% contribution to the energy in that volume.
- 11:44: Add these two numbers together, and you get that matter and dark energy both produce a significant effect for around two doublings.
- 13:08: Is there something about the tipping point between the dominance of matter versus dark energy that makes the universe more hospitable for life?
- 13:17: Or should we take this as evidence that our simple idea of a constant dark energy density is wrong?
2016-06-01: Is Quantum Tunneling Faster than Light?
- 03:19: We can imagine an alpha particle as being like a ball trapped in a steep valley of potential energy.
- 03:26: It can roll around inside, but unless it has a very large kinetic energy, it will never roll over the edges.
- 10:47: ... that episode we'll also be giving the solution to the dark energy challenge question, as well as telling you about some pretty amazing ...
2016-05-25: Is an Ice Age Coming?
- 12:01: Last week, we wrapped up our conversation on dark energy, talking about anti-gravity, negative pressure, and conservation of energy.
- 12:46: ... Lidster and a few others have wondered whether the energy lost in the cosmological redshift of photons could account for the ...
- 12:55: So to summarize, as the universe expands, the energy in matter in any one co-moving volume or expanding volume is conserved.
- 13:09: But photons also get spread out and they get red shifted, so they do lose energy inversely proportional to the increasing scale factor.
- 13:23: So could this lost energy become dark energy?
- 13:28: ... far less, even, than baryonic matter, which itself is far less than dark energy. ...
- 13:42: These days, photons just don't have enough energy left to contribute.
- 13:47: Yet dark energy continues to be created.
- 13:50: Eugene Khutoransky points out that the idea that energy is not conserved in an expanding universe is still pretty speculative.
- 13:58: ... it's a speculative statement to say that the law of conservation of energy, as we learned when we studied Newtonian mechanics, is a feature of flat ...
- 14:12: ... requires the invention of a new quantity-- gravitational potential energy-- in order to preserve energy ...
- 14:23: Described in general relativity, you can still come up with conserved quantities-- energy analogies that are invariant in, say, an expanding universe.
- 14:32: But, for example, a stress energy momentum pseudo tensor isn't mathematically the same thing as classical energy.
- 14:51: Conservation of energy is one such law that work in flat space time.
- 14:55: But energy itself is not a thing.
- 14:57: We draw energy life bars in our animation sometimes, but the universe doesn't have any hidden energy counter.
2016-05-18: Anti-gravity and the True Nature of Dark Energy
- 00:02: The true nature of dark energy confounds even the world's smartest astrophysicists.
- 01:00: This is only possible if we missed some unknown type of energy pervading all of space.
- 01:21: We call it dark energy.
- 01:24: This dark energy is described by the cosmological constant in the equations of general relativity.
- 01:37: It means we have dark energy's number, its fingerprints at the crime scene.
- 01:42: Knowing a possible theoretical form for dark energy will unlock many of its mysteries.
- 01:48: Today, we're going to talk about the simplest interpretation of dark energy, one where the cosmological constant really is constant.
- 02:03: A constant cosmological constant represents a nonzero energy of empty space, a vacuum energy.
- 02:12: The more space you have, the more dark energy you have.
- 02:15: It's a constant energy density.
- 02:18: OK, the big, weird fact about a constant vacuum energy density is that leads to exponential expansion.
- 02:31: But what physical thing about dark energy is producing this outward push, this anti-gravity?
- 02:45: It only tells us that dark energy produces an exponential change in the size of the universe, not necessarily an exponential growth.
- 02:59: To see why dark energy pushes outwards and accelerates the expansion, we need to go deeper.
- 03:48: The more matter and energy in the universe, the harder gravity pulls inwards, trying to stop the expansion or speed up the collapse.
- 04:18: In general relativity, energy slash mass and pressure both curve space time.
- 04:36: ... particles produce an outward push in pressure, then is this how dark energy is causing expansion to accelerate, by causing positive ...
- 05:25: See, high pressure from regular matter and energy means very fast-moving particles.
- 05:39: ... a region where the particles are moving more slowly, even if the overall energy density of those regions is the same Positive pressure pulls the ...
- 06:47: The cosmological constant was designed to work in the opposite direction to regular matter and energy.
- 07:00: Dark energy is real physical stuff.
- 07:08: The effect of the cosmological constant is the combined effect of dark energy's own density and pressure.
- 07:17: ... diluted away and will only have the density and pressure due to dark energy, rho lambda and p ...
- 07:27: Now, the energy density of dark energy is positive, just like regular matter.
- 07:33: It has to be, because dark energy helps regular matter flatten the geometry of the universe.
- 07:50: So dark energy's density isn't causing expansion to accelerate by itself.
- 08:03: It turns out that dark energy does produce an enormous pressure.
- 08:20: That's where dark energy's crazy anti-gravity effect comes from.
- 08:44: Both have positive energy density.
- 08:54: Weirdly, the inward pulling pressure of dark energy ultimately drives expansion outwards.
- 09:05: The direct effect of dark energy's negative pressure doesn't do anything, because that negative pressure is the same everywhere in the universe.
- 09:38: Part of the problem is that negative pressure doesn't come from the motion of dark energy particles, whatever they might be.
- 09:46: Instead, it comes directly from the fact that the density of dark energy is constant.
- 09:53: Let's say I'm holding a volume of the universe that has a constant energy density.
- 09:59: If I expand it, then it has more energy in it than it did before, because it has more volume.
- 10:04: I would have to provide that energy, which means I'd have to do work to expand it.
- 10:22: Negative pressure means energy is gained on expansion.
- 10:26: That's what happens with dark energy.
- 10:29: As the universe expands, more dark energy is created because its energy density has to stay constant.
- 11:01: But both agree that a constant energy density and the resulting negative pressure leads to accelerating expansion.
- 11:14: And the energy turns into new dark energy.
- 11:20: Where does the energy come from?
- 11:29: See, the law of conservation of energy no longer applies in an expanding universe.
- 11:48: Energy can be forever lost or gained from nothing within an expanding curved spacetime.
2016-05-11: The Cosmic Conspiracy of Dark Energy Challenge Question
- 00:03: ... into cosmology, building up the tools we need to really understand dark energy and its influence on the ...
- 00:14: Pretty soon you'll understand as much as anyone, with the possible exception of people who are actually paid to understand dark energy.
- 00:36: The balance between dark energy and matter in the modern universe is on the side of dark energy.
- 00:42: ... large enough for regular matter to dilute away enough so that dark energy ...
- 01:05: If you add up the energy in any large volume of space, about 70% of it is dark energy and the remaining 30% is in the form of regular matter.
- 01:25: I'm talking about the relative amount of energy.
- 01:36: Say a cubic million light years, around 70% dark energy, 30% matter.
- 01:41: So there's more dark energy than the other stuff.
- 02:16: ... and in the Friedmann equations that are derived from those, dark energy is described by a positive cosmological ...
- 02:25: If that constant truly stays constant over time, then it represents an energy of the vacuum.
- 02:30: Its density stays constant and so the amount of dark energy increases at the same rate as the volume of the universe.
- 02:38: When the universe has doubled in size, there'll be twice as much dark energy, joule for joule.
- 02:59: At some point in the past, there was a perfect balance between dark energy and matter.
- 03:05: Very roughly, it was when the universe was half its current volume because that would mean half the current amount of dark energy.
- 03:14: A given giant box in the universe currently has around 30 parts matter and around 70 parts dark energy.
- 03:22: Halve its volume, and it still has those 30 parts matter, but only around 35 parts dark energy.
- 04:06: Dark energy has dominated the universe only during the tenure of life on Earth, although its effect has been felt for a bit longer than that.
- 04:49: For the vast majority of those past 100 doublings, dark energy has had an extremely tiny energy contribution.
- 05:01: And for the vast majority of future doublings, regular matter will have diluted away and be an infinitesimal influence compared to dark energy.
- 05:17: For how many of those past 100 doublings has dark energy had any significant effect-- let's say at least 10% of the energy density?
- 05:29: ... for how many of those infinite future doublings will regular matter and energy have any significant effect-- again, at least 10% of the energy ...
- 05:43: ... question I just asked, but also tell me how many billion years ago dark energy started to have a significant effect and how many billion years in the ...
- 06:34: Email your answers to email@example.com with the subject line Dark Energy Challenge within two weeks.
2016-05-04: Will Starshot's Insterstellar Journey Succeed?
- 06:40: ... to point the cameras and then beam that info back to Earth with whatever energy can be stored on ...
- 07:50: ... engineer Freeman Dyson, the UK astronomer royal, Martin Rees, dark energy Nobel Laureate, Saul Perlmutter, and several other very prominent ...
- 08:35: ... here on "Space Time." In the last episode, we talked about how dark energy causes this exponentially accelerating expansion of the universe and you ...
- 08:56: Does dark energy cause expansion?
- 08:58: Does expansion cause dark energy?
- 09:01: Dark energy does drive the expansion rate, causing a sort of anti-gravity effect.
- 09:06: But if dark energy diluted away, like regular matter does, that effect would diminish as the universe expanded.
- 09:15: However, dark energy doesn't dilute.
- 09:19: That means the larger the universe is, the more dark energy there is and so the more of this anti-gravity.
- 09:26: So expansion results in more dark energy and more dark energy results in faster expansion.
- 09:51: So that depends on what dark energy actually is.
- 10:20: The one where space time rips itself apart at a fundamental level, the so-called Big Rip, happens when the density of dark energy increases.
- 10:33: Sandeep Siwach would like to know why dark energy only effects the space between galaxies and not within galaxies.
- 10:40: So dark energy only has an observable effect when its density is at least comparable to the density of regular matter.
- 10:59: There's just not enough dark energy in these regions to do very much.
2016-04-27: What Does Dark Energy Really Do?
- 00:09: However, we now know that the evolution of our universe is driven by something even more mysterious-- dark energy.
- 00:40: And this is only allowed if we introduce a new type of energy represented by the cosmological constant.
- 00:47: We call it dark energy.
- 00:49: But what does this dark energy thing actually do?
- 04:57: That something would be a high-mass energy content that could in the future cause it to recollapse.
- 06:50: ... the Nobel Prize in 2011, and it's considered to be the discovery of dark energy. ...
- 07:10: However, this accelerating expansion can be explained with the same bit of math, the cosmological constant, pointing to the same physics, dark energy.
- 07:36: This lets us interpret the cosmological constant as representing a sort of vacuum energy, a property of space itself.
- 07:48: But why should a constant vacuum energy cause the universe to accelerate?
- 09:04: Currently, there's still enough matter in the universe to influence the expansion rate, but we're already at the point where dark energy dominates.
- 09:33: That all depends on what this energy of empty space really is.
- 09:38: ... relativistic description of the expansion of the universe requires dark energy. ...
- 10:42: Even if the greater universe is curved, we still need dark energy.
2016-04-20: Why the Universe Needs Dark Energy
- 00:08: ... to do so have revealed the existence of a strange influence called "dark energy." [THEME MUSIC] Einstein's general theory of relativity allows us to ...
- 00:35: ... us that the fate of the universe is governed by something we call "dark energy." To truly understand dark energy, we're glimpsing into the workings of ...
- 01:22: And this is true even though we haven't taken dark energy into account yet.
- 07:38: As the universe expands, regular matter and energy get diluted away.
- 07:51: So the bigger the universe, the more of this energy.
- 07:54: We call it "dark energy," and we interpret it as an energy possessed by empty space itself-- by the vacuum.
- 08:04: ... of regular matter will, at some point, drop below that of this vacuum energy, as described by the cosmological-constant ...
- 08:14: At that point, dark energy will govern expansion.
- 08:31: We now live in a universe dominated by dark energy.
- 08:39: Soon, we'll get to the second and most compelling piece of evidence for dark energy and for the cosmological constant.
- 08:46: ... equation, which will give us the insight we need to understand dark energy's effect on the future of ...
- 10:10: Now there are certain models of dark energy that could have space on smaller scales expand, resulting in the so-called Big Rip.
- 11:05: ... for bachelor's or masters physicists, like medical imaging or radiology, energy industries, meteorology, science education, science journalism, and ...
2016-04-13: Will the Universe Expand Forever?
- 00:46: ... by a mysterious influence that physicists have come to call "dark energy." In order to get a truly meaningful sense of the forces governing the ...
- 01:17: For today's episode, we're going to start by describing the universe without dark energy.
- 01:57: And it describes all of the energy, the pressure, the momentum, and more-- all of the stuff within that spacetime.
- 03:07: The mathematical step from Newton's gravity to escape velocity comes from thinking about energy.
- 03:14: As the apple rises, its kinetic energy, its energy of motion, is sapped by the gravitational field and converted into potential energy.
- 03:24: Remember, energy is always conserved.
- 03:27: There's a minimum kinetic energy that the apple needs in order to escape the energy-sucking gravitational-potential well of the Earth.
- 03:36: That minimum kinetic energy tells you the escape velocity.
- 03:40: ... this Newtonian analogy-- and, remember, ignoring dark energy-- the universe also has an escape velocity that lets distant galaxies ...
- 05:17: It reflects the same balance between kinetic and gravitational potential energy that we saw in our rising apple.
- 05:25: In fact, this Friedmann equation is an energy equation.
- 05:29: That first piece, the a-dot over a squared, is analogous to the kinetic energy of expansion-- how much outflowing oomph the universe has.
- 05:40: But that oomph is resisted by the gravitational effect of all the master and energy in the universe.
- 05:53: So this second piece represents the capacity of the universe to slow itself down and is analogous to the gravitational potential energy.
- 06:01: The balance between these two energy like terms tells us the fate of the universe.
- 06:09: ... the kinetic energy of expansion and the potential energy of collapse are perfectly ...
- 06:39: There will be some expansion energy remaining after gravity is diluted to nothing, and the universe will expand forever, never stopping.
- 09:05: That something is dark energy.
- 09:08: ... show you why the Friedmann equations tell us that dark energy must exist in this universe, and what these equations can tell us about ...
- 09:20: Dark energy won't save us from infinite expansion.
- 09:26: Dark energy accelerates the expansion.
- 09:36: It'll shatter our intuitions about energy conservation and gravity on the largest scales of spacetime.
2016-04-06: We Are Star Stuff
- 00:31: Space, time, energy, mass.
- 03:13: The secret of the success of this relationship is that it takes a lot more energy for those quarks to be apart than to be together.
- 03:54: ... once these nucleon are close enough, the binding energy of the strong nuclear force is stronger than the repulsion of the ...
- 04:03: The components are in a lower energy state together compared to when they're apart.
- 04:40: As well as providing us with all of their glorious entropy-resisting energy, stars are element factories, stellar alchemists.
- 06:23: ... every single reaction previous had liberated energy, and kept the core hot and puffed up, outflowing radiation pressure, ...
- 06:38: You gain energy by fusing nuclei into it, but you also gain energy by breaking up larger nuclei to get iron by fission.
- 06:47: In order to go in either direction from iron, either increasing or decreasing the number of protons, you actually have to put energy in.
- 06:57: That means that as soon as iron starts to fuse, it sucks energy out of the star rather than adding to it.
- 09:27: ... remnants will eventually spiral in as they radiate away their orbital energy in gravitational ...
2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!
- 01:08: So what could cause such an insane energy output?
2016-03-23: How Cosmic Inflation Flattened the Universe
- 07:23: Incidentally, it also describes the effect of dark energy, and that may not be a coincidence.
- 07:57: We'll delve pretty deep into how this works in terms of general relativity on a future episode on dark energy.
- 08:15: ... expansion and will do so if the vacuum contains a ubiquitous constant energy ...
2016-03-16: Why is the Earth Round and the Milky Way Flat?
- 07:11: Here the pressure comes from the upward flow of energy from the nuclear fusion engine in the core.
- 10:26: They also give us things like the Laws of Conservation of Energy and of Linear and Angular Momentum, topics that we will get to.
- 11:28: See, the Big Bang didn't happen as a sudden presence of energy at some point.
2016-03-02: What’s Wrong With the Big Bang Theory?
- 02:36: We can create energies needed to produce the electroweak states in the Large Hadron Collider.
- 03:30: We need to produce energies a trillion times larger than is possible with the Large Hadron Collider.
2016-02-24: Why the Big Bang Definitely Happened
- 08:05: We've recreated those insane energies in our particle accelerators.
- 08:19: Earlier than 10 to the power of minus 32 seconds, we just can't produce the energies needed to test our understanding of physics in those conditions.
2016-02-11: LIGO's First Detection of Gravitational Waves!
- 02:30: But gravitational waves carry energy, which is sapped from the orbital energy of the system.
- 02:45: The amount of energy being lost in these systems is exactly what we predict it should be if caused by gravitational radiation.
2016-02-03: Will Mars or Venus Kill You First?
- 05:27: This is when a magnetic storm on the sun's surface sends out a blast of extremely high energy particles, most notably protons and electrons.
2016-01-27: The Origin of Matter and Time
- 06:50: At each interaction, particles exchange energy, charge, and other properties that result in change.
2016-01-13: When Time Breaks Down
- 00:02: In the last episode, we saw how matter fills mass because of the energy of its internal moving parts.
- 06:38: ... its component particles and fields, in which the internal parts exchange energy, momentum, and other properties-- interactions which hold the atom ...
- 08:18: In that case, the box's mass increases by the amount equal to the energy of the contained photons, divided by the speed of light squared.
2016-01-06: The True Nature of Matter and Mass
- 00:54: ... showed that most of the mass of atoms comes from the kinetic and binding energy of the quarks that make up protons and ...
- 01:05: But saying that mass is energy doesn't really get us very far.
- 01:08: It just begs the question, what is energy?
- 01:14: For now, let's look at this energy in terms of what's actually happening in an object when it exerts this property we call mass.
- 03:10: It's the energy of the photons divided by the square of the speed of those photons.
- 03:23: But E equals Mc squared describes the universal relationship between mass and confined energy, not just confined photons.
- 03:31: So let's look at another example of confined energy.
- 03:34: A compressed spring holds more energy than a relaxed spring.
- 04:16: ... the compressed spring-- both give the same translation between mass and energy, E equals Mc squared, because the underlying cause is the same-- the ...
- 04:55: 99% of the mass of the proton is in the vibrational energy of the quarks plus the binding energy of the gluon field.
- 05:08: ... field, which itself acts like a compressed spring, holding potential energy. ...
- 07:23: The presence in the flow of energy and momentum as well as pressure all have their quite different effects on the curvature of space-time.
2015-12-16: The Higgs Mechanism Explained
- 00:36: Most of the atom's mass is the confined kinetic and binding energy of those quarks.
- 00:47: I want to show you that even in this case, mass is still just bound or confined energy.
- 01:32: But now, add some energy to that field at a particular spot, and it's like plucking a guitar string.
- 01:43: ... and these vibrations and fields interact with each other, transferring energy, momentum, charge, et cetera, between particles and ...
- 07:24: Could the Higgs field also explain things like dark energy, inflation?
- 08:55: ... so gravitational waves carry a lot of energy, and some of it can get dumped into a star by squeezing and stretching as ...
2015-12-09: How to Build a Black Hole
- 00:56: Yet, to actually form a black hole, Einstein's descriptions of mass energy and space time are not enough.
- 01:53: Fusing two ion nuclei absorbs energy.
- 01:58: So starved of an energy source, the stellar core collapses on itself.
- 06:04: ... that particular pairs of quantities, position and momentum or time and energy, must, when taken together, contain a minimum degree of ...
- 12:18: ... Earth's orbit-- which was another suggestion-- would take vastly more energy than just nudging it off ...
2015-11-25: 100 Years of Relativity + Challenge Winners!
- 00:36: ... relativity's profound description of space and time, of matter and energy, emerged from the simplest of thought experiments, simple statements ...
2015-11-18: 5 Ways to Stop a Killer Asteroid
- 01:40: Meteors 20-100 meters in size have the kinetic energy equivalent of a thermonuclear explosion.
- 01:54: For a rock around 500 meters in diameter, the strike will have the energy equivalent of all currently operational nuclear weapons in the world.
- 07:20: This uses the nuke's energy much more efficiently, sending shockwaves through the asteroid, that will break it into much smaller pieces.
2015-10-28: Is The Alcubierre Warp Drive Possible?
- 01:27: That limit, the speed of light, refers to things-- mass, energy, information-- traveling through space.
- 02:03: ... by solving Einstein's field equations around a point of extreme positive energy ...
- 02:12: Basically, mass and energy tell us how space should warp.
- 03:05: ... equations backwards to figure out what arrangement of matter and energy would be needed to create ...
- 03:24: ... for the warp field, you find that you need to produce a ring of negative energy density in a band around the ship to produce the right warp ...
- 03:38: Unfortunately, it may not even be possible to make negative energy densities on large enough scales.
- 04:46: ... proposed solutions, one of which is to lay down the external negative energy conditions along the path before you leave, sort of like a warp ...
- 05:02: Last tricky thing-- as Alcubierre devised the warp bubble, he figured it would take a lot of negative energy.
- 05:08: In fact, it would take significantly more negative energy than there is positive mass/energy in the entire observable universe.
- 06:02: Quantum scale manipulation of the vacuum energy a la the Casimir effect may be enough.
- 06:18: Now, this would be a field created by positive, not negative, energy density.
2015-10-22: Have Gravitational Waves Been Discovered?!?
- 04:20: Gravitational waves carry energy.
- 04:22: ... to produce a lot of this gravitational radiation, their obits will lose energy and decay, causing them to spiral in towards each ...
- 09:48: A 10 milligram grain would strike with the kinetic energy of around 100 kilograms of TNT if your spaceship was moving at 10% the speed of light.
2015-10-15: 5 REAL Possibilities for Interstellar Travel
- 02:48: We just want the fuel with maximum energy density.
- 02:51: So direct conversion of rest mass into energy seems like the way to go.
- 04:40: But fusion turns less than 1% of rest mass into energy.
- 04:50: When matter meets it's antimatter counterpart, both particles are annihilated, liberating most of the rest mass as energy.
- 05:37: That's something like 50 times more energy per kilogram of fuel than the best fusion options.
- 07:56: ... sufficient energy density of laser light focused in a small enough region would bend the ...
2015-10-07: The Speed of Light is NOT About Light
- 09:19: ... relativity-- time dilation, length contraction, and, of course, mass to energy equivalence, as described by the famous equation, E equals mc ...
- 09:53: Because it would take infinite energy to make any mass.
2015-09-30: What Happens At The Edge Of The Universe?
- 04:22: But for now, let's just assume we have a nice Alcubierre-class warp-ship and we burn the mass energy of entire stars to chase the particle horizon.
- 08:42: To collapse completely into a star-sized object, it would have to lose a lot more energy.
2015-08-12: Challenge: Which Particle Wins This Race?
- 04:31: ... equations in the presence of a spherically symmetric perfect fluid whose energy density is the same when measured locally by an observer that's ...
2015-08-05: What Physics Teachers Get Wrong About Tides!
- 10:53: ... quantum version of gravity tells you on very small scales or very high energies, that a lot of infinities start popping up in the theory that you can't ...
2015-07-29: General Relativity & Curved Spacetime Explained!
- 07:32: Its curvature in geodesics are determined by how much energy is present at those events via set of rules called, no surprise, the Einstein equations.
- 07:40: So for example, say you stick the energy distribution of the sun into the Einstein equations and turn a crank.
2015-06-24: The Calendar, Australia & White Christmas
- 06:40: acappellascience suggested that we put photovoltaics on the billboards as an energy source.
2015-06-17: How to Signal Aliens
- 03:06: But as with radio, the continuous energy usage would be very expensive.
- 04:23: And a sequence of louvered slits would look especially distinct and artificial, all without any transmissions or energy requirements.
2015-05-27: Habitable Exoplanets Debunked!
- 01:04: ... as the sweet spot of orbital distances from that star at which the energy from starlight would produce the right temperature on a planet's surface ...
- 06:50: If everyone on Earth picked up a hammer at the same time, by how much would Earth's mass increase due to the excess gravitational potential energy?
- 07:01: ... more gravitational potential energy in the hammers, but that was previously stored as chemical energy in the ...
- 07:17: Energy would have been injected into the system, and Earth's mass would negligibly increase.
- 08:09: Energy's escaping.
- 08:26: ... your drop in body temperature alone would mean there's less thermal energy contributing to the total ...
- 08:36: Tim Chapelle asked how both fusion and fission could end up releasing energy.
- 08:41: ... there's a configuration in which something has less total potential energy than it did before, then that configuration will have less mass, and the ...
- 08:50: Sometimes you have less total potential energy by putting things together.
- 08:54: Sometimes there's less potential and kinetic energy if you pull things apart.
- 09:00: It's just the total energy budget that determines whether something will release or not release energy.
- 09:04: Natalia B, Pablo Herrero, and Gorro Rojo all asked whether photons actually have mass if they have energy.
- 09:24: Gareth Dean asked, if all the photons in the universe have been red shifting as the universe expands, that means they're losing energy.
- 09:31: Where did all that energy go?
- 09:34: You can loosely think of that energy as going into the expansion, but even that's not quite correct.
- 09:38: The bottom line answer is that in general relativity, there actually is no such thing as energy conservation for the universe as a whole.
- 09:45: How that can be, even though locally, in local pockets, you can have energy conservation, seems weird and contradictory.
2015-05-20: The Real Meaning of E=mc²
- 00:39: You'll often see statements like "mass is a form of energy" or "mass is frozen energy" or "mass can be converted to energy." That's the worst one.
- 01:38: Well, the hands and gears in the running watch are moving, so they have some kinetic energy.
- 01:42: ... are also wound up springs in the running watch that have potential energy, and there's a little bit of friction between the moving parts of that ...
- 01:53: That's thermal energy, or equivalently, randomized kinetic energy on a more microscopic level.
- 01:59: ... what M equals E over c squared says is that all of that kinetic energy and potential energy and thermal energy that resides in the watch's ...
- 02:11: ... just add up all that energy, divide it by the speed of light squared, and that's how much extra mass ...
- 03:37: ... light carries energy, and that energy was previously stored as electrochemical energy inside ...
- 03:45: Once that energy escapes, you're not weighing it anymore.
- 04:06: So does this mean that the sun converts mass to energy?
- 04:10: All the energy in sunlight came at the expense of other energy, kinetic and potential energy, of the particles that make up the sun.
- 04:17: ... that light was emitted, there was simply more kinetic and potential energy contained within the volume of the sun manifesting as part of the sun's ...
- 04:25: Those 4 billion kilograms that the sun loses every second is really a reduction in the kinetic and potential energies of its constituent particles.
- 04:32: What we've been weighing is the energies of the particles in objects all along.
- 04:53: ... it's true that the scale is registering less electrochemical energy, but it's also registering an exactly equal amount of extra light energy ...
- 05:03: ... even though light itself is massless, if you confine it in a box, its energy still contributes to the total mass of that box via m equals E over c ...
- 05:29: It's because potential energy can be negative.
- 05:32: Suppose we call the potential energy of a proton and electron zero when they're infinitely far apart.
- 05:37: ... they attract each other, their electric potential energy will drop when they get closer together, just like your gravitational ...
- 05:48: So the potential energy of the electron and proton in a hydrogen atom is negative.
- 05:52: Now the electron in hydrogen also has kinetic energy, which is always positive, due to its movement around the product proton.
- 05:58: ... as it turns out, the potential energy is negative enough that the sum of the kinetic and potential energies ...
- 06:22: ... less than two oxygen atoms because the combined kinetic and potential energies of those atoms once they form a chemical bond is ...
- 06:41: Basically, quark potential energy.
- 06:48: Every time he says "gluons" in that video, just substitute "quark potential energy," and you'll have a roughly correct picture of what's going on.
- 07:05: Well, that's a subtle question, but crudely speaking, you can think even of this mass as being a reflection of various kinds of potential energies.
- 07:12: For instance, there's the potential energy associated with the interactions of electrons and quarks with the Higgs field.
- 07:17: ... there's also potential energy that electrons and quarks have from interacting with the electric fields ...
- 07:29: Doesn't that have to be thought of as mass being converted into energy?
- 07:34: There's a way to conceptualize even this process as simple conversions of one kind of energy to another-- kinetic, potential, light, and so forth.
- 07:40: You never need mass to energy alchemy.
- 07:43: But please take my word for it, you don't actually have to talk about converting mass to energy ever.
- 07:54: It's a property, a property that all energy exhibits.
- 07:58: ... in the material sense, you can think of it as an indicator of amount of energy. ...
- 08:06: So without realizing it, you've really been measuring the cumulative energy content of objects every time you've ever used a scale.
- 08:35: ... second configuration has more gravitational potential energy than the first because the second block is higher up, so it will have ...
2015-04-29: What's the Most Realistic Artificial Gravity in Sci-Fi?
- 01:16: And no, for technical reason, I don't think dark energy would be a solution to this problem.
2015-04-08: Could You Fart Your Way to the Moon?
- 01:21: ... the rocket's propellant oxidizes, chemical bond energy is released, raising its temperature and causing it to expand until it ...
2015-04-01: Is the Moon in Majora’s Mask a Black Hole?
- 09:17: Finally, Paul Ansel emailed me a calculation working out how much energy it would take to break Earth apart atom by atom.
2015-03-18: Can A Starfox Barrel Roll Work In Space?
- 06:04: In fact, automotive engineers are trying to make flywheels the braking mechanism in cars to avoid losing energy to friction every time you saw.
- 09:05: But even if Ceres is an asteroid, it's only about three and a half times as massive as 4 Vesta, still not enough energy to destroy the Earth.
- 09:13: ... wanted to know how much energy it would take, not just to overcome the gravitational attraction between ...
- 09:25: ... just need to know how much energy there is in interatomic bonds, per atom on Earth, and multiply that by ...
2015-03-11: What Will Destroy Planet Earth?
- 00:09: ... including planets, is pretty straightforward-- just add enough energy to the individual chunks to overcome the attractive forces gluing them ...
- 00:30: So separating the chunks takes an obscene amount of energy.
- 00:34: About as much solar energy as a whole Earth receives over 40 million years.
- 00:45: So realistically, could anything deliver that much energy to Earth and end the planet as we know it?
- 01:07: ... was enough energy to level everything for more than 20 miles in every direction in ...
- 01:46: Sorry, kids, also not enough energy.
- 01:49: ... Tsar-Bomb detonations, which is huge but still only one billionth of the energy needed to blow up a ...
- 01:58: Even 4-Vesta, the biggest object that's still classified as an asteroid, would only care about half a percent of the required energy.
- 02:27: Now with those speeds, an object could only carry enough energy to destroy Earth if it had a huge mass, which asteroids don't.
- 03:26: In one simulation, about four billion years from now, Earth and Mars actually collide with enough energy to do serious structural damage.
- 05:04: ... material permeating the cosmos that physicists have dubbed "dark energy". ...
- 05:29: ... measured, among other things, a few properties of this mysterious dark energy that can be used to do some space expansion ...
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