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	2022-12-14: How Can Matter Be BOTH Liquid AND Gas? 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. 01:52: At these melting and boiling boundaries the material is momentarily a mix of both states.
	2022-12-08: 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 ...
	2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics? 04:54: ... relationship if those properties  really are decided at the moment of ... 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 ... 02:36: ... to molecular scale, and the entangled property could be spin,  momentum, or any other quantum ... 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 ...
	2022-10-19: 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 ...
	2022-10-12: 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 ...
	2022-09-28: 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.
	2022-09-14: Could the Higgs Boson Lead Us to Dark Matter? 09:42: Total moment in a collision is conserved, but also the momentum in each separate direction is conserved independently of the other directions. 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. 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 in-going 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. 09:28: ... another part to this trick that makes it very precise. We can do our momentum audit in a way that ensures that in-going momentum is known completely ... 10:56: And that lepton will be detected, meaning we can account for the momentum lost to neutrinos. 09:51: ... momentum perpendicular to the direction of the particle beams is called the transverse ... 08:48: ... of momentum tells us that the product of velocity times mass of all particles going into a ... 10:30: ... of momentum tells us that there should be more stuff firing out in the opposite direction ...
	2022-08-03: 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 ...
	2022-07-20: 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.
	2022-06-30: 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 ...
	2022-06-01: 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 ...
	2022-05-25: 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 ...
	2022-05-18: 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 ...
	2022-04-20: 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 ...
	2022-03-23: 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. 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.
	2022-03-16: 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 right-handed chirality if their spin is clockwise relative to their momentum vector and left-handed chirality if it's ...
	2022-02-23: 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 ...
	2022-02-16: Is The Wave Function The Building Block of Reality? 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 ... 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 ...
	2022-02-10: 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 ...
	2022-01-27: How Does Gravity Escape A Black Hole? 02:28: Imagine for a moment that the Sun just disappeared.
	2022-01-19: 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.
	2022-01-12: How To Simulate The Universe With DFT 15:23: The the fast-moving black hole slows-down inside the Earth because exchanges momentum with or eats stationary material on its way through.
	2021-12-10: 2021 End of Year AMA! 00:02: ... proton and in doing so you sum over all possible and so all possible momenta that those exchange particles could have um in a sense every way ...
	2021-11-17: Are Black Holes Actually Fuzzballs? 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. 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.
	2021-11-10: What If Our Understanding of Gravity Is Wrong? 07:55: In 1984 he diverted his attention for a moment  to work with Mordehai Milgrom in fixing MOND. 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? 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 ... 12:59: ... states underpins modern quantum theory. Back to Paul Dirac just for a moment. His eponymous equation was derived to describe the quantum evolution of ... 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 ... 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 ... 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 ...
	2021-08-18: 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 ...
	2021-08-10: 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 ... 07:14: ... wavefunction. The normal linear observables are things like position, momentum, spin - the physical stuff that makes up our world. Extra observables would be ...
	2021-08-03: How An Extreme New Star Could Change All Cosmology 09:18: ... neutron stars when LIGO detected the gravitational waves from the last moment of those inspirals. But it should happen with white dwarfs ... 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. ... 09:51: ... 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 ...
	2021-07-21: 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.
	2021-07-13: Where Are The Worlds In Many Worlds? 04:23: ... particle position and momentum and orientation is chosen from a vast array of possibilities, a ...
	2021-07-07: Electrons DO NOT Spin 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 ... 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  ... 11:34: ... right values of the  electron spin angular momentum and magnetic moment by looking at the energy and charge  currents in the so called ... 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 ... 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 alignments ... 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 ... 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 whatever  ... 00:47: ... electrons are acting like tiny bicycle wheels, and their shifted angular momenta is compensated by the rotation of the ... 12:13: ... intrinsic angular momenta can only be observed as plus or minus a half times the reduced Planck ... 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 ... 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 ... 03:48: ... would have to be moving faster than light to give the required angular momentum. And that’s assuming that electrons even have a size - as far as we know ... 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 ... 07:02: ... without rotation, but the direction of the underlying magnetic  momentum is fundamentally quantum.   The direction of this "spin" ... 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 ... 04:40: ... intrinsic angular momentum that plays into the conservation of angular momentum like  in the Einstein de-Haas effect, and it also gives electrons a magnetic ... 00:22: ... a demonstration of the conservation of angular momentum. The angular momentum  of the wheel is changed in one direction, so the angular momentum of the ... 10:22: To get some insight into what spin really is,   think not about angular momentum,  but regular or linear momentum. 10:58: If position is the companion variable of momentum,  what's the companion of angular momentum?
	2021-06-23: 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 ...
	2021-06-16: 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 electron-ness. That also means increasing the ... 03:47: ... now you have a new problem. Light carries energy and momentum - and the shorter the   wavelength, the more it carries. If you ...
	2021-06-09: 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.
	2021-05-25: 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.
	2021-05-19: 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. 02:37: ... reasoned that the photon would give the particle a momentum kick, which would account for a greater uncertainty in its momentum after the ...
	2021-04-21: The NEW Warp Drive Possibilities 16:45: Momentum, which incorporates velocity, is as fundamental as position.
	2021-04-07: Why the Muon g-2 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. 03:50: 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. 06:34: By the way, the anomalous in the anomalous magnetic dipole moment, refers to that little bit extra after the two. 04:56: All those virtual photons could do something weird like momentarily becoming an electron-positron pair. 03:43: For a rotating charge, that depends on the objects rate of rotation, or angular momentum, it's charge and it's mass.
	2021-02-10: 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 ...
	2020-12-08: 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.
	2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces 04:50: ... outcomes being measured for observables like particle position and momentum. ...
	2020-10-27: 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 ...
	2020-10-20: 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 ...
	2020-08-24: Can Future Colliders Break the Standard Model? 07:03: And there are other anomalies like the muon’s magnetic moment.
	2020-08-10: 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 ...
	2020-07-28: 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 ...
	2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing? 08:50: ... anti-hydrogen is electrically neutral, it does have a small magnetic moment - like a tiny bar magnet. ALPHA introduces a new magnetic field that ... 09:19: ... their orbital angular momentum, their magnetic and electric dipole moments, and even the strength of the coupling between the particles and the ... 08:50: ... anti-hydrogen is electrically neutral, it does have a small magnetic moment - like a tiny bar magnet. ALPHA introduces a new magnetic field that ... 09:19: ... their orbital angular momentum, their magnetic and electric dipole moments, and even the strength of the coupling between the particles and the ...
	2020-06-30: 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 frame-dragged 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.
	2020-06-22: 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 Hawking-like ...
	2020-06-15: 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.
	2020-05-18: Mapping the Multiverse 10:18: You caught a glimpse of the entire history of that universe the moment you crossed into the white hole.
	2020-05-04: 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 - ... 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 had a ... 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 - ...
	2020-04-28: Space Time Livestream: Ask Matt Anything 00:00: ... you get used to the camera yeah maybe someone can go away just for the moment okay so this is bahar bahar created this amazing piece of art okay and ...
	2020-04-22: 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 ...
	2020-04-07: 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 ...
	2020-03-31: 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 ...
	2020-03-24: 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 ...
	2020-03-16: 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 ... 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 raises ...
	2020-03-03: 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 ...
	2020-02-18: 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.
	2020-01-27: Hacking the Nature of Reality 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. 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. 14:29: ... some places it gives up angular momentum - it's orbital energy - to the gas, causing it to migrate inwards, while ...
	2020-01-20: 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 ...
	2020-01-13: How To Capture Black Holes 06:15: ... further out in the disk - or “migrates outward”. If it loses angular moment it migrates ... 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 ...
	2019-12-09: The Doomsday Argument 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, ... 11:05: ... you could be a momentary entropy fluctuation that caused a brain with exactly your current mental ...
	2019-11-18: 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 ...
	2019-10-15: Loop Quantum Gravity Explained 04:06: In the first formulations of quantum mechanics, that wavefunction describes the distribution of possible positions and momenta of, say, a particle. 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 so-called 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 vector-like thing that also represents a quantum of angular momentum - or ... 05:19: ... you calculate changing properties of a particle- - like its position or momentum - relative to the background coordinate ... 08:20: ... a spinor - a vector-like thing that also represents a quantum of angular momentum - or ... 05:19: ... you calculate changing properties of a particle- - like its position or momentum - relative to the background coordinate ... 03:33: ... classical physics, we have variables like position, time, momentum, energy - mathematical expressions that represent the observable properties of ... 04:16: These can then be resolved into concrete, measured values by acting on the wavefunction with so-called position and momentum operators.
	2019-10-07: 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.
	2019-09-30: 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 ...
	2019-07-18: 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 ... 03:27: ... some moment in time Relative to their distance at some other reference moments that reference moment is typically taken to be right now So the scale ... 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 ...
	2019-07-01: Thorium and the Future of Nuclear Energy 02:49: ... human error Even the smartest nuclear engineer can have a perma Simpson moment One way around the coolant issues is to use molten metals or molten ...
	2019-06-06: 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 ...
	2019-05-16: 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 light-filled stelliferous era; Probably the ...
	2019-05-09: Why Quantum Computing Requires Quantum Cryptography 04:38: ... of certain pairs of properties – for example, a particle’s position and momentum. ...
	2019-04-24: 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 ...
	2019-04-10: The Holographic Universe Explained 04:26: Let’s ignore string theory for the moment and just think about how to create an extra dimension.
	2019-04-03: The Edge of an Infinite Universe 05:49: ... horizontal-ish contours are our old time ticks - moments of constant time across the universe, while the vertical-ish lines are ...
	2019-03-28: 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 ...
	2019-03-20: 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.
	2019-03-06: 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 ...
	2019-02-20: 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 ...
	2019-01-30: 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 ... 06:36: ... presence of active gravitational mass, and of energy, momentum, pressure, and more, change the geometry of spacetime and that new geometry defines ...
	2019-01-24: 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.
	2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe 01:48: ... of cobalt-60 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 ...
	2019-01-09: 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. 04:06: Forgetting that pressure stuff for a moment, positive masses and energies always have a positive gravitational effect.
	2018-12-20: 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 ...
	2018-12-12: 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 ...
	2018-12-06: 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 ...
	2018-11-07: 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 ...
	2018-10-31: Are Virtual Particles A New Layer of Reality? 06:39: Their momenta are pointing from positron to electron rather than electron to positron. 07:29: The Heisenberg uncertainty principle tells us that the perfectly defined momenta of virtual particles means completely undefined position. 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. 07:39: In contrast, real particles are mixed up combinations of many excitations, many different momentum modes.
	2018-10-18: 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 ...
	2018-10-03: How to Detect Extra Dimensions 15:18: I just told you that a moment ago.
	2018-09-20: Quantum Gravity and the Hardest Problem in Physics 07:01: ... wave functions that include extremely high frequencies or extremely high momenta, i.e., the more certain its position, the less certain its ... 07:18: And so large momenta are possible. 06:28: Steady viewers will remember that the uncertainty principle talks about the trade-off 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. 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 ...
	2018-09-12: How Much Information is in the Universe? 09:05: ... the moment the universe reaches information limit, it would immediately become a ... 04:21: ... space, which includes position, but also other degrees of freedom, like momentum, spin direction, et ...
	2018-09-05: The Black Hole Entropy Enigma 06:09: So you know how nothing can escape black holes, ignoring Hawking radiation for the moment.
	2018-08-23: 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.
	2018-08-15: 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. 04:20: 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. 04:20: So electrons have a magnetic dipole moment, meaning they feel magnetic fields and act as little bar magnets. 02:21: Let's break down these magnetic dipole moment thing. 03:32: As we'll see, their nature is predicted by quantum theory, measure electromagnetic moments, and you verify your quantum picture of reality. 05:23: This difference between the quantum versus classical magnetic moments for the electron is called the G factor. 04:02: Nonetheless, electrons do have a sort of intrinsic, angular momentum, a fundamental quantum spin that is as intrinsic as mass and charge. 05:09: ... expect for a tiny classical sphere with the same charge and angular momentum as an ...
	2018-07-18: 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 ...
	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. 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 ... 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. 06:57: ... 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 of the ...
	2018-06-20: 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 quantum-observable complimentary observables, like position and momentum, that can't both be perfectly measured at the same ...
	2018-06-13: What Survives Inside A Black Hole? 13:18: Exactly what happens at the moment of observation is still debated. 01:09: ... properties are mass, electric charge, and angular momentum, or at least this is the proposition behind the famous no-hair 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 mass-energy 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. 03:06: So how does mass, electric charge, and angular momentum communicate their influence across the uncrossable horizon? 09:19: ... material with angular momentum falls into a black hole, whether it's a spinning star or a whirlpool of gas, ...
	2018-05-16: Noether's Theorem and The Symmetries of Reality 09:27: ... be thankful that she took a moment to offer a little of her genius to physics, taking us a big step closer ... 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. ... 03:34: Momentum doesn't appear to be conserved. 03:26: If two cars collide on that road, the sum of their combined momentum stays the same.
	2018-04-25: Black Hole Swarms 09:40: Gravitational waves are produced when the quadrupole moment of a mass distribution changes. 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.
	2018-04-11: 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 ...
	2018-04-04: The Unruh Effect 05:46: Even momentary acceleration generates a Rindler horizon.
	2018-03-28: The Andromeda-Milky Way Collision 06:16: Meanwhile, the black holes lose angular momentum and fall towards the center.
	2018-03-21: 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. 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 ... 06:55: At both of these points, the weight is momentarily still.
	2018-03-15: 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 ...
	2018-03-07: Should Space be Privatized? 04:06: That's where the profit is for the moment.
	2018-02-28: The Trebuchet Challenge 07:26: My question-- how fast is the stone traveling at the moment of impact?
	2018-02-21: 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.
	2018-02-14: What is Energy? 10:36: Our universe looks fundamentally different from one moment to the next, at least on cosmic scales, where it's expansion becomes significant. 01:43: Besides the whole co-inventing 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.
	2018-01-31: 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.
	2018-01-17: Horizon Radiation 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. 09:35: Infinite spatially undefined particles with defined momenta, and these just happen to cancel each other out, leaving 0 particles or a vacuum. 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. 06:04: That momentum field also has infinite oscillators, but now each one represents a different possible momentum for the particle. 08:51: ... at a time, by changing the number of particles or oscillations in each momentum mode. ... 06:24: Now, each one of these momentum modes exists at all spatial points in the universe. 08:12: However, changing the momentum modes does affect the superposition-- the sum of all oscillations, for example, by creating or destroying particles. 09:29: In momentum space, we can think of it as a superposition of infinitely many momentum modes. 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. 06:24: Now, each one of these momentum modes exists at all spatial points in the universe. 06:13: ... oscillation can also be described as an infinite number of unlocalized momentum oscillations. ... 06:31: ... we add these momentum oscillations together with the right weightings, they cancel out everywhere except at ... 07:48: Those momentum oscillations have two important qualities. 06:40: The superposition of infinite universe size momentum oscillators-- momentum particles can represent a single spatial oscillator. 05:56: So let's take our spatial quantum field-- our drum skin, with its single, localized particle, and transform to momentum space. 06:13: ... in momentum space, that single, perfectly localized position oscillation can also be ... 07:37: But why exchange a single spatial equation for infinite equations in momentum space? 08:22: OK, so a single particle can be described as many oscillations in momentum space. 09:29: In momentum space, we can think of it as a superposition of infinitely many momentum modes. 08:00: The field at each momentum spot oscillates independently from its neighboring momenta.
	2017-12-13: 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 ... 10:22: That means momentum approaches infinity for any object with mass that's approaching the speed of light. 09:50: [INAUDIBLE] Leonard asks whether a particle can have momentum higher than its mass times the speed of light.
	2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series 07:29: ... being smeared over possible positions or as a combination of many momenta with accompanying intensities, in which case the particle would be ... 07:50: 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. 10:26: ... as infinite oscillations in momentum space, spanning all possible momenta. ... 10:39: But each of these oscillations in momentum space are equivalent to particles with highly specific momenta. 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 ... 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. 10:51: So a perfectly specially localized particle is equally an infinite number of momentum particles that themselves occupy all locations in the universe. 07:29: ... accompanying intensities, in which case the particle would be smeared in momentum space. ... 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. 11:01: ... only by manipulating quantum fields in this strange momentum space, by adding and removing these spatially infinite particles, that we can ... 10:26: ... at one spot in space, can so be described as infinite oscillations in momentum space, spanning all possible ... 09:00: The result is a very fat momentum wave function that gives a wide range of possible momenta. 09:06: ... function, and so the less certain we become about its momentum, as that momentum wave function gets ... 09:00: The result is a very fat momentum wave function that gives a wide range of possible momenta. 09:06: ... function, and so the less certain we become about its momentum, as that momentum wave function gets ...
	2017-11-22: Suicide Space Robots 00:19: Let's take a moment to remember them.
	2017-11-08: Zero-Point 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 ...
	2017-10-25: 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.
	2017-10-19: The Nature of Nothing 01:21: Fix a particle's position, and its momentum, and so its motion, becomes a quantum blur of many possible momenta. 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.
	2017-10-11: 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. 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.
	2017-10-04: 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 ... 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.
	2017-09-28: Are the Fundamental Constants Changing? 05:17: Now, quantum spin gives electrons what we call a magnetic moment.
	2017-08-10: The One-Electron Universe 10:05: As long as the incoming and outgoing particles have the same momenta, these two are part of the same overall interaction. 09:44: ... one case, we have a positron and an electron influencing each other's momentum by exchanging a virtual photon-- similar to electron-electron ... 10:05: As long as the incoming and outgoing particles have the same momenta, these two are part of the same overall interaction.
	2017-08-02: 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. 10:24: By themselves, they don't obey momentum conservation. 10:30: Incoming and outgoing particles must obey energy and momentum conservation.
	2017-07-26: The Secrets of Feynman Diagrams 07:51: As well as infinite possibilities for particle momenta, we have to consider even impossible faster than light paths. 07:21: ... photons with themselves at different stages in the process, or photons momentarily splitting into virtual electron-positron ... 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. 07:51: As well as infinite possibilities for particle momenta, we have to consider even impossible faster than light paths. 04:35: ... because of conservation laws-- energy and momentum conservation requires that particles not just vanish or appear from nothing, which ...
	2017-07-19: 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 space-time. 16:24: All we know is the momenta of all of those electrons.
	2017-07-12: Solving the Impossible in Quantum Field Theory 05:39: Or any of those photons might do something crazy, like momentarily split into a virtual anti-particle-particle pair. 07:43: ... emitting and reabsorbing a virtual photon, or the exchanged photon momentarily exciting a virtual electron-positron ... 08:21: ... is especially true for so-called loop interactions, like when a photon momentarily becomes a virtual particle-anti-particle pair and then reverts to a ... 05:39: Or any of those photons might do something crazy, like momentarily split into a virtual anti-particle-particle pair. 07:43: ... emitting and reabsorbing a virtual photon, or the exchanged photon momentarily exciting a virtual electron-positron ... 08:21: ... is especially true for so-called loop interactions, like when a photon momentarily becomes a virtual particle-anti-particle pair and then reverts to a ... 07:43: ... emitting and reabsorbing a virtual photon, or the exchanged photon momentarily exciting a virtual electron-positron ... 05:39: Or any of those photons might do something crazy, like momentarily split into a virtual anti-particle-particle pair. 02:35: One electron excites a photon, and that photon delivers a bit of the first electron's momentum to the second electron.
	2017-06-28: 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. 13:44: In fact, Schrodinger followed the same approach, starting with Einstein's mass energy momentum equation. 07:43: So Dirac described a space of quantum states, including position and momentum/frequency, like an infinite array of springs.
	2017-06-21: Anti-Matter 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. 04:05: ... down degrees of freedom were the direction of pointing of the angular momentum axis. ...
	2017-06-07: 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.
	2017-04-26: 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 ...
	2017-04-05: 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.
	2017-03-29: 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.
	2017-03-22: 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.
	2017-03-15: Time Crystals! 04:07: These atoms have spin values, quantum mechanical angular momenta from their electrons.
	2017-03-08: 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 ...
	2017-02-22: The Eye of Sauron Reveals a Forming Solar System! 02:51: Conservation of angular momentum has the central star spinning rapidly.
	2017-01-19: 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 ... 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 ...
	2017-01-11: 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. 02:33: The law of conservation of momentum demands this. 03:01: ... those photons actually escape the cavity, then any momentum exchange between the cavity and radiation field gets redistributed again, because ...
	2016-12-21: Have They Seen Us? 15:12: Although we never saw the moment of its crossing, that did happen.
	2016-12-14: 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 ...
	2016-12-08: 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. 14:38: ... theory was chosen partly because the internet happens to love it at the moment. ... 04:48: ... in one dimension of space and red horizontalish lines are fixed moments in ... 14:14: ... about how pilot wave theory might explain the apparent conservation of momentum-breaking ...
	2016-10-12: 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.
	2016-09-21: Quantum Entanglement and the Great Bohr-Einstein Debate 02:08: And our experience of a well-defined 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 ...
	2016-08-24: Should We Build a Dyson Sphere? 07:22: ... from heat generated from infalling material, or by extracting angular momentum from the black hole's ...
	2016-08-03: 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.
	2016-07-27: 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.
	2016-07-20: The Future of Gravitational Waves 05:10: ... the moment, LIGO isn't particularly good at figuring out the direction that the wave ...
	2016-07-06: 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.
	2016-06-22: 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.
	2016-06-15: 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. ... 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.
	2016-06-01: 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.
	2016-05-25: 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.
	2016-04-27: 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.
	2016-04-13: Will the Universe Expand Forever? 05:14: Let's stick to the left-hand side of the equation for the moment. 01:57: And it describes all of the energy, the pressure, the momentum, and more-- all of the stuff within that spacetime.
	2016-04-06: 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 ...
	2016-03-30: 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.
	2016-03-23: 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 ...
	2016-03-16: Why is the Earth Round and the Milky Way Flat? 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. 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.
	2016-02-24: 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 ...
	2016-02-11: 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. ...
	2016-02-03: 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 high-energy craziness, ...
	2016-01-13: 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 ...
	2016-01-06: 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 space-time. 02:29: Momentum lost by the box is transferred to the photons. 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.
	2015-12-16: The Higgs Mechanism Explained 01:43: ... vibrations and fields interact with each other, transferring energy, momentum, charge, et cetera, between particles and ...
	2015-12-09: How to Build a Black Hole 02:39: And it's a quantum phenomenon that saves it, for the moment, from final collapse. 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. 06:32: Therefore, the Heisenberg uncertainty principle tells us that they must have highly undefined momenta. 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. 04:16: Every spatial location and every momentum location connected to those special locations contains a neutron. 04:09: In the case of a neutron star, position momentum phase space is completely full of neutrons. 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.
	2015-11-18: 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.
	2015-11-05: Why Haven't We Found Alien Life? 02:51: ... based proto-cells; three, DNA and the first actual cell-- this is the moment of a biogenesis, life from not life; four, increasingly complex single ...
	2015-10-22: Have Gravitational Waves Been Discovered?!? 01:51: Here's a technical term-- you need to change the quadrupole moment of a mass distribution.
	2015-10-15: 5 REAL Possibilities for Interstellar Travel 02:10: Conservation of momentum sucks.
	2015-09-23: Does Dark Matter BREAK Physics? 09:14: ... the free-falling 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.
	2015-08-19: 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.
	2015-07-22: 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 ...
	2015-07-15: Can You Trust Your Eyes in Spacetime? 02:28: Rather, they are events, each of which occurs somewhere along my axis in a one-dimensional 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.
	2015-06-24: 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.
	2015-06-17: 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.
	2015-06-10: 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.
	2015-05-06: 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 ... 09:14: Fortstorm asks, wouldn't a rotating stations have trouble turning because its angular momentum vector would have trouble being shifted?
	2015-04-22: 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.
	2015-04-15: 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. 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. 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 ...
	2015-04-08: 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?
	2015-04-01: 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.
	2015-03-25: 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 forward-pointing angular momentum ... 06:00: ... solution is to have two flywheels, both with forward-pointing 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 ... 05:50: ... momentum vectors produced as a flywheel with forward-pointing angular momentum rotates to end up with backward-pointing angular ...
	2015-03-18: Can A Starfox Barrel Roll Work In Space? 05:17: They're called control moment gyros. 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 forward-pointing 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, forward-pointing 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. 05:33: ... 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 partially-sideways 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. 04:56: Space telescopes, like Hubble and Kepler, also use angular momentum conservation to turn without thrusters. 04:23: That, combined with the wheel's angular momentum, nets out to the same total angular momentum vector we began with. 04:04: When I flip the flywheel 180 degrees, its individual angular momentum starts pointing toward the rear of the ship, i.e. 02:23: To do that, the shipments needs to acquire a forward-pointing angular momentum vector. 03:47: So its angular momentum vector points toward the nose of the ship, which here is the top of your screen. 04:23: That, combined with the wheel's angular momentum, nets out to the same total angular momentum vector we began with. 06:18: In the process, both of flipping and of flipping back, its angular momentum vector sweeps through a bunch of partially-sideways 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. 03:47: So its angular momentum vector points toward the nose of the ship, which here is the top of your screen. 06:18: In the process, both of flipping and of flipping back, its angular momentum vector sweeps through a bunch of partially-sideways 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.
	2015-02-25: 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.

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