Search PBS Space Time


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

  • 16:44: ... you open the box. But   electron spin also has a directional axis - e.g. up-down, left-right, forward-back - and that ...

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

  • 03:06: Let’s say we have a pair of electrons; each is in a superposition of spin states, say, with spin axis simultaneously up and down.
  • 04:06: Upon measurement it will become fixed along the axis of the measurement device.
  • 04:51: ... certain peculiar correlations between their choices of measurement axis and the other’s measured ...
  • 08:18: Let’s play out the Bell test on something called a space-time diagram - with one dimension of space only on the x axis and time on the y.

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

  • 04:56: ... point of view, think of it as  a particle’s orientation - a spin axis that   can point either up or down. But really the  ...

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

  • 09:00: ... simple symmetry that  it’s the same if you reflect it around the y axis. ...

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

  • 09:47: Just flip the timel axis and you have a white hole containing a bubble of expanding space that looks much like our universe.

2022-03-16: What If Charge is NOT Fundamental?

  • 02:30: ... it can be +1/2 or -1/2, loosely corresponding to the spin axis being aligned or anti-aligned with your measurement device, which we’ll ...

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

  • 07:25: An equation is separable if the solution along one axis - in one dimension - doesn’t depend on the solutions on any other axis.

2021-10-13: New Results in Quantum Tunneling vs. The Speed of Light

  • 10:40: In 2020, a paper was published in the journal Nature that used the swiveling axis of a particle’s quantum spin as the clock hand.
  • 10:48: ... which a particle’s dipole magnetic field, which is defined by its spin axis, precesses like a top in an external magnetic ...

2021-07-07: Electrons DO NOT Spin

  • 07:02: ... manifesting as something like the direction  of a rotation axis, or the north-south pole of the magnetic ...

2021-06-23: How Quantum Entanglement Creates Entropy

  • 15:02: ... curve where it seems to go rapidly vertical   depends on the axis choice. If you zoom in on that kink you’ll see - what? An ...
  • 17:55: ... - which means a   range in possible momentum along each axis is roughly the momentum of the ...

2021-04-07: Why the Muon g-2 Results Are So Exciting!

  • 09:49: The muons interact with the magnetic field and their own magnetic dipole axis, rotate like a top just before it falls.

2021-02-17: Gravitational Wave Background Discovered?

  • 00:00: ... intense magnetic fields they also rotate rapidly with the rotational axis offset from the magnetic poles causing those jets to sweep through space ...

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

  • 04:33: ... - all events corresponding to your notion of a given tick on the time axis. ...

2020-12-22: Navigating with Quantum Entanglement

  • 04:12: This “declination” points towards the magnetic poles, which are offset from the true poles defined by Earth’s rotational axis.

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

  • 04:36: Time increases upwards, while the horizontal axis is separation in space.

2020-10-13: Do the Past and Future Exist?

  • 05:38: ... had a single time axis that everyone agreed on, and everyone agreed what slice of the block was ...

2020-03-16: How Do Quantum States Manifest In The Classical World?

  • 02:56: ... quantum particles have a property called quantum spin. That spin has an axis that points in some direction, analogous to the axis of a rotating ball. ...
  • 03:12: ... vertically and you might see that the spin axis is pointing up or down, measure horizontally and it’ll be pointing left ...

2019-10-21: Is Time Travel Impossible?

  • 07:13: It’s simple: just build an infinitely long cylinder of extreme density and set it rotating insanely quickly about its main axis.
  • 08:20: His involved an entire universe, rotating about a central axis and with matter and dark energy perfectly balancing it against collapse or expansion.

2019-09-03: Is Earth's Magnetic Field Reversing?

  • 06:21: As a result, the starting magnetic field gets wound up into rings around the axis of rotation – into a torus shape.
  • 06:47: Those loops form magnetic tubes around Earth’s rotational axis.
  • 07:54: The north and south gomagnetic poles are close to the geographic poles – so, close to Earth’s rotation axis, but are not quite exactly aligned.

2019-05-09: Why Quantum Computing Requires Quantum Cryptography

  • 11:25: ... where the entanglement comes in: choose an axis or basis on which to measure one of those particles – say up-down for ...

2019-05-01: The Real Science of the EHT Black Hole

  • 09:19: ... mass and spin rate, while they were able to nail down the rotational axis rotation based on the jet that we see leaving the ...
  • 10:01: ... us the rotational direction of the vortex, so combine that with the axis direction from the jet and we have the rotation direction of the black ...

2019-01-16: Our Antimatter, Mirrored, Time-Reversed Universe

  • 00:42: ... an electron out in the opposite direction to their nucleus speed axis but in a mirror reflected universe the same decay should be in the ...

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

  • 00:02: ... 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 minus ...

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

  • 02:29: But these are what we call discrete symmetries-- single flips around one axis or rotation by specific amounts.

2018-04-04: The Unruh Effect

  • 01:34: A space-time diagram has two axes, time and, well, space, with time on the vertical axis.
  • 02:04: On the space-time diagram, this is a line with a 45-degree angle from the vertical axis.

2017-12-20: Extinction by Gamma-Ray Burst

  • 07:40: The fact that the spiral appears to be face on suggests that the axis of the entire system is pointed directly at the Earth.
  • 07:48: The rotational axis of the star will define the direction of the jet in the event that this Wolf-Rayet star does produce a gamma-ray burst.
  • 08:16: Also, further observations with the Keck telescopes indicate that the system's orbital axis isn't pointed directly at the Earth.
  • 08:26: It's the star's rotational axis that defines the direction of the jet.
  • 08:30: But the orbital axis of a binary system and the rotational axis of its stars are often correlated, so we may have dodged a bullet in this case.

2017-09-20: The Future of Space Telescopes

  • 02:12: The wave nature of light causes it to bend or diffract around the edges of a coronagraph back towards the central optical axis.
  • 03:16: ... petal geometry is designed to diffract light away from the central axis, not towards ...
  • 06:16: Light diffracts around the disk, coming to focus on the optical axis where the light's wavefronts line up in constructive interference.

2017-08-16: Extraterrestrial Superstorms

  • 02:06: Earth is, of course, rotating on its axis.

2017-07-12: Solving the Impossible in Quantum Field Theory

  • 03:23: The other axis represents space, although the actual distances aren't relevant.

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

  • 02:55: The axis of spin can point in different directions; for example, up or down.
  • 04:05: ... of freedom were the direction of pointing of the angular momentum axis. ...

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

  • 05:40: Ahead along our time axis and at right angles to all of our space axes.
  • 06:18: Your future light cone and your time axis begin to blur together with the inward radial axis of the black hole.

2017-03-22: Superluminal Time Travel + Time Warp Challenge Answer

  • 02:08: In the olden days, the same time axis of a space time diagram would apply to everyone, but no longer.
  • 02:34: Everyone draws their space time diagram time axis parallel to their direction of motion, because that's their experience of stillness.
  • 02:42: The tick marks on that time axis also depend on velocity and represent the speed of everyone's personal clock in their proper time.
  • 02:50: And everyone also has a different space axis, representing chains of simultaneous events according to their perspective.
  • 06:05: Their time axis is their own world line, and their space axis is symmetrically reflected around the path of light.
  • 07:46: ... moving forward in time, upwards according to the Annihilator's own time axis. ...
  • 08:09: ... does appear to travel backwards in time according to this new time axis. ...

2017-02-22: The Eye of Sauron Reveals a Forming Solar System!

  • 02:58: And that rotation allows it to resist falling towards the central axis.

2017-02-02: The Geometry of Causality

  • 03:16: Motion at a constant velocity appears as a sloped line, and the time axis is scaled so that the speed of light is a 45 degree line.
  • 03:48: My world line is only through time, and the tick marks on the time axis correspond to my own proper time clock ticks.
  • 05:06: They see themselves as stationary, so their time axis is just their own constant velocity world line.
  • 06:18: Even just doing this graphically, we see that the traveler's x-axis is rotated by the same angle as their time axis.

2016-12-08: What Happens at the Event Horizon?

  • 03:04: It lives at x=0 on the space axis, but exists through all the times on the graph.

2016-09-29: Life on Europa?

  • 09:57: ... is if you measure the spins of both particles with the same measurement axis. ...
  • 10:17: ... same direction, depending on the relationship of the chosen measurement axis with the hidden spins of the ...
  • 10:42: That's because the measurement of its entangled twin forces its alignment to be 90 degrees to its own measurement axis.

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

  • 05:20: We define spin direction according to the spin axis.
  • 05:23: That axis can point in any direction.
  • 05:26: But to measure spin direction, we need to choose an axis to align our measuring device.
  • 05:31: We always find that the observed quantum spin aligns itself with our chosen measurement axis.
  • 06:28: But there'll be no correlation due to our choice of measurement axis.
  • 06:51: Both particles should then manifest opposite spins along whichever axis we choose for one of the particles.
  • 06:59: That should lead to a correlation between our choice of measurement axis for the first particle and the spin direction then measured for the second.
  • 08:11: ... there was a correlation between the choice of polarization measurement axis for one photon and the final polarization direction of its entanglement ...

2016-06-22: Planck's Constant and The Origin of Quantum Mechanics

  • 11:50: ... is perfectly circular around the line connecting the three-- the optical axis-- then the light source will be stretched out into a ...
  • 12:19: The quasar is away slightly offset from the optical axis.
  • 12:22: Also, the lens mass distribution is never perfectly circularly symmetric around its axis.
  • 12:50: ... for at least part of the galaxy to be located directly on the optical axis. ...

2016-05-25: Is an Ice Age Coming?

  • 03:31: Two, the pointing of Earth's axis precesses.
  • 03:41: In addition, the long axis of Earth's elliptical orbit also precesses.
  • 04:11: Our spin axis is now tilted at 23 1/2 degrees relative to the axis of our orbit.

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

  • 01:58: They can be rotated around one axis and keep their basic shape.
  • 09:14: The gas can't fall any closer to the axis of rotation because it's orbiting that axis.
  • 09:21: However, gravity is pulling both inward towards the axis and down towards the center.

2016-02-17: Planet X Discovered?? + Challenge Winners!

  • 01:10: ... elongated orbits, orbits that are roughly aligned with each other in the axis of their ...
  • 04:25: By definition, ticks correspond to intervals on our time axis.

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

  • 05:41: So what this means is that there's no single preferred vertical time axis, or indeed, horizontal space axis.
  • 05:48: We can draw that time axis along any constant velocity time-like path, and just Lorentz transform to get a valid perception of space time.

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

  • 01:01: Place a strong gravitational field on an axis between a light source and an observer and voila, you basically have a lens.

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

  • 03:08: So the ant can use his axis as rulers and protractors within a patch, but not between patches.
  • 03:47: ... world lines will be geodesics, and their axis and clocks can serve as local inertia frames, provided that we think of ...

2015-07-15: Can You Trust Your Eyes in Spacetime?

  • 01:55: My clock and my axis together make a frame of reference, which should also have y and z-axes, but I want to keep things visually simple.
  • 02:01: To represent this set up in a diagram, let's copy my x-axis onto a blackboard and add a vertical axis to show the time on my clock.
  • 02:09: ... that vertical axis is showing the distance ct that light travels per tick of my clock, ...
  • 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.
  • 03:04: I get a nice 45 degree line thanks to the funky vertical axis units I was using.
  • 03:46: It coincides with my time axis.
  • 07:58: ... of tracking changes in the monkey's position on my axis with respect to ticks of my clock-- that's ordinary velocity-- I'm going ...

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.
  • 01:11: You might expect that torque to tilt the axis back to zero degrees.
  • 01:14: But instead, it causes the spin axis to precess, like a top.
  • 01:29: ... the fact is that Earth's axis precesses in the opposite sense of Earth's orbit around the sun, so that ...
  • 04:28: The rotation axis wobbles.
  • 04:29: The simple precession of the axis that we've discussed today is just the tip of the iceberg.

2015-05-06: Should the First Mars Mission Be All Women?

  • 09:43: The reason is that if he's driving along the axis of the space station, there would be no Coriolis effects.
  • 09:47: The Coriolis effects would only be there if you move along the rim, not along the axis.
  • 10:10: You might be able to have something on the axis to sort of inject more air out and artificially increase the air pressure there.

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

  • 07:12: ... long and half a kilometer in radius spinning around its longitudinal axis. ...
  • 07:46: ... that objects or people that are at rest near the center of the central axis don't fall toward the ...

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

  • 05:21: The board, its points and geometric facts, are simply there whether we put axis on that board or not.

2015-04-08: Could You Fart Your Way to the Moon?

  • 01:35: ... along the longitudinal axis, there's only one wall to strike, and the particles push the rocket ...
  • 07:44: ... to orbit around the planet at the same rate that the planet spins on its axis, which I agree is not something that should happen if the moon is also ...

2015-03-18: Can A Starfox Barrel Roll Work In Space?

  • 01:08: The net force will push up on one wing, down on the other, torquing the plane like a doorknob around its longitudinal axis.
  • 01:56: ... a planet, will continue to spin at exactly the same rate, along the same axis, until something applies a torque to change that ...
  • 02:09: ... speaking, that narrow points along the axis of rotation, in the same direction that the thumb of your right hand ...
  • 03:29: ... the axis of my torso is a longitudinal axis of the Arwing, with the ship's nose ...
  • 06:46: Can you come up with a simple design to keep the ship on axis during the barrel rolls without thrusters?
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