Search PBS Space Time


2022-08-03: What Happens Inside a Proton?

  • 11:28: ... each time step results a complex-valued  phase shift at each spatial point. Those   complex numbers are fine in the Feynman ...

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

  • 06:01: ... that reveals that a   particular type of universe with three spatial  dimensions is encoded on its own 2-D surface.   The power of ...

2022-05-04: Space DOES NOT Expand Everywhere

  • 02:24: ... a metric in GR is the coordinate system of a chunk of spacetime with 3 spatial and 1 temporal ...
  • 02:38: ... Earth, the FLRW metric gives the geometry or shape of the universe. The spatial part of that geometry could be the 3-D analog of our surface of a ...

2022-04-20: Does the Universe Create Itself?

  • 15:24: ... energy. If you just consider the positive effect of gravity, then the spatial geometry dictates the final fate. But dark energy screws everything up. ...

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

  • 06:02: Those three spatial dimensions just loop back on themselves.

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

  • 00:03: ... the big difference is that it became impossible to define a single spatial stage a single slice of space as some kind of definite now or ...

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

  • 03:05: Of course the real universe has 3 spatial dimensions, so for most real applications we’d want Psi(x,y,z).

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

  • 16:33: ... of the string vibrations. It’s holographically projected into 2 spatial dimensions, and in its experience it keeps falling. Meanwhile from the ...

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

  • 07:13: ... this for the somewhat unrealistic case of a black hole horizon with 4 spatial dimensions, but it was a decisive step and it gave us a compelling ...
  • 11:54: Instead of the 4 spatial dimensions of a Strominger-Vafa or the 3 dimensions of regular black holes, let’s think about a 1-D black hole.
  • 12:20: In string theory we have extra compact dimensions - spatial dimensions that are coiled up on the Planck scale so we can’t see them.
  • 12:43: The extra compact dimensions contract and pinch off, so all spatial dimensions end in that direction.

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

  • 09:27: And she argues that only a "superinformation medium" - aka a quantum field - could mediate the entanglement of two spatially separated qubits.

2021-07-13: Where Are The Worlds In Many Worlds?

  • 11:02: Well, sort of - in the sense that the position wavefunctions of the two yous can be mapped to these spatial locations.

2021-04-21: The NEW Warp Drive Possibilities

  • 03:37: It includes a comfortable, flat region of space surrounded by a region of extreme spatial curvature.

2021-03-16: The NEW Crisis in Cosmology

  • 13:38: ... It's the minus the sum of squares of the x,   y, and z spatial intervals, plus the square of time interval times the speed of ...

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

  • 06:40: That temporal component is rotated into the downward spatial direction, which translates into falling.

2021-02-24: Does Time Cause Gravity?

  • 07:39: If photons are already fully rotated into the spatial direction, how is it that they’re also affected by gravitational fields?

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

  • 10:03: ... ladder also has a certain length in the spatial direction - initially longer than the barn, but when the ladder starts ...

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

  • 13:15: "You could say the forwardness of memory is a spatial phenomenon.
  • 13:37: ... information of a future collision is spread out, spatially, before the collision: to "remember" the future collision you have to ...

2020-12-08: Why Do You Remember The Past But Not The Future?

  • 09:54: ... universe started in a state of extremely low entropy - spatially separated regions were definitely uncorrelated with each other, and even ...

2020-10-20: Is The Future Predetermined By Quantum Mechanics?

  • 14:59: ... it would need to be the instantaneous state of the brain, the momentary spatial configuration of its particles at that instant that gives rise to our ...

2020-06-30: Dissolving an Event Horizon

  • 12:00: Then the third dimension is just a way to represent the strength of the spatial curvature and the connections between different regions.

2020-05-27: Does Gravity Require Extra Dimensions?

  • 03:24: In general, gravity drops off as 1/r to some power - and that power is the number of spatial dimensions minus one.
  • 03:36: Newton’s inverse square law for gravity tells us there are 2+1 = 3 spatial dimensions.
  • 04:20: Now we perceive the 3rd dimension, but perhaps our 3 spatial dimensions are similarly embedded in a higher dimensional space that we can’t perceive.
  • 04:32: ... wave detection from LIGO seemed to rule out the possibility of extra spatial ...
  • 04:48: And by large I mean they stretch out over astronomical scales like the familiar 3 spatial dimensions.
  • 05:45: And that’s the sense in which there may be more than 3 spatial dimensions in this universe.
  • 05:57: ... string theory, and in modern superstring theory there are 6 additional spatial dimensions, coiled-up tight at every point in the extended 3-D ...

2020-04-22: Will Wormholes Allow Fast Interstellar Travel?

  • 03:33: ... instant in time. The technical name is an embedding diagram - a 2-D spatial sheet sliced out of 4-D ...
  • 03:45: ... keep time frozen for the moment and add back the 3rd spatial dimension. The ring of the wormhole is actually a sphere the size of the ...

2020-04-07: How We Know The Earth Is Ancient

  • 00:00: ... call deep time is very recent - as recent as our discovery of the true spatial vastness of our universe. And it came as scientists tried to measure the ...

2020-02-18: Does Consciousness Influence Quantum Mechanics?

  • 15:19: So by the mathematical definition, a spatially-farying constant would be a field.

2020-02-11: Are Axions Dark Matter?

  • 14:39: ... inflation. Of course all of this is assuming that the universe is spatially finite. The simplest interpetation of the cosmological equations derived ...

2019-11-04: Why We Might Be Alone in the Universe

  • 14:32: Some One asks if a circle in 2 spatial dimensions would allow for closed time like curves.

2019-10-15: Loop Quantum Gravity Explained

  • 04:30: ... and momentum of quantum mechanics literally describes location on a spatial coordinate system and the change in that location over ...
  • 06:07: ADM starts by defining this abstract space of spaces - 3-D spatial metrics, 3-D space slices cut out of 4-D spacetime.
  • 09:04: ... they could fully solve the Wheeler-deWitt equation by representing spatial metrics using Ashketar's spin ...
  • 11:37: ... LQG has background independence in terms of different 3-D spatial geometries, it’s not actually clear that this independence extends to ...

2019-07-18: Did Time Start at the Big Bang?

  • 04:38: ... could end up as hot and dense as you like But it'll still be infinite, spatially, the scale factor is incredibly small But an incredibly small number ...
  • 05:15: ... in any one place because a point is zero dimensional there weren't spatial dimensions for it to happen in At the same time we say the Big Bang ...

2019-04-24: No Dark Matter = Proof of Dark Matter?

  • 00:03: ... cook for 20 informs is that while we may feel that we live in a three spatial dimension universe serve up down left right forward back we're actually ...

2019-04-10: The Holographic Universe Explained

  • 11:04: In good string-theorist style, Maldacena defined incorporated that scale factor into be a new spatial dimension.
  • 13:41: ... doesn’t appear to be negatively curved AdS space, nor does it have 4 spatial dimensions as in Maldecena’s ...
  • 15:41: Part of the confusion comes from the fact that Maldacena's derivation is for a volume with 4 spatial dimensions, which would have a 3-D surface.
  • 16:12: So first - the "surface" in current AdS/CFT spacetime is 3+1. 3 spatial, one temporal dimensions.
  • 16:27: ... of AdS/CFT is that gravity arises naturally when you add an extra spatial dimension, which ends up looking like the volume contained by the "3-D" ...

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

  • 05:49: ... while the vertical-ish lines are set locations in space in only one spatial ...
  • 11:40: So this disk can represent an infinite anti-de Sitter universe with 2 spatial dimensions at a single instant in time.
  • 12:43: They give you a cylinder and representing an AdS spacetime with 2 spatial and one temporal dimensions – let’s call that 2+1 dimension.

2019-01-09: Are Dark Matter And Dark Energy The Same?

  • 11:39: Just quickly, the density fluctuations seen in the afterglow of the Big Bang reveal a universe that is spatially flat.
  • 11:47: ... the energy of both regular and dark matter, are needed to explain this spatially flat ...

2018-12-20: Why String Theory is Wrong

  • 07:25: ... theory, or at least at the simplicity of just one extra circular spatial ...
  • 07:41: Imagine only one extended and one compactified spatial dimension.
  • 12:43: In all superstring theories the extra spatial dimensions are wrapped, not in simple loops, but in complicated geometries called Calabi-Yau manifolds.
  • 15:37: ... last week we peered into the looking-glass and saw how a universe that's spatially reflected in a mirror has fundamentally different laws of physics to our ...

2018-12-12: Quantum Physics in a Mirror Universe

  • 00:02: ... to save us in the end parity transformations involve the flipping of spatial axis if we define the mirror to be in the XY plane reflection sin z2 ...

2018-11-14: Supersymmetric Particle Found?

  • 15:43: It may have implications for the single extra extended spatial dimension of M-theory, but I need to research that more.

2018-11-07: Why String Theory is Right

  • 01:14: And, by the way, these strings exist in six compact spatial dimensions on top of the familiar three.
  • 11:57: ... and the photon, out of string theory for a very specific number of spatial dimensions, nine to be ...
  • 12:23: Our universe has three spatial dimensions.

2018-10-18: What are the Strings in String Theory?

  • 05:05: ... single framework of m-theory, all for the low price of adding only one spatial dimension for an 11-dimensional ...
  • 10:13: In fact, the theory only works in precisely nine spatial dimensions, plus one for time, plus one for M theory, which we'll come back to.
  • 11:40: Modern M theory proposes an additional large spatial dimension.

2018-10-10: Computing a Universe Simulation

  • 12:07: ... waves were used to search for and rule out the existence of an extra spatial dimension beyond our familiar ...

2018-10-03: How to Detect Extra Dimensions

  • 02:26: ... adding the extra spatial dimensions beyond the usual three could actually explain a lot, from the ...
  • 04:21: But even there, Einstein's general relativity describes gravity perfectly with three spatial dimensions.
  • 05:36: One fun way to do that is to throw in an extra spatial dimension.
  • 05:48: But you restrict all the other stuff in the universe-- matter, radiation, astronomers-- to only three spatial dimensions.
  • 06:20: But in string theory, all but three spatial dimensions of the brane are inaccessible.
  • 06:25: They're finite and coiled up on themselves, compactified, allowing us to cram them into three spatial dimensions.
  • 06:35: ... a three-dimensional brane, a 3-brane, embedded in a space-time with four spatial dimensions, where the extra dimension of space is extended rather than ...
  • 06:55: ... just right, and you get normal physics for matter and radiation in three spatial dimensions-- for example, the usual inverse square law for ...
  • 07:05: On some spatial scales, you even get the inverse square law for gravity.
  • 07:10: But on other spatial scales, gravity can behave very differently.
  • 07:48: In our hypothetical universe with four spatial dimensions, gravity is already weak on the scale of the solar system and the galaxy.
  • 07:59: ... square law on galactic scales, where it's sort of coupled to the three spatial dimensions of the ...
  • 08:14: ... observable universe exists, can actually expand into the extra fourth spatial ...
  • 08:41: ... the gravitational field can extend into this hypothetical extra spatial dimension, then gravitational waves should lose energy to that extra ...
  • 09:29: Does that match what you expect in a universe with three spatial dimensions?
  • 10:49: There was no observable leakage of gravity into extra spatial dimensions, pretty much ruling this out as an explanation for dark energy.

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

  • 15:56: But that spatial sprint really just tells us the probability of finding the electron, say, here or here or here.

2018-05-16: Noether's Theorem and The Symmetries of Reality

  • 02:45: For example, a long road in the middle of nowhere is continuously symmetric under spatial translations in the direction of the road.
  • 03:17: We have symmetry to spatial translation.

2018-03-15: Hawking Radiation

  • 04:11: But spatial curvature can mess with the balance of the underlying quantum field modes by introducing horizons.

2018-02-14: What is Energy?

  • 10:06: For example, the law of conservation of momentum is due to spatial translation symmetry.

2018-01-17: Horizon Radiation

  • 05:56: So let's take our spatial quantum field-- our drum skin, with its single, localized particle, and transform to momentum space.
  • 06:24: Now, each one of these momentum modes exists at all spatial points in the universe.
  • 06:31: ... with the right weightings, they cancel out everywhere except at the spatial location of the original ...
  • 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?
  • 09:35: Infinite spatially undefined particles with defined momenta, and these just happen to cancel each other out, leaving 0 particles or a vacuum.

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

  • 11:01: ... fields in this strange momentum space, by adding and removing these spatially infinite particles, that we can describe how the quantum vacuum changes ...

2017-11-08: Zero-Point Energy Demystified

  • 05:36: That means the vacuum energy between Casimir plates still produces positive spatial curvature, not the negative curvature required for warp drives.

2017-11-02: The Vacuum Catastrophe

  • 05:26: It should also massively increase the spatial curvature of the universe.

2017-10-25: The Missing Mass Mystery

  • 11:29: Yet, it would still push the universe towards positive spatial curvature.

2017-10-04: When Quasars Collide STJC

  • 04:12: In fact, the spatial resolution is equivalent to what you would get with a telescope equal in size to the separation of the radio antenna.

2017-09-28: Are the Fundamental Constants Changing?

  • 07:57: Looking in the new direction, they found that Alpha was larger in the past, suggesting both a temporal and a spatial variation.
  • 08:05: The significance of the spatial variation was claimed to be 4 sigma-- so still tentative.

2017-08-02: Dark Flow

  • 10:53: Well, actually, the spatial positions and even directions of motions of particles in the diagrams don't mean much at all.

2017-03-29: How Time Becomes Space Inside a Black Hole

  • 05:46: Our future light cone stares fixedly forwards, encompassing all spatial directions equally.
  • 09:02: Those directions, those spatial freedoms, are now described by what was once the time coordinate.
  • 09:47: Below the event horizon, there's still a sense of spatial upness and downness.
  • 12:20: It doesn't also have to be a regular crystal that has a repeating spatial pattern.

2017-01-25: Why Quasars are so Awesome

  • 01:57: ... were only blobby because those early radio antennae had some pretty bad spatial resolution, making it difficult to pinpoint exactly where on the sky ...

2017-01-19: The Phantom Singularity

  • 09:17: And once inside, inward spatial movement continues to be the only way to fuel the ticking of an object's proper time clock.

2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer

  • 03:14: The effect is a telescope thousands of kilometers in diameter, at least in terms of its spatial resolution.

2016-12-21: Have They Seen Us?

  • 06:24: That is to increase the spatial resolution of your observations.

2016-11-16: Strange Stars

  • 11:07: It's definitely spatially three-dimensional.

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

  • 10:41: ... bridges, wormholes that allows instantaneous contact even between great spatial ...

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

  • 02:35: k is, in a sense, the shape of the universe-- its spatial curvature, as well as its spatial extent, finite or infinite.
  • 02:44: Notice I said "spatial" curvature.
  • 02:53: But the spatial geometry of the universe at a fixed instant in time can be flat or curved.
  • 03:05: "k equals plus 1" means the universe has a positive-curvature spatial geometry.
  • 03:12: Spatial snapshots of the cosmos at an instant in time will be curved like the surface of a sphere-- except the 3D surface of a 4D hypersphere.
  • 03:39: But the total spatial volume of such a universe is finite.
  • 04:13: Zero spatial curvature, at any given time.
  • 04:16: Geometry works just as you learned in school, and a flat universe is still infinite-- open-- in all three spatial dimensions.

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

  • 08:35: It describes the shape of the universe-- its spatial curvature.

2016-04-06: We Are Star Stuff

  • 11:10: So constant time spatial curvature, which is different to the curvature of spacetime.
  • 11:39: ... spatial curvature refers to the fact of the geometry of space on the largest ...

2016-03-16: Why is the Earth Round and the Milky Way Flat?

  • 02:48: Gravity exerts itself equally along the three spatial dimensions.

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

  • 01:37: So we define a thing as its complete spatial and temporal existence.

2015-12-09: How to Build a Black Hole

  • 04:16: Every spatial location and every momentum location connected to those special locations contains a neutron.
  • 07:06: If we can somehow add more matter to a neutron star-- throw another star at it, maybe-- it won't get spatially larger.

2015-08-19: Do Events Inside Black Holes Happen?

  • 03:24: According to observers like the monkey who are at those events, those events take place at spatial locations inside that black blob we see in the sky.
  • 03:58: ... blob you see in the sky is just what it ends up looking like in ordinary spatial and temporal terms when you delete entire occurrences from every ...

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

  • 12:33: So you down project everything into 3D spatial and temporal terms with respect to that not inertial frame.

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

  • 01:54: ... lines of other inertial observers are straight, indicating constant spatial ...
  • 02:08: ... other force, that would cause some world lines to become curved, i.e, spatially ...
  • 06:48: ... or even the pictures we sometimes use on this show, they all suggests spatial curvature only, so they're somewhat ...
  • 07:07: ... it's curved time that makes the free fall orbits of satellites looks spatially circular in frames of reference that cover too big a space time ...
  • 07:50: ... when you translate those geodesics into 3D spatial and temporal terms, what you find is planetary orbits or spatially ...

2015-07-22: SPECIAL ANNOUNCEMENT + Flat Spacetime Geometry Comments

  • 04:41: They're moving at constant spatial velocity.

2015-04-22: Are Space and Time An Illusion?

  • 06:32: So why do we perceive reality in such a vividly spatial and temporal way?
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