
20221214: How Can Matter Be BOTH Liquid AND Gas?
 01:52: At these melting and boiling boundaries the material is momentarily a mix of both states.
 08:01: But we’re approaching our strange new region of the phase diagram, where the rules are going to change Let's talk about density for a moment.


20221208: How Are Quasiparticles Different From Particles?
 11:26: ... electrons that were attracted by this momentary convergence of positive charge are jostled so much that this effect is ...


20221026: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
 02:36: ... to molecular scale, and the entangled property could be spin, momentum, or any other quantum ...
 04:54: ... relationship if those properties really are decided at the moment of ...
 06:51: Spin is the quantum version of angular momentum.
 06:54: ... spin hadn’t changed in this transition, in order to conserve angular momentum the pair of photons needed to have a total spin of zero, which ...
 07:18: Hidden variable theories, on the other hand, allow the polarization to be set at the moment the photons are created.
 08:27: So what if that orientation has some influence on the polarization direction of the photons at the moment of their creation?
 10:10: ... that the photons can’t know how they’re going to be measured at the moment of their creation, which if you recall was the potential loophole in ...


20221019: The Equation That Explains (Nearly) Everything!
 04:05: ... will reveal the existence of a conserved quantity like energy or momentum. And this is Noether's Theorem, and we also have an episode about ...
 06:02: ... particles with integer spin are called bosons. They transmit energy and momentum according to the symmetries of each force. Some parts of the standard ...


20221012: The REAL Possibility of Mapping Alien Planets!
 06:05: ... Just as regular sails accelerate a ship by catching the momentum of the wind, solar sails catch the momentum of light  of photons ...


20220928: Why Is 1/137 One of the Greatest Unsolved Problems In Physics?
 05:34: Those probabilities depend on many things, like the particles’ positions and momenta, spins, charges, masses, etc.


20220914: Could the Higgs Boson Lead Us to Dark Matter?
 08:39: In this case, it’s by using a 350 year old law of physics known as conservation of momentum.
 08:48: ... of momentum tells us that the product of velocity times mass of all particles going ...
 09:00: ... know pretty well the momentum of the particles going into our collision, and we can measure and add up ...
 09:11: If total momentum seems to have decreased, this implies something invisible has sneaked that missing momentum past the detectors.
 09:19: ... if we just looked at the total momentum, there’d be a lot of uncertainty due to the fact that there’s variation ...
 09:28: ... another part to this trick that makes it very precise. We can do our momentum audit in a way that ensures that ingoing momentum is known completely ...
 09:42: Total moment in a collision is conserved, but also the momentum in each separate direction is conserved independently of the other directions.
 09:51: ... momentum perpendicular to the direction of the particle beams is called the ...
 10:01: ... forwards, back or sideways. But any of that sideways or transverse momentum has to add up to ...
 10:30: ... of momentum tells us that there should be more stuff firing out in the opposite ...
 10:56: And that lepton will be detected, meaning we can account for the momentum lost to neutrinos.
 11:33: ... the same direction as the beam, making the calculation of the transverse momentum very ...
 11:44: Physicists at the Large Hadron Collider’s ATLAS experiment have been adding up the outgoing transverse momenta for many, many events like this.


20220803: What Happens Inside a Proton?
 16:44: ... that means the actual direction gets randomly chosen at the moment of measurement. Now if the spin direction could only be ...


20220720: What If We Live in a Superdeterministic Universe?
 09:28: But that’s only weird if Alice’s choices themselves are independent events defined wholly in the present moment.
 13:38: Let’s stay neutral for the moment and look at what we know.


20220630: Could We Decode Alien Physics?
 07:38: ... everywhere in physics, for example in calculating torque, angular momentum, and through Maxwell’s equations. The right hand rule is another ...
 16:39: ... problem is worse than that actually. Without an external source of momentum exchange like with a light sail, you need to to carry your entire ...


20220601: What If Physics IS NOT Describing Reality?
 04:56: ... question with a Stern Gerlach apparatus, where the magnetic moment of the particles interact with a magnetic field gradient to ...
 08:49: ... of the measurement error in a particle’s position and momentum has to be greater than the Planck constant divided by ...


20220525: The Evolution of the Modern Milky Way Galaxy
 01:09: ... we see galactic cannibalism everywhere. We see moments that appear frozen on the human timescale, but are really ...


20220518: What If the Galactic Habitable Zone LIMITS Intelligent Life?
 02:06: ... average in terms of mass, age, even location. But consider for a moment the ancient human’s perspective, without the help or hindrance of ...


20220420: Does the Universe Create Itself?
 13:29: ... survey. We love hearing your ideas and thoughts and if you have a moment, there’s a link in the ...


20220323: Where Is The Center of The Universe?
 17:22: ... observers reference frame, given that it’s defined in reference to the momentum vector of the ...
 17:49: The answer is that chirality isn’t as simple as a projection of spin onto the momentum vector.


20220316: What If Charge is NOT Fundamental?
 02:23: For example electrons have this thing called spin  a quantum analogy to angular momentum.
 09:52: ... have righthanded chirality if their spin is clockwise relative to their momentum vector and lefthanded chirality if it's ...


20220223: Are Cosmic Strings Cracks in the Universe?
 04:51: ... found itself sitting at a higher energy than it needed. It was momentarily stable at that point, just like a ball sitting at the top of ...


20220216: Is The Wave Function The Building Block of Reality?
 13:19: ... or subjective fiction? Did I measure position precisely or was it momentum? Who put my cat in that funny box, and why isn’t he purring any more? But ...
 17:42: ... an object being frozen at the event horizon if the light emitted at the moment it crosses the horizon from its perspective takes infinite time to reach ...


20220210: The Nature of Space and Time AMA
 00:03: ... of space as some kind of definite now or universal simultaneous moment the relativity of simultaneity showed us i guess that my perception ...


20220127: How Does Gravity Escape A Black Hole?
 02:28: Imagine for a moment that the Sun just disappeared.


20220119: How To Build The Universe in a Computer
 10:14: And then we have cosmological simulations which create entire virtual universes, from the moment the first atoms formed to the modern day.


20220112: How To Simulate The Universe With DFT
 15:23: The the fastmoving black hole slowsdown inside the Earth because exchanges momentum with or eats stationary material on its way through.


20211210: 2021 End of Year AMA!
 00:02: ... actually be attracted given that the photon is expected to exchange momentum with the proton and that photon is moving in a particular direction ...


20211117: Are Black Holes Actually Fuzzballs?
 01:14: ... from outside a black hole are its mass, electric charge, and angular momentum. ...
 02:27: But these few numbers emerge from the motion of every air molecule — and to describe that we’d need the positions and momenta of 10^27ish particles.


20211110: What If Our Understanding of Gravity Is Wrong?
 06:06: It doesn’t respect conservation of energy or momentum or angular momentum.
 07:55: In 1984 he diverted his attention for a moment to work with Mordehai Milgrom in fixing MOND.


20211102: Is ACTION The Most Fundamental Property in Physics?
 01:22: ... were some efforts  for example Euler considered properties involving momentum and kinetic energy  but to no avail. In the meantime Isaac Newton came ...
 07:09: ... Action simplifies into just the integral over proper time. Let's take a moment to think about that. Before Action was a somewhat vague notion of change ...
 12:16: ... space could mean phase space  the space of possible positions and momenta  or it could be more general state space, representing all the quantum ...
 12:59: ... states underpins modern quantum theory. Back to Paul Dirac just for a moment. His eponymous equation was derived to describe the quantum evolution of ...


20210818: How Vacuum Decay Would Destroy The Universe
 12:07: ... outpace the expanding bubble to warn us of its approach. One moment you might be watching your favorite YouTube show, the ...


20210810: How to Communicate Across the Quantum Multiverse
 07:14: ... wavefunction. The normal linear observables are things like position, momentum, spin  the physical stuff that makes up our world. Extra observables ...
 14:02: ...  first is that a white dwarf could potentially gain a lot of angular momentum or spin by absorbing material from another star, hence perhaps ...


20210803: How An Extreme New Star Could Change All Cosmology
 02:13: ... under its own gravitational crush due to conservation of angular momentum. But typical white dwarfs take from a few hours to a few days to rotate. ...
 09:18: ... neutron stars when LIGO detected the gravitational waves from the last moment of those inspirals. But it should happen with white dwarfs ...
 09:51: ... be spinning really really fast because it doesn’t just have the angular momentum from its spinning parent stars  it has the angular momentum from the ...


20210721: How Magnetism Shapes The Universe
 09:53: Magnetic fields generated by collapsing gas clouds help to slow the rotation of those clouds  expel angular momentum.


20210713: Where Are The Worlds In Many Worlds?
 04:23: ... particle position and momentum and orientation is chosen from a vast array of possibilities, a ...


20210707: Electrons DO NOT Spin
 00:22: ... on the chair. It’s a demonstration of the conservation of angular momentum. The angular momentum of the wheel is changed in one direction, so ...
 00:47: ... speed. At first glance this appears to violate conservation of angular momentum because there was nothing spinning to start with. Except there was ...
 01:26: ... And yet they do seem to possess a very strange type of angular momentum that somehow exists without classical rotation. In fact the spin of an ...
 02:25: ... moving in circles around the atom, that motion leads to a magnetic moment  a dipole magnetic field like a tiny bar magnet. The different ...
 03:20: ... sort of works is to say that each electron has its own magnetic moment  by itself it acts like a tiny bar magnet. So you have the alignment of ...
 03:48: ... huge problems. For example, in order to produce the observed magnetic moment they’d need to be spinning faster than the speed of light. This ...
 04:40: ... aren’t spinning, but somehow they act like they have angular momentum. And this is how we think about quantum spin now. It’s an intrinsic ...
 05:31: A lone electron in the outer shell of the silver atoms grants the atom a magnetic moment.
 05:37: ... on the atoms that depends on the direction that these little magnetic moments are pointing relative to that field. Those that are perfectly ...
 07:02: ... not only do electrons have this magnetic moment without rotation, but the direction of the underlying magnetic ...
 10:22: To get some insight into what spin really is, think not about angular momentum, but regular or linear momentum.
 10:30: A particle's momentum is fundamentally connected to its position.
 10:33: ... in coordinate location gives us the law of the conservation of momentum. For related reasons in quantum mechanics position and momentum are ...
 10:58: If position is the companion variable of momentum, what's the companion of angular momentum?
 11:09: ... one way to think about the angular momentum of an electron is not from classical rotation, but rather ...
 11:21: They have undefined orientation, but perfectly defined angular momentum.
 11:34: ... that you can derive the right values of the electron spin angular momentum and magnetic moment by looking at the energy and charge currents ...
 11:44: ... imply that even if the electron is point like, it's angular momentum can arise from an extended though still tiny ...
 12:13: ... intrinsic angular momenta can only be observed as plus or minus a half times the reduced Planck ...
 15:31: ... we can’t really talk about the t=0 beginning of time, because that moment lost in our ignorance about quantum gravity and inflation and ...


20210623: How Quantum Entanglement Creates Entropy
 16:39: ... preferred angle. That’s the basis for the conservation of angular momentum, which we know is obeyed. Another issue with the simple ...
 17:55: ... to measure position, I said that the uncertainty in the final momentum of the particle is roughly equal to the momentum of the ...


20210616: Can Space Be Infinitely Divided?
 03:47: ... now you have a new problem. Light carries energy and momentum  and the shorter the wavelength, the more it carries. If ...
 04:30: ... photon’s momentum is the Planck constant divided by its wavelength. So ...
 04:49: ... It also applies to other pairs of variables besides position and momentum. ...
 05:08: ... as long as we’re happy to have infinite uncertainty in momentum. But it turns out that the Planck constant defines a new source of ...
 06:02: ... distance with perfect precision, and who cares about momentum. We keep decreasing the wavelength of our measuring photon  ...
 08:37: ... that when we do that we increase the uncertainty in momentum of that bundle of electronness. That also means increasing the ...


20210609: Are We Running Out of Space Above Earth?
 02:23: Space is, as the name implies, spacious, and so collisions are relatively rare, or at least for the moment they're rare.


20210525: What If (Tiny) Black Holes Are Everywhere?
 14:16: Those photons are entangled with each other because various properties are correlated  in particular phase, polarization, and momentum.


20210519: Breaking The Heisenberg Uncertainty Principle
 01:31: Perfect knowledge of a particle’s position means its momentum is undefined.
 02:37: ... reasoned that the photon would give the particle a momentum kick, which would account for a greater uncertainty in its momentum ...
 02:47: ... kick the object even harder, causing an even greater uncertainty in the momentum. ...
 04:30: ... to extreme precision as long as we’re happy to have no knowledge of its momentum. ...
 06:56: In this case, the complementary variables in question are not position and momentum, but rather phase and amplitude.


20210421: The NEW Warp Drive Possibilities
 16:45: Momentum, which incorporates velocity, is as fundamental as position.


20210407: Why the Muon g2 Results Are So Exciting!
 01:18: And that's the anomalous magnetic dipole moment of the muon.
 01:35: What's an anomalous magnetic dipole moment?
 01:41: We've actually talked at about the anomalous magnetic dipole moment before in terms of the electron.
 03:37: The strength of that rotational pool or the talk, is defined by the objects dipole moment.
 03:43: For a rotating charge, that depends on the objects rate of rotation, or angular momentum, it's charge and it's mass.
 03:50: Here's the equation for the classical dipole moment for a nonquantum rotating charge.
 04:00: An electron also has a dipole field and a dipole moment which depends on the electron spin charge and mass.
 04:07: But the electron dipole moment is different from the classical one by this factor g.
 04:56: All those virtual photons could do something weird like momentarily becoming an electronpositron pair.
 06:34: By the way, the anomalous in the anomalous magnetic dipole moment, refers to that little bit extra after the two.


20210210: How Does Gravity Warp the Flow of Time?
 07:42: ... perception of what is “simultaneous” to current moment flips at the turnaround point, so that she misses a bunch of the ticks ...


20201208: Why Do You Remember The Past But Not The Future?
 07:56: Just rewind the clock to the moment before the asteroid’s very last interaction with the outside universe.


20201104: Electroweak Theory and the Origin of the Fundamental Forces
 04:50: ... outcomes being measured for observables like particle position and momentum. ...


20201027: How The Penrose Singularity Theorem Predicts The End of Space Time
 13:38: ... So we can look for those extra things  the moment of wavefunction collapse, the guiding function or the empty ...


20201020: Is The Future Predetermined By Quantum Mechanics?
 03:41: Now exploring those interpretations again, may help us understand the state of the universe beyond our immediate selves and the immediate moment.
 04:23: ... way, perfectly defined by the equations of quantum mechanics but at the moment of measurement, a single reality is randomly selected from the ...
 14:59: ... then it would need to be the instantaneous state of the brain, the momentary spatial configuration of its particles at that instant that gives rise ...


20200824: Can Future Colliders Break the Standard Model?
 07:03: And there are other anomalies like the muon’s magnetic moment.


20200810: Theory of Everything Controversies: Livestream
 00:00: ... weinberg afterwards pulled me aside and in very appropriate for that moment um tone he said can i give you some advice and i said sure and he ...


20200728: What is a Theory of Everything: Livestream
 00:00: ... will get into our lives uh our teaching tends to take us away uh at a moment's notice but she will be joining us next week and we'll have more ...


20200708: Does Antimatter Explain Why There's Something Rather Than Nothing?
 08:50: ... antihydrogen is electrically neutral, it does have a small magnetic moment  like a tiny bar magnet. ALPHA introduces a new magnetic field that ...
 09:19: ... the precise mass and charge of the particles, their orbital angular momentum, their magnetic and electric dipole moments, and even the strength of the ...


20200630: Dissolving an Event Horizon
 04:57: In both cases, the amount of angular momentum or charge you can fit into a black hole before it becomes extremal depends on the mass.
 06:06: This can’t happen with rotating black holes because they leak away their angular momentum as well as their mass.
 07:11: Rotating black holes gain their angular momentum from things they swallow.
 07:20: It’s that orbital angular momentum that is fed to the black hole.
 07:24: But in order for an object orbiting a black hole to fall into it, it actually has to lose at least some of that angular momentum.
 07:31: ... hole like in a quasar, then the gas only spirals inwards because angular momentum is carried outwards by ...
 07:42: By the time the gas reaches the black hole it has lost much of the angular momentum it started with.
 07:49: The faster a black hole is rotating, the more angular momentum that gas has to lose in order to fall in.
 07:55: ... of boost so it can still orbit even with very little of its own angular momentum. ...
 08:06: ... riding on the carousel of framedragged state, and has no angular momentum of its ...
 08:30: More generally, there is no trajectory into an extremal black hole that can add angular momentum from the trajectory or the “orbit” itself.
 08:43: An alternative is to throw in something that’s actually spinning itself  so it has intrinsic angular momentum.


20200622: Building Black Holes in a Lab
 07:24: ... vortex black hole analog. In fact, both the analog of energy and angular momentum seems to be sapped by this Hawkinglike ...


20200615: What Happens After the Universe Ends?
 14:35: Before we get to comments, I just want to take a moment to thank everyone who supports us on Patreon.


20200518: Mapping the Multiverse
 10:18: You caught a glimpse of the entire history of that universe the moment you crossed into the white hole.


20200504: How We Know The Universe is Ancient
 00:55: ... the birthday of the universe. Actually, you know what? Forget for a moment knowing the age of the universe  our knowledge that the universe even ...
 09:39: ... its age as between 7 and 13 billion years old. Now there were some moments of confusion. For a while we thought we’d found globular clusters  ...


20200428: Space Time Livestream: Ask Matt Anything
 00:00: ... they grow in mass when they swallow things they conserve angular momentum and charge because they acquire those properties when they swallow ...


20200422: Will Wormholes Allow Fast Interstellar Travel?
 03:45: ... keep time frozen for the moment and add back the 3rd spatial dimension. The ring of the wormhole is ...


20200407: How We Know The Earth Is Ancient
 03:43: ... of years and centuries, etc. etc. ... Creation is not the work of a moment.” By the way, Kant was also the first to have speculated about the ...


20200331: What’s On The Other Side Of A Black Hole?
 01:53: ... try to trace a path across the horizon in terms of their own clock, the moment of crossing never happens. It’s like Achilles chasing the tortoise in ...


20200324: How Black Holes Spin Space Time
 01:44: ... be rotating. The spin of a black hole comes from the combined angular momentum of everything that went into forming it. That includes the rotation of ...
 02:26: ... black holes might not have MUCH spin  because angular momentum can cancel out if objects fall in with different spins or in different ...


20200316: How Do Quantum States Manifest In The Classical World?
 00:57: ... for example a particle’s position can be expressed as a superposition of momentum states. I’ll come back to another example of this in a second. But this ...
 04:28: ... to be in opposite directions in order to cancel out and conserve angular momentum. But besides being opposite to each other they can be aligned in any ...


20200303: Does Quantum Immortality Save Schrödinger's Cat?
 00:39: ... at the same time, to having only one clear observable state at the moment of ...
 01:29: ... the wavefunction branches that we don’t observe somehow vanish at the moment of ...


20200218: Does Consciousness Influence Quantum Mechanics?
 05:53: John von Neumann believed that wavefunction collapse must happen at the moment of conscious awareness of the result of an experiment.
 06:55: So we have this weird moment  somewhere between the landing of that electron on the screen and your friend telling you the result.


20200127: 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 assumption of a ...
 07:56: Two go in, and two go out  the out particles could be the different to the in particles, or they could be the same just with different momenta.
 14:29: ... some places it gives up angular momentum  it's orbital energy  to the gas, causing it to migrate inwards, while ...
 14:41: And between these inward and outward migration regions are places where no angular momentum is exchanged. And, well, the black hole is trapped.


20200120: Solving the Three Body Problem
 10:30: ... consistent with some basic properties like the energy and angular momentum of the system. The system explores what we call a phase space  a space ...


20200113: How To Capture Black Holes
 04:50: ... dragged out of the disk, tugged by the black hole’s gravitational field. Momentum is transferred from black hole to gas, slowing the black hole down a bit ...
 06:15: ... of the disk, that can cause the object to either gain or lose angular momentum. If it gains angular momentum the size of its orbit increases, so it ...


20191209: The Doomsday Argument
 11:05: ... you could be a momentary entropy fluctuation that caused a brain with exactly your current mental ...
 13:11: ... you access to our new Space Time discord channel, where at this very moment brilliant and curious individuals are discussing the future of humanity, ...


20191118: Can You Observe a Typical Universe?
 00:00: The moment you started observing reality, you hopelessly polluted any conclusions you might make about it.
 12:13: ... world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by ...


20191015: Loop Quantum Gravity Explained
 03:33: ... classical physics, we have variables like position, time, momentum, energy  mathematical expressions that represent the observable ...
 04:06: In the first formulations of quantum mechanics, that wavefunction describes the distribution of possible positions and momenta of, say, a particle.
 04:16: These can then be resolved into concrete, measured values by acting on the wavefunction with socalled position and momentum operators.
 04:30: ... all, the position and momentum of quantum mechanics literally describes location on a spatial ...
 05:19: ... you calculate changing properties of a particle  like its position or momentum  relative to the background coordinate ...
 05:35: So maybe instead of thinking about the quantum fuzziness of position and momentum we can think about the quantum fuzziness of the metric itself.
 06:37: You can also imagine analogies of the position and momentum in this space of metrics.
 08:20: ... a spinor  a vectorlike thing that also represents a quantum of angular momentum  or ...


20191007: Black Hole Harmonics
 09:05: .69 means this is a rapidly rotating black hole, which is unsurprising seeing as it just absorbed the orbital angular momentum of two black holes.


20190930: How Many Universes Are There?
 09:44: So, the first intelligence appears in our universe after exactly 10 billion years – we’ll call that moment “second one”.
 10:45: ... result is that at any one moment, almost all of the intelligent beings in the eternally inflating ...


20190718: Did Time Start at the Big Bang?
 03:27: ... scale factor That's the distance between any two points in space at some moment in time Relative to their distance at some other reference moments that ...
 11:36: ... of our ideas Just push back the uncomfortable something from nothing moments physicists have a thing or two to say about that from quantum ...


20190701: Thorium and the Future of Nuclear Energy
 02:49: ... nuclei in H2O are around the same mass as neutrons they absorb a lot of momentum in Neutron collisions and Conveniently that same water can also work as ...


20190606: The Alchemy of Neutron Star Collisions
 02:47: ... daughter products exactly reflect the abundances of the parents of the moment the meteorite material was formed now this study focused on curium 247 ...


20190516: The Cosmic Dark Ages
 01:34: ... transparent for the first time, and we see the light freed at that moment as the cosmic microwave background. THAT is the oldest light that we see ...
 06:39: ... the epoch of reionization. But before we get to that, I want to take a moment to talk about quasars. It’s relevant, trust ...
 12:16: ... the meantime, let’s take a moment to be grateful for our own lightfilled stelliferous era; Probably the ...


20190509: Why Quantum Computing Requires Quantum Cryptography
 04:38: ... of certain pairs of properties – for example, a particle’s position and momentum. ...


20190424: No Dark Matter = Proof of Dark Matter?
 00:03: ... have happened but they emphasize that these are just guesses for the moment perhaps these UD G's form from gas and stars ejected in a past collision ...


20190410: The Holographic Universe Explained
 04:26: Let’s ignore string theory for the moment and just think about how to create an extra dimension.


20190403: The Edge of an Infinite Universe
 05:49: ... horizontalish contours are our old time ticks  moments of constant time across the universe, while the verticalish lines are ...


20190328: Could the Universe End by Tearing Apart Every Atom?
 10:03: ... Earth's own gravitational binding energy and the planet is disrupted. Moments later at the 10^19 of a second, before absolute disruption, it will ...


20190320: 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.


20190306: The Impossibility of Perpetual Motion Machines
 02:12: ... at the same time increases the separation between those masses, so that moment of inertia is ...
 14:25: Abe Dillon asks whether the "moment" of recombination should depend on the local density.
 15:07: ... in galaxy rings were blurred out quite a bit because the universe took a moment to become fully ...


20190220: Secrets of the Cosmic Microwave Background
 02:05: ... when light decoupled from matter at the formation of the first atoms the moment of Recombination As the universe evolved those frozen shells collapsed ...


20190130: Perpetual Motion From Negative Mass?
 05:40: It MIGHT be, but more likely you’re having a crackpot moment.
 06:36: ... presence of active gravitational mass, and of energy, momentum, pressure, and more, change the geometry of spacetime and that new ...
 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 ...


20190124: The Crisis in Cosmology
 08:38: The state of the oscillations at the moment of that release...
 08:59: ...at the moment the CMB was released.
 15:31: ...both linear and angular momentum.


20190116: Our Antimatter, Mirrored, TimeReversed Universe
 01:48: ... of cobalt60 atoms in a magnetic field, the cobalt nuclei have angular momenta that will align with a magnetic field let's say upwards so the decay ...
 03:02: ... in the opposite direction to regular matter relative to their angular momentum the magnetic field in our clock will align antimatter nuclei in the ...
 10:54: ... you're not converting matter to antimatter  you're just reversing all momentum and spin. Essentially you're taking all particles in the universe and ...


20190109: Are Dark Matter And Dark Energy The Same?
 04:06: Forgetting that pressure stuff for a moment, positive masses and energies always have a positive gravitational effect.
 06:05: That’s a bizarre situation, but as I’ll explain in a moment it’ll give us our dark matter replacement.


20181220: Why String Theory is Wrong
 04:07: Momentum in that loop dimension has the exact behavior of electric charge, with the direction of rotation determining the sign of the charge.
 08:55: ... times radius, or mode number divided by radius can be used to define the momentum of a particle produced by this ...
 09:07: ... you can construct a theory in which momentum increases with the size of the compact dimension, or where momentum ...


20181212: Quantum Physics in a Mirror Universe
 00:02: ... vectors point in the opposite direction same with the velocity / momentum through our board the mirror away from yourself and its reflection looks ...


20181206: Did Life on Earth Come from Space?
 00:37: ... fossils are now dated to only a few hundred million years after the moment earth first became habitable is it really reasonable to imagine that ...


20181107: Why String Theory is Right
 03:07: ... and bolts of how string theory predicts gravity, it's worth taking a moment to see how stringy gravity avoids the problem of black ...


20181031: Are Virtual Particles A New Layer of Reality?
 03:25: ... interacts once with the EM field, transferring between them energy momentum and one photon worth of quantum properties in a single packet that we ...
 05:18: ... they don't need to obey Einstein's relationship between energy mass and momentum. ...
 06:39: Their momenta are pointing from positron to electron rather than electron to positron.
 07:20: In a way, a virtual particle represents a pure excitation of the field, an idealized case of perfectly defined momentum.
 07:29: The Heisenberg uncertainty principle tells us that the perfectly defined momenta of virtual particles means completely undefined position.
 07:39: In contrast, real particles are mixed up combinations of many excitations, many different momentum modes.
 07:46: And that uncertain momentum gives them real locations, real trajectories through space.
 07:57: It can move between our electron and positron even if its momentum is pointing in the wrong direction.


20181018: What are the Strings in String Theory?
 02:09: ... pairs of mesons, as well as an odd relationship between their angular momenta and masses suggested that the quarks in mesons are connected by you ...


20181003: How to Detect Extra Dimensions
 15:18: I just told you that a moment ago.


20180920: Quantum Gravity and the Hardest Problem in Physics
 06:28: Steady viewers will remember that the uncertainty principle talks about the tradeoff between position and momentum.
 06:34: But large momentum also means large energy.
 07:01: ... its position wave function needs to be constructed from a wide range of momentum wave functions that include extremely high frequencies or extremely high ...
 07:18: And so large momenta are possible.
 07:24: And then momentum becomes extremely uncertain and includes the possibility of ridiculously high values.
 14:25: As they lose spin, angular momentum, they become more spherical.


20180912: How Much Information is in the Universe?
 04:21: ... space, which includes position, but also other degrees of freedom, like momentum, spin direction, et ...
 09:05: ... the moment the universe reaches information limit, it would immediately become a ...


20180905: The Black Hole Entropy Enigma
 06:09: So you know how nothing can escape black holes, ignoring Hawking radiation for the moment.


20180823: How Will the Universe End?
 02:05: And what will happen to the universe as it approaches that moment?
 13:46: OK, onto your comments for last week's episode on the most accurate prediction in all of science, the anomalous magnetic moment of the electron.
 14:56: It's not that the moment should be 1.
 15:43: All they have is their quantum wave function, which tells the probability of the particle's location, momentum, spin, direction, et cetera.


20180815: Quantum Theory's Most Incredible Prediction
 01:53: ... G factor, or in simple English, measuring the anomalous magnetic dipole moment of the ...
 02:10: What is the anomalous magnetic dipole moment?
 02:14: Well, it's just like the regular magnetic dipole moment but more anomalous.
 02:21: Let's break down these magnetic dipole moment thing.
 02:42: The tendency of a dipole magnet to rotate in an external magnetic field is its magnetic dipole moment.
 02:50: ... with a dipole magnetic field has a magnetic dipole moment is basically a measure of how much it would interact with an external ...
 03:32: As we'll see, their nature is predicted by quantum theory, measure electromagnetic moments, and you verify your quantum picture of reality.
 04:02: Nonetheless, electrons do have a sort of intrinsic, angular momentum, a fundamental quantum spin that is as intrinsic as mass and charge.
 04:20: So electrons have a magnetic dipole moment, meaning they feel magnetic fields and act as little bar magnets.
 04:57: It also gives you completely the wrong answer if you try to calculate the electron's magnetic moment.
 05:09: ... fact, weirdly, if you measure the magnetic dipole moment of an electron, you get almost exactly twice the value you'd expect for ...
 05:23: This difference between the quantum versus classical magnetic moments for the electron is called the G factor.
 07:02: And this is the anomalous magnetic dipole moment.
 09:04: ... with the magnetic field when we calculate the electrons magnetic dipole moment and it's G ...
 11:41: So it's really the relationship between the electron magnetic moment and the fine structure constant that we're verifying.


20180718: The Misunderstood Nature of Entropy
 06:32: ... an analogy for all possible combinations of all properties position, momentum, spin, vibration, really any degree of freedom that the system can ...


20180711: 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.
 02:49: The best we can do is make a measurement of physical observables, like position or momentum.
 06:08: Among other things, messing with local phase really screws up our prediction for the particle's momentum.
 06:15: See, momentum is related to the average steepness of the wave function.
 06:19: Change the shape of that wave function with local phase shifts and you actually break conservation of momentum.
 06:45: To do that, we need to alter the part of the Schrodinger equation that gives us the momentum of a particle, the momentum operator.
 06:54: After all, momentum is what got screwed up.
 06:57: ... turns out that we can add a mathematical term to the momentum operator that's specially designed to undo any mess we make to the phase ...


20180620: The Black Hole Information Paradox
 01:54: It states that black holes can only exhibit three properties mass, electric charge, and angular momentum.
 08:11: ... pairs of quantumobservable complimentary observables, like position and momentum, that can't both be perfectly measured at the same ...


20180613: What Survives Inside A Black Hole?
 01:09: ... properties are mass, electric charge, and angular momentum, or at least this is the proposition behind the famous nohair conjecture ...
 01:45: ... that no other properties besides mass, electric charge, and angular momentum should emerge from beneath the event ...
 02:28: ... the black hole are its massenergy content, electric charge, and angular momentum. ...
 03:06: So how does mass, electric charge, and angular momentum communicate their influence across the uncrossable horizon?
 08:30: But what about the magnetic part of electromagnetism, and what about angular momentum?
 09:19: ... material with angular momentum falls into a black hole, whether it's a spinning star or a whirlpool of ...
 09:30: Its angular momentum is remembered in the frame dragging as though the entire black hole was spinning.
 09:36: I hope I've given you a sense of why mass, charge, and angular momentum are remembered by the space outside a black hole.
 13:18: Exactly what happens at the moment of observation is still debated.


20180516: Noether's Theorem and The Symmetries of Reality
 03:24: That quantity is momentum.
 03:26: If two cars collide on that road, the sum of their combined momentum stays the same.
 03:34: Momentum doesn't appear to be conserved.
 04:07: ... then, Noether's theorem predicts another conserved quantity, angular momentum. ...
 09:27: ... be thankful that she took a moment to offer a little of her genius to physics, taking us a big step closer ...


20180425: Black Hole Swarms
 03:07: The black hole can also slingshot stars outwards, losing momentum in that process, too.
 03:12: The key is that the more massive object usually, the black hole tends to donate its momentum to the less massive object.
 09:40: Gravitational waves are produced when the quadrupole moment of a mass distribution changes.


20180411: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)
 10:28: ... I guess that makes you a little eddy of order, a momentary fluctuation of interesting but ultimately, in service of the spread of ...


20180404: The Unruh Effect
 05:46: Even momentary acceleration generates a Rindler horizon.


20180328: The AndromedaMilky Way Collision
 06:16: Meanwhile, the black holes lose angular momentum and fall towards the center.


20180321: Scientists Have Detected the First Stars
 04:56: We know exactly it's temperature at the moment of the creation of the CMB so there's a limit to how much it could have cooled since then.
 06:55: At both of these points, the weight is momentarily still.
 07:15: ... don't know anything about the kinetical potential energies at the moment of release, but we do know that the final potential energies of the ...


20180315: Hawking Radiation
 10:32: ... example, uncertainty in position or momentum can lead to particle pairs that we'll want in the same location or modes ...


20180307: Should Space be Privatized?
 04:06: That's where the profit is for the moment.


20180228: The Trebuchet Challenge
 07:26: My question how fast is the stone traveling at the moment of impact?


20180221: The Death of the Sun
 00:21: In just a moment, our star will fuse the last of the hydrogen in its core, triggering a cataclysmic sequence of events.


20180214: What is Energy?
 01:43: Besides the whole coinventing calculus thing, Leibniz's vis viva seen as a competition to Newton's idea of conservation of momentum.
 02:01: Besides, this vis viva thing wasn't conserved in the event of friction, while momentum was.
 02:20: When she introduced the idea of gravitational potential energy, she put the laws of conservation of energy and momentum on equal footing.
 10:06: For example, the law of conservation of momentum is due to spatial translation symmetry.
 10:36: Our universe looks fundamentally different from one moment to the next, at least on cosmic scales, where it's expansion becomes significant.


20180131: Kronos: Devourer Of Worlds
 09:05: It tugs on the Earth gravitationally, increasing our angular momentum.
 09:10: The asteroid loses angular momentum in the process, but it regains it as it flies by Jupiter.
 09:15: Essentially, we steal angular momentum from Jupiter via the asteroid, which increases our orbit.


20180117: Horizon Radiation
 05:35: Quantum wave functions and quantum fields can be described in terms of variation with position or variations with momentum.
 05:44: So instead of writing the field as having a value at every possible position in space, we can write it as having a value for every possible momentum.
 05:56: So let's take our spatial quantum field our drum skin, with its single, localized particle, and transform to momentum space.
 06:04: That momentum field also has infinite oscillators, but now each one represents a different possible momentum for the particle.
 06:13: ... in momentum space, that single, perfectly localized position oscillation can also be ...
 06:24: Now, each one of these momentum modes exists at all spatial points in the universe.
 06:31: ... we add these momentum oscillations together with the right weightings, they cancel out ...
 06:40: The superposition of infinite universe size momentum oscillators momentum particles can represent a single spatial oscillator.
 07:37: But why exchange a single spatial equation for infinite equations in momentum space?
 07:48: Those momentum oscillations have two important qualities.
 08:00: The field at each momentum spot oscillates independently from its neighboring momenta.
 08:05: Dealing with uncoupled equations allows you to add and subtract oscillations without affecting the neighboring momenta.
 08:12: However, changing the momentum modes does affect the superposition the sum of all oscillations, for example, by creating or destroying particles.
 08:22: OK, so a single particle can be described as many oscillations in momentum space.
 08:51: ... at a time, by changing the number of particles or oscillations in each momentum ...
 09:29: In momentum space, we can think of it as a superposition of infinitely many momentum modes.
 09:35: Infinite spatially undefined particles with defined momenta, and these just happen to cancel each other out, leaving 0 particles or a vacuum.
 10:18: If we introduce an event horizon, then we lose access to some momentum modes, while other modes behave very differently.
 10:51: Now when you use the new, rejigged field operator to describe the vacuum, some momentum modes that once canceled out no longer cancel out.


20171213: The Origin of 'Oumuamua, Our First Interstellar Visitor
 09:50: [INAUDIBLE] Leonard asks whether a particle can have momentum higher than its mass times the speed of light.
 09:56: In other words, shouldn't there be an upper limit to momentum if the speed of light is limited?
 10:00: Well actually, momentum can be arbitrarily high, even when speed is limited to the speed of light.
 10:05: The equation for momentum, P = M times V, only works at low speeds approaching the speed of light.
 10:22: That means momentum approaches infinity for any object with mass that's approaching the speed of light.
 10:30: How can a photon's frequency be generalized as momentum?
 10:36: Well we generalize frequency as momentum because the Heisenberg uncertainty principle applies to momentum in general.
 10:42: In the case of matter, uncertainty in momentum can manifest in both velocity and mass.
 11:03: ... the photon passing through the slit, we increase the uncertainty in its momentum and hence, its direction of motion after it exits the ...


20171206: Understanding the Uncertainty Principle with Quantum Fourier Series
 01:40: The uncertainty principle is most often expressed in terms of position and momentum.
 01:44: We cannot simultaneously know both position and momentum for a quantum system with absolute precision.
 01:51: Try to perfectly nail down a particle's position, and we have complete uncertainty about its momentum.
 01:59: And it's not just because our measurement of position requires us to interact with the particle, therefore changing its momentum, no.
 06:39: The second of this pair is momentum, not frequency.
 06:43: See, momentum is sort of the generalization of frequency for what we call a matter wave.
 06:49: In the early days of quantum mechanics, it was realized that photons are electromagnetic wave packets whose momentum is given by their frequency.
 06:58: ... De Broglie relation generalizes the relationship between frequency and momentum of a matter ...
 07:08: ... waves wave functions, and we can describe them in terms of position or momentum, just as a traveling sound wave can be expressed in terms of time or ...
 07:29: ... being smeared over possible positions or as a combination of many momenta with accompanying intensities, in which case the particle would be ...
 07:41: And of course, this means that position and momentum have the same kind of uncertainty relation that time and frequency had in the sound wave.
 07:50: But what does it even mean for a particle to be comprised of waves of many different positions or momenta?
 08:30: If we apply the Born rule to the momentum function, then we learn the range of momenta the particle is likely to have.
 08:48: ... as a superposition of waves with a very large range of different momenta via a Fourier ...
 09:00: The result is a very fat momentum wave function that gives a wide range of possible momenta.
 09:06: ... its position wave function, and so the less certain we become about its momentum, as that momentum wave function gets ...
 09:22: ... particle by narrowing the slit, we also increase the uncertainty of its momentum as it passes the ...
 09:55: Waves that can be represented in terms of either position or momentum.
 10:18: Well, the key to understanding these things is to be able to switch between thinking about quantum fields in terms of position versus momentum.
 10:26: ... at one spot in space, can so be described as infinite oscillations in momentum space, spanning all possible ...
 10:39: But each of these oscillations in momentum space are equivalent to particles with highly specific momenta.
 10:51: So a perfectly specially localized particle is equally an infinite number of momentum particles that themselves occupy all locations in the universe.
 11:01: ... only by manipulating quantum fields in this strange momentum space, by adding and removing these spatially infinite particles, that ...


20171122: Suicide Space Robots
 00:19: Let's take a moment to remember them.


20171108: ZeroPoint Energy Demystified
 06:02: The fact is, any acceleration of a real particle involves a transfer of momentum between real particles via virtual particles.
 06:15: However, it's not possible to transfer momentum from a particle to the vacuum without getting another real particle out the other end.
 06:23: That momentum must be given up by the vacuum to produce real particles again.
 06:28: Those particles would become the propellant carrying momentum away.
 06:41: ... particles are somehow extracting momentum from the resonant cavity, then they're giving it up again to real ...


20171025: The Missing Mass Mystery
 03:44: It's the light released at the moment the first atoms formed nearly 400,000 years after the Big Bang.


20171019: The Nature of Nothing
 01:09: ... that perfect stillness implies that a particle's position and momentum are simultaneously perfectly defined, and this is impossible according ...
 01:21: Fix a particle's position, and its momentum, and so its motion, becomes a quantum blur of many possible momenta.
 03:39: We saw that it's impossible to simultaneously fix position and momentum.


20171011: Absolute Cold
 04:52: Well, its position relative to its neighbors would be fixed, and its momentum would be 0.
 05:11: For example, the more precisely a quantum particle's position is defined, the less defined is its momentum.
 05:20: A particle with a perfectly defined position has a perfectly undefined momentum.
 05:26: So try to fix a particle's position perfectly, try to hold it still, and its momentum enters a state of quantum haziness.
 05:34: That momentum can then fluctuate, potentially, to very high values.
 08:38: ... years for this black hole binary to spiral together from losing angular momentum to gravitational ...
 09:03: So they probably lose angular momentum by dragging against gas in the center of galaxies, but we don't know how long that takes.


20171004: When Quasars Collide STJC
 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.
 08:52: ... but it's going to take many billions of years to lose enough angular momentum to merge that ...


20170928: Are the Fundamental Constants Changing?
 05:17: Now, quantum spin gives electrons what we call a magnetic moment.


20170810: The OneElectron Universe
 09:44: ... one case, we have a positron and an electron influencing each other's momentum by exchanging a virtual photon similar to electronelectron ...
 10:05: As long as the incoming and outgoing particles have the same momenta, these two are part of the same overall interaction.


20170802: Dark Flow
 10:24: By themselves, they don't obey momentum conservation.
 10:30: Incoming and outgoing particles must obey energy and momentum conservation.
 10:35: For example, in order to conserve momentum, an annihilating electron and positron must produce two photons, not one.
 11:01: Each incoming and outgoing particle is identified with a numerical position and momentum.


20170726: The Secrets of Feynman Diagrams
 03:52: The photon vanishes as its momentum is completely transferred to the electron.
 04:35: ... because of conservation laws energy and momentum conservation requires that particles not just vanish or appear from ...
 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.
 07:02: We know the momentum of the ingoing and outgoing electrons.
 07:13: Simple examples are the exchange of a single photon to transfer momentum between electrons, or the exchange of two or more photons.
 07:21: ... photons with themselves at different stages in the process, or photons momentarily splitting into virtual electronpositron ...
 07:51: As well as infinite possibilities for particle momenta, we have to consider even impossible faster than light paths.


20170719: The Real Star Wars
 12:31: For the most part, and for the moment, saner heads have prevailed, and humanity remains committed to the peaceful use of outer spacetime.
 16:24: All we know is the momenta of all of those electrons.


20170712: Solving the Impossible in Quantum Field Theory
 02:35: One electron excites a photon, and that photon delivers a bit of the first electron's momentum to the second electron.
 05:39: Or any of those photons might do something crazy, like momentarily split into a virtual antiparticleparticle pair.
 07:43: ... emitting and reabsorbing a virtual photon, or the exchanged photon momentarily exciting a virtual electronpositron ...
 08:21: ... is especially true for socalled loop interactions, like when a photon momentarily becomes a virtual particleantiparticle pair and then reverts to a ...


20170628: The First Quantum Field Theory
 05:52: It follows the changing position and momentum and generally the physical quantum state of every individual particle but that's extremely inefficient.
 07:12: Instead of quantizing particles' physical properties like position and momentum, as did Schrodinger, Dirac quantized the electromagnetic field itself.
 07:43: So Dirac described a space of quantum states, including position and momentum/frequency, like an infinite array of springs.
 13:44: In fact, Schrodinger followed the same approach, starting with Einstein's mass energy momentum equation.


20170621: AntiMatter and Quantum Relativity
 02:21: ... as simple wave functions, distributions of possible positions and momenta that have no internal ...
 02:42: But spin does result in a sort of quantum angular momentum.
 04:05: ... down degrees of freedom were the direction of pointing of the angular momentum ...
 04:54: He wrote down Einstein's famous equation, E equals mc squared, but in its full form, including momentum.
 05:02: He then used quantum mechanical expressions for energy and momentum.


20170607: Supervoids vs Colliding Universes!
 01:37: It's the light that was released at the moment that the first atoms formed 380,000 years after the Big Bang.


20170426: Are You a Boltzmann Brain?
 10:12: ... assuming we don't blink out of existence in the next instant, as momentary fluctuations in the infinite chaos of a max maximally entropic space ...


20170405: Telescopes on the Moon
 03:28: I'm going to come back to a couple of the most promising in a moment.
 08:46: But momentum is building.


20170329: How Time Becomes Space Inside a Black Hole
 07:49: At the moment of crossing, light rays from the event horizon itself are suddenly visible.


20170322: Superluminal Time Travel + Time Warp Challenge Answer
 05:38: I'm really curious about what the crew of the Annihilator sees at that moment you pass them.
 07:06: Well, you just trace the photon paths, assuming for a moment that an FTL ship doesn't produce infinitely red or blue shifted photons.


20170315: Time Crystals!
 04:07: These atoms have spin values, quantum mechanical angular momenta from their electrons.


20170308: The Race to a Habitable Exoplanet  Time Warp Challenge
 03:23: What does the captain of the Annihilator see at the moment the Paradox overtakes?
 04:21: ... the beginning of the race, the beginning in both space and time at the moment the Annihilator is ...


20170222: The Eye of Sauron Reveals a Forming Solar System!
 02:51: Conservation of angular momentum has the central star spinning rapidly.


20170119: The Phantom Singularity
 10:00: At the moment of crossing, the denominator here in the Schwarzschild metric is 0, and the whole equation leads up to infinity.
 14:04: I'll come back to that in a moment, but the amount of work being done on it currently is equal to or greater than what is warranted by its promise.
 14:45: But these sorts of, huh, that's odd, moments are exactly what burst open new fields of study.
 14:52: ... it's important to remember that 999 out of 1,000, huh, that's odd, moments are due to some unaccounted factor that is totally within our current ...


20170111: The EM Drive: Fact or Fantasy?
 02:06: ... direction, the fat end for the EmDrive, can be achieved by extracting momentum from the internal radiation field, but with no ...
 02:33: The law of conservation of momentum demands this.
 02:56: Which is to say, this explanation breaks the law of conservation of momentum.
 03:01: ... those photons actually escape the cavity, then any momentum exchange between the cavity and radiation field gets redistributed ...
 07:02: The paper invokes pilot wave theory as a way to justify treating the quantum vacuum as a sort of plasma with which it can exchange momentum.
 07:28: To exchange momentum with virtual particles over a distance longer than a Planck length, those particles need to become real.
 07:49: Or if they escaped, they'd be a propellant, and momentum would be exchanged with no more efficiency than a photon thruster.


20161221: Have They Seen Us?
 15:12: Although we never saw the moment of its crossing, that did happen.


20161214: Escape The Kugelblitz Challenge
 06:32: ... impossible EM Drive technology that allows it to ignore conservation of momentum, so the satellites don't get ricocheted back to ...


20161208: What Happens at the Event Horizon?
 04:48: ... in one dimension of space and red horizontalish lines are fixed moments in ...
 07:25: The progress of the monkey appears to slow to a halt very close to the event horizon, and the final signal at the moment of crossing never reaches us.
 14:14: ... about how pilot wave theory might explain the apparent conservation of momentumbreaking ...
 14:38: ... theory was chosen partly because the internet happens to love it at the moment. ...


20161012: Black Holes from the Dawn of Time
 02:11: The universe was very slightly lumpy at the moment the CMB was created, about 400,000 years after the Big Bang.
 03:57: Discovering PBHs and learning their masses would tell us a huge amount about the earliest moments of our universe.


20160921: Quantum Entanglement and the Great BohrEinstein Debate
 02:08: And our experience of a welldefined material universe only has meaning at the moment of measurement.
 06:00: ... to all possible spin measurements is encoded in each particle at the moment of their creation as hidden variables local to each ...


20160824: Should We Build a Dyson Sphere?
 07:22: ... from heat generated from infalling material, or by extracting angular momentum from the black hole's ...


20160803: Can We Survive the Destruction of the Earth? ft. Neal Stephenson
 05:40: Space is trying to kill us, the Earth is trying to kill us, and at the moment we are trying to kill us.


20160727: The Quantum Experiment that Broke Reality
 05:52: In fact, several quantum properties, like momentum, energy, and spin, all display similar waviness in different situations.


20160720: The Future of Gravitational Waves
 05:10: ... the moment, LIGO isn't particularly good at figuring out the direction that the wave ...


20160706: Juno to Reveal Jupiter's Violent Past
 04:12: A planet can lose angular momentum to the debris, causing its orbit to shrink.
 04:25: The planet can even migrate outwards, stealing angular momentum from the debris.
 05:27: Drag from that gas would have sapped angular momentum from Jupiter, causing it to migrate inwards until it stalled at around 1.5 AU.


20160622: Planck's Constant and The Origin of Quantum Mechanics
 07:21: In what he described as a moment of desperation, he tried something pretty silly.
 10:27: And that little number that Max Planck came up with in his moment of desperation the Planck constant remains at the heart of all things quantum.


20160615: The Strange Universe of Gravitational Lensing
 11:28: The idea is that a physical system doesn't have the familiar classical properties like position, momentum, spin, et cetera, until it is observed.
 12:39: ... wave function into the classical physical properties like position and momentum. ...


20160601: Is Quantum Tunneling Faster than Light?
 02:23: See an object's de Broglie wavelength depends on its momentum, so mass times velocity.
 02:31: Higher momentum means a smaller wavelength.
 02:33: In fact, it's the minuscule Planck constant divided by momentum.


20160525: Is an Ice Age Coming?
 03:08: That's the north at the moment.
 14:32: But, for example, a stress energy momentum pseudo tensor isn't mathematically the same thing as classical energy.


20160427: What Does Dark Energy Really Do?
 10:02: We can't rule out curvature below our current best sensitivity, which at the moment is 0.4% of perfect flatness.


20160413: Will the Universe Expand Forever?
 01:57: And it describes all of the energy, the pressure, the momentum, and more all of the stuff within that spacetime.
 05:14: Let's stick to the lefthand side of the equation for the moment.


20160406: We Are Star Stuff
 05:58: At the last moment of a super giant's life, it has onion shells of burning elements.
 10:58: ... curved, I should say that the curvature of space at a single, constant moment in time has to be one of these ...


20160330: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!
 03:08: ... average distance a photon could travel through the universe before the moment of recombination, the moment when the cosmic microwave background was ...
 04:38: We need to find their density at the moment of recombination.
 05:42: All of those electrons existed at the moment of recombination.
 06:11: ... we get that there were 200 million electrons in every cubic meter at the moment of ...
 08:00: That hot plasma at the moment of recombination wasn't the thick searing fog that we sometimes imagine.


20160323: How Cosmic Inflation Flattened the Universe
 09:25: ... fact, the instant that inflation ended can perhaps be thought of as the moment that our universe as we know it came into ...
 12:52: ... the rate of accretion, the viscosity of the material, the way angular momentum is lost by that material, stuff like ...


20160316: Why is the Earth Round and the Milky Way Flat?
 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.
 12:16: And at the moment of recombination, when the CMB was emitted, it was emitted by all of the observable universe and beyond at the same time.


20160224: Why the Big Bang Definitely Happened
 03:51: ... at a very particular moment when the universe was around 400,000 years old and about 1,000 times ...
 04:11: In the same moment, the infrared light that had previously been trapped in this fog was free to travel the width of the cosmos.
 06:29: ... ripples should have been frozen into the distribution of matter at the moment the CMB was created, and those ripples should still be visible in the ...


20160211: LIGO's First Detection of Gravitational Waves!
 00:10: The Advanced LIGO Observatory has seen the spacetime ripples caused by black holes at the moment of merger.
 01:57: ... produce gravitational waves strong enough for us to detect, at the moment. ...


20160203: Will Mars or Venus Kill You First?
 08:54: ... imagine a clock that magically appeared at the moment of the Big Bang and somehow survived all of that highenergy craziness, ...


20160113: When Time Breaks Down
 06:38: ... particles and fields, in which the internal parts exchange energy, momentum, and other properties interactions which hold the atom ...


20160106: The True Nature of Matter and Mass
 01:22: Let's ignore the gravitational effect of mass for the moment, and just consider mass as the degree to which an object resists being accelerated.
 02:20: The photons exert a force on the box, the box also exerts a force on the photons Newton's Third Law, which gives us the conservation of momentum.
 02:29: Momentum lost by the box is transferred to the photons.
 02:33: Now, if the box stops accelerating, then everything jiggles around and momentum gets shared out evenly between the box and the photons again.
 03:14: And you can derive the famous E equals Mc squared just by looking at how momentum transfers between the photons in the box under acceleration.
 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 spacetime.


20151216: The Higgs Mechanism Explained
 01:43: ... vibrations and fields interact with each other, transferring energy, momentum, charge, et cetera, between particles and ...


20151209: How to Build a Black Hole
 02:39: And it's a quantum phenomenon that saves it, for the moment, from final collapse.
 03:04: For a neutron star, this is the space of both 3D position and 3D momentum.
 03:52: So two fermions can apply the same physical location just fine, as long as their momenta or any other quantum property is different.
 04:09: In the case of a neutron star, position momentum phase space is completely full of neutrons.
 04:16: Every spatial location and every momentum location connected to those special locations contains a neutron.
 06:04: ... principle tells us that particular pairs of quantities, position and momentum or time and energy, must, when taken together, contain a minimum degree ...
 06:32: Therefore, the Heisenberg uncertainty principle tells us that they must have highly undefined momenta.
 06:44: To put it another way, the neutrons are packed so close together in position space that their momentum space becomes gigantic.
 06:55: And here's the thing the denser the neutron star becomes, the more momentum space you get.
 07:22: The star expands in momentum space.
 09:17: Well, momentum space expands accordingly, with the corresponding enormous velocities all inward pointing.


20151118: 5 Ways to Stop a Killer Asteroid
 05:10: A one ton impact gives the necessary one part to a million momentum change needed to divert city killers.


20151105: Why Haven't We Found Alien Life?
 02:51: ... based protocells; three, DNA and the first actual cell this is the moment of a biogenesis, life from not life; four, increasingly complex single ...


20151022: Have Gravitational Waves Been Discovered?!?
 01:51: Here's a technical term you need to change the quadrupole moment of a mass distribution.


20151015: 5 REAL Possibilities for Interstellar Travel
 02:10: Conservation of momentum sucks.


20150923: Does Dark Matter BREAK Physics?
 09:14: ... the freefalling monkey doesn't see anything weird about space at the moment it crosses the event ...
 09:48: But is the monkey saved at the last moment as the black hole evaporates way beneath it?
 10:18: But the moment of horizon crossing is never seen.


20150819: Do Events Inside Black Holes Happen?
 02:31: Even if the ponies and I were immortal, all of us would agree that the monkey's life just doesn't progress past this frozen moment.


20150722: SPECIAL ANNOUNCEMENT + Flat Spacetime Geometry Comments
 05:06: That accelerating car, at any given moment, from its point of view, is always stationary instantaneously relative to one of those inertial observers.
 05:15: ... of inertial frames of reference, relative to which, at any given moment, the car is instantaneously ...


20150715: Can You Trust Your Eyes in Spacetime?
 02:28: Rather, they are events, each of which occurs somewhere along my axis in a onedimensional physical space and at some moment according to my clock.
 02:51: And at that same moment, I shoot a photon from a laser pointer to the right.


20150624: The Calendar, Australia & White Christmas
 00:57: Since Earth's axis is tilted, one half of that bulge is a little closer to the sun than the other half at any given moment.


20150617: How to Signal Aliens
 00:13: [THEME MUSIC] Let's leave aside for the moment the fact that signaling aliens might not be a good idea.
 09:09: And now the moment you've all been waiting for the answer to the challenge question.


20150610: What Happens to a Helium Balloon in Freefall?
 00:39: And at the same moment that I let go, I want to cut the string that holds the helium balloon to the floor.


20150506: Should the First Mars Mission Be All Women?
 08:45: It should tilt slightly to the right because of the already tangential momentum that it had.
 09:14: Fortstorm asks, wouldn't a rotating stations have trouble turning because its angular momentum vector would have trouble being shifted?
 09:22: ... so that there would be gravity here and gravity here but no net angular momentum, and thus no net gyroscope ...


20150422: Are Space and Time An Illusion?
 01:14: Fact they don't fully agree on how much space there is between things at any given moment.


20150415: Could NASA Start the Zombie Apocalypse?
 05:04: And they come out from straight up momentum conservation.
 05:23: ... to take that loss of mass into account and use a more correct version of momentum conservation called the rocket equation that compensates for ...
 05:32: Dariodario alluded to the rocket equation in that form of calculating momentum conservation in his comment.


20150408: Could You Fart Your Way to the Moon?
 02:58: Conservation of momentum.
 03:00: After a propulsion event, the net momentum of you and your fuel must remain zero.
 03:05: So your forward momentum must be equal and opposite to the backward momentum of the gas you expel.
 03:10: So how much momentum is that?
 04:57: So the net result for momentum conservation?


20150401: Is the Moon in Majora’s Mask a Black Hole?
 08:49: With each passing moment of time, any observer sitting anywhere will see photons that were emitted from progressively more distant locations.


20150325: Cosmic Microwave Background Explained
 03:43: So at this moment, it was as if flash bulbs were constantly going off everywhere in space, but the light was being snuffed out by a fog.
 05:50: ... trick was to cancel out all the intermediate angular momentum vectors produced as a flywheel with forwardpointing angular momentum ...
 06:00: ... solution is to have two flywheels, both with forwardpointing angular momentum that you rotate into the reverse orientation in opposite ...
 06:08: That way, any sideways intermediate angular momentum that gets produced is canceled out.
 06:43: ... could be spun sufficiently fast, you could store up a lot of angular momentum with very little ...


20150318: Can A Starfox Barrel Roll Work In Space?
 02:03: That tendency to keep rotating is called an objects' angular momentum, and physicists represent it by a vector or an arrow.
 02:23: To do that, the shipments needs to acquire a forwardpointing angular momentum vector.
 02:27: To stop, that angular momentum must be removed.
 02:59: But what if you could store up the angular momentum in advance and carry it with you?
 03:04: And I don't mean having the ship doing a nonstop barrel roll, I mean happy angular momentum on demand without thrusters.
 03:23: By rotating the flywheel quickly, I end up transferring its angular momentum to myself, so I start spinning.
 03:47: So its angular momentum vector points toward the nose of the ship, which here is the top of your screen.
 03:53: ... can also think of this vector as the net angular momentum of the entire ship flywheel system, all of which currently happens to ...
 04:04: When I flip the flywheel 180 degrees, its individual angular momentum starts pointing toward the rear of the ship, i.e.
 04:12: But the net angular momentum of the entire ship wheel system must remain unchanged.
 04:17: That can happen only if the entire fuselage acquires its own large, forwardpointing angular momentum.
 04:23: That, combined with the wheel's angular momentum, nets out to the same total angular momentum vector we began with.
 04:56: Space telescopes, like Hubble and Kepler, also use angular momentum conservation to turn without thrusters.
 05:17: They're called control moment gyros.
 05:33: ... fast they'd have to spin in the first place to store up enough angular momentum for the barrel ...
 05:50: ... unlike with thrusters, you can keep storing and reusing that angular momentum to do as many barrel rolls as you ...
 06:18: In the process, both of flipping and of flipping back, its angular momentum vector sweeps through a bunch of partiallysideways directions.
 06:25: To compensate, the ship would have to do some wonky rotating as the flywheel flips, in order to keep the total angular momentum vector unchanged.


20150225: How Do You Measure the Size of the Universe?
 02:40: ... universe, you need to know how quickly space has been expanding at every moment in history, ...
 03:00: Let me take a moment to explain.
 04:12: And from that, how fast the universe was expanding at every moment ever.
