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2022-08-24: What Makes The Strong Force Strong?

  • 18:07: After all, Hawking radiation is sometimes portrayed as a virtual particle-antiparticle pair being separated by a black hole event horizon.
  • 18:15: ... answer is that the story about separation of virtual particles by the event horizon is a meant to be an intuitive picture of what’s happening, and has only ...
  • 18:28: Hawking’s original derived his radiation by calculating the disturbances on the quantum fields due to the appearance of an event horizon.
  • 18:42: But the event horizon changes the balance of these modes causing imperfect canceling, which looks like particles are being radiated by the black hole.

2022-06-22: Is Interstellar Travel Impossible?

  • 19:10: Otinane Yos asks whether we can be sure that virtual particle - antiparticle pairs get separated near a Black Hole event horizon.

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

  • 03:20: ... each other. If these particles get separated by a black hole event horizon   before they can annihilate, one particle escapes and becomes real, ...

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

  • 18:41: ... field. You may have heard me say that space  flows across the event horizon of a black hole   at the speed of light - that’s the ...

2022-05-04: Space DOES NOT Expand Everywhere

  • 11:22: ... radiation seems to emerge from sub-Planck-wavelength radiation at the event horizon of a black hole. Its solution takes us to the realm of the holographic ...

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

  • 16:10: ... Actually, we should expect a type of Hawking radiation from the cosmic event horizon even if the universe isn’t a black hole. All event horizons will lead to ...
  • 17:39: ... all the stars, dark matter, other black holes, etc - then it’s event horizon is the same size as our cosmological even horizon. Sounds too much ...

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

  • 01:01: In general relativity, that looks like a point of infinite density surrounded by an event horizon.
  • 01:07: We can think of the event horizon as the surface where the flow of space itself is like a river moving at the speed of light.
  • 01:15: ... fact that nothing that not even light can travel back out from below the event horizon. ...
  • 01:26: The universe also has a singularity and an event horizon.
  • 01:46: That expansion gives us our event horizon.
  • 02:09: This is the cosmological event horizon.
  • 02:22: ... the accelerating expansion of the universe means the cosmological event horizon is closer to us than the spot where recession equals the speed of ...
  • 05:19: ... is the all-encompassing future for the spacetime that lives beneath the event horizon in the same way that the big bang is the encompassing past for the for ...
  • 06:13: ... past, space-like singularity of the white hole is surrounded by an event horizon that is the opposite to a black hole event horizon - it can only be ...
  • 06:24: Space flows at the speed of light across the event horizon from within.
  • 06:28: That’s starting to look like our universe - a past, space-like singularity and an event horizon that can’t be crossed from the outside.
  • 08:36: ... thing collapses under its own gravity and an event horizon forms around it, but within the collapsing cloud the matter remains ...
  • 09:30: And that’s true even after the black hole’s event horizon forms.
  • 12:11: If we’re within the event horizon of a black/white hole, what’s on the outside?

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

  • 14:52: ... wave whose wavelength is short compared to the black hole’s event horizon can be completely swallowed, while a larger gravitational wave will get ...
  • 16:15: ... time dilation that we talk about approaching the black hole event horizon is not from the point of view of falling matter, but from the point of ...
  • 16:48: ... asks if an outsider observer sees matter slow and freeze at the event horizon, what happens when the event horizon grows? Does that matter get ...
  • 17:42: ... observe an object being frozen at the event horizon if the light emitted at the moment it crosses the horizon from its ...
  • 18:37: ... Thomas asks another related question. If we never see anything cross the event horizon, why do we say information is lost? When people talk about information ...

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

  • 00:00: ... the very center Fact: every black hole singularity is surrounded by an event horizon. ...
  • 00:10: Nothing can escape from within the event horizon unless it can travel faster than light.
  • 01:01: ... of infinite density surrounded by this boundary of no return - the event horizon. ...
  • 02:56: ... of light, and all of the mass of a black hole is hidden beneath the event horizon, how does its gravity get out to influence the surrounding ...
  • 03:07: Shouldn’t a black hole’s event horizon protect the universe from its own malicious influence?
  • 03:27: There’s no question here - a black hole’s gravity doesn’t care about the event horizon at all.
  • 04:38: Falling from very far away, an observer and the patch of space that they occupy reach light speed at the event horizon of the black hole.
  • 04:56: At some point it exceeds the swimming speed of any possible fish - that’s the event horizon.
  • 05:13: The water at the “event horizon” doesn’t know about the fall.
  • 06:42: If gravity is really communicated by a particle, how does that particle escape the event horizon?
  • 06:47: Actually, even in this picture, the event horizon has no way to halt the force of gravity.
  • 07:33: ... location of the singularity, and they don’t have to travel through the event horizon to do their ...
  • 08:25: But if we’re describing the gravitational field as being built up by virtual gravitons then the event horizon is no barrier at all.
  • 08:39: ... this idea of sending information across an event horizon brings us to our last argument, and this one works whether we’re talking ...
  • 09:12: ... present mass of a black hole is hidden below the event horizon, but we can see its past mass, and it’s the gravitational effect of the ...
  • 09:27: As it approaches the surface that is to become the event horizon, it approaches light speed with respect to someone watching from a distance.
  • 09:39: It appears to freeze at the event horizon, and the light it emits becomes stretched out and sapped of energy.
  • 10:01: So we can still “see” the mass of a black hole - it’s imprinted on the event horizon.
  • 10:55: ... inside the black hole, but from your point of view it’s frozen on the event horizon, but is happily exerting its influence on the surrounding ...
  • 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.
  • 11:53: To sum up - don’t mess around near black holes hoping that the event horizon will protect you from the black hole’s gravity.

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

  • 04:26: ... then it’s probably already happened. This PBH would be small - its event horizon - its surface of no-return - would be around the size of an atom. And it ...
  • 05:13: ... Martian moon phobos - 10^16 kg like a large asteroid. That gives it an event horizon the size of a hydrogen atom. At interstellar speeds it spends around a ...
  • 06:02: ... black hole, gravity accelerates matter to incredible speeds. Near the event horizons, particles collide with each other sizable fractions of the speed of ...
  • 07:05: ... tiny event horizon of a micro black hole is a very narrow choke-point for matter trying to ...
  • 16:33: ... in free space. That means that an observer falling through a black hole event horizon shouldn’t notice anything special about that boundary - except the fact ...
  • 18:16: ... - lasts longer for fuzzballs than for regular black holes due to the event horizon being less cleanly defined. It’s also been suggested that the Event ...

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

  • 00:39: ... is surrounded by a surface from which even light can’t escape - the event horizon. ...
  • 01:10: And at the event horizon another paradox arises.
  • 02:56: The no-hair theorem says that there’s no information beyond charge, mass and spin that’s observable above the event horizon.
  • 04:29: But this is also the problem at the event horizon.
  • 05:09: ... gravity starts to get quantum even above the event horizon, then it may be possible to actually encode information on that surface ...
  • 06:17: It turns out that though, that string theory can make sense of the black hole event horizon also.
  • 06:55: ... stumbled on the mechanism by which information could be encoded on the event horizon. ...
  • 08:06: ... or how they form, or how structure can actually be supported on the event horizon. ...
  • 09:09: ... this is right, then black holes don’t have an empty event horizon at all, but rather a real surface that looks like a tangled nightmare of ...
  • 10:37: The resulting fuzzball doesn’t have a local event horizon - in that there’s no single surface of no-return.
  • 12:10: The event horizon is just the pair of equidistant points on the line inside of which escape is impossible.
  • 12:38: For a fuzzball, spacetime closes on itself at the event horizon.

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

  • 15:36: ... monopole would manifest as a black hole - in that it would have an event horizon. ...

2021-09-21: How Electron Spin Makes Matter Possible

  • 15:48: ... slingshot, so at most they can appear to be coming from the edge of the event horizon. ...
  • 16:12: ... that’s exactly why the event horizon telescope image looks like that. Although in that case the dark area is ...

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

  • 13:06: ... mass is growing and at some point soon it’ll form an inescapable event horizon and we’ll be   stuck inside an actual black hole. Escape ...

2021-09-07: First Detection of Light from Behind a Black Hole

  • 01:08: Now you might remember the picture of the black hole captured by the event horizon telescope.

2021-07-21: How Magnetism Shapes The Universe

  • 11:40: Intense magnetic fields live just above the event horizon of some of thses black hole, and thread the infalling disk.
  • 11:54: ... light surrounding the M81 supermassive black hole observed by the event horizon ...

2021-05-25: What If (Tiny) Black Holes Are Everywhere?

  • 00:23: They’re surrounded by this surface we call the event horizon, whose defining property is that nothing that falls beneath it can ever emerge.
  • 02:06: ... used a sort of a hack - a brilliant workaround - to prove that if an event horizon forms in a vacuum, then the vacuum states of the quantum fields have to ...
  • 02:36: In the common pop-sci description of Hawking radiation you often hear about particle-antiparticle pairs appearing at the event horizon.
  • 02:45: This is misleading; for one thing, the radiation doesn’t appear right above the event horizon.
  • 02:52: ... the wavelength of the emitted particles are about the size of the whole event horizon, so they sort of emerge from the entire region surrounding the black ...
  • 03:02: For the black hole left behind when a massive star dies, the event horizon is several kilometers in radius.
  • 04:19: One big assumption is that the space near the event horizon isn’t TOO strongly curved compared to the smallest quantum scale.
  • 06:41: Such a black hole would have an event horizon of around 10^-35 meters - the Planck length.
  • 09:58: A way around this has been proposed - what if space inside black holes actually expands to a region larger than the event horizon?

2021-05-11: How To Know If It's Aliens

  • 15:39: ... of the bubble in a similar way to how things appear to freeze at the event horizon of a black hole. Nothing actually passes into the bubble, so the ship is ...

2021-04-13: What If Dark Matter Is Just Black Holes?

  • 06:38: ... though these black holes would have microscopic event horizons, at those insane abundances, they’d be wreaking absolute havoc in various ...

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

  • 04:37: ... the event horizon of the black hole, gravitational time dilation is so strong that clocks ...

2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time

  • 01:17: ... be surrounded by a surface where time froze.   Beneath that “event horizon” all matter, light, space itself was doomed to fall inwards towards ...
  • 01:58: ... of matter could reach the densities  high enough to produce an event horizon - nor   even whether such dense matter would  really ...
  • 04:06: ... why did this deserve a Nobel prize? Penrose set out to show that an event horizon   and a singularity would form for any distribution of matter, no ...
  • 05:55: ... about  black holes is that null geodesics beneath   the event horizon that are trying  to travel outwards also converge.   ...

2020-08-24: Can Future Colliders Break the Standard Model?

  • 14:28: ... asks a tricky one: when two black holes merge and share a single, warped event horizon, shouldn’t there be a thin sliver of space in between that is not flowing ...
  • 15:06: ... general relativity calculations reveal an event horizon cross-section that’s called the pair-of-pants function - it looks like ...
  • 15:16: They start separate, and the event horizons move towards each other as they join, and at some point the event horizons touch and then merge.
  • 15:28: ... flow of space anywhere on the event horizon has to be exactly perpendicular to the face of the event horizon - so at ...

2020-08-17: How Stars Destroy Each Other

  • 11:04: Zack Hamburg asks how we know that a black hole isn’t just a neutron star behind an event horizon.
  • 11:27: So what happens to the neutron star after it collapses enough to form an event horizon?
  • 11:32: Well, below that event horizon, we can think of space flowing downwards faster than the speed of light.
  • 13:37: Frank and Jim asked how the event horizons of merging black holes change just before they combine.
  • 13:42: ... do deform into a sort of 8 or hourglass shape - in the sense that the event horizons sort of reach out to each other, connect, before coming together into an ...
  • 13:56: ... about the shape of the stuff inside the black hole - we’re just the event horizon - the surface below which there’s a faster-than-light flow of ...
  • 14:07: Here’s a simulation from the SXS - simulating extreme spacetimes group at ... that shows how the event horizons merge.

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

  • 05:42: ... of being black holes, which by definition have an escape velocity at the event horizon equal to the speed of ...
  • 06:49: It’s like a phantom event horizon.
  • 06:52: In the case of the earth the phantom event horizon is about a centimeter in diameter.
  • 07:00: As you increase a neutron star’s mass, its phantom event horizon grows while its actual surface shrinks.
  • 12:18: ... In our last two episodes we talked about how to dissolve a black hole event horizon by adding rotation or charge to the black hole, and also about ...
  • 12:34: ... trying to disolve an event horizon by throwoing more and more electric charge into it - Ultimantis points ...
  • 13:03: ... Cimo has a good one: What if I cross the event horizon just for a plank lenght and the instant later the black hole shrinks due ...
  • 13:34: ... someone watching from far away, you appear to freeze smeared out at the event horizon - and then yes, they would see your energy exit again as the black hole ...

2020-06-30: Dissolving an Event Horizon

  • 00:44: ... surrounding all of this weirdness is the event horizon: the surface around the central singularity where the inward flow of ...
  • 01:07: The event horizon sounds dire, but it’s a blessing.
  • 01:30: ... states that every gravitational singularity must be surrounded by an event horizon. ...
  • 02:12: So let’s talk about how to dissolve an event horizon, although I would ask you to please not try this at home, for the sake of all of physics.
  • 02:45: With nothing to counter the inward flow of space, an event horizon is inevitable.
  • 03:25: It’s like the eye of the storm, and it’s separated from the surrounding cascade by the inner event horizon.
  • 04:43: ... hole with the maximum amount of spin or charge while still having an event horizon. ...
  • 05:59: The outer event horizon will shrink until it meets the inner horizon, and again you have an extremal black hole.
  • 06:21: Hawking radiation is a direct result of there being an event horizon.
  • 06:58: ... will always stop a gravitational singularity being stripped of its event horizon - but it doesn’t tell us the physical ...
  • 08:06: ... Kerr black hole - one that’s rotating nearly fast enough to lose its event horizon - the gas near the event horizon orbits entirely riding on the carousel ...
  • 10:23: In fact the field itself will always generate enough mass to prevent the black hole from losing its event horizon.
  • 11:16: ... covering two episodes - building black holes in the lab with analog event horizons, and Roger Penrose’s conformal cyclic ...

2020-06-22: Building Black Holes in a Lab

  • 00:16: ... thing about never being able to see inside one beneath the inescapable event horizon. Then there’s the fact that real black holes are, thankfully, very far ...
  • 03:05: ... point where the waterfall of space equals the speed of light is our event horizon. No information - from fish or astronauts or anything - can reach us from ...
  • 03:26: ... that this was just an illustrative, evocative example of the power of event horizons. But by 1982 he realized the two situations had much more in common, ...
  • 04:08: ... mathematically analogous situations and found a number of systems with event horizons Analog theoretical black holes are all very well, but their real value ...
  • 04:55: At some point the flow is faster than the waves - and that’s your analog event horizon.
  • 05:01: ... the speed of ripples on the tank surface you again have an analog event horizon. ...
  • 05:25: ... these event horizons, physicists can look for black hole-like behavior. For example, Hawking ...
  • 08:04: ... passes through the black hole’s ergosphere. That’s the region around the event horizon where the circular flow of space becomes irresistible. It turns out that ...

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

  • 13:29: ... week’s episode we talked about the strange regions that lie beneath the event horizon of a rotating black hole - regions like the Carter time machine and the ...

2020-05-18: Mapping the Multiverse

  • 00:52: Back then we stopped short of dropping below the event horizon - the boundary of no return.
  • 01:11: The inescapable surface surrounding a black hole is called the event horizon.
  • 02:29: ... the event horizon is the ergosphere - a place where the fabric of space itself is whipped ...
  • 02:40: The event horizon itself is distorted - wider at the equator than the poles, just like the rotating earth.
  • 02:50: Now let’s peek below the event horizon to see how weird things really get.
  • 04:20: This leads to a second event horizon called the inner horizon.
  • 07:50: For one thing, the lack of event horizons above you means the ring is a naked singularity, as well as being repulsive.
  • 11:10: ... fact of your utter obliteration before you ever cross the inner event horizon in the first ...
  • 11:21: The complete Penrose diagram for the Kerr spacetime has not one, but two inner event horizons leading to two parallel wormholes.
  • 11:38: ... correspond to the region below the event horizon but they’re causally disconnected, the difference being that time flows ...

2020-05-04: How We Know The Universe is Ancient

  • 14:28: Devansh Rana asks Can wormholes exist without black holes ie without the event horizon.
  • 14:36: ... the Schwarzschild wormhole definitely has an event horizon - although at its most open, entering the event horizon ejects you into ...
  • 16:15: ... the distance has to be short. When the wormhole is fully open, the event horizons of the wormholes ...
  • 16:44: Pass thorugh one event horizon at that instant you exit the other.

2020-04-28: Space Time Livestream: Ask Matt Anything

  • 00:00: ... dead I hope you're okay Bob which is that when mass is just about the event horizon of a black hole is the event horizon slightly distorted due to the ...

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

  • 03:45: ... ring of the wormhole is actually a sphere the size of the Schwarzschild event horizon. If we could pass through that event horizon we would not find ourselves ...
  • 04:50: ... coordinates are blended and mutated so that time doesn’t freeze at the event horizon, which itself becomes this 45 degree path. Sub-lightspeed paths are ...
  • 05:17: ... if you travel to the left at any possible speed you’ll find the event horizon and enter the interior of the black hole. But what if you could travel ...
  • 05:43: ... throat has narrowed in width and passing through means crossing two event horizons - and the region in between is the inside of a black hole. When that ...
  • 11:03: ... useless circumstances like on quantum scales or if they’re hidden by an event horizon. Combined with Roger Penrose’ cosmic censorship conjecture, which ensures ...

2020-03-31: What’s On The Other Side Of A Black Hole?

  • 00:00: ... maps are useless inside black holes. At the event horizon - the ultimate point of no return as you approach a black hole - time ...
  • 01:53: ... hole. It even works inside the black hole - beneath the inescapable event horizon. Although it works in both these regions, the Schwarzschild metric canNOT ...
  • 02:56: ... catch the tortoise, and a plummeting cartographer would fall through the event horizon. The event horizon is just a coordinate singularity like the earth’s ...
  • 03:14: ... infinite stretching of time so that gridlines pass smoothly across the event horizon. ...
  • 03:46: ... coordinates, and they revealed that the singularity of the event horizon was an illusion. Kruskal–Szekeres coordinates improved our map by ...
  • 04:14: ... makes very clear what parts of the universe are accessible. Close to the event horizon, even a light-speed path has only a narrow window of escape. Once inside ...
  • 07:32: ... speed - then you could take these horizontal which would dip beneath the event horizons and emerge in the mirror universe. You’ve just traversed an ...
  • 09:00: ... - and if you can travel faster than light you’ll emerge from the same event horizon that swallowed you. Or you can plunge faster than light towards the ...

2020-03-24: How Black Holes Spin Space Time

  • 00:21: ... And if that mass is sufficiently compressed, the metric predicts an event horizon - a spherical surface where the fabric of space cascades downwards at ...
  • 01:01: ... our own galaxy, and we’ve even taken an image of a black hole with the event horizon telescope. But none of these real black holes are particularly well ...
  • 03:54: ... It’s tempting to just say that some physical thing deep beneath the event horizon is rotating. But if nothing can escape the event horizon, how can that ...
  • 04:11: ... fact, how can any effect of gravity extend from beneath the event horizon? In fact it sort of doesn’t actually. Both the gravitational field and ...
  • 04:26: ... holes are self-sustaining holes in the fabric of spacetime. Space at the event horizon cascades downwards, dragging more space behind it, sort of like how ...
  • 05:49: ... to the common misconception, as long as you don’t get too close to the event horizon it’s possible to orbit a black hole in a perfectly stable way. For a ...
  • 07:27: So yeah, you can orbit “safely” pretty close to the Kerr black hole’s event horizon.
  • 07:33: ... above the event horizon is a particularly bizarre region called the ergosphere. There, frame ...
  • 07:50: ... situation here is actually similar to the state below the event horizon where space moves downwards faster than light. In the math, that ...
  • 08:34: The ergosphere extends all the way down to the event horizon.
  • 08:37: ... the event horizon in the rotating case is not spherical - it’s squished at the poles, like ...
  • 08:54: ... I know you would love to drop below the event horizon right now - but you’re going to have to wait. There’s still plenty to do ...
  • 09:17: ... at exactly the right point, one half will go plummeting through the event horizon while the other is ejected from the ergosphere and escapes. In fact it ...
  • 12:11: ... singularities. And we'll encounter all of these when we drop below the event horizon into the deeper weirdness of the Kerr ...

2019-12-17: Do Black Holes Create New Universes?

  • 03:38: ... it sort of bounces - but unable to exit the event horizon of the black hole, it forms a new region of spacetime, effectively ...

2019-10-21: Is Time Travel Impossible?

  • 08:51: The maelstrom of spinning spacetime may generate closed timelike curves deep down below the event horizon.

2019-10-15: Loop Quantum Gravity Explained

  • 15:49: ... the black hole rotates more than a certain amount then the event horizon evaporates, exposing the singularity to the universe - or in the case of ...

2019-10-07: Black Hole Harmonics

  • 01:30: Imagine it: two event horizons – two roughly spherical black surfaces that are literal boundaries to our universe.
  • 02:06: The event horizon seems to define the surface of the black hole, but really it’s the fabric of spacetime itself that’s vibrating.
  • 03:46: The harmonic oscillations of 2-D surfaces – like drum skins, bells, or the event horizons of black holes – are a good bit more complex than in 1-D.
  • 03:56: In the case of the event horizon, or any spherical-ish surface, we break down the oscillations not into sine waves but into spherical harmonics.
  • 04:33: They leak away over time, but while present they warp the shape of the event horizon.

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

  • 08:27: ... of the art modern observatories like the Gemini Observatory, and the Event Horizon Telescope, and LIGO, which we visited throughout this ...

2019-07-01: Thorium and the Future of Nuclear Energy

  • 17:49: ... this definitely doesn't extend more than 10 or so times the black hole event horizon Oppie asks why NASA isn't dedicating more resources to investigating all ...

2019-06-06: The Alchemy of Neutron Star Collisions

  • 02:47: ... field of the newly formed black hole presumably doomed to fall into the event horizon but that same beta decay process the converted neutrons back to protons ...

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

  • 14:46: ... - our episode on the galaxy without dark matter, and our coverage of the event horizon telescope's black hole ...
  • 15:56: Tommy Barlow states that nor the event horizon, nor anything near it, was imaged.
  • 16:02: The event horizon is invisible.
  • 16:05: But the telescope DID resolve down to the size of the event horizon.
  • 16:16: That's probably around 5 times larger than the event horizon, in the case of this quasar.
  • 16:21: ... seriously, the "light from outside the event horizon because we can't actually see the event horizon telescope" doesn't have ...

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

  • 00:18: ... first ever actual bona fide photo of a black hole, made by the Event Horizon Telescope and revealed to the world in a press conference on April ...
  • 01:00: It has an estimated mass of several billion times that of the Sun, which gives it an event horizon larger than the solar system.
  • 03:31: ... to observe the event horizon of the M87 black hole you need to resolve one one-millionth of 1% of one ...
  • 04:24: ... Event horizon Telescope - the EHT - consists of nine radio observatories across the ...
  • 05:58: The event horizon itself is the point where even outward-pointing light can’t escape the black hole.
  • 06:04: For a non-rotating black hole the size of the event horizon is called the Schwarzschild radius, and it’s proportional to the mass of the black hole.
  • 06:13: But we’re not seeing the event horizon here – that’s somewhat smaller.
  • 09:37: ... found that monster has a mass over 6 billion solar masses, with an event horizon that's about 1/5 the size of that ring– so that’s VERY big, even by ...
  • 10:54: ... this actual picture given to us by the Event Horizon Telescope and its brilliant team – finally hits us with visceral reality ...

2019-04-10: The Holographic Universe Explained

  • 02:41: And while it’s waiting to be radiated, that information should be encoded on the event horizon.
  • 02:52: Things that fall into a black hole do actually experience crossing the event horizon and being inside the black hole.

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

  • 01:22: To review: the particle horizon defines the limit of the visible past, and there’s also cosmic event horizon defining the limit of the visible future.
  • 04:20: ... infinite spacetime –to the edge of an infinite universe or across the event horizon of a black ...
  • 04:49: The first efforts were designed to allow physicists to cross the event horizon of black holes – mathematically.
  • 05:03: ... defeated the artificial infinity – the coordinate singularity - of the event horizon – also something we’ve discussed (the phantom singularity) It was Roger ...
  • 05:31: We’ve used these before to understand black hole event horizons, but these were originally conceived to understand the boundaries of the universe.
  • 15:45: ... all, if space is expanding faster than light at the event horizon, that should counter the light-speed flow of space into the event ...
  • 16:01: ... he suggests that the shrinking cosmological horizon could merge with the event horizon to produce a global state where everything just looks like an ...

2019-03-28: Could the Universe End by Tearing Apart Every Atom?

  • 07:02: ... us to the nearest inaccessible region of space is called the 'cosmic event horizon'. Now, if the expansion is accelerating, then, over time the distance ...
  • 07:38: But as long as we have a nice gravitationally bound galaxy to live in, the cosmic event horizon can never shrink to a size smaller than that galaxy.
  • 07:47: ... increasing dark energy there's no protection from the encroaching cosmic event horizon. ...
  • 08:10: That is the big room scenario, It happens when the cosmic event horizon is smaller than the smallest possible structure.
  • 09:26: ... this doesn't mean that the cosmic event horizon is quite inside the Milky Way just yet, just that the effect of phantom ...
  • 09:38: In fact, at this point the cosmic event horizon is still about 200 million light years away.

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

  • 13:52: ... everyone, I'm back from the event horizon, aka. Australia, which as you know is the CPT inverted version of Canada. ...

2018-10-31: Are Virtual Particles A New Layer of Reality?

  • 00:21: Near black holes, virtual matter and antimatter pairs are separated by the event horizon to create Hawking radiation.
  • 11:11: ... of virtual matter-antimatter pairs being separated by the black hole event horizon, allowing one of the pair to escape to beautiful freedom and ...
  • 11:28: In his actual mathematical derivation, he instead talks about vibrational modes of the quantum vacuum being cut off by the event horizon.

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

  • 13:50: ... incidentally, what it would take to compute a universe simulation on the event horizon of a black ...
  • 14:03: Roman R. asks whether computation at an event horizon would experience massive time dilation relative to an outside observer.
  • 14:17: Really, you can't read off the result of an event horizon computation until practically ever.

2018-10-10: Computing a Universe Simulation

  • 04:13: ... at the Bekenstein bound, essentially, your memory device is the event horizon of a black ...
  • 04:50: Again, the Bekenstein bound is the event horizon surface area in Planck areas with an extra factor of a quarter that Stephen Hawking figured out.
  • 05:24: The radius I gave is the Schwarzschild radius, the radius of the event horizon of a non-rotating neutral black hole, again, like Switzerland.
  • 11:34: It's not clear that programming and then reading out from an event horizon computer is even possible.

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

  • 05:57: ... to put into that region of space would make a tiny black hole with an event horizon one Planck length in ...
  • 13:20: A few of you asked why it is that the surface area of a black hole's event horizon must always increase and how mass and radius can actually decrease.
  • 13:46: Event horizon radius is proportional to mass.
  • 14:30: In that process, the event horizon only changes shape.
  • 15:56: Clue-- you'll need to go beyond the formula for the Bekenstein bound in terms of event horizon surface area.

2018-09-12: How Much Information is in the Universe?

  • 01:57: Jacob Bekenstein figured this out by realizing that the entropy of a black hole is proportional to the surface area of its event horizon.
  • 07:25: And for black holes, that entropy is the Bekenstein bound, the number of Planck areas on its event horizon.
  • 07:32: Because the information about the black hole's previous state is lost, to fully describe it, you need to fully describe its event horizon.
  • 07:54: Its event horizon is around 12 billion meters, giving it a surface area of 10 to the power of 90 to 10 to the power of 91 Planck units.
  • 09:05: ... information limit, it would immediately become a black hole with an event horizon as big as the current cosmic ...
  • 09:42: Essentially, they're computing on the surface of a black hole event horizon.

2018-09-05: The Black Hole Entropy Enigma

  • 02:47: He described a mechanism by which the information contained by infalling particles could be preserved on the event horizon of the black hole.
  • 04:49: At the instant the star collapses far enough to form an event horizon, it becomes a black hole.
  • 06:02: The surface area of a black-hole event horizon can never decrease, at least not according to general relativity.
  • 06:53: That's the surface area of the event horizon.
  • 08:37: ... which is going to be directly proportional to the surface area of the event horizon. ...

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

  • 03:13: ... dragged all galaxies beyond the Virgo Supercluster outside of the cosmic event horizon. ...

2018-07-04: Will A New Neutrino Change The Standard Model?

  • 11:22: So, how does that work with the cosmic event horizon?
  • 11:26: Shouldn't regions outside the event horizon be lost to our access and therefore impossible to trace backwards?
  • 11:33: The statement about the retraceability of the universe doesn't actually care about event horizons, whether cosmic or black hole.

2018-06-20: The Black Hole Information Paradox

  • 00:22: [MUSIC PLAYING] Black holes are engines of destruction that remove from our universe anything that crosses their event horizon.
  • 02:01: The inescapable event horizon shields the outside universe from any other influence within the black hole.
  • 06:07: The motivation for this idea is the fact that, from the point of view of an outside observer, nothing ever actually crosses the event horizon.
  • 10:00: ... how the information on an event horizon gets attached to Hawking radiation is still contentious, but a number of ...
  • 14:49: ... with the interior or just the persistence of the field at the event horizon is a matter of ...

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

  • 00:16: ... massive body, a point of hypothetical infinite density surrounded by an event horizon. ...
  • 00:40: Nothing can travel faster than light, and so nothing can escape from below the event horizon-- not matter, not light, not even information.
  • 01:45: ... electric charge, and angular momentum should emerge from beneath the event horizon. ...
  • 02:20: Nothing beneath the event horizon can influence the exterior universe because no signal can escape the event horizon to carry that influence.
  • 02:44: Given the one-way nature of the event horizon, the loss of this information makes some intuitive sense.
  • 04:20: ... the case of the event horizon, the outside universe can't see the mass inside the black hole, but that ...
  • 04:32: In fact, the space at the event horizon is already falling inwards.
  • 05:22: In the case of a black hole, at least a nonrotating one, the event horizon is a closed spherical surface with a singularity at its center.
  • 06:04: This means that the electric field above the event horizon of a black hole remembers all of the electric charge that fell through that surface.
  • 06:12: Black holes act as though their charge is spread across the event horizon.
  • 09:14: It dramatically changes the shape of the event horizon and the orbit of anything nearby.
  • 09:19: ... of gas, it will either add or subtract from this flow of space above the event horizon. ...

2018-05-02: The Star at the End of Time

  • 10:25: ... the Event Horizon Telescope has now detected radio emission from pretty close to the event ...

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

  • 12:26: Moma the Belly Dancer asks whether this means that the expansion of the universe also causes an event horizon?
  • 12:34: The cosmic event horizon is that service from beyond which we can never obtain new information.
  • 13:09: On the other hand, during the inflationary epoch in the extremely early universe, the cosmic event horizon was very close to every point.

2018-04-04: The Unruh Effect

  • 00:06: Every time you accelerate, put your foot on the gas, quicken your step, get out of your chair, you generate an event horizon behind you.
  • 00:58: It creates a type of event horizon.
  • 04:59: In fact, the active acceleration does create a type of event horizon called a Rindler horizon.
  • 05:06: ... physicist Wolfgang Rindler who, by the way, also invented the term event horizon. ...
  • 07:00: The only observers who don't see Hawking radiation are those plummeting in freefall towards the event horizon.
  • 10:12: ... gravitational acceleration can get that high, and that's right above the event horizon of a black ...
  • 10:21: If you hover close enough to that event horizon, you would actually be bathed in Unruh radiation.
  • 10:29: ... relationship between the Unruh particle seen by someone hovering at the event horizon and the particles of Hawking radiation seen by a distant ...

2018-03-15: Hawking Radiation

  • 00:50: ... to create a hole in the universe, a boundary in spacetime called an event horizon that could be entered, but from beyond which nothing could ...
  • 02:03: ... near a black hole, sometimes, one of the pair will be swallowed by the event horizon, leaving the other free to escape and taking its stolen energy with ...
  • 05:17: It emerges barely ahead of the forming event horizon.
  • 06:55: They are nudged off their narrow escape path and so are lost behind the forming event horizon.
  • 07:29: It produces particles that also have wavelengths about as large as the event horizon.
  • 07:53: More directly, it's proportional to the surface area of the event horizon.
  • 08:07: OK, so what about the whole picture of particle/antiparticle pairs being pulled apart by the event horizon?
  • 08:27: And for the escaping modes, there exist a corresponding set of modes linked by quantum entanglement that are trapped behind the event horizon.
  • 08:51: Remember that Hawking radiation has wavelengths the size of the event horizon, the size of the entire black hole.
  • 09:09: Not from specific points on the event horizon.
  • 10:17: ... Hawking radiation by thinking about particles escaping from beneath the event horizon through quantum ...
  • 10:32: ... modes that we'll want on the same world line becoming separated by the event horizon. ...

2018-01-24: The End of the Habitable Zone

  • 11:56: If the event horizon swallows one half of a virtual matter anti-matter pair, then how does the black hole lose mass?

2018-01-17: Horizon Radiation

  • 01:01: ... example, the event horizon of a black hole, out of which no information can travel or the ...
  • 01:11: And a strange type of apparent event horizon even appears when we accelerate.
  • 10:18: If we introduce an event horizon, then we lose access to some momentum modes, while other modes behave very differently.
  • 11:53: So this year, keep your eye on the horizon-- the event horizon and the strange things it does to the quantum contents of space time.

2017-10-25: The Missing Mass Mystery

  • 12:21: ... particles control faster than the speed of light, can't they escape the event horizon of black holes via Hawking ...

2017-10-04: When Quasars Collide STJC

  • 01:49: The largest have event horizons that would envelop most of our solar system.

2017-09-20: The Future of Space Telescopes

  • 08:19: However, it would be able to see x-rays right down to the event horizons of super massive black holes in distant galaxies.
  • 12:42: ... stars don't manage to stop before the core is smaller than its own event horizon, forming a black ...
  • 12:56: So it's reasonable to imagine that neutron star-like conditions exist extremely briefly before the event horizon forms.

2017-08-30: White Holes

  • 01:31: ... a region of inward flowing space time with a one way boundary called the event horizon, from inside of which nothing can ever ...
  • 01:45: It also has an event horizon, but that horizon prohibits entry, not exit.
  • 03:03: We've talked quite a bit about the bizarre behavior of space and especially time at and below the event horizon of a black hole.
  • 03:24: ... the perspective of an outside observer, any events occurring at the event horizon, including folding into it, happen infinitely far in the ...
  • 05:17: If we place an eternal black hole far to the left, then the future left boundary represents the black hole's event horizon.
  • 05:26: Any movement the left brings you closer to that event horizon.
  • 05:30: The event horizon itself is a 45 degree line.
  • 05:39: ... traveling at that 45 degree angle takes infinite time to escape the event horizon, and the region beyond that line represents the interior of the black ...
  • 06:32: ... but instead of flowing towards the singularity, it flows away, and the event horizon is now a barrier to entry, not to ...
  • 06:51: Imagine that something in our past was traveling at the speed of light and trying to reach the past event horizon.
  • 07:03: Oh, it'll reach an event horizon, but only the event horizon of our future, where it plunges into a regular old black hole.
  • 07:13: Remember that all of this is from our perspective far from the event horizon.
  • 07:30: ... the past region of the eternal black hole has an event horizon that's a barrier to entry, but also light rays within that region must ...
  • 08:11: The past singularity and past event horizon are infinitely far in the past from our point of view.

2017-04-05: Telescopes on the Moon

  • 10:30: Last week on "Space Time," we talked about time space, the way time and space, which rolls, beneath the event horizon of a black hole.
  • 10:52: You could transform the gravitational potential energy of things falling towards the event horizon into usable energy.

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

  • 00:06: ... of space and time that occurs in the mathematics when we drop below the event horizon of a black ...
  • 03:14: That rs is the Schwarzschild radius, the radius of the event horizon.
  • 03:20: Very far from the event horizon, the Schwarzschild interval becomes the good old Minkowski interval.
  • 03:29: ... if an object gets close to the event horizon, so r just a little bit bigger than rs, that stuff in the two brackets ...
  • 03:41: But as long as you are outside the event horizon, time behaves itself mostly.
  • 03:56: Things change radically below the event horizon when r gets smaller than rs.
  • 04:10: Below the event horizon, there is only one way to maintain the respectable causal progression expected of a well-mannered temporal entity.
  • 06:12: As you approach the event horizon of a black hole, more and more light rays are turned towards the event horizon.
  • 06:57: This entire diagonal line represents the event horizon.
  • 07:06: Our entire future light cone encompasses more and more of the event horizon.
  • 07:20: Meanwhile our past light cone now encompasses light that has been struggling to escape from just above the event horizon since the distant past.
  • 07:49: At the moment of crossing, light rays from the event horizon itself are suddenly visible.
  • 08:20: ... that first formed the black hole, emitted long before we entered the event horizon. ...
  • 08:48: This is light that entered the event horizon after we did and appears to reach us from above.
  • 09:47: Below the event horizon, there's still a sense of spatial upness and downness.
  • 10:28: In fact the Schwarzschild metric really gives two separate spacetime maps in a single equation, one for above and one for below the event horizon.

2017-02-02: The Geometry of Causality

  • 00:32: Recently, we've been talking about the weirdness of spacetime in the vicinity of a black hole's event horizon.
  • 10:23: ... leads to some incredible predictions when we try to calculate the sub event horizon interval of ...
  • 12:22: One idea is that the inside of an event horizon is composed of a ball of raw strings, a so-called fuzzball, and that no infinite density exists.

2017-01-25: Why Quasars are so Awesome

  • 04:43: However, a lot of it never makes it below the event horizon.

2017-01-19: The Phantom Singularity

  • 02:39: An example of a frame dependent singularity that might be familiar to space time viewers is the event horizon of the black hole.
  • 07:51: If you haven't guessed, this bad behavior corresponds to the event horizon.
  • 08:00: Imagine an object sitting at the event horizon but not moving, so its delta r would be 0.
  • 08:12: The entire space time interval for a non-moving point at the event horizon is 0.
  • 08:26: So does that mean time doesn't pass for an object hovering at the event horizon?
  • 08:33: Time certainly doesn't pass at the event horizon.
  • 08:40: ... the prohibition against objects experiencing time at the event horizon is actually a prohibition against objects spending time at the event ...
  • 08:59: At the event horizon the only way to get a non-zero space time interval is to have a non-zero delta r.
  • 09:08: An object at the event horizon has to change its distance from the black hole to keep its clock ticking.
  • 09:14: That means falling below the event horizon.
  • 09:42: ... a photon exists in a single instant, and so it can hang out at the event horizon, which also only exists at 1 infinitely stretched out ...
  • 09:54: The act of crossing the event horizon is where this singularity really starts to behave badly.
  • 10:13: ... t and delta r, doesn't let us trace a world line smoothly across the event horizon. ...
  • 10:55: Anyway the upshot is that it's really a breeze to drop through the event horizon, both physically and mathematically.
  • 11:03: Of course, once inside the event horizon, we still have that central singularity to deal with.
  • 11:34: ... in Einstein's theory, we have to go back to that coordinate shift at the event horizon. ...

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

  • 02:49: The Event Horizon Telescope is right now in the process of mapping space around the Milky Way's Sag A star black hole.
  • 03:36: Now, the actual event horizon is even smaller than this insane resolution, but EHT isn't finished yet.
  • 03:43: ... online, it will actually see the dark circular shadow of the Sag A star event horizon. ...
  • 04:28: ... the Event Horizon Telescope and microlensing studies, and of course, more LIGO ...
  • 05:12: It has enough energy to produce a black hole with a mass of 100,000 suns and an event horizon that almost reaches the moon's orbit.
  • 06:37: Eventually, it gets small enough for the event horizon to form.
  • 06:46: This is because there are regions of the universe that are doomed to end up in the singularity even before the true event horizon forms.
  • 07:25: ... is concentrated in a volume smaller than its own Swarzschild radius, an event horizon forms as spacetime flows faster than the speed of light towards that ...
  • 07:53: Even after the true event horizon forms, there remains this shrinking patch of normal flat spacetime.
  • 08:15: We generate a perfectly reflective sphere at approximately half the radius of the eventual event horizon.
  • 08:24: The light shell passes the moon's orbit, and a true event horizon forms.
  • 08:51: See, once the event horizon forms, all paths below it lead to that singularity, even outgoing light paths.
  • 09:01: ... diagram, that's seen as the future light cone of everything below the event horizon leading to the singularity, even of the reflected light ...
  • 09:19: As long as the event horizon has not yet formed, the incoming light can be stopped.
  • 09:39: Just above the sphere, which is only a bit larger than that event horizon that was going to form, the spacetime curvature is pretty insane.
  • 09:53: ... suns of the near Kugelblitz to appreciably increase the size of the event horizon. ...

2016-12-21: Have They Seen Us?

  • 13:18: A couple of weeks ago, we looked back into black holes and studied the nature of the event horizon.
  • 13:27: Luca$sino asks what we would really see if we followed the monkey directly through the event horizon?
  • 13:33: Would it appear ahead of us despite previously appearing frozen on the event horizon?
  • 13:41: The light from the instant of the monkey's crossing of the event horizon is eternally trapped at that horizon.
  • 14:57: ... light emitted by everything that fell into it as it crossed the event horizon. ...
  • 15:49: The event horizon itself just wouldn't apply within your warp bubble.
  • 16:31: ... the event horizon, you need to travel at the speed of light relative to the black hole's ...
  • 16:49: ... happen to get exactly the right size for the event horizon if you use Newtonian gravity to calculate the distance at which the ...
  • 17:06: But the concept of escape velocity at the event horizon is still as meaningful as it is from the surface of the Earth.

2016-12-14: Escape The Kugelblitz Challenge

  • 00:14: ... the infinitely stretched space-time in the vicinity of a black hole's event horizon. ...
  • 02:11: If the star's core collapses to a size smaller than its own Schwarchild radius, then the event horizon forms, engulfing what's left of the star.
  • 02:40: Outside the black hole, the event horizon becomes the new edge of the universe on our Penrose diagram.
  • 03:09: There's a region where all forward light cones only include the singularity, even before the true event horizon forms.
  • 03:18: For anything in this region, there isn't enough time to clear the impending event horizon, even traveling at the speed of light.
  • 03:27: On the Penrose diagram, we should extend our effective event horizon backwards to include that space.
  • 03:34: This invisible horizon of doom grows as the star shrinks and finally merges with the true event horizon.
  • 03:41: Any observers within this extended event horizon are cut off from any future causal connection with the rest of the universe.
  • 04:59: So the kugelblitz event horizon forms just after the shell of light passes the moon.
  • 05:33: Space inside the collapsing kugelblitz would remain comfortably flat until the collapsing shell overtakes it, even after the event horizon forms.

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

  • 00:06: At the event horizon of the black hole, space and time are fundamentally changed.
  • 00:16: But there is a powerful tool in physics that can give us real intuition into the true nature of the event horizon.
  • 00:29: Black holes, objects with densities so high that there's this region, the event horizon, where the escape velocity reaches the speed of light.
  • 00:38: ... that falls below the event horizon can never escape and is lost to the universe forever while we see ...
  • 00:50: And anything that happens below the event horizon stays below the event horizon.
  • 01:38: For example, are objects falling through the event horizon really physically frozen there from the point of view of the outside universe?
  • 01:48: Would you see the entire future history of the universe playing fast forward at the instant that you crossed the event horizon?
  • 03:10: It has a point of infinite density, the singularity, and an event horizon a bit further out.
  • 03:16: ... and time so that light rays appear to crawl out of the vicinity of the event horizon before escaping to flat space-time, no longer following 45 degree ...
  • 03:32: As it approaches the event horizon, its future light cone bends towards the black hole as fewer and fewer of its possible trajectories lead away.
  • 03:42: Below the event horizon, all possible trajectories lead towards the singularity.
  • 05:51: Its event horizon becomes the end of the line in that direction.
  • 06:03: The compactified grid lines there now represent the stretched space-time near the event horizon.
  • 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.
  • 07:45: First, what would happen if the monkey remembered to fire its jet pack at the last instant before reaching the event horizon?
  • 08:15: ... monkey is probably doomed to a graceful reverse swan dive through the event horizon, watching the entire future history of the universe play out above it at ...
  • 08:54: ... it could instead hover above the event horizon, then it would see the universe in fast forward, although that view would ...
  • 09:04: Watching the monkey frozen on the event horizon is going to make us feel a bit guilty, after a while.
  • 09:35: ... it only appears that way to us because as long as we're outside the event horizon, no times that we can witness correspond to the monkey crossing that ...
  • 09:50: In order to see that crossing, we would have to cross the event horizon ourselves.

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

  • 09:28: A billion-ton black hole has an event horizon around the size of a proton, so it would pass through the planet as though the Earth were made of air.

2016-06-15: The Strange Universe of Gravitational Lensing

  • 08:00: The lightspeed flow of spacetime at the event horizon results in old light paths pointing inwards.
  • 08:10: Light falling below the event horizon is lost forever, so we don't describe it as being lensed.
  • 08:16: But just outside the event horizon, we find the most extreme gravitational lensing in the universe.
  • 08:23: The photon sphere hovers at about half, again, the height of the event horizon.

2016-04-06: We Are Star Stuff

  • 12:44: It's happening below the event horizon of black holes.

2016-03-23: How Cosmic Inflation Flattened the Universe

  • 13:05: However, the shape of the event horizon of the black hole itself does depend on spin.

2016-02-11: LIGO's First Detection of Gravitational Waves!

  • 05:49: The signals are expected to carry information about the strange warping of space in the region of the event horizon.

2015-12-16: The Higgs Mechanism Explained

  • 07:46: AFastidiousCuber wants to know how a black hole can grow if anything falling into it appears to freeze before it crosses the event horizon.
  • 07:55: ... although an outside observer can never witness anything cross the event horizon, as something falls to the horizon, the light it emits is red shifted ...
  • 08:06: ... infalling stuff does vanish, and the event horizon that an outside observer sees does grow because anything falling into ...
  • 08:21: Casterverus would like to know if the potential event horizon that we talk about is the same thing as the Schwarzschild radius.
  • 08:29: The Schwarzschild radius is the radius of the event horizon of a non-rotating black, and it depends on the mass.

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

  • 07:58: And yet, below the star's surface, their lurks the potential event horizon, the surface of infinite time dilation.
  • 08:05: Now, the event horizon doesn't actually exist as long as the neutron star stays larger than the would be horizon.
  • 08:12: However, if we can increase the mass of the neutron star, the actual star shrinks, and the event horizon expands.
  • 08:22: There's a mass where the radius of the neutron star and the event horizon overlap.
  • 08:28: At this point, the event horizon actually comes into being.
  • 08:38: But what happens to the star when it slips below its event horizon?
  • 09:46: But on our timeline, nothing ever happens beyond the event horizon again.
  • 09:54: Beneath the event horizon, there is no corresponding now.
  • 10:10: To us, there is only the event horizon.

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

  • 01:51: ... below the event horizon of a black hole, spacetime cascades towards the central singularity ...

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

  • 02:51: Just as black holes have event horizons, so too do universes.
  • 02:55: ... event horizon of a black hole is that point beyond which we can never receive ...
  • 03:23: We can ever get to anything beyond the cosmic event horizon because that space will be moving away from us faster than light before we reach it.
  • 03:33: The event horizon of the universe is actually closer to us than the particle horizon.
  • 03:37: Given our best measurements of cosmological parameters, we think that the cosmic event horizon is around 16 billion light years away.
  • 03:56: As our universe expands, more and more of it will cross the event horizon and eventually almost all of that will be lost to it forever.

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

  • 07:48: ... and others asked whether a monkey falling through a black hole's event horizon should see the entire future history of the universe happen in the ...
  • 08:02: ... time would approach infinity as the monkey drew extremely close to the event horizon. ...
  • 08:59: ... that a free-falling monkey is eternally frozen on the event horizon with respect to a distant observer, shouldn't the black hole evaporate ...
  • 09:14: ... doesn't see anything weird about space at the moment it crosses the event horizon. ...
  • 09:30: The idea of the event horizon as this boiling hot sea of Hawking radiation isn't right.
  • 09:43: So at the instant of crossing the event horizon, the monkey is not actually bathing in this stuff.
  • 09:54: ... falling through the event horizon, the monkey's clock, its universe, now contains events that happen at the ...

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

  • 04:25: OK, this final batch of events for all objects that enter that black void taken together is called the event horizon of the black hole.
  • 10:05: ... black hole that didn't form from anything, a spacetime that has an event horizon even though there's no stuff anywhere, including behind the ...
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