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2022-12-08: How Are Quasiparticles Different From Particles?

  • 05:16: And we can make another one by making a very different tweak to the local energy in the crystal.
  • 13:28: ... are magnons - quanta of waves in that lattice, or skyrmions, which are localized, stable topological field configurations sort of like knots - all very ...

2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics?

  • 11:49: Bell’s theorem can be used to rule out the existence of local hidden variables.
  • 11:55: It can rule out that the secret information about the entangled particle states lives in the particles themselves - that’s what local means here.
  • 12:09: ... ruled out local hidden variables, but that may mean they ruled out locality rather  than hidden ...
  • 12:18: Any violation of locality still means that some sort of influence travels faster than light - the sort of spookiness that Einstein hated.

2022-07-20: What If We Live in a Superdeterministic Universe?

  • 00:00: Today we’re going to try to save reality - or at least save realism. Actually just local realism.
  • 07:24: According to the Bell theorem, any local-realist theory must obey the Bell inequality.
  • 07:32: So the violation of the inequality could be a violation of realism OR of locality.
  • 07:40: ... a local realist theory, every point in space and time - every event - can only ...
  • 07:52: There are ways to save realism in quantum mechanics by crossing Einstein and abandoning locality.
  • 08:04: On the other hand, Many Worlds interpretation of quantum mechanics saves local realism at the cost of requiring multiple realities.
  • 08:34: ... travels a 45 degree angle, and so if local realism holds, only events in what we call the past light cone of Bob’s ...
  • 08:54: That violates local realism.
  • 09:36: Locality and realism would have been saved if it turned out that the states of the electrons were fixed when their past lightcones overlapped.
  • 09:52: In Bell’s theorem, his inequality is satisfied in local-realist theories - but there is another condition to the validity of the theorem.
  • 10:35: It may still be possible to violate Bell’s inequality without saying anything about local realism.
  • 12:53: ... inequality with extremely high significance, which they claim ensures no local-realist influences could have messed with Alice and Bob’s decisions except in ...
  • 13:20: That pushed back any possible local-realist influence more than half the age of the universe.
  • 13:43: ... many Bell tests, cosmic and regular, tell us that either locality or realism are wrong OR there are multiple realities OR the universe ...

2022-06-22: Is Interstellar Travel Impossible?

  • 06:08: ... cubic centimeter, however the Sun is in an under-dense region called the local ...

2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?

  • 02:43: ... a measure of how much quantum information   is not stored locally in the system itself,  but rather in whatever it’s entangled ...

2022-06-01: What If Physics IS NOT Describing Reality?

  • 07:23: ... chose to  align it. Our distributed information becomes   local to each electron, and in the process  appears to force an ...

2022-05-25: The Evolution of the Modern Milky Way Galaxy

  • 13:17: ... than its meal. That’s  going to change with the final merger of our local   group of galaxies - when Andromeda and the  Milky Way collide. This ...

2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life?

  • 04:32: ... demonstrated that most stars have planets  - at least in the local part of the galaxy.   Kepler also revealed that there are ...
  • 06:56: ... that filled the universe after the Big Bang. As  it cooled, our local lump started to pull itself   together under its own gravity. ...

2022-05-04: Space DOES NOT Expand Everywhere

  • 01:24: ... in the mutual gravity of their galaxies, galaxies whirl and collide in local groups and clusters. But if you expand your view to large enough scales, ...

2022-04-27: How the Higgs Mechanism Give Things Mass

  • 02:31: ... wavefunction from one point in space to the   next - local phase - doesn’t affect measurable  quantities - only relative phase ...
  • 03:09: ... that the laws of physics are invariant  under changes in local phase. The set   transformations that can change local phase ...
  • 09:34: ... symmetry. Repeating  our electromagnetism trick means requiring local   U(1) invariance. We need the laws of physics  to still make sense ...
  • 12:59: ... and electromagnetic   interactions, so we need simultaneous local  U(1) and SU(2) symmetry. Let’s just do U(1)   because that ...

2022-03-30: Could The Universe Be Inside A Black Hole?

  • 06:35: But there’s still an “outside” in which the white hole appears as a bright, localized point in space.

2022-03-23: Where Is The Center of The Universe?

  • 18:46: So it looks like local interferenced.

2022-02-16: Is The Wave Function The Building Block of Reality?

  • 08:02: ... theory that inspired many subsequent models, like Continuous Spontaneous Localization. In CSL, physicists imagined that the localizing mechanism was a randomly ...

2022-02-10: The Nature of Space and Time AMA

  • 00:03: ... of time is entirely defined by the direction of entropy then does a local decrease in entropy does uh a even even if the entire cosmos is ...

2022-01-27: How Does Gravity Escape A Black Hole?

  • 03:42: ... directly interacting with the Sun itself, it’s interacting only with the local part of the gravitational ...
  • 07:02: Virtual particles aren’t localized like that.
  • 11:18: You interact with the local curvature of spacetime, which is produced by the past mass, which from your point of view is on the event horizon.
  • 16:08: But on small scales, local gravitational influences dominate.

2022-01-12: How To Simulate The Universe With DFT

  • 07:15: In the Newtonian case, particles only interact locally, and that means the Newtonian equations of motion are what we call separable.

2021-12-29: How to Find ALIEN Dyson Spheres

  • 11:40: ... or so we’ll either discover one or rule out anything interesting in the local part of the Milky ...

2021-12-20: What Happens If A Black Hole Hits Earth?

  • 05:13: ... But I do not recommend standing right under a falling black hole - locally the encounter is catastrophic. Which is actually a good thing if you ...

2021-11-17: Are Black Holes Actually Fuzzballs?

  • 10:37: The resulting fuzzball doesn’t have a local event horizon - in that there’s no single surface of no-return.

2021-10-20: Will Constructor Theory REWRITE Physics?

  • 09:04: That entanglement has to be initially induced by a local interaction - the qubits must come into contact.

2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe

  • 08:15: ... wavefunction is so spread out   that it becomes hard to even localize  it to being inside a given nucleus.   By the time we reach the ...

2021-08-18: How Vacuum Decay Would Destroy The Universe

  • 05:03: ... prefer to spend its time given the choice. And then there’s another local minimum with a higher   energy - what we call that a false ...

2021-08-10: How to Communicate Across the Quantum Multiverse

  • 11:11: ... wavefunction to a non-linear field. That field sort of spreads the local information from each branch - each world - through the entire electron ...

2021-07-21: How Magnetism Shapes The Universe

  • 06:08: These specks tend to align with the local magnetic field of the Galaxy in exactly the same way as our iron filings align around a bar magnet.

2021-06-16: Can Space Be Infinitely Divided?

  • 00:00: ... Assuming perfect coordination and the ability   to localize my palms to the quantum level. 15 halvings gets them to within a ...
  • 08:37: ... energy induces a process called   pair production. The act of localiuzing the  electron causes pairs of virtual electrons   and ...

2021-04-21: The NEW Warp Drive Possibilities

  • 00:05: His whole “nothing travels faster than light” rule seems to ensure that exploration of even the local part of our galaxy will be an excruciating slow.

2021-03-16: The NEW Crisis in Cosmology

  • 08:03: ... satellite, which tracked the motion of 100,000 stars in our local patch of the galaxy But to really nail down the lowest  rung of the ...

2021-03-09: How Does Gravity Affect Light?

  • 09:46: The only thing that’s not relative is the speed of light - everyone observes the same local speed of light - 300,000 km/s in a vacuum.
  • 09:55: But notice that I said LOCAL speed of light - that means everyone measures the same speed of light passing through their own local patch of space.

2021-01-19: Can We Break the Universe?

  • 07:45: Relativity tells us that there’s not a preferred LOCAL frame of reference.

2020-12-15: The Supernova At The End of Time

  • 02:54: On one of those planets - the third one out - a steamship is making its slow journey to a place that the local carbon based lifeforms call “England”.

2020-11-18: The Arrow of Time and How to Reverse It

  • 04:13: ... a statistical effect - it’s possible for small fluctuations to happen, local drops in entropy, but the larger the system the less likely it is for ...

2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces

  • 05:42: So there we go - we insisted on a symmetry - that the Schrodinger equation is invariant to changes in the local phase of the wavefunction.
  • 06:20: ... is the magnitude of the wavefunction, and the rotation amount is our local phase ...
  • 08:50: ... in the Schrodinger equation so that it would no longer be invariant to local phase ...

2020-08-10: Theory of Everything Controversies: Livestream

  • 00:00: ... do with foundations of quantum mechanics with the notion of space of locality and that the overall set of problems stemming from cosmology the ...

2020-07-20: The Boundary Between Black Holes & Neutron Stars

  • 12:03: We’re shipping it to you from a little star cluster in Sagittarius - made locally from humanely sourced o-giant star of course.

2020-05-11: How Luminiferous Aether Led to Relativity

  • 16:14: ... 85 million light years across. That’s about half again the size of the local Virgo supercluster. That's so weird to think about - the most distant ...

2020-01-13: How To Capture Black Holes

  • 06:15: ... exert a gravitational tug on the surrounding particles. Depending on the local properties of the disk, that can cause the object to either gain or lose ...
  • 06:53: ... the local properties of a disk will change with the distance from the center. In ...

2019-09-30: How Many Universes Are There?

  • 14:43: Alexander has been traveling the bubble universes for many years, supporting local youtube space shows where he finds them.

2019-08-19: What Happened Before the Big Bang?

  • 03:43: Guth's idea is that there's a local minimum in potential energy that allows the inflaton field to get stuck in a false vacuum state.
  • 04:35: ... idea of slow roll inflation is that the inflaton field isn't stuck at a local minimum in the potential but rather it's on a very weakly sloping ...

2019-08-06: What Caused the Big Bang?

  • 06:47: For now, let's just go with it. One possibility is that the field could have what we call a local energy minimum.
  • 06:55: If such a quantum field found itself near that local minimum then it would roll to the bottom and get stuck there.
  • 07:46: But then, it gets stuck in this local energy minima.
  • 08:43: Somewhere in the inflating universe, the inflaton field is going to fluctuate to the other side of this local minimum barrier.
  • 09:07: ... of space adjacent to that point would also be dragged out of the local minimum towards the true vacuum and so the entire inflaton field would ...

2019-07-25: Deciphering The Vast Scale of the Universe

  • 06:50: As we zoom out, now at several trillion times the speed of light, our local group of galaxies comes into view.
  • 07:03: That’s the Virgo cluster – the nearest big city, of which our local group is an outlying suburb.

2019-06-17: How Black Holes Kill Galaxies

  • 01:35: ... directly responsible for the speed of stellar orbits outside their local region Sure, Galaxies and their Black Holes probably grew together but ...
  • 02:54: ... very first generation of stars they would fall to the centres of their local wispy protor galaxy and when wisps merged their central Black Holes ...

2019-04-10: The Holographic Universe Explained

  • 06:25: By making this a conformal field theory we’ve added a symmetry –invariance under local changes in scale – also known as Weyl invariance.
  • 07:15: ... which the rules of physics stay the same, and c) imposes some kind of locality – for example, elements of that number line need to be next to each ...

2019-04-03: The Edge of an Infinite Universe

  • 07:44: ... represent a universe that is “asymptotically flat” – it may have some local curvature due to gravity of massive objects inside, but at its ...
  • 11:02: The other feature of a conformal mapping is that shapes are preserved – at least locally.

2019-03-06: The Impossibility of Perpetual Motion Machines

  • 14:25: Abe Dillon asks whether the "moment" of recombination should depend on the local density.

2018-11-07: Why String Theory is Right

  • 08:35: ... the Schrodinger equation that fixes these phase differences preserving local phase ...
  • 11:07: ... as local phase invariance required us to add the electromagnetic field to the ...

2018-10-25: Will We Ever Find Alien Life?

  • 04:14: Thrillingly, one proposed explanation was an alien mega structure, perhaps a vast fleet of solar collectors built by the local inhabitants.

2018-09-20: Quantum Gravity and the Hardest Problem in Physics

  • 11:09: The non-renormalizability of quantized general relativity is connected to the idea that precisely localized particles produce black holes.

2018-08-23: How Will the Universe End?

  • 03:40: There'll be no evidence of a universe beyond the local galaxy and no evidence that there was ever a Big Bang.

2018-07-11: Quantum Invariance & The Origin of The Standard Model

  • 05:16: This position dependent phase shift is called a local phase shift, instead of a global phase shift.
  • 05:21: We'll try this because, well, we already know that the magnitude squared of the wave function should still stay the same under local phase shifts.
  • 05:38: ... if we do a local phase shift, say, only this point here, only that location changes, as ...
  • 05:50: If you allow this sort of local phase shift, you can change each point in a different way and really mess up the wave function.
  • 06:08: Among other things, messing with local phase really screws up our prediction for the particle's momentum.
  • 06:19: Change the shape of that wave function with local phase shifts and you actually break conservation of momentum.
  • 06:26: Local phase is not a gauge symmetry of the basic Schrodinger equation.
  • 06:38: Just for funsies, maybe we can change the Schrodinger equation to find a version that really is invariant to local phase shifts.
  • 07:06: If we choose this term correctly, it absorbs any local changes we make to the phase.
  • 07:34: ... we've discovered that the only way for particles to have local phase invariance is for us to introduce a new fundamental field that ...
  • 08:24: Any particle that has this kind of charge will interact with and be affected by the electromagnetic field and be granted local phase invariance.
  • 08:35: In order to have this particular type of local phase invariance, particles must possess electric charge.
  • 08:48: In this case, the symmetry is local phase invariance and the conserved quantity is electric charge.
  • 09:41: It turns out that local phase invariance is just the simplest of the larger suite of gauge symmetries of the standard model.

2018-06-13: What Survives Inside A Black Hole?

  • 09:54: However, there are some important conserved properties that are entirely local.

2018-04-18: Using Stars to See Gravitational Waves

  • 11:36: But you decrease entropy locally.

2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)

  • 06:58: ... this local rise in complexity would all cease when the system reaches thermal ...
  • 09:39: ... internal entropy than its chaotic surroundings, but the source of that local incidence of low entropy is the streamline flow that it formed ...

2018-03-28: The Andromeda-Milky Way Collision

  • 05:20: They also included the Triangulum, or Pinwheel Galaxy, the third-largest member of the Local Group.

2018-03-15: Hawking Radiation

  • 08:47: Firstly, this radiation is not localized.
  • 09:17: To them, space is locally flat.

2018-01-17: Horizon Radiation

  • 04:35: A particle perfectly localized in space-- a single spring or a single point on the drum skin.
  • 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 described as an infinite number of ...

2018-01-10: What Do Stars Sound Like?

  • 06:58: The Doppler shifts due to local gas moving are completely washed out.
  • 07:58: But at least for the sun, it's possible to learn about current local events that are hidden from our view.

2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor

  • 11:23: Actually, I think you need an infinite series of PBS Space Time to get a Space Time localization of PBS infinite series.

2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series

  • 08:38: So if we measure a particle's position, then from our point of view, it's wave function is highly localized in space.
  • 10:26: ... a single particle, a quantum field vibration, perfectly localized at one spot in space, can so be described as infinite oscillations in ...
  • 10:51: So a perfectly specially localized particle is equally an infinite number of momentum particles that themselves occupy all locations in the universe.

2017-08-02: Dark Flow

  • 07:26: Since 1973, we've noticed that galaxies in the local part of the universe seem to be drawn in that direction due to an unseen gravitational influence.

2017-06-21: Anti-Matter and Quantum Relativity

  • 14:02: ... vacuum field can have one or more local minima, where the vacuum energy can come to a rest in an eternally ...

2017-04-26: Are You a Boltzmann Brain?

  • 03:37: For example, tiny, localized dips in entropy happen all the time, when you get a chance convergence of a few particles in one corner of the room.

2017-04-10: Here's Why I Love PBS

  • 00:13: ... for Public Broadcasting, which provides critical financial support to local PBS stations, is one such organization on the chopping ...
  • 01:18: One way you can help is to contact your local congressperson or go to a town hall meeting.
  • 01:23: Tell them what your local station and PBS mean to you.

2017-03-01: The Treasures of Trappist-1

  • 10:48: ... is the maximum size region of cloud can be before it fragments, because local gravitational collapse happens faster than pressure can equalize across ...

2016-12-21: Have They Seen Us?

  • 05:56: Perhaps we miss each other because we can't easily peer through our own local VHF soups.
  • 06:10: Two radio telescopes separated by a large enough distance can filter out local transmissions.
  • 06:38: ... TV bubble to many light years and that is large enough to filter out local ...
  • 12:35: If anyone else inhabits this very local region of the galaxy, then they may have been aware of us for some time now.

2016-11-30: Pilot Wave Theory and Quantum Realism

  • 08:27: It turns out that the restriction against hidden variables only applies to local hidden variables.
  • 08:57: This helped the resuscitation of pilot-wave theory, because Bohmian mechanics doesn't use local hidden variables-- its hidden variables are global.

2016-11-02: Quantum Vortices and Superconductivity + Drake Equation Challenge Answers

  • 04:05: ... all wiped themselves out before even making the slightest dent in the local interstellar ...
  • 06:34: That tells me that we may be the only advanced-ish civilization to have emerged in the local region, but probably not within the whole galaxy.

2016-10-19: The First Humans on Mars

  • 03:35: That means either living underground or building dense shelters from local material.

2016-10-12: Black Holes from the Dawn of Time

  • 03:00: ... were, at some point in the early expansion, intense enough to resist the local expansion of the universe and form a black ...

2016-09-29: Life on Europa?

  • 09:57: ... first, the simplest observable difference between the predictions of a local hidden variable theory versus pure quantum mechanics is if you measure ...
  • 10:17: ... the local hidden variable theory, you'd expect to sometimes measure spins in the ...
  • 10:54: ... contrast, a local hidden variable prediction is that the second particle doesn't care how ...

2016-09-21: Quantum Entanglement and the Great Bohr-Einstein Debate

  • 02:40: ... of realism, you also had to abandon a concept almost as sacred-- locality. ...
  • 03:00: Locality is the idea that each bit of the universe only acts on its immediate surroundings.
  • 04:01: ... instantly across any distance, and even back in time, violating locality and possibly violating ...
  • 04:17: ... universe must be real and physical and defined by knowable quantities, local hidden variables that could affect each other no faster than the speed ...
  • 06:00: ... in each particle at the moment of their creation as hidden variables local to each ...
  • 07:13: ... to see in the case that Einstein was right and quantum mechanics needs local hidden ...
  • 07:27: But if an entanglement experiment violates the Bell inequalities, then local realism is also violated.
  • 08:41: ... inequalities are violated, suggesting that the wave function cannot have local hidden ...
  • 08:56: So does this confirm the Copenhagen interpretation and kill both locality and realism?
  • 09:15: The results of these entanglement experiments do seem to violate local realism.
  • 09:19: But that may mean a violation of realism, or just of locality.
  • 09:25: In fact, it was Doctor Bell's opinion that the violation of his inequalities disproved only locality.
  • 10:33: However, realist and hidden variable interpretations are also consistent as long as they abandon locality.
  • 11:01: There is even a way around all of this without sacrificing realism or locality.

2016-08-10: How the Quantum Eraser Rewrites the Past

  • 13:04: In the event of End of World, you guys should show up at your local spaceport.

2016-04-20: Why the Universe Needs Dark Energy

  • 09:53: ... field of the Milky Way and Andromeda to not dominate the shape of local ...

2016-04-13: Will the Universe Expand Forever?

  • 08:14: Over billions of years, they will slip beyond our cosmic horizon, leaving only darkness beyond the local region of the Milky Way.

2016-01-27: The Origin of Matter and Time

  • 06:02: It's defined locally for any observer, or indeed, thing.
  • 06:10: What defines that local time flow?

2015-10-28: Is The Alcubierre Warp Drive Possible?

  • 01:40: ... faster than light, even if the galaxies are relatively still in their local frames of ...

2015-09-30: What Happens At The Edge Of The Universe?

  • 06:01: The surface of the Earth looks pretty flat to us because we really can't see the curvature locally.

2015-09-23: Does Dark Matter BREAK Physics?

  • 08:48: The monkey may see some time dilation effects from the local part of its universe.
  • 09:36: In fact, in the vicinity of the black hole, this radiation is poorly localized, having a wavelength of all of the Schwarzschild radius.

2015-08-12: Challenge: Which Particle Wins This Race?

  • 04:31: ... symmetric perfect fluid whose energy density is the same when measured locally by an observer that's instantaneously at rest at any location in that ...

2015-08-05: What Physics Teachers Get Wrong About Tides!

  • 14:27: In other words, Einstein says the standard of non-acceleration can only be defined locally in small spacetime patches.

2015-07-29: General Relativity & Curved Spacetime Explained!

  • 03:01: Stated another way, a sphere can accommodate local Euclidean grids in tiny patches, but not global ones.
  • 03:47: ... world lines will be geodesics, and their axis and clocks can serve as local inertia frames, provided that we think of them as being reset in each ...

2015-07-02: Can a Circle Be a Straight Line?

  • 06:38: ... those lines might close on themselves, but locally, snippet by snippet, geometry and straightness and tangency and ...
  • 06:53: Topology is global, but geometry and curvature are local.

2015-05-27: Habitable Exoplanets Debunked!

  • 09:45: How that can be, even though locally, in local pockets, you can have energy conservation, seems weird and contradictory.

2015-05-20: The Real Meaning of E=mc²

  • 08:58: ... Challenge." Submit your answers no earlier than 5:00 PM New York City local time on this ...

2015-04-29: What's the Most Realistic Artificial Gravity in Sci-Fi?

  • 00:58: There's simply no known way to produce the equivalent of 1 Earth g on stacked, flat surfaces, like decks of a ship, in any localized region of space.
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