2022-12-14: How Can Matter Be BOTH Liquid AND Gas?
- 16:21: ... about the recent detection of neutrinos coming from a supermassive black hole. ...
- 19:09: Quasars or “active galactic nuclei” glow from the heat energy of matter being ripped to shreds as it spirals towards a supermassive black hole.
- 19:30: The limit for the Milky Way’s black hole is around 100-billion times brighter than the Sun.
2022-11-23: How To See Black Holes By Catching Neutrinos
- 00:08: Black holes are probably the most bizarre of astrophysical objects.
- 01:03: They report seeing neutrinos produced in the colossal magnetic fields surrounding a black hole with the mass of 10 million Suns.
- 08:25: As with most galaxies, including our own, there’s a gigantic black hole at its core.
- 08:34: But unlike most galaxies, M77's supermassive black hole is not quiet.
- 08:40: ... a whirlpool of searing plasma - an accretion disk - as it falls into the black hole. ...
- 09:26: ... see jets of high energy particles blasted out from the vicinity of the black hole, and these have all the signatures of having been accelerated and focused ...
- 11:25: ... stand to learn a ton about the regions around these gigantic black holes, and eventually from the many other energetic environments that probably ...
- 11:35: Supernovae, colliding neutron stars and black holes, tidal disruption events when black holes rip apart stars, you name it.
2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
- 18:57: ... example, there are black hole coordinate systems that seem to imply alternate universes beyond ...
2022-10-12: The REAL Possibility of Mapping Alien Planets!
- 01:25: ... than New York City. You might recall these pictures of the black holes in the M31 galaxy and the center of the Milky Way. These were ...
- 12:52: ... exoplanets. And, actually, for distant galaxies and black holes and literally anything else for which we want extreme resolution ...
2022-09-14: Could the Higgs Boson Lead Us to Dark Matter?
- 04:26: ... sources like pulsars, supernovae, and things being eaten by black holes. ...
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.
- 18:42: But the event horizon changes the balance of these modes causing imperfect canceling, which looks like particles are being radiated by the black hole.
2022-06-30: Could We Decode Alien Physics?
- 06:55: ... are spinning the wrong way then, I dunno, maybe we create a black hole that eats the planet. But the definition of handedness ...
2022-06-22: Is Interstellar Travel Impossible?
- 12:29: These things are accelerated in the monstrous magnetic fields of black holes and supernovae and of the galaxy itself.
- 15:16: ... then we covered a new idea that might solve the black hole information paradox, involving a pretty crazily abstract idea including ...
- 17:20: ... On to the black hole stuff. Robert Pruitt asks whether the fundamental forces of nature ...
- 17:31: ... answer is that yes, towards the singularity at the center of a black hole matter should reach arbitrarily high densities and energies - as high as ...
- 18:03: And we even have ideas for black holes in theories of quantum gravity - for example, the fuzzball of string theory, which we did an episode on.
- 18:11: ... the information from the entangled particles that emerge from a black hole as Hawking radiation, could we in principle learn about the inside of ...
- 18:26: Could this, for example, show us how black holes deviate from theory?
- 18:31: ... answer is yes - if hawking radiation really is entangled with the black hole then in principle we can learn about the black hole interior by ...
- 18:42: Actually, simply gaining information about the interior of the black hole this way is counter to the orthodox black hole theory.
- 18:50: ... which tells us that the only things that can be observed about a black hole from its exterior are mass, spin, and ...
- 19:10: Otinane Yos asks whether we can be sure that virtual particle - antiparticle pairs get separated near a Black Hole event horizon.
- 19:50: ... quips: Physicists looking at a wormhole say "Can this solve the black hole information paradox?" While Normal people looking at a wormhole are like ...
2022-06-15: Can Wormholes Solve The Black Hole Information Paradox?
- 00:00: ... Black holes are very real, but are also a theoretical nightmare. ...
- 00:26: ... that might provide a way forward. I’m talking about the black hole information paradox. Efforts to resolve it have led to ...
- 01:40: ... from me, should be enough. Stephen Hawking discovered that black holes aren’t quite as, well, black and inescapable as we thought. They ...
- 02:24: ... - information not observable in the system’s gross properties. Black holes have huge entropy because every black hole looks the same no ...
- 03:20: ... you can entangle a particle you can entangle a black hole. One way to think about Hawking radiation is that the black ...
- 04:21: ... over time as the internal information of the black hole evaporates and the black hole loses its internal ...
- 04:44: ... should contain no information about anything besides the black holes gross properties. Efforts to resolve the black hole ...
- 05:20: ... occur if Hawking radiation is our information escape route from the black hole. Any theory trying to solve the black hole information ...
- 08:14: ... For example, you could use this to study the evaporation of a black hole, as its geometry changes with each outgoing particle of Hawking ...
- 08:36: ... to consider a lot of different geometries - after all, black holes are pretty simple objects - it’s not like there are many ...
- 10:06: ... black holes rather than just one. The entropy of many black holes is an example of a quantity called the Rényi entropy. You ...
- 10:42: ... integral. For a spacetime geometry where none of the black holes interact with each other, the entropy doesn’t change from Hawkings’ ...
- 11:13: ... topology into account, and then you set n equal to 1 single black hole, you end up with a new equation for the entropy of the Hawking ...
- 11:25: ... the wormholes seem to disappear when there’s just a single black hole, you’d expect their effect to disappear, but amazingly, the math ...
- 12:09: ... allow the radiation to leak quantum information from the black hole ...
- 12:40: ... that tells us that information can escape from the black hole. But what’s the real physical picture here? Well, no one ...
2022-06-01: What If Physics IS NOT Describing Reality?
- 13:41: ... van Oosterhout asks what happens to the central black holes of galaxies that the milky way eats. The answer is simple - ...
- 15:25: ... case where this is believed to have happened due to a black hole or neutron star ...
2022-05-25: The Evolution of the Modern Milky Way Galaxy
- 18:41: ... have heard me say that space flows across the event horizon of a black hole at the speed of light - that’s the velocity of an inertial frame ...
2022-05-04: Space DOES NOT Expand Everywhere
- 10:06: ... future or past until they hit a singula,rity - the big bang or a black hole. As the universe expands, we don’t have new patches of space appearing ...
- 11:22: ... 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 principle, and so ...
2022-04-20: Does the Universe Create Itself?
- 14:37: ... universe? (if it even has one) and could a universe actually be inside a black hole. ...
- 16:10: ... of detecting Hawking radiation in the case that the universe is a black hole. Actually, we should expect a type of Hawking radiation from the cosmic ...
- 16:56: ... argues that the universe can't be a black hole because the difference between the masses of our largest black holes in ...
- 17:08: ... would mean for the universe, for the universe to be a black hole would require very different physics. In a way that’s right. If the ...
- 17:39: ... the way - fun fact - if you calculate the size of a black hole with the mass of our observable universe - adding together all the ...
2022-03-30: Could The Universe Be Inside A Black Hole?
- 00:00: What is inside a black hole?
- 00:07: If you’ve ever wanted to know then you might be in luck - Some physicists have argued that you’re inside a black hole right now.
- 00:25: But we know it must: at the centers of black holes and at the Big Bang.
- 00:36: Well it turns out that black holes and the Big Bang have more in common than vexing Einstein.
- 00:41: ... that the big bang is in fact the singularity of an absurdly gigantic black hole. ...
- 00:56: First up, black holes.
- 01:15: ... the outside, the black hole looks like an orb of blackness at a particular location in space, due to ...
- 02:41: Complications aside, there are striking similarities between the black hole and the universe.
- 02:46: ... obvious difference is that the black hole singularity seems to us to be a point of infinite density in space, ...
- 03:01: ... the big bang and black hole singularities do occupy all of space - the difference is that the big ...
- 05:01: A black hole contains a future, space-like singularity.
- 05:05: Which means that all geodesics within a black hole spacetime end at the singularity in the future.
- 05:12: No, that doesn’t mean you’re doomed to be crushed by a black hole.
- 05:19: ... black hole singularity is the all-encompassing future for the spacetime that lives ...
- 05:50: We’ll need to make the black hole interior mathematically indistinguishable from a universe for somebody inside that black hole.
- 06:03: A time-reversed black hole is easy enough.
- 06:13: ... white hole is surrounded by an event horizon that is the opposite to a black hole event horizon - it can only be crossed from the inside to the ...
- 07:06: Now the white hole was “discovered” by messing around with the coordinates of the OG black hole solution by Karl Schwarzschild.
- 07:48: And the space-time curvature is nearly flat, so no crazy tidal forces like in a white or black hole.
- 08:15: ... very first “realistic” mathematical description of a black hole formation was discovered in 1939 by Robert Oppenheimer - of atomic bomb ...
- 08:56: But the Oppenheimer-Snyder solution gave our first insights into black hole formation.
- 09:30: And that’s true even after the black hole’s event horizon forms.
- 09:35: So you can have what looks like a black hole from the inside, but looks like comfortably flat space inside the still-collapsing star.
- 09:43: If it works for the black hole then it should work for the white hole.
- 10:00: This was the basic proposal by Indian physicist Raj Pathria in his Black Hole Cosmology hypothesis back in 1972.
- 10:14: There’s also the idea that universes are born as white holes produced after the collapse of a black hole.
- 10:27: ... that case, black holes don’t form singularities, but rather bounce back outward to create a new ...
- 10:40: OK, so we need one last ingredient to be able to answer “maybe” to the question we started with: Are we in a black hole?
- 10:48: ... 1999, Stephen Hawking once showed that if a black hole is leaking its mass via Hawking radiation in perfect equilibrium with ...
- 11:08: ... from within, and Hawking’s argument that equates white holes with black holes, then there’s a roundabout way to argue we might not NOT be in a black ...
- 11:25: So is the universe a black hole?
- 11:32: There’s no good reason to believe that this is the case, so we shouldn’t believe the universe is a black hole.
- 11:52: However if we are in a black hole then there’s a huge upside: we now know what the interior of a black holes look like. It looks like this.
- 12:02: And there are indeed libraries in this black hole.
- 12:16: ... exactly the same question, with the same answer, that they are in a black hole and so on ad infinitum in a series of black holes, forming an infinitely ...
2022-03-23: Where Is The Center of The Universe?
- 10:48: By the way, there are close parallels with the singularity of the black hole.
- 10:53: We might ask whether the Big Bang is a reverse black hole - also called a white hole.
2022-02-16: Is The Wave Function The Building Block of Reality?
- 14:42: Last time we tackled a question of utmost gravity. Literally. How does gravity itself escape the inescapable gravity of a black hole.
- 14:52: ... BuzzBen asks what happens when gravitational waves pass through black holes. Is there gravitational lensing? Well that’s exactly right. Gravitational ...
- 16:00: ... R asks how we can know that a black hole’s mass has time to crush down to the singularity, given that time dilation ...
- 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 ...
- 16:48: ... that the definition of the event horizon is also tricky. In an idealized black hole, the event horizon is defined from the perspective of an observer at ...
- 17:42: ... takes infinite time to reach us. So to lose an object beneath a growing black hole means that the event horizon envelopes that final photon, not the ...
- 18:05: And so everything that went into the black hole remains frozen on the horizon.
- 18:15: ... asks a related question, but now it’s for black holes that shrink due to Hawking radiation. This is a lot more speculative. ...
- 18:37: ... information is lost? When people talk about information being lost in a black hole, they’re usually referring to the fact that lots of information goes into ...
2022-02-10: The Nature of Space and Time AMA
- 00:03: ... i played which were the most popular questions that were not about black holes and i apologize for missing the many questions that were on black ...
2022-01-27: How Does Gravity Escape A Black Hole?
- 00:00: ... in a black hole, all of the mass is concentrated at the singularity at the very center ...
- 00:20: So how does a black hole manage to communicate its gravitational force to the outside universe?
- 00:27: How does gravity escape a black hole?
- 00:48: Einstein’s theory predicted the existence of the ultimate gravitational object: the black hole.
- 02:56: ... gravity travels at the speed of light, and all of the mass of a black hole is hidden beneath the event horizon, how does its gravity get out to ...
- 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.
- 03:53: Same for a black hole.
- 03:54: ... space around a black hole doesn’t need to know about the mass of the central singularity - it only ...
- 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.
- 05:40: This explanation works for the black holes of general relativity.
- 05:51: For example, at the black hole singularity.
- 06:03: So can gravity escape from a “real” black hole of quantum gravity?
- 06:38: But doesn’t that make things worse for black holes?
- 07:44: The gravitational field around the black hole is already abuzz with virtual gravitons.
- 07:50: Now you might ask why those gravitons themselves don’t get swallowed by the black hole.
- 08:34: Unfortunately you still can’t send an SOS message from inside of a black hole that way.
- 09:06: And it might surprise you to learn that you actually CAN see the mass of black hole.
- 09:12: ... present mass of a black hole is hidden below the event horizon, but we can see its past mass, and ...
- 09:24: Think about a star collapsing into a black hole.
- 09:56: That’s ignoring the whole Hawking radiation, black hole evaporation thing.
- 10:01: So we can still “see” the mass of a black hole - it’s imprinted on the event horizon.
- 10:19: ... as always being in your past lightcone - and that has to be outside the black hole. ...
- 10:30: And this last argument also tells us how it can be that a black hole can possess electric charge.
- 10:37: If a black hole swallows electric charge, the electromagnetic field around the black hole grows.
- 10:45: Because when you look at a charged black hole you still have causal contact with all the charge that fell into it.
- 10:55: ... the point of view of that charge, it’s inside the black hole, but from your point of view it’s frozen on the event horizon, but is ...
- 11:09: In a black hole, where is the mass?
- 11:37: To get a consistent definition for mass you need to integrate - add up - the contributions to infinite distance from the black hole.
- 11:45: By that definition the mass of a black hole is everywhere - so it’s not surprising that it can escape the 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.
- 12:00: ... seemingly different pictures all point to the same result - the black hole will eat you right up, and even as you’re getting crushed into an ...
2022-01-19: How To Build The Universe in a Computer
- 07:57: ... stars, it forms whirlpools and jets around new stars and black holes. ...
2022-01-12: How To Simulate The Universe With DFT
- 14:43: ... we have the one about black holes puncturing the Earth, and then the one about how we might search for ...
- 14:52: Black holes first.
- 14:53: We told you that an asteroid-mass, atom-sized black hole would pass straight through the earth if it impacted.
- 15:07: The assumption in this calculation is that the black hole came from interstellar space and fell into the solar system.
- 15:23: The the fast-moving black hole slows-down inside the Earth because exchanges momentum with or eats stationary material on its way through.
- 15:31: But the narrow column carved by the black hole has a mass much lower than the black hole itself, so it doesn’t slow down much.
- 15:37: Most likely the black hole was moving faster than 42 km/s - that would only be the case if it had exactly the same galactic orbit as the sun.
- 15:57: ... possible to imagine a scenario where the black hole had multiple interactions on its way to the Earth - perhaps it punctured ...
- 16:21: And speaking of black holes hitting the Sun, Christian asks whether that would be detectable.
- 16:50: I did see a paper that claimed we might be able see the high-frequency seismic fluctuations set up inside a star after a black hole passage.
- 17:14: Oromandias asks whether the scenario of the Neil Stephenson's book Seveneves is plausible - in which a primordial black hole destroyed the moon.
- 17:33: The black hole could never deposit enough energy on its passage through the moon to break it apart.
2021-12-29: How to Find ALIEN Dyson Spheres
- 13:11: In the past couple of years researchers have been thinking about Dyson spheres built around the supermassive black holes in the centers of galaxies.
2021-12-20: What Happens If A Black Hole Hits Earth?
- 00:00: ... remember when I first learned about black holes I imagined these gigantic cosmic vacuum cleaners that must eventually ...
- 00:12: ... nonsense. And I imagined that it was just a matter of time before a black hole finally found its way to the Earth. So that part might actually ...
- 00:29: ... big black holes are very, very far. The nearest known is - the Cygnus X-1 black hole - ...
- 01:18: A glob of that material in the modern universe would immediately collapse into a black hole.
- 01:23: ... in density eventually collapsed into stars and galaxies instead of black holes. ...
- 01:49: ... of the early universe that saved all of matter from collapsing into black holes. But that doesn’t mean that no black holes were formed. There would have ...
- 02:10: ... call these primordial black holes, and we’ve talked about them before. We’ve also talked about how these ...
- 02:27: ... when they formed, PBHs could have virtually any mass - from tiny ‘micro’ black holes all the way up to the supermassive black holes in the centers of ...
- 02:50: ... example, if there were enough of these black holes then they’d frequently pass in front of more distant stars, magnifying ...
- 03:00: ... kilograms - or around 15% the mass of our Moon. Meanwhile, if primordial black holes had masses smaller than around a trillion kilograms then they'd have all ...
- 03:25: ... window of possible masses, comparable to the masses of large asteroids. Black holes this big don’t devour stars like Cygnus X-1, and they don’t warp the ...
- 04:01: ... in the solar system at any given time. If that dark matter is tiny black holes then we might expect dozens, maybe even thousands, of them to be in the ...
- 04:26: ... what happens if a black hole hits the Earth? It turns out this is actually a scientifically very ...
- 05:13: ... talk specifics. We’ll say our black hole has the mass of the Martian moon phobos - 10^16 kg like a large ...
- 06:02: ... talk about what happens when our black hole first enters the atmosphere. In the immediate surroundings of any black ...
- 06:35: ... there’s a limit to how much radiation a black hole can produce. That same radiation causes an outward pressure that partly ...
- 06:56: ... Eddington limit - it’s the maximum brightness that the material around a black hole can radiate before radiation pressure cuts off the ...
- 07:05: ... tiny event horizon of a micro black hole is a very narrow choke-point for matter trying to flow in. Its Eddington ...
- 07:29: ... such a black hole passed into our atmosphere, it would look like the brightest shooting ...
- 08:05: ... impact led some physicists in the 1970s to suggest that maybe this was a black hole punching through the ...
- 08:16: ... there was only one shockwave detected in the Earth’s atmosphere, and a black hole’s exit on the other side of the planet should have made another. These ...
- 08:31: But we can’t be 100% sure. This was, after all, 1908 - and if the black hole exited in the middle of the ocean it could have been missed.
- 08:41: ... devastation is only for black holes at the top end of our mass range. The smaller the black hole, the more ...
- 08:51: ... the passage of the black hole through the Earth itself might still be detected. This black hole bullet ...
- 09:03: ... the Earth’s surface. Even at the lowest mass possible for a primordial black hole it will produce the equivalent of a magnitude 4 earthquake. That's ...
- 09:24: ... would be rare. For the smallest PBH masses, there may only be one black hole hitting the earth every million years. For the Phobos-mass black holes ...
- 10:16: ... the earth’s atmosphere nor its surface would keep a good record of micro black holes hitting the earth. Earth’s dynamic interior and its eroding atmosphere ...
- 10:44: ... apart craters made by black holes and those made by regular old rocks is hard, but not impossible thanks ...
- 11:02: ... of contact, and a gentle sloping ‘ejecta blanket’ around it. But when a black hole hits, it doesn’t stop- it goes straight through. The pressure from the ...
- 12:01: ... the incredible heat of the plasma around the black hole should quickly sear the rock around it into exotic high-pressure phases ...
- 12:24: ... a serious search has not yet been done. OK guys, to wrap up- have any black holes ever hit the earth? We don’t know. We probably wouldn’t have noticed if ...
- 12:44: ... not be discounted. But the discovery would also tell us that primordial black holes are a thing, and it would tell us about their ...
- 14:10: ... matter, and the one on fuzzballs - the stringy theory version of the black hole. ...
- 16:10: ... by Rob. To summarize: It would look just like falling into a regular black hole for the person falling, but it would look like you got smeared over the ...
- 16:33: ... motion in free space. That means that an observer falling through a black hole event horizon shouldn’t notice anything special about that boundary - ...
- 17:55: ... should look almost exactly the same as those produced when classical black holes merge. Emphasis on the ...
- 18:16: ... back into a spheroid - lasts longer for fuzzballs than for regular black holes due to the event horizon being less cleanly defined. It’s also been ...
- 19:14: ... fact that the connection between multi-dimensional cats, hairballs and black holes can’t possibly be wrong. I agree that this is a compelling reason to ...
2021-12-10: 2021 End of Year AMA!
- 00:02: ... space i like to look at quasars that way quasars being gigantic black holes in the process of consuming material from their surrounding galaxy ...
2021-11-17: Are Black Holes Actually Fuzzballs?
- 00:02: Black holes are a paradox.
- 00:20: ... in the black holes of string theory - fuzzballs - are perhaps even weirder than the regular ...
- 00:50: And we see these black holes - or at least their incontrovertible evidence - in many places out there in the universe.
- 00:57: But black holes are also impossible.
- 01:14: ... relativity insists that no information from the matter that fell into a black hole should be observable on the surface - the so-called no-hair theorem, ...
- 01:34: ... other hand, if we calculate the amount of information that goes into a black hole to build it up, we get a prodigiously large number - 10^10^77 bits for a ...
- 01:48: Black holes should have an enormous number of so-called microstates - hidden configurations - and this translates to an enormous entropy.
- 01:58: ... formula for black hole entropy was discovered by Jakob Bekenstein, who, incidentally, also ...
- 02:52: Not so in the black holes of general relativity.
- 03:04: The information contributing to black hole entropy could be beneath the horizon, but if we add one more fact we run into serious trouble.
- 03:13: Black holes evaporate by emitting Hawking radiation.
- 03:17: ... Hawking radiation should be completely random, and so leaks away the black hole’s mass without any of the information that went into building the black ...
- 03:29: When the black hole eventually vanishes, so does its enormous information content.
- 03:40: This threat of erasure of quantum information in a hairless black hole is the black hole information paradox.
- 03:48: So yeah, black holes seem to be paradoxes.
- 04:07: While we’ve covered these black hole paradoxes before, and have even hinted at possible solutions - we’ve never actually solved them.
- 04:17: Ultimately, the black hole paradoxes stem from the disagreement between quantum mechanics and general relativity.
- 04:49: ... was able to describe the black hole using pure general relativity but then analyze its effect on the ...
- 05:09: ... surface in a way that saves that information from destruction as the black hole ...
- 05:28: Black hole paradoxes may be solved by string theory.
- 05:32: In string theory, black holes are not hairless at all - in fact all of those strings make them positively fuzzy.
- 06:01: ... theory immediately solves the problem of the black hole singularity, because instead of collapsing all of a black hole’s mass ...
- 06:17: It turns out that though, that string theory can make sense of the black hole event horizon also.
- 06:22: ... this was in 1996, when Andrew Strominger and Cumrun Vafa created a black hole using string theory - in theory-space, not ...
- 06:49: And the number they found exactly agreed with the Bekenstein formula for black hole entropy.
- 07:13: ... that Strominger and Vafa did this for the somewhat unrealistic case of a black hole horizon with 4 spatial dimensions, but it was a decisive step and it ...
- 07:31: But in order to solve the information paradox, we still have to get that information out of the black hole as it evaporates.
- 07:40: ... State dug into that model to see if it could reproduce properties of black holes beyond the ...
- 08:00: This was another stunning match to theory, and also a way for stringy black holes to leak out their information.
- 08:06: ... good, but I realize that I haven’t really told you what these stringy black holes look like, or how they form, or how structure can actually be supported ...
- 08:22: First, a thing that’s weird about even regular black holes.
- 08:26: If you were to dial up the strength of gravity, black holes would get bigger.
- 08:39: This property of black holes is actually quite hard to reproduce in theories of quantum gravity.
- 08:45: ... while he was exploring stringy black holes, Samir Mathur found that the strings that formed the black hole would ...
- 08:55: In fact, if you have a bunch of strings dense enough to form a black hole in general relativity, it wouldn’t actually collapse.
- 09:02: Rather it would grow to produce an agglomerate of strings with the same radius as a classical black hole.
- 09:09: ... this is right, then black holes don’t have an empty event horizon at all, but rather a real surface that ...
- 09:39: ... quantum gravity effects might not just be important at the center of the black hole but instead may pile up to the horizon ...
- 10:46: But from a distance, fuzzballs would look like black holes.
- 11:02: All classical effects of black holes from general relativity would be preserved.
- 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.
- 12:04: One dimension means a line, so a 1-D black hole is just a segment of a line with a point of infinite density on it.
- 12:29: Adding a single coiled dimension to our 1-D black hole turns our line into a drinking straw.
- 12:50: As a side benefit, this eliminates the problem of the gravitational singularity at the center of a black hole.
- 13:00: ... of fuzzballs in string theory radically changed our vision of what a black hole could be and provided a satisfying potential resolution to several ...
- 13:13: The model has only been carried out for simplified and nonrealistic-cases like the Strominger-Vafa black hole.
- 13:19: Constructing fuzzballs that more closely match real astrophysical black holes remains a major theoretical effort.
- 13:26: I should also add that fuzzballs are not the only quantum extension of the GR black hole.
- 13:35: Black holes, or something like them, definitely exist.
2021-11-10: What If Our Understanding of Gravity Is Wrong?
- 01:02: ... speculative ideas of what it might be made of - from exotic particles to black holes. ...
- 07:43: ... from such hit ideas as the Bekenstein bound, which connects black hole information content to entropy, as well as other black-hole-related ...
- 14:31: For instance, CuriosityStream has Black Holes: Messages from The Edge of Space, which examines not only black holes, but neutrino astronomy.
2021-10-13: New Results in Quantum Tunneling vs. The Speed of Light
- 15:23: Erik says that if magnetic monopoles are massive enough to collapse the early univeres, wouldn’t we only find them inside black holes?
- 15:36: ... certainly possible that magnetic monopoles to end up inside black holes, in fact some recent work suggests that an individual magnetic monopole ...
- 15:48: ... a monopole managed to get into a black hole, one thing is clear - it would still behave like a monopole in that the ...
- 15:57: Same as if the black hole held electric charge; it would produce an electric field.
- 16:01: And presumably if black holes had enormousmagnetic charges we’d see that in the way they interact with matter.
- 16:08: As it is, the magnetic fields we observe around black holes seem more consistent with regular dipole fields, with both north and south poles.
2021-10-05: Why Magnetic Monopoles SHOULD Exist
- 16:32: ... pressure that supports white dwarf stars and instead produces a black hole or neutron ...
2021-09-21: How Electron Spin Makes Matter Possible
- 15:34: ... - the one about reverberation mapping, where we map the stuff around black holes by watching how light bounces ...
- 15:48: ... Gorman says that he imagined that black holes would look more like dim stars rather than, well, black holes because ...
- 16:12: ... a bit further out - the photosphere where light can actually orbit the black hole. ...
- 16:27: ... speeds out of the Milky Way. Happily the winning hypothesis of enormous black holes was as awesome as all the others. Dave Lawrence rightly calls me out ...
- 18:19: ... lines of quasars show that the gas is typically moving away from the black hole a few perecent to 10% the speed of light, and in rare cases even faster. ...
2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe
- 00:00: ... to lots of weird places on this show - from the interiors of black holes to the time before the big bang. But today I want to ...
- 00:25: ... arguably the strangest objects in the universe - if we don’t count black holes as actual objects. And honestly, neutron stars are even weirder ...
- 10:06: ... much weaker than the signals we’ve detected when neutron stars or black holes merge, and so it’s much harder to detect them. But instead ...
- 13:06: ... event horizon and we’ll be stuck inside an actual black hole. Escape will become even more impossible than it already ...
2021-09-07: First Detection of Light from Behind a Black Hole
- 00:07: Our cleverest astronomers have figured out ways to catch light that skims the very edge of black holes.
- 00:20: A few weeks ago a story made the rounds of pop-sci media proclaiming that for the first time light had been detected from behind a black hole.
- 00:28: The reports were about a paper that claimed to have seen X-rays that came not from inside but from the back end black hole.
- 00:36: This is obviously cool stuff - I mean, really anything new with black holes captures the public attention.
- 00:46: ... years - trying to understand what happens in the vicinity of the largest black holes in the ...
- 01:08: Now you might remember the picture of the black hole captured by the event horizon telescope.
- 01:13: We talked about this soon after it came out - but to remind you, here we have radio light from charged particles whirling around the black hole.
- 01:21: And the more recent version of this in polarized light shows the grain of the magnetic field right near the black hole’s edge.
- 02:08: ... in which we watch as a flare of light from a violent event near the black hole radiates and reflects - reverberates - its way through the complex ...
- 03:01: ... deep in the belly of the beast - uncomfortably close to the supermassive black hole. ...
- 03:13: ... by the way, is the actual technical term for the largest black holes in the universe - anything more than a million or so times the mass of ...
- 03:31: ... you get this gigantic whirlpool of searing plasma screaming around the black hole. ...
- 03:57: However it happens, when a flare is generated near the black hole it expands outwards, and it causes a lot of trouble on the way.
- 04:37: ... by a combination of the incredible gravitational field of the black hole and the continuous blaze of high energy radiation from the inner ...
- 06:07: Is this stuff pouring towards the black hole?
- 06:52: One - it’s pouring in, rivers of gas dragged down by the black hole’s gravity.
- 07:25: Also, in this scenario the gas on the far side of the black hole is moving towards the black hole and so towards us.
- 07:41: Meanwhile the gas closer to us is actually moving away from us as it falls towards the black hole - it’s redshifted to longer wavelengths.
- 08:11: ... now the gas on the far side of the black hole is moving away while the gas on our side is moving towards us - so the ...
- 09:23: OK, it’s time we got back to the discovery that started our little journey - the light that was detected from behind a black hole.
- 09:31: The events described in the paper happened extremely close to a relatively nearby supermassive black hole.
- 09:47: Near the black hole there are sources of light that I haven’t mentioned yet.
- 09:57: That leads to a haze of high-energy electrons surrounding the black hole.
- 10:12: ... winds of matter flowing at incredible speeds - but this close to the black hole only the heaviest elements like iron can hold on to any of their ...
- 10:33: The X-ray corona flared bright, probably in a small region right above the black hole.
- 10:39: ... but some also reflected off the disk on the opposite side of the black hole. ...
- 10:49: A portion of that light was then grabbed by the black hole’s gravitational field and slung right back around towards us, and magnified in the process.
- 11:33: ... detail than this - lots of good stuff like measuring the mass of the black hole - 30 million Suns - to verifying Einstein’s general theory of ...
- 11:54: ... just love it when we can map the space around black holes by watching flickering points in the sky, and in that flickering ...
2021-08-03: How An Extreme New Star Could Change All Cosmology
- 08:29: ... the Chandrasekhar limit then it collapses into a neutron star or a black hole. But If you already have a white dwarf and then slowly add more mass ...
- 09:18: ... that saps away their orbital energy. We’ve seen the result of this with black holes and neutron stars when LIGO detected the gravitational waves from the ...
2021-07-21: How Magnetism Shapes The Universe
- 00:43: Threads tugged lightly towards the Earth, tightly towards the Sun, or into inescapable knots towards black holes.
- 11:25: Those occur deep in galactic cores near the gigantic black hole that dwells there.
- 11:30: ... that black hole is feeding and surrounded by a disk of gas, we have what is known as an ...
- 11:40: Intense magnetic fields live just above the event horizon of some of thses black hole, and thread the infalling disk.
- 11:54: ... magnetic field - in the polarized light surrounding the M81 supermassive black hole observed by the event horizon ...
2021-06-23: How Quantum Entanglement Creates Entropy
- 00:27: ... arrow of time and is a key ingredient in solving the black hole information paradox—a solution that may one day unite quantum ...
2021-06-16: Can Space Be Infinitely Divided?
- 07:48: ... But that photon has enough effective mass to produce a black hole with a Planck-length event horizon - so any attempt to ...
- 09:58: ... get virtual spacetime fluctuations, and even virtual black holes and wormholes - a fluctuating roil of spacetime that John ...
2021-06-09: Are We Running Out of Space Above Earth?
- 14:14: Last episode was on Planck Relics, those subatomic scale black holes that could be literally everywhere and even explain dark matter.
- 14:25: Matt Kelly asks what happens to normal matter when it interacts with one of these tiny black holes.
- 14:56: The problem then is that the black hole will immediately Hawking-radiate back down to a Planck relic.
- 15:24: But the planck mass defines the mass of a black hole one Planck length in radius, and remember, black holes are massive!
- 16:05: ... of you hypothesized that there being tiny black holes everywhere perfectly explains one of the most vexing paradoxes in the ...
2021-05-25: What If (Tiny) Black Holes Are Everywhere?
- 00:00: It’s fair to say that black holes are the scariest objects in the universe.
- 00:20: Black holes are scary because they’re so… final..
- 00:31: ... if nothing can emerge from a black hole, then black holes must be A) black - they can’t emit light, and B) ...
- 00:41: At least, that’s the black hole as it appears in the mathematics of Einstein’s general theory of relativity.
- 00:50: ... you bring quantum mechanics into the equation, quite literally, then the black hole is neither black nor ...
- 01:01: He showed that black holes must radiate, and so slowly leak away their mass in what we now call Hawking radiation.
- 01:07: In a way quantum mechanics saves us from the eternal black hole … except perhaps that it doesn’t.
- 01:16: ... you calculate the evaporation of the black hole all the way to the very last instant - quantum mechanics may well play a ...
- 01:31: These remnant black holes, or Planck relics, may be everywhere.
- 01:46: Hawking’s discovery of his black hole radiation was really ingenious.
- 01:51: It came from thinking about how black holes interact with the quantum fields from which all elementary particles arise.
- 02:17: To a distant observer it would look like the black hole is radiating particles.
- 02:28: The distribution of particle energies should follow a blackbody spectrum, as though the black hole has a real temperature.
- 02:52: ... horizon, so they sort of emerge from the entire region surrounding the black hole. ...
- 03:02: For the black hole left behind when a massive star dies, the event horizon is several kilometers in radius.
- 03:08: ... such black holes the Hawking radiation is just photons - electromagnetic waves with ...
- 03:20: Such a black hole would appear very cold, and would leak away its energy very slowly.
- 03:25: But as the black hole shrinks in mass and in size, its Hawking radiation also decreases in wavelength - but it increases in energy.
- 03:33: That means the black hole appears to heat up, and the evaporation rate increases.
- 03:45: ... far distant future in which the stars have gone out and we only have black holes, which one by one vanish in bright pops of Hawking ...
- 04:26: ... enabled him to mathematically connect the high-gravity region near the black hole with a very distant zero-gravity region where the Hawking radiation is ...
- 04:37: ... reasonable for most sizes of black hole, but Hawking’s entire calculation falls apart when the black hole has ...
- 04:53: ... that theory, we have no way to describe the final stage of black hole evaporation - so it’s reasonable to ask - does that final pop really ...
- 05:31: So a large black hole is like our entire poker - there are many ways that the quantum fields can fluctuate around it.
- 05:39: The black hole loses energy one photon at a time, but the process seems smooth and continuous.
- 05:45: But as the black hole gets very small, the allowed vibrational modes start to get restricted.
- 05:49: You no longer have a smooth, statistical spectrum to your thermal radiation - the black hole will leak its remaining mass in sudden, discrete steps.
- 05:59: And at some point, there may be no allowed transitions that can take away the last of the black hole’s mass.
- 06:05: In which case the Hawking radiation ceases, and the black hole becomes stable.
- 06:11: If it happens at all, it’ll be when the average energy of the Hawking radiation is close to the entire rest-mass energy of the remaining black hole.
- 06:20: In other words, when you get to the point where a single photon would take away the rest of the black hole’s mass.
- 06:31: This would be when the black hole’s mass is around 20 micrograms - what we call the Planck mass.
- 06:41: Such a black hole would have an event horizon of around 10^-35 meters - the Planck length.
- 06:59: So might Planck-sized black hole relics, or Planck relics, actually exist?
- 07:04: ... relics do exist they probably don’t look just like mini versions of big black holes. ...
- 07:22: The only way to make black holes in the modern universe is in the deaths of massive stars.
- 07:29: The smallest such black holes will take something like 10^66 years to Hawking-radiate their entire mass away.
- 07:37: That’s much longer than the current age of the universe, none of these black holes will have become Planck relics.
- 07:45: For Planck relics to exist now we need a way to make black holes that are much smaller than a star.
- 07:51: A black hole with a mass of a billion tons or lower could have decayed to a relic by now - and fortunately there’s a way to make those.
- 07:59: It’s something we discussed before - primordial black holes.
- 08:03: ... Big Bang, there are a few different ways to produce enormous numbers of black holes, potentially of a wide range of ...
- 08:12: There are some scenarios that allow extremely large numbers of very tiny black holes.
- 08:19: ... the most important consequence of having Plank relics from primordial black holes is that these could potentially explain dark ...
- 08:41: It may have been possible to create this insane abundance of black holes if they formed during the epoch of cosmic inflation.
- 08:56: Back then, the density fluctuations may have been strong enough to generate crazy numbers of tiny black holes.
- 09:02: ... a vexing difficulty that was introduced with Hawking radiation - the black hole information ...
- 09:14: ... did a video on this also, but long story short: if black holes radiate a perfect thermal spectrum then, by definition, that radiation ...
- 09:28: So you completely evaporate a black hole and then all the quantum information that went into it is deleted from the universe.
- 09:41: But what if black holes never fully evaporate?
- 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?
- 10:08: I mentioned this inflation thing earlier - what if at the singularity of a black hole a new inflation is triggered?
- 10:22: This conjures images of insane numbers of minuscule black holes swarming through the universe, and in each one a new inflation - a new universe?
- 11:07: ... just ponder on the coolness that somewhere nearby there may be an actual black hole, a tiny hole punctured in your neighborhood’s fabric of ...
2021-05-19: Breaking The Heisenberg Uncertainty Principle
- 09:13: ... events - events from further away, and involving lower-mass mergers of black holes and neutron ...
2021-05-11: How To Know If It's Aliens
- 14:35: ... one about whether dark matter can be explained by enormous numbers of black holes - tldw - it probably ...
- 15:39: ... 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 safe. When the ...
- 16:32: ... Williams asks what the difference between super small black holes or naked singularities and WIMPs be. Normally when people talk about ...
- 17:14: ... Chaps correctly points out that there are scientists who have pushed the black hole dark matter hypothesis for years, so it hasn’t been overlooked as I ...
- 18:02: ... many of you commented that you thought of the idea that dark matter is black holes years ago. That’s impressive - you’re in the company of some very smart ...
- 18:16: ... matter ain’t black holes. That may have sounded unnecessarily snarky - and it wasn’t meant to be - ...
- 18:32: ... for dark matter in, say, string theory, before you check whether it’s black holes is like looking for your keys in the freezer before checking your ...
2021-04-21: The NEW Warp Drive Possibilities
- 03:01: For example inside black holes where we can think of space as flowing downwards faster than light.
- 10:47: It’s hard to see how packing that much mass into these strips would NOT create a black hole.
- 11:47: ... remain - can the required energy densities be created without creating black holes for any useful sized warp ...
2021-04-13: What If Dark Matter Is Just Black Holes?
- 00:00: ... be that for every star in the universe there are billions of microscopic black holes streaming through the solar system, the planet, even our bodies every ...
- 01:03: What if dark matter is just black holes?
- 01:13: As we’ve discussed many times before, black holes are regions of gravitational field so intense that not even light can escape.
- 01:21: Evidence for the reality of black holes is now pretty convincing - and we’ve talked about this evidence before.
- 01:25: ... fact that we know black holes are actually real seems like a significant point in their favor as an ...
- 01:53: ... for black holes to be dark matter they’d need to be abundant enough to make up all of ...
- 02:02: In other words, most of the physical universe needs to be vast swarms of black holes that outweigh all the atoms in the universe by a factor of four.
- 02:15: The main remaining variable is the mass of the individual black holes.
- 02:19: We could get to the required dark matter mass with lots of massive black holes, or ludicrously many smaller black holes.
- 02:28: We have, of course, been trying to find evidence for black hole dark matter for some time.
- 02:32: Any given study is sensitive to a particular range of black hole masses.
- 02:37: If a study doesn’t find enough of black holes in that range, then that mass range is ruled out as a main contributor to dark matter.
- 02:50: Our hypothesis is that dark matter is made of black holes.
- 02:53: ... we’re going to go through the mass spectrum of black holes, and close one window after another - we’ll see at the end whether there ...
- 03:06: ... before we start eliminating specific black holes masses, let’s rule out an entire class of black holes. In face we're ...
- 03:16: We know black holes form from the remaining cores of the most massive stars, after they explode as supernovae.
- 03:21: ... can make a pretty good estimate of the maximum possible number of these black holes by estimating the number of stars that formed and died through cosmic ...
- 03:37: ... can also see the products of the supernova explosions- not so much the black holes produced in those explosions, but the heavy elements forged in the cores ...
- 03:47: ... us there haven’t been anywhere near enough supernovae to give us enough black holes to make up all of dark ...
- 04:18: So if dark matter is made of black holes then those black holes must have been with us from the beginning.
- 04:23: Fortunately for our hypothesis, there is a reason to think that colossal numbers of black holes may have formed in the very early universe.
- 04:32: We call these primordial black holes.
- 04:35: Now, we’ve talked about them before, but let’s dig much deeper into the question of whether primordial black holes could explain dark matter.
- 04:44: There are a few ways primordial black holes could form.
- 05:03: ... strong enough that the most massive of them would have collapsed into black holes. ...
- 05:13: ... those black holes should have all formed at around the same mass - but that mass depends ...
- 05:28: Because of this, to really falsify the primordial black hole as dark matter hypothesis, we need to rule out this entire mass range.
- 05:43: The most massive black holes in the universe weigh in at millions to billions of times the mass of our Sun.
- 05:48: We see these “supermassive black holes” in the centers of essentially all galaxies.
- 06:00: At the opposite end of the mass spectrum we have the black holes under a billion tons or around the mass of a small mountain.
- 06:17: We can also rule out black holes a bit larger than this as dark matter.
- 06:20: ... dark matter to be made of black holes with masses around that of a larger asteroid or small moon, we’d need ...
- 06:38: ... though these black holes would have microscopic event horizons, at those insane abundances, ...
- 07:14: They're so dense, that they would stop a microscopic black hole in its tracks.
- 07:18: The black hole would then swallow the neutron star from the inside out.
- 07:30: Probably no more than a few percent of the dark matter mass can be from these micro black holes.
- 07:36: Ok, let’s move up the black hole mass spectrum to masses around that of a planet.
- 07:44: ... a compact mass like a black hole passes in front of a distant light source, the warped spacetime around ...
- 07:58: ... doesn’t necessarily tell you whether the lensing object is a black hole or some other dark compact mass like a brown dwarf star, neutron star, ...
- 09:22: And we can’t rule out these as primordial black holes, nor as Reapers - but there’s no good evidence of either.
- 09:30: So far we’ve mostly ruled out black holes around the Sun’s mass or lower as an explanation for dark matter.
- 09:37: ... black holes are tricky, because you need fewer of them to make up the mass of dark ...
- 09:46: ... I mentioned, the most massive black holes trickle to the center of our galaxy, but there’s an intermediate mass ...
- 10:01: ... galaxies are so small and dense that even black holes with tens of solar masses should have trickled to the center by now, and ...
- 10:11: ... dwarf galaxies tells us that no more than 4% of the dark matter could be black holes of tens to thousands of solar ...
- 10:20: ... our galaxy gives us similar constraints - if there were lots of black holes of several tens times the Sun’s mass then these binaries would long ago ...
- 10:37: We have some evidence ruling out most of the black hole mass spectrum as the main source of dark matter.
- 10:57: ... dark matter probably isn’t black holes - but don’t be sad - that means dark matter is probably something that ...
- 11:16: ... speculated that an evaporated black hole might leave behind a tiny naked singularity - a speck of infinite ...
2021-03-23: Zeno's Paradox & The Quantum Zeno Effect
- 13:04: ... the course you’ll explore everything from time in quantum mechanics to black hole entropy and learn what cutting-edge science has to say about the nature ...
- 15:08: But it's different with gravitational waves from merging black holes.
- 15:21: ... black holes spiral towards each other, the frequency of the last phase of the ...
2021-03-16: The NEW Crisis in Cosmology
- 10:40: ... of this is when a distant quasar - a giant, gas-guzzling black hole - happens to be closely aligned behind a more nearby galaxy. ...
- 11:57: ... long we may even be able to use gravitational waves from merging black holes to measure the Hubble constant. These waves get stretched by the ...
2021-03-09: How Does Gravity Affect Light?
- 00:38: ... stop, and fall back - and so was the first to predict the existence of black holes. ...
- 04:37: ... the event horizon of the black hole, gravitational time dilation is so strong that clocks stop and the ...
2021-02-17: Gravitational Wave Background Discovered?
- 00:00: ... built this giant machine that spotted gravitational waves from colliding black holes well we've just taken it to the next level with a galaxy spanning ...
2021-01-26: Is Dark Matter Made of Particles?
- 01:13: Now it’s possible that dark matter is not particles - it could be black holes or failed stars or even weirder so-called “compact objects”.
2021-01-19: Can We Break the Universe?
- 00:02: Black holes, gravitational waves, he was even the first to realize that friggin lasers could be a thing.
2020-12-22: Navigating with Quantum Entanglement
- 14:12: ... then quantum tunneling will cause the neutron star to collapse into a black hole over an absurdly long timescale of 10^10^20-70 or so ...
- 14:28: And then those black holes evaporate into radiation on a comparitifly short timescale.
2020-12-15: The Supernova At The End of Time
- 00:35: ... interesting thing to happen will be the final explosions as the last black holes evaporate - and even those will be relatively weak-sauce as far as space ...
- 02:06: Much more climactic that the previous version, which had black holes fizzling out - at least this one has some decent ka-booms.
- 06:17: We now know that the end result is either a neutron star or a black hole, accompanied by a powerful supernova explosion.
- 09:20: ... those iron stars are also doomed - they’ll quietly become black holes themselves through countless aeons of more quantum tunneling - something ...
- 09:33: And those black hole will evaporate rather quickly by comparison - leaking away as pure radiation in 10^60 years.
2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces
- 13:32: ... Theorems, and how they show that the singularities at the heart of the black hole and at the Big Bang are inevitable if you follow only general ...
- 13:57: ... up to infinite values, like the density or curvature at the center of a black hole. ...
- 14:10: ... the case of the black hole singularity, or the singularity of the big bang, it’s bad because it ...
- 14:41: Dr Kres von Panzer asks how we know that two light rays inside a black hole converge and don’t just perpetually pass each other.
- 15:07: In the case of the perfect spherical symmetry inside of a Schwarzschild black hole, all geodesics do indeed converge.
2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time
- 00:00: ... by the astronomers who revealed to us the Milky Way’s central black hole and by Roger Penrose, who proved that in general relativity, every ...
- 00:34: ... Black holes have haunted our theories of gravity since the 1700s. ...
- 01:17: ... in the theory. Einstein himself doubted that the black holes could form in the real universe, and even if they could, ...
- 01:58: ... It only showed that, once so-contracted, the resulting black hole was ...
- 02:16: ... the intriguing and terrifying possibility that black holes might really exist inspired some of our greatest minds ...
- 03:38: ... took a young Camridge physicist named Roger Penrose to prove that black hole singularities were utterly unavoidable in ...
- 04:35: ... to Einstein’s theory plus a couple of assumptions, black holes must contain singularities. And this is true regardless of how the ...
- 05:01: ... of spacetime literally comes to an end inside a black hole. In general relativity we map the fabric of spacetime with gridlines ...
- 05:55: ... null geodesics traveling down into a black hole are going to converge - no big surprise there. But the crazy ...
- 08:11: ... your northness - and started traveling south again. Well, in a black hole you don’t reach the end of north, you reach the end of ...
- 08:49: ... actually show what type of singularity would form in a black hole - just that some type was inevitable. In a Schwarzschild black ...
- 09:31: ... Roger Penrose’s discovery, black holes and the singularities within had to be taken more ...
- 10:36: ... showed that Penrose’s arguments about black holes also applied to the universe - that geodesics traced ...
- 12:11: ... for his contributions to our theoretical understanding of black holes. He shared it with Andrea Ghez and Reinhard Genzel, who ...
2020-09-08: The Truth About Beauty in Physics
- 09:42: ... or a photon bouncing between mirrors - but the resulting theory predicts black holes, gravitational waves, and even the big ...
2020-08-24: Can Future Colliders Break the Standard Model?
- 14:28: ... get to your questions Jason Carter asks a tricky one: when two black holes merge and share a single, warped event horizon, shouldn’t there be a ...
- 14:49: Think of the case of the rotating black hole - the singularity is a ring, and relatively few geodesics - free-falling paths - hit the singularity.
- 14:59: In the case of the merging black holes, you can think of space as more flowing towards the center of mass - although it’s not quite that simple.
2020-08-17: How Stars Destroy Each Other
- 02:16: ... produced by white dwarfs, to X-ray binaries created by neutron stars and black holes - and much weirder things ...
- 04:59: Just replace the white dwarf with a neutron star or black hole.
- 05:18: And its mass is high enough it sucks itself into a black hole.
- 05:33: Once again, if the two are close enough, gas is syphoned from the star onto the black hole or neutron star.
- 06:33: Black hole x-ray binaries seem a bit more boring by comparison, because the black hole has no surface for the gas to fall onto - so no x-ray flares.
- 06:42: The nearest such system is the famous Cynus X1 X-ray binary, where a black hole the mass of 15 Suns is busy gorging on a blue giant star.
- 10:43: ... new observation by LIGO: gravitational waves from the merger of a black hole with ... something ...
- 10:54: ... that seemed to straddle the mass between black holes and neutron stars, and which will change the way we think about ...
- 11:04: Zack Hamburg asks how we know that a black hole isn’t just a neutron star behind an event horizon.
- 11:25: That’s when it becomes a black hole.
- 12:00: Catinboots81 and Vivallamannen asks whether the strange smaller object in the merger might have been a primordial black hole.
- 12:10: Dead stars aren’t the only way to make black holes.
- 12:12: ... black holes may have formed from the extremely dense matter of the early universe, ...
- 12:21: ... fact, people have considered primordial black holes as an explanation for other LIGO mergers - which often involve black ...
- 12:32: ... it’s also possible that primordial black holes could be less massive than black holes that come from stars, so might ...
- 12:44: ... primordial black holes exist in some abundance at these masses, then the universe should be ...
- 12:56: LIGO hasn’t seen that background yet - which actually limits how many such primordial black holes there might be.
- 13:03: ... this background then it’ll become less and less likely that primordial black holes are responsible for any LIGO ...
- 13:27: Compared to a black hole or neutron star, regular stars are giant puffed up balls.
- 13:37: Frank and Jim asked how the event horizons of merging black holes change just before they combine.
- 13:42: ... an ovoid and then finally a sphere, or flattened sphere for a rotating black hole. ...
- 13:56: ... that this doesn’t say anything about the shape of the stuff inside the black hole - we’re just the event horizon - the surface below which there’s a ...
2020-08-10: Theory of Everything Controversies: Livestream
- 00:00: ... in the very early universe towards the big bang or in the center of black holes but also in principle every time we bring a particle into a ...
2020-07-28: What is a Theory of Everything: Livestream
- 00:00: ... it works it explains gravitate it predicts gravitational waves and black holes all these zany things that have been observed experimentally it takes ...
2020-07-20: The Boundary Between Black Holes & Neutron Stars
- 00:10: And we just did - an object on the boundary between neutron stars and black holes, which promises to reveal the secrets of both.
- 00:29: ... ripples in the fabric of spacetime due to a cataclysmic collision of black holes billions of light years ...
- 01:14: One was a hefty 23 times the mass of our Sun - making it definitely a black hole, and pretty similar to other LIGO mergers.
- 01:29: ... a neutron star, and it’s lighter than what was thought possible for a black hole. ...
- 03:34: ... tore themselves apart in their collision before they collapsed into a black hole. ...
- 04:18: ... would be the case if both objects were black holes, but even if the smaller object was a neutron star it could well have ...
- 04:39: To understand that, we have to understand a bit more about black holes and neutron stars.
- 05:42: ... fact neutron stars are on the verge of being black holes, which by definition have an escape velocity at the event horizon equal ...
- 05:51: If only you could cram a little more matter into the neutron star, the escape velocity would increase and it would become a black hole.
- 05:58: Now in the case of normal matter, you can’t just add mass to make a black hole because as you do so the radius of the object increases.
- 06:42: For any given mass, there’s a certain size that if you could crunch an object down below that size it would be a black hole.
- 07:07: When they overlap you have a black hole.
- 07:11: This basic picture is pretty well accepted, but we still aren’t sure just how massive a neutron star can be before becoming a black hole.
- 09:27: So why can’t it just be another black hole?
- 09:33: So far we’ve never observed a black hole with masses lower than around 5 times that of the Sun.
- 09:40: We see those in X-ray binaries - when a black hole is orbiting and cannibalizing another star.
- 09:47: ... to be a gap in masses between the biggest neuron stars and the smallest black holes, but actually we very much expect ...
- 09:58: New black holes are formed when the most massive stars die and the core is too big to become a neutron star.
- 10:04: But you don’t get this smooth transition from neutron stars to black holes.
- 10:17: But if that neutron star then becomes a black hole, some of the infalling material just gets sucked into the black hole.
- 10:24: That increases the black hole’s mass quite a bit.
- 10:28: Based on our calculations and simulations of how stars die, that minimum black hole mass of 5 Suns seems about right.
- 10:36: A black hole with 2.6 solar masses is difficult to explain.
- 10:41: ... models of how stars die - or find some other way to make extra-teensie black holes. ...
- 11:53: It’s a brand new 2.6 solar mass black hole.
- 11:57: I know, it’s small as far as black holes go - but we hope it adequately reflects our thanks.
- 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 ...
- 12:34: ... points out that it would be increasingly difficult to do so as the black hole gain ...
- 12:52: However it never actually becomes impossible to keep charging up a black hole if you can put enough energy behind your electron beam.
- 13:03: ... the event horizon just for a plank lenght and the instant later the black hole shrinks due to ...
- 13:15: Would I find myself outside again and have seen the inside of the black hole?
- 13:34: ... horizon - and then yes, they would see your energy exit again as the black hole shrank - but it would itslef be as hopelessly scrambled hawking ...
2020-06-30: Dissolving an Event Horizon
- 00:00: Black hole singularities break physics - fortunately, the universe seems to conspire to protect itself from their causality-destroying madness.
- 00:28: Strange things happen inside black holes.
- 00:57: In the most real possible sense, the interior of the black hole is its own separate spacetime, excised from our universe.
- 02:22: According to the so-called no-hair theorem, black holes can have only three properties - mass, electric charge, and spin.
- 02:31: Mass is what makes a black hole a black hole, and so the simplest black holes have only this property.
- 02:37: These are Schwarzschild black holes, and with only mass that means they also only have inward-pulling gravity.
- 02:51: In recent episodes we also explored the rotating, or Kerr black hole.
- 03:34: As the spin of a Kerr black hole increases, the spacetime waterfall is beaten back, and so the inner horizon grows.
- 04:02: There’s a similar situation with the charged black hole - which, absent rotation, is described by the Reisner-Nordstrom metric.
- 04:20: Reisner-Nordstrom black holes also have an inner horizon, interior to which space and time seem normal-ish.
- 04:28: The more electric charge you drop into a black hole, the larger its inner horizon becomes.
- 04:33: And just as with the rotating black hole, at some point the inner and outer horizons become one and vanish and you’re left with a naked singularity.
- 04:43: ... are right next to each other - you have what we call an extremal black hole - a black hole with the maximum amount of spin or charge while still ...
- 04:57: In both cases, the amount of angular momentum or charge you can fit into a black hole before it becomes extremal depends on the mass.
- 05:07: More mass means more inward gravity, and so the black hole can hold more spin and charge before going extremal.
- 05:14: So that’s how you make an extremal black hole - or even a naked singularity.
- 05:20: Just add enough spin or charge to an existing black hole.
- 05:24: And actually there’s another way to do it in the case of the charged black hole.
- 05:29: Normal black holes leak their mass away by emitting Hawking radiation.
- 05:33: That radiation cian be any type of elementary particle - but in the case of the most massive black holes, it’s mostly just photons.
- 05:40: That’s because the more massive the black hole the lower the temperature of the radiation.
- 05:45: In very massive black holes the Hawking radiation has trouble mustering the energy for anything but weak photons.
- 05:52: So that means a massive CHARGED black hole will slowly leak away its mass while retaining its charge.
- 05:59: The outer event horizon will shrink until it meets the inner horizon, and again you have an extremal black hole.
- 06:06: This can’t happen with rotating black holes because they leak away their angular momentum as well as their mass.
- 06:13: Once you have an extremal black hole by whatever method, it lasts for a very, very long time - if not forever.
- 06:25: So naked singularities don’t Hawking-radiate, and extremal black holes radiate only very slowly.
- 06:47: At first glance, it appears that extremal black holes are certainly possible.
- 07:11: Rotating black holes gain their angular momentum from things they swallow.
- 07:15: Stuff doesn’t normally fall straight into a black hole - it spirals in as its orbit decays.
- 07:20: It’s that orbital angular momentum that is fed to the black hole.
- 07:24: But in order for an object orbiting a black hole to fall into it, it actually has to lose at least some of that angular momentum.
- 07:31: ... example, if there’s a disk of gas surrounding the black hole like in a quasar, then the gas only spirals inwards because angular ...
- 07:42: By the time the gas reaches the black hole it has lost much of the angular momentum it started with.
- 07:49: The faster a black hole is rotating, the more angular momentum that gas has to lose in order to fall in.
- 07:55: ... because space gets dragged around the rotating black hole, giving the gas a sort of boost so it can still orbit even with very ...
- 08:06: ... the case of an extremal Kerr black hole - one that’s rotating nearly fast enough to lose its event horizon - the ...
- 08:23: Therefore just on the verge of becoming extremal, the black hole can’t gain spin from accretion anymore.
- 08:30: More generally, there is no trajectory into an extremal black hole that can add angular momentum from the trajectory or the “orbit” itself.
- 08:55: ... any rate, our observations of gravitational waves from colliding black holes and various other methods for estimate black hole spin has not yet ...
- 09:09: For charged black holes the situation is in some ways easier, but has its own weirdness.
- 09:17: We don’t actually expect real, astrophysical black holes to retain any significant change.
- 09:23: A charged black hole in the vicinity of any matter would repel like charges and attract and swallow opposite charges, and so quickly neutralize.
- 09:32: But imagine we create a charged black hole and isolate it from all other matter.
- 09:37: Then surely we can just throw charged particles into the black hole.
- 09:41: ... have to be careful, because those particles increase the mass of the black hole as well as the charge - and if the mass increases too much it won’t go ...
- 09:51: ... charge - just factoring the electrons mass, it should be easy to send a black hole over the extremal limit by feeding it a stream of ...
- 10:15: And there’s an enormous amount of energy in the electric field of all those electrons that you smooshed together into the black hole.
- 10:23: In fact the field itself will always generate enough mass to prevent the black hole from losing its event horizon.
- 11:16: ... responses last week, so today we’re covering two episodes - building black holes in the lab with analog event horizons, and Roger Penrose’s conformal ...
- 11:34: In representations of black holes as funnels, or wormholes as tubes, what does that funnel or tube really represent?
- 11:42: Is it, for example, some extra dimension that the black hole leads into?
- 11:46: ... a 3-dimensional space and take a two dimensional slice out of it, so the black hole or wormhole ends are circular instead of ...
- 12:08: ... the case of the black hole funnel - moving towards the bottom means moving towards the central ...
2020-06-22: Building Black Holes in a Lab
- 00:00: Black holes are very real, but our understanding of them remains highly theoretical. If only we could build one in the lab. Oh wait, we can.
- 00:16: ... Black holes are about the worst subjects for direct study in the universe. First ...
- 01:11: ... ourselves of their existence. Actually studying the physics of real black holes is much, much harder. I mean, we could try to make one - but that’s way ...
- 01:29: ... it turns out we don’t need to make a real black hole to at least get started with the lab work. We can instead study analog ...
- 01:54: ... whole idea of analog black holes was started in 1972 by Bill Unruh - most known for his Unruh radiation, ...
- 03:05: ... sound with light and the water with spacetime itself and you have a black hole. The surface around the central, massive point where the waterfall of ...
- 03:26: ... And a vortex expressed in those equations of fluid flow resembles a black hole - right down to the emission of Hawking radiation. The details are a bit ...
- 04:08: ... and found a number of systems with event horizons Analog theoretical black holes are all very well, but their real value is that they tell us we might be ...
- 05:25: ... these event horizons, physicists can look for black hole-like behavior. For example, Hawking radiation. All the gory details of ...
- 06:12: This perturbs the quantum fields in a way that look likes escaping particles if you’re very far away from the black hole.
- 06:20: ... in the case of an analog watery black hole you just replace “vibration in the quantum field” with “ripple on ...
- 06:33: ... in fact Hawking-like radiation has been observed in these analog black holes. Or at least, the perturbations in the frequencies of the surface ripples ...
- 07:24: ... exactly the expected sapping of the “gravitational field” in a vortex black hole analog. In fact, both the analog of energy and angular momentum seems to ...
- 07:41: ... vortices are fantastic laboratories for spinning black holes in particular. Now we’ve looked deeply into rotating, or Kerr black ...
- 08:04: ... thing we saw was that rotating black holes can donate some of their rotational energy to particles or waves that ...
- 08:42: ... Weinfurtner demonstrated this in a brilliant analog black hole setup. It consists of a giant, 2000 litre tank of fluorescent water.. ...
- 09:19: ... quantum mechanical effect. Deeper insights may require an analog quantum black hole. Enter the Bose-Einstein condensate. Bose-Einstein condensates, or BECs, ...
- 10:13: ... as with real black holes, some atoms do escape as Hawking radiation. Here you can measure not just ...
- 10:44: ... optical analogs are at best, approximations of the dynamics at play with black holes. ...
- 11:04: ... crux of the matter is as much philosophy as physics: How much can analog black holes actually tell us about real black holes? Early arguments in the late ...
- 12:12: They say black holes are unique aberrations, and analog is just that: an imperfect analogy incapable of truly capturing the extreme dynamics at play.
- 12:23: ... able to travel to the stars, or to build - and hopefully control - real black holes in the lab, the black hole analog is the best physical experiment we can ...
- 12:34: ... black hole theorists will continue to theorize, but now we have a new daring breed ...
2020-06-15: What Happens After the Universe Ends?
- 00:45: ... has expanded exponentially to to an unthinkably large size, and every black hole and particle has decayed into faint radiation .... that infinite stretch ...
- 07:06: ... all stars will die and their remnants will decay - black holes will evaporate by Hawking radiation, and particles of matter will decay ...
- 12:48: To do that, black holes must swallow entropy - and destroy information.
- 13:28: Penroses proposes that the collisions of super massive black holes in the previous universe may leave rings on the sky in the next.
- 14:09: ... advanced civilization could manipulate the dances of gigantic black holes, they could potentially send information between ...
- 14:49: ... names encoded in the orbital frequencies of colliding suppermassive black holes at the end of time to be propogated across the conformal infinity into ...
- 18:05: ... wonder, is it possible to be devoured by a black hole while being blasted by a supernova, and frozen by the heat death of the ...
2020-05-27: Does Gravity Require Extra Dimensions?
- 07:52: ... John Mitchell - the same guy who first hypothesized the existence of black holes. ...
- 13:29: ... the strange regions that lie beneath the event horizon of a rotating black hole - regions like the Carter time machine and the infinite string of ...
- 13:49: ... his hunch which is that the “multiverse” you get from traveling through black holes has nothing to do with the multiverse predicted by quantum ...
- 14:16: Now the multiverse through the black hole arises from tracing the paths of spacetime through the black hole mathematically.
- 14:24: ... almost certainly a mathematical figment, arising from idealized types of black hole that don't really ...
- 14:48: Well, the universe on the other side of the black hole is probably a figment in the math - which I suppose you can call broken math if you like.
- 15:16: And in the case of the black holes, several unreasonable assumptions allow us to trace geodesics into alternate universes.
- 15:24: ... example, the parallel universe through the non-rotating Schwarzschild black hole requires the assumption that the black hole has been there ...
- 15:33: ... the string of universes through the rotating Kerr black hole requires the assumption that the impossibly unstable inner structure of ...
2020-05-18: Mapping the Multiverse
- 00:09: ... when you solve Einstein’s equations of general relativity for a rotating black hole, the universe does not come to an abrupt halt at the bottom of the ...
- 00:36: ... a little while ago when we explored the region just above a rotating black hole. ...
- 01:01: ... black hole results when enough mass is concentrated in a small enough space that ...
- 01:11: The inescapable surface surrounding a black hole is called the event horizon.
- 01:16: ... and does not have any electric charge, the result is a Schwarzschild black hole, which is about as simple as these bizarre objects can ...
- 01:33: Now, we’re going to focus on rotating black holes here, but a lot of this also applies to charged black holes, as we’ll see.
- 01:41: A rotating black hole is described mathematically by the Kerr metric.
- 01:53: We sometimes call a rotating black hole with no electric charge a Kerr black hole.
- 02:16: Well, in a Kerr black hole that rotation results in an outward pressure that partially counteracts the inward flow due to gravity.
- 03:47: When we first enter the Kerr black hole, we find it’s just like every non-rotating Schwarzschild black hole we’ve ever visited.
- 04:02: In a regular black hole we’d be crushed by the central singularity pretty quickly.
- 04:06: But now as we fall the outward pressure due to the black hole’s rotation starts to win against that inward flow.
- 04:50: Below you is the black hole singularity - but it looks odd.
- 06:13: Same with the interior of a Schwarzschild black hole - every ball, every geodesic reaches the same point and, very importantly, ends there.
- 06:24: But within a Kerr black hole, the singularity is a ring, and the trillion balls would fall towards the disk bounded by that ring.
- 06:33: Only the ones exactly on the equator hit the ring and, those geodesics do end - same infinite squish as in a Schwarzschild black hole.
- 08:34: This time travel and naked singularity stuff is good reason to think this part of the mathematical structure of the Kerr black hole is NOT real.
- 09:10: That’s a little confusing because black holes are supposed to be inescapable.
- 09:14: So what’s with this conveyor belt of space taking you out of the black hole?
- 09:31: The black hole is in your past.
- 09:49: Now we saw that in the Schwarzschild solution, a white hole exists in the past of a purely hypothetical eternal non-rotating black hole.
- 10:00: The Kerr black hole also has a white hole in the past, but it has one in the future too.
- 10:11: But not only is the black hole in your past - the entire universe that you came from is in your past.
- 10:25: That white hole will eject you as forcibly as the black hole pulled you down.
- 10:49: If you try to head back to the white hole, you won’t find it - you’ll only find a new black hole that lies in its future.
- 11:30: You reach one if you embrace your fall and head down, the other if you try to resist and exit the black hole.
- 11:58: This would be okay-ish if the black hole was empty, but it’s not okay if there’s even the tiniest bit of matter or radiation.
- 12:06: ... there’s any stuff at all in the black hole then the forward flow of time carries a current of positive energy, ...
- 12:23: That pressure produces its own gravitational effect on par with the black hole itself, accelerating the streams further.
- 12:42: ... this so-called mass inflation means the inner structure of the Kerr black hole is catastrophically unstable, and the whole thing collapses, shutting ...
- 12:58: This whole counter-streaming instability thing was figured out by Roger Penrose in the context of charged, non-rotating black holes.
- 13:08: But it almost certainly applies to Kerr black holes also because the two are very similar.
- 13:13: ... electrically charged, or Reissner-Nordström black holes the electromagnetic field within causes massive tension, or negative ...
- 13:26: That resists the inward flow just like rotation does in a Kerr black hole.
- 13:50: Just a little wishful thinking, a rotating black hole, and don’t forget to slip your map in your back pocket.
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.
2020-04-28: Space Time Livestream: Ask Matt Anything
- 00:00: ... community tab asks if I can describe how dark energy and evaporating black holes with virtual particles do not violate conservation laws so let's start ...
2020-04-22: Will Wormholes Allow Fast Interstellar Travel?
- 00:23: ... of general relativity - a solution that we now understand describes a black hole. But before black holes were ever taken seriously, the Schwarzschild ...
- 03:45: ... could pass through that event horizon we would not find ourselves in a black hole - we’d be instantly transported to the region ...
- 04:08: ... it through. To see that we need to turn back to a representation of the black hole that we saw in our parallel universe episode. This is the ...
- 04:50: ... discovered is represented as a mirror reflection to our universe. The black hole also has a mirror reflection that we call the white ...
- 05:17: ... black hole represented here is a so-called “eternal” black hole - no matter where ...
- 05:43: ... two event horizons - and the region in between is the inside of a black hole. When that time-slice hits the singularity the wormhole has ...
- 06:35: ... really represents two things - it accurately describes a non-rotating black hole if you just consider its future state where the wormhole is pinched off. ...
- 07:03: ... Kip Thorne. Sagan’s initial idea was to make the wormhole a two-sided black hole. Of course we all know that such a Schwarzschild wormhole cannot be ...
- 11:48: ... exotic matter - and that’s the wormhole through a rotating or charged black hole. Now I’ve promised a more in-depth episode on rotating black hole ...
- 14:15: ... structures, that seem to have erupted from near the Milky Way central black hole. The Fermi ...
- 14:59: ... these bubbles might be caused by dark matter interactions with the black hole. I'm afraid I don't know of any theory of dark matter that would do that. ...
2020-04-14: Was the Milky Way a Quasar?
- 00:47: ... only is it home to an enormous black hole four million times the mass of the Sun, but it also swarms with smaller ...
- 01:10: Our central black hole, Sagittarius A*, has been in a quiet or “inactive” phase for as long as we’ve been observing it.
- 01:28: In these, the supermassive black hole at the galactic core is in the process of sucking down a blazing hot vortex of gas.
- 01:49: ... researchers in the field believe that all supermassive black holes went through violent AGN phases in the past — and that includes our very ...
- 07:43: All of those supernovae would have had to leave remnants behind - neutron stars and black holes.
- 08:01: Could the Fermi Bubbles have been created by activity from our supermassive black hole?
- 08:11: To answer that we need to consider how active the black hole would have to have been.
- 08:25: ... lot of that mass goes into the black hole, but 10% or more is converted into energy in the form of light before it ...
- 09:54: A mini AGN phase is triggered either by an influx of gas or by a random massive star getting too close to the black hole.
- 11:07: Just like the Fermi Bubbles, these radio bubbles seem to originate from our central black hole and extend in opposite directions above and below.
- 11:41: ... both cases — some combination of accretion onto the Milky Way’s central black hole and a flurry of star formation egging each other ...
- 12:47: ... of astronomers presented evidence that the X-ray activity of our central black hole has been increasing over the past four ...
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 ...
- 00:10: ... need new coordinate systems to trace paths into the black hole interior. But the maps we draw using those coordinates reveal something ...
- 01:38: ... spacetime also have coordinate singularities - for example around the black hole. ...
- 01:53: ... first map of the spacetime of a black hole was the Schwarzschild metric - a relatively simple bit of algebra ...
- 02:56: ... and to make a smooth map through it we need a Mercator projection of a black hole. ...
- 03:14: ... at the poles, to cancel out the converging lines of longitude. For black holes we instead fuse time with a something called a tortoise coordinate, ...
- 05:00: ... place geodesics end is at true singularities, like at the center of the black hole. On our Penrose diagram, we see that light rays can either travel away ...
- 05:49: ... of the Penrose coordinates within the Schwarzschild description of the black hole. If we trace those coordinates to their full extent, we get what we call ...
- 06:15: ... from our universe we encounter a region that looks just like the black hole - but with time reversed. This is the white hole, and we’ve this before ...
- 06:51: ... say - the map I just drew is for the case of an eternal Schwarzschild black hole. One whose coordinates do not change over time, implying that it always ...
- 07:10: We’ll see later how things change in the case of a black hole born of the collapse of a star.
- 07:16: For now, let’s see if we can travel to the parallel universe of the eternal black hole.
- 07:57: ... say you drop into a black hole to try to get to the other side. Within the black hole, space and time ...
- 08:22: ... inside the black hole what do you see? Light can reach you from the universe behind - those ...
- 08:44: ... for now you overtake that light and get a glimpse of the black hole’s past. You never actually see the singularity - that is manifest as an ...
- 09:00: ... through the parallel horizon into the parallel universe. Within the black hole, you see an event horizon both behind AND ahead of you. But only ...
- 09:39: ... white hole are just coordinate reflections of the regular universe and black hole - that they don’t have an independent ...
- 09:55: ... from the past “white hole” traveling forward in time, or from the future black hole but traveling backwards in time. Which would just look like falling into ...
- 10:30: Not only is faster than light travel impossible, but eternal black holes don’t exist either.
- 10:35: ... and white hole are needed in the map of the eternal Schwarzschild black hole in order for geodesics to have somewhere to come from. But real black ...
- 10:58: ... though the parallel universe of the Schwazschild black hole isn’t likely to be real, there are intriguing possibilities. That ...
- 11:37: ... we’re doing comments for the last two episodes which are on rotating black holes and quantum darwinism. Let’s see what you had to ...
- 13:31: ... Cramer wants to know how big an explosion you can get from a black hole bomb, and kindly requests a whole video. Well for the video I'm going to ...
2020-03-24: How Black Holes Spin Space Time
- 00:03: ... there’s one thing cooler than a black hole it’s a rotating black hole. Why? Because we can use them as futuristic ...
- 00:21: ... It predicts the inescapable region of space that we now call the black hole. ...
- 01:01: ... observations of the universe have since told us that black holes are very real. We’ve seen the gravitational waves caused by their ...
- 01:35: According to the no-hair theorem, black holes can have three and only three properties: mass, electric charge, and spin.
- 01:44: ... black hole must have mass. Compacting a lot of mass into a tiny region is what ...
- 02:26: ... black holes might not have MUCH spin - because angular momentum can cancel out if ...
- 02:36: ... the importance of spin in black holes, it took nearly half a century before Einstein’s equations were solved ...
- 03:18: It can be used to calculate the path of any body moving near or even within a Kerr black hole - or indeed any rotating mass.
- 03:27: ... the Kerr solution can tell us about the spacetime outside a rotating black hole. We’ll save the even weirder details of the Kerr black hole’s interior ...
- 03:54: ... start by talking about what is actually rotating in a Kerr black hole. It’s tempting to just say that some physical thing deep beneath the ...
- 04:26: ... Black holes are self-sustaining holes in the fabric of spacetime. Space at the event ...
- 05:14: ... flow of space around a rotating black hole is known as frame-dragging. We see it around any rotating mass. In frame ...
- 05:49: ... approach our Kerr black hole. Contrary to the common misconception, as long as you don’t get too close ...
- 06:48: ... circular orbits is ... innermost stable circular orbit. Or ISCO. For a black hole that is currently feeding - perhaps devouring a companion star or, in ...
- 07:27: So yeah, you can orbit “safely” pretty close to the Kerr black hole’s event horizon.
- 07:33: ... called the ergosphere. There, frame dragging carries space around the black hole at faster than the speed of light. That means everything - even light - ...
- 07:50: ... coordinate becomes time-like - it’s as difficult to resist orbiting the black hole than it is to travel backwards in time - which is to say it’s ...
- 08:54: ... still plenty to do in the ergosphere - like building a hyper-advanced black hole ...
- 09:06: ... like this: a massive object is dropped into the ergosphere of a kerr black hole on a carefully tuned ...
- 09:37: ... is extracted from the rotational energy in the ergosphere, slowing the black hole’s spin. To get a little more technical - it works because the weird ...
- 10:00: ... there’s your black hole engine: maneuver rocks into a Kerr black hole, blow them apart at the ...
- 10:27: ... with, in principle, 100% efficiency. Oh, and you can also build a black hole bomb this way - by surrounding the Kerr black hole with mirrors. Then ...
- 10:51: ... you have a magnetic field produced by the flow of material around the black hole in an accretion disk. The flow of space in the ergosphere spins up the ...
- 11:31: ... produced by fast-rotating black holes are also a contender for another astrophysical phenomenon - gamma ray ...
- 12:11: ... black holes are very real and powerful players in the energetics of our universe - ...
2020-02-18: Does Consciousness Influence Quantum Mechanics?
- 14:37: This is a great image - galaxies falling apart as they turned into black holes and other stellar corpses.
2020-02-03: Are there Infinite Versions of You?
- 07:55: ... be prohibited by a combination of conservation laws and the formation of black holes. ...
2020-01-27: Hacking the Nature of Reality
- 13:58: ... so previously we talked about a compelling new idea for how black holes might merge - perhaps they're captured and then brought together in the ...
- 14:41: And between these inward and outward migration regions are places where no angular momentum is exchanged. And, well, the black hole is trapped.
- 14:50: Adam Wulg asks whether gas surrounding a pair of merging black holes might significantly affect the gravitational wave signature.
- 15:01: ... causes the black holes to merge faster, so that should increase the frequency of the those ...
- 15:10: ... all gas is going to be ejected from the near region of these merging black holes before they actually collide, and LIGO only sees the merger in the last ...
- 15:37: ... it's oxymoronic to say that “All you need is a little quasar" to catch black holes. Suggesting that there's no such thing as a little ...
- 15:56: ... quasars our powered by supermassive black holes a few tens of millions to 10 billion times the mass of the sun - and the ...
- 16:14: ... accretion disks are still very capable of capturing even smaller black holes - and may in fact be better at it because densities can be higher in the ...
2020-01-20: Solving the Three Body Problem
- 11:21: ... of dense regions of the universe, where three-body systems of stars or black holes may form and then disintegrate very ...
2020-01-13: How To Capture Black Holes
- 00:00: ... black holes are awesome, but how about black holes being captured by the screaming ...
- 00:24: ... - LIGO - detected its first gravitational wave from the merger of two black holes. That was stunning enough, but the real promise lay ahead. Every time we ...
- 00:59: ... black hole mergers themselves were not so surprising. Einstein’s general relativity ...
- 01:54: ... expected to see black hole mergers, but there was some striking surprises. For one thing, many of ...
- 02:16: ... the most awesome possibility: what if black hole mergers actually occur in orbit around supermassive black holes, ...
- 02:50: ... we know that the center of almost every galaxy contains a supermassive black hole of millions to billions of times the mass of the Sun. Recently we’ve ...
- 03:34: ... so, a black hole swarm surrounding a supermassive black hole sounds like a recipe for ...
- 04:08: ... there’s a way to massively accelerate the mergers of these black holes: all you need is a little quasar. For the most part the supermassive ...
- 04:50: ... is how supermassive black holes can grow to such enormous sizes, but what does the presence of an ...
- 05:37: ... these disk-crossing black holes should be swept into the accretion disk. There they gorge on the gas of ...
- 05:58: ... are two ways this can happen: If a binary black hole pair gets captured by the disk, the surrounding gas saps their orbital ...
- 06:15: ... accretion disks also allow lone black holes to find each other. This is really cool, because the process is similar ...
- 07:17: ... build into planets. In the case of accretion disks, the “planets” are black holes - captured single black holes end up in the same migration trap, ...
- 08:27: ... exciting and fun - and it may explain why so many surprisingly massive black hole mergers are observed. And if we spot more and more high-mass mergers ...
- 08:50: ... test? That’s where the paper by McKernan and collaborators comes in. If black holes merge in empty space then the event should invisible - it should emit no ...
- 09:15: These captured black hole binaries will be surrounded by their own mini-vortices of gas.
- 09:21: ... it can carry away up to several percent of the original mass of the two black holes. ...
- 09:31: ... moving too quickly for the reduced gravitational field of the final black hole. It creates an expanding expanding shock-front that then collides with ...
- 09:53: ... the release of gravitational waves delivers a kick to the final black hole - a bit like the recoil of a gun. This drives the black hole and its ...
- 10:18: ... thousands of regular galaxies. Any of those could be the source of the black hole ...
- 11:07: ... researchers are currently scouring the follow-up observations of past black hole mergers for just such a signature, and will be keeping a close eye on ...
- 11:18: ... LIGO now detected a black hole merger event every week or so, there’s a good chance this will be ...
- 11:32: ... mysteries and strange phenomena. Now we have the amazing possibility of black holes merging and growing to enormous size while trapped within the blazing ...
- 11:59: ... selection - Lee Smolin's idea that maybe new universes are born inside black holes. ...
- 12:17: ... similar observation/question: Shouldn't a universe that's born inside a black hole be limited in mass by the amount of stuff that falls into that black ...
- 12:49: ... couple of you point out that the idea of black holes birthing universes still doesn't explain where the first ...
- 13:26: ... asks what happens when a black hole is absorbed by another black hole? Do the universes collide? Do the ...
- 14:13: ... people also commented that they'd thought of the whole black holes creating new universes thing independently to Lee Smolin. I'm making a ...
2019-12-17: Do Black Holes Create New Universes?
- 00:03: What if every single black hole that formed in our universe sparked the big bang of a new universe?
- 01:10: You only need to accept two things: that our universe formed inside a black hole, and that universes can evolve.
- 01:54: It goes like this: the formation of a black hole triggers the formation of a new universe “on the other side” in a new big bang.
- 02:02: Those daughter universes go on to expand and make their own black holes and hence their own daughter universes.
- 02:20: Some of those shifts improve the daughter universe’s ability to form new black holes.
- 02:25: ... gradually the ensemble of all universes get better and better at making black holes, just as biological organisms with helpful mutations can get better at ...
- 02:43: Now by happy chance there’s a correlation between making lots of black holes and making life - both require stars.
- 03:12: First up, for any of this to make sense black holes need to create universes.
- 03:26: ... one of Lee Smolin’s mentors, Bryce deWitt, who postulated that when a black hole collapses, its mass doesn’t all end up stuck in the central, infinitely ...
- 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 creating a new ...
- 04:02: ... Archibald Wheeler expanded on the procreating black hole idea by suggesting that the fundamental constants of these new universes ...
- 04:14: ... the highest possible energy environments, which is exactly the end of a black hole ...
- 05:14: ... very quickly be dominated by ones that are extremely good and making black holes. ...
- 05:36: ... there’s a prediction: the fundamental constants that define black hole production should be close to optimal in a given universe, at least for ...
- 05:49: In our modern universe, black holes are made when the most massive stars explode as supernovae.
- 05:56: There are other ways to make black holes, and we’ll come back to them.
- 07:00: ... water, and chemistry in general, far fewer stars and so far fewer black holes would form - and of course these factors also seem to be essential for ...
- 07:12: But what about other sources of black holes?
- 07:16: ... the distant future, quantum fluctuations of that near vacuum will cause black holes to spontaneously appear - and given infinite time these will eventually ...
- 07:38: ... all this is true then the most black holes would be produced by the biggest universes - more space means more ...
- 08:09: ... the landscape of possible fundamental constants where different types of black hole are ...
- 08:22: This would lead to multiple branches of the cosmic genetic tree - some of which correspond to producing lots of stellar black holes.
- 08:51: ... natural selection is true, then the fundamental parameters favouring black hole production should be optimized completely independently to those that ...
- 09:09: ... of neutrons so dense that they teeter on the edge of collapsing into a black hole. ...
- 09:20: Black holes only form when the neutron stars is above a certain mass limit.
- 09:48: That in turn means less massive neutron stars would be able to collapse into black holes.
- 09:54: ... then, if universes evolve to maximize the number of black holes, then the strange quark mass should be optimized to make the cutoff ...
- 10:14: So, if this universe is optimized for black hole production then there should be no neutron stars more massive than 2 solar masses.
- 10:59: ... the anthropic principle by proposing a natural selection that favours black hole production, and it’s just a happy coincidence that the same factors also ...
- 11:13: ... just so happens that carbon and oxygen are good for both black hole production and organic molecules ... but what if it was, I dunno, ...
- 12:19: Or, you know, our universe's momma might be a black hole, and we live in an endlessly evolving, proliferating space time.
- 13:24: ... our friends at the large hadron collider - they’re going to make you a black hole ...
2019-11-18: Can You Observe a Typical Universe?
- 06:01: ... life in a state of extreme disorder and high entropy - iron stars, black holes, and a mist of cold elementary particles, not very hospitable to ...
2019-11-11: Does Life Need a Multiverse to Exist?
- 12:21: ... Lee Smolin’s idea that universes are born when black holes form, with each new universe having slightly different fundamental ...
2019-10-21: Is Time Travel Impossible?
- 04:41: ... ways they might – from connections between universes in the interiors of black holes to miniscule wormholes appearing and vanishing on the tiniest scales of ...
- 05:06: They collapses on themselves instantly, leaving inescapable black holes.
- 08:46: Another one is the interior of a rotating black hole – a so-called Kerr black hole.
- 08:59: ... back to your own past, but never to the time before you fell into the black hole, which is probably the only thing you really want to do at that ...
- 09:08: Unless it’s an Interstellar-style black hole . . . general relativity doesn’t directly refute black hole time machine libraries.
2019-10-15: Loop Quantum Gravity Explained
- 01:16: ... mechanics breaks down when we think about the extreme densities of the black hole or the big bang ...
- 11:20: ... for example, the theory seems to predict Hawking radiation and black hole entropy consistent with Hawking and Bekenstein’s ...
- 14:09: Now, last time we talked about Black Hole Harmonics, let's see what you had to say.
- 14:20: But first the context: this year LIGO detected two black hole merger signals within 20 minutes of each other and in similar patches of the sky.
- 14:30: ... it's really really really hard to come up with a scenario for two actual black hole pairs to colliding at the same time in the same general ...
- 14:38: ... alternative possibility is that it was just one black hole merger, but the gravitational wave from it was deflected by a galaxy or ...
- 15:35: ... there's a limit to the rotation of a black hole which comes from the fact that the outward centrifugal force of rotation ...
- 15:49: ... the black hole rotates more than a certain amount then the event horizon evaporates, ...
- 16:02: ... expected to be impossible, and so we expect a maximum rotation rate for black holes. The details of all this need their own episode, so I'll leave it at ...
- 17:07: Especially given that I kept saying a struck black hole rings like a bell.
2019-10-07: Black Hole Harmonics
- 00:04: ... Black holes are crazy enough on their own – but crash two together and you end up ...
- 00:22: Today on space time journal club we’ll explore two papers that claim to have detected black hole harmonics.
- 00:41: ... physicists talk about black holes they’re usually referring to highly theoretical objects – static, ...
- 00:53: This makes everything clean and simple enough to attempt the already notoriously complex calculations of black hole physics.
- 01:00: But real black holes are created in the violent deaths of massive stars, and there’s nothing clean about that.
- 01:08: ... now know that black holes also merge – and in the process produce gravitational radiation that ...
- 01:22: In the instant after its merger, the new, joined black hole looks nothing like the idealized theoretical black hole.
- 01:43: Technically, in that instant we go from two black holes to one.
- 01:47: But in the beginning this new black hole looks nothing like its progenitors.
- 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.
- 02:14: ... two inspiralling black holes make powerful spacetime ripples – gravitational waves – which intensify ...
- 02:27: ... then the merged black hole continues to radiate these spacetime ripples as it oscillates, but these ...
- 02:56: A “struck” black hole also vibrates with many different harmonic frequencies.
- 03:02: ... harmonics of a vibrating sphere – be it a blob of water in zero-g or a black hole – are analogous to the harmonics of a vibrating guitar string or piano ...
- 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.
- 04:24: For a black hole, another way to think of its quasinormal modes is as a set of gravitational waves trapped in orbit around the black hole.
- 04:39: OK, so a black hole can ring like a bell when struck – in that case a black hole merger is the biggest hammer strike of all.
- 04:46: But what does the ring-down of a black hole really look like?
- 04:57: ... overtones you’d need to look at the tail end of the ring-down, when the black hole was approaching a more spherical ...
- 05:08: ... thought that right after merger the black hole would be too chaotic – the oscillations should be “non-linear” or in ...
- 05:37: They looked for overtones in the ring-down from right at the point of black hole merger.
- 05:43: Now this wasn’t a real black hole merger – we’ll get to that shortly.
- 05:49: Giesler and team first they found the harmonics in a fake black hole merger.
- 05:53: ... relativity and, among other things, telling it to collide thousands of black holes. ...
- 06:10: ... 2) you know exactly what parameters went into the signal – in particular black hole mass and spin, so you know if you got the right answer when you try to ...
- 07:12: Similarly, the overtone structure of a black hole ringdown can identify the fundamental properties of that black hole – namely its mass and spin.
- 07:22: ... found that they could pinpoint the mass and spin of the simulated black holes with much greater precision than if they’d just used the gravitational ...
- 07:48: Now for this to be useful probably we’d want to look at some real black hole mergers.
- 08:04: looked at the merger and ring-down signal from the largest black hole merger we’ve seen.
- 08:09: ... in fact, was also the first one LIGO reported: GW150914 – a pair of black holes, each 30 or so times the mass of the sun, spiraling into each other one ...
- 08:43: By analyzing the harmonics, the team calculates the mass of the final black hole as 68.5 solar masses.
- 08:50: ... also get a spin for the final black hole – a so-called dimensionless spin magnitude of .69 – where the spin ...
- 09:05: .69 means this is a rapidly rotating black hole, which is unsurprising seeing as it just absorbed the orbital angular momentum of two black holes.
- 09:24: ... so this tells us that all information on the nature of the final black hole properties is embedded in those final ...
- 09:44: General relativity predicts that black holes should be completely defined by three properties – their mass, spin, and electric charge.
- 09:53: ... doesn’t matter what fell in to make the black hole – atoms, photons, dark matter, monkeys – all that information should be ...
- 10:01: And this is the no-hair theorem – black holes have no hair.
- 10:08: ... astrophysical black holes are also expected to have no electric charge, so mass and spin should ...
- 10:34: The oscillations are consistent with a black hole purely defined by its mass and spin.
- 10:43: ... way from the confirmation of the theorem – but with the analysis of more black hole mergers, any deviations from the pure-general relativity, hairless black ...
- 12:00: ... far the list of high-confidence events includes around 20 new black hole-black hole mergers, a few black hole-neutron star, and neutron star-neutron ...
- 12:19: And on August 28th, two black hole mergers were seen separated by only 20 minutes, and potentially in the same part of the sky.
- 12:29: ... hard to come up with a plausible explanation for why two pairs of binary black holes should merge near each other at the same ...
- 12:52: We’re seeing many, many mergers of black holes and neutron stars, and we’re learning an awful lot about these objects.
- 12:59: ... wave spectroscopy, we can now listen to the harmonics of ringing black holes, and through them better understand the fundamental nature of extreme ...
2019-09-23: Is Pluto a Planet?
- 01:00: ... classify galaxies based on their shape, black holes based on how they feed and how they're oriented, stars based on their ...
2019-07-25: Deciphering The Vast Scale of the Universe
- 07:58: They look small from here, but each is a maelstrom of gas falling into a giant black hole, and each shines out from the core of its own galaxy.
- 08:16: ... see these most distant quasars, as well as the earliest galaxies or even black holes or worlds around other stars, Mt. Wilson's Hooker Telescope wouldn't cut ...
2019-07-18: Did Time Start at the Big Bang?
- 07:22: ... completeness and it also happens at the singularity in the center of a black hole all timelines end this time in the forward direction The analogy with ...
- 08:04: from the pure Einsteinian point of view It's meaningless to ask what happened before the Big Bang or after reaching the black hole Center?
- 11:12: ... lead to all particles randomly converging back to the same spot Or maybe black holes birth new universes as in Lee Smolin's "Fecund Universe" ...
- 11:36: ... a poetry to that last one. The geodesics approaching the black hole singularity Become the geodesics emerging from the new Big Bang ...
2019-07-01: Thorium and the Future of Nuclear Energy
- 15:29: ... further futures in space-time In a recent episode we talked about how black holes influence the galaxies they formed in often by killing them Let's see ...
- 16:45: ... full blown quasars the most luminous of accreting black holes or active galactic nuclei are Typically in bowl-like elliptical ...
- 16:59: ... isn't so important. Proghead777 asks, whether the central supermassive black holes gravitational Influence is extended by frame dragging Well, the answer ...
- 17:49: ... objects orbit in the same direction as a black hole's rotation that can be stable much closer in but if they orbit in the ...
2019-06-20: The Quasar from The Beginning of Time
- 01:50: ... the speck was a quasar - a vortex of radiant matter falling into a giant black hole. ...
- 06:21: And what about the supermassive black hole at the center of the quasar?
- 06:24: ... are also broadened due to the extreme speeds of matter moving near the black hole. That allows us to estimate the mass of the black hole: 800 million ...
2019-06-17: How Black Holes Kill Galaxies
- 00:00: Thanks to Brilliant.org for supporting PBS Digital Studios Black Holes are really only dangerous if you get too close Who am I kidding ?
- 00:08: ... Star formation across the entire Universe When we first realized that Black Holes could have masses of Millions or even Billions of times that of the Sun ...
- 01:35: ... of the Galaxy including Dark Matter so why shouldn't a Galaxy and its Black Hole be closely connected A couple of things you need to know Even though ...
- 02:54: ... extreme star formation called Star Busts as galaxies grew so did their Black Holes they would've started as a ready mass of seed Black Holes formed by the ...
- 04:05: ... Things: In order for the Black Hole to grow in lock step with the galaxy you need to get a consistent ...
- 05:09: how does a galaxy know to stop growing when its 1000 times larger than the Central Black Hole?
- 05:14: ... the best contender is that the black holes kill galaxies and by "kill" , I mean make them dead which I guess is the ...
- 05:24: ... Billions of more years of ongoing star formation A likely culprit is the Black Hole it kills star formation in those giant galaxies fixing the maximum size ...
- 06:33: ... are couple different ways it can happen via Black Hole but all of them involve a Quasar switching on and blasting the crap out ...
- 07:21: ... puffed up as well as killing star formation quasar activity limits the Black Hole's own growth it grows relating the new supply of gas but then its energy ...
- 10:49: ... modern universe Giant Dead galaxies harbor fossil quasars supermassive Black Holes whose close connection to their surrounding galaxy is a clue ...
2019-06-06: The Alchemy of Neutron Star Collisions
- 02:47: ... fact that they are on the verge of complete gravitational collapse into black holes so take a pair of neutron stars in binary orbit perhaps twin remnants of ...
2019-05-16: The Cosmic Dark Ages
- 06:54: ... elements. Stars that large and luminous burn out fast and leave behind black holes. These ravenous stellar corpses found themselves in an all-you-can-eat ...
- 07:19: ... were born the first supermassive black holes with millions, even billions of times the Sun’s mass – inescapable ...
- 10:10: ... reionization. All of this light comes from the material falling into the black hole, or being blasted back out again. This is the redshifted Lyman-alpha ...
2019-05-09: Why Quantum Computing Requires Quantum Cryptography
- 14:46: ... without dark matter, and our coverage of the event horizon telescope's black hole ...
- 14:57: AspLode asks about the interaction between dark matter and black holes.
- 15:02: Can dark matter form a black hole?
- 15:04: ... is some sort of exotic particle - which is the going hypothesis - then black holes would definitely attract dark matter gravitationally, and occationally ...
- 15:27: Occasional dark matter particles would be snared by black holes - and they would add to its mass just like regular matter.
- 15:35: But dark matter alone could never clump together densely enough to produce a black hole by itself.
2019-05-01: The Real Science of the EHT Black Hole
- 00:04: How do you take a picture of a black hole and what have we learned from seeing one for the very first time?
- 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 ...
- 00:32: It’s a freaking black hole.
- 00:54: The beast in question is the supermassive black hole in the center of the M87 elliptical galaxy.
- 01:09: ... is 53 million light years away, so resolving that black hole is equivalent to resolving a grain of sand on the beach in LA – if ...
- 03:31: ... to observe the event horizon of the M87 black hole you need to resolve one one-millionth of 1% of one degree on the sky – ...
- 05:15: So black holes are, of course, black.
- 05:21: In this case it’s the energy released by matter falling into the black hole.
- 05:26: ... supermassive black hole at the heart of the M87 galaxy is currently active – it’s currently ...
- 05:39: It’s also blasting out a jet of energetic particles, channeled by the intense magnetic fields around the black hole.
- 05:51: To understand exactly where the light we're seeing comes from let’s look more closely at the regions around the black hole.
- 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.
- 06:17: What we’re seeing here is the black hole shadow inside the bright ring of the photon sphere.
- 06:24: The photon sphere is where gravity is so strong that light itself can orbit the black hole.
- 06:29: That orbiting light will eventually leave the photon sphere– either falling into the black hole or escaping outwards.
- 06:42: For a non-rotating black hole the sphere should be at 1.5 times the Schwarzschild radius.
- 06:47: If the black hole is rotating then you can get photon orbits over a range of distances.
- 06:53: Measuring the radius of the photon sphere potentially gives you both black hole mass and spin.
- 07:05: That disk terminates at a few times the Schwarzschild radius – again depending on black hole spin.
- 07:10: That’s the innermost stable circular orbit – the ISCO – and it’s the closest you can get to the black hole and still orbit in a stable way.
- 07:19: Any closer and anything besides light will quickly spiral into the black hole.
- 08:38: ... light from the magnetized plasma vortex is beamed on the side of the black hole where it’s moving towards us – or at least forwards before the light ...
- 08:51: On the opposite side of the black hole the emission is dimmed by the same effect.
- 08:55: ... fields, in this case with the addition of the warped spacetime of a black hole using Einstein’s theory of general ...
- 09:19: ... team simulated a wide range of parameters like black hole mass and spin rate, while they were able to nail down the rotational ...
- 09:37: ... 1/5 the size of that ring– so that’s VERY big, even by supermassive black hole ...
- 09:51: The black hole is indeed spinning – almost as fast as it can spin.
- 09:56: So the plasma vortex should be rotating in the same direction as the black hole.
- 10:01: ... axis direction from the jet and we have the rotation direction of the black hole – roughly clockwise from our perspective, with an axis pretty close to ...
- 10:17: ... like those gravitational wave signals from a couple of years ago, the black hole looks just like we predict based on Einstein’s general theory of ...
- 10:33: ... then when black holes emerged from Karl Schwarzschild’s solution to the Einstein equations, ...
- 10:54: ... and its brilliant team – finally hits us with visceral reality of the black hole, Einstein’s wildest prediction and the strangest object in all of space ...
- 11:22: ... of the late, great Hawking, as well as everything from the Big Bang to Black Holes. ...
2019-04-24: No Dark Matter = Proof of Dark Matter?
- 00:03: ... dark compact bodies like failed stars or stellar corpses or primordial black holes then we'd see the warping of of more distant stars in their ...
2019-04-10: The Holographic Universe Explained
- 01:02: We’ve moved from quantum field theory to black hole thermodynamics to string theory.
- 01:19: The story started with black holes, and with Jacob Bekenstein, who derived an equation to describe their entropy.
- 01:27: A black hole’s entropy represents the amount of quantum information of everything that ever fell into it.
- 02:01: Steven Hawking confirmed the Bekenstein bound by calculating the amount of information leaked by a black hole as it evaporated in Hawking radiation.
- 02:11: ... discovery of Hawking radiation led to the black hole information paradox, because this radiation was expected to erase the ...
- 02:30: ... t’ Hooft to show that the information of all material that fell into the black hole could be imprinted on that outgoing Hawking ...
- 02:52: Things that fall into a black hole do actually experience crossing the event horizon and being inside the black hole.
- 02:59: So the interior of the black hole has a dual existence.
- 03:03: ... but from the PoV of anyone falling in they are definitely inside the black hole, plummeting to their doom in full 3-D ...
- 11:58: ... strong gravitational fields in the higher dimensional space – like in black holes – look like a solvable configuration of particles in the low-D ...
- 12:09: ... other things, this provided a new resolution to the black hole information paradox: the information lost in a black hole persists ...
2019-04-03: The Edge of an Infinite Universe
- 04:20: ... –to the edge of an infinite universe or across the event horizon of a black hole. ...
- 04:49: The first efforts were designed to allow physicists to cross the event horizon of black holes – mathematically.
- 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.
- 08:26: Then he placed a black hole in between these points and calculated how it perturbed the balance of a quantum field traced between them.
- 08:37: He found that two “infinitely distant” regions could not both be in a perfect vacuum state if a black hole lay between them.
- 08:44: He concluded that the black hole must generate particles – Hawking radiation.
- 15:32: Many of you asked what happens to black holes in the big rip.
- 15:39: So I thought that the answer was that black holes would be eroded into nothing.
- 15:45: ... into the event horizon, causing the event horizon to shrink and the black hole to ...
2019-03-28: Could the Universe End by Tearing Apart Every Atom?
- 12:53: ... a long cold heat death in which the stars of our galaxy wink out become black holes and then evaporate over an unthinkably long future. But maybe if you ...
2019-03-20: Is Dark Energy Getting Stronger?
- 06:41: Quasars are a black hole feeding frenzy.
- 06:44: When matter falls too close to a black hole, it forms a superheated vortex pouring into the black hole – an accretion disk.
- 06:52: If it’s a supermassive black hole doing the feeding, its accretion disk shines so bright that it can be seen to the ends of the universe.
- 07:07: They can have a huge range of energy output, depending on the mass of the black hole and how much fuel it’s getting.
- 15:02: ... deeper into astrophysics, then you'll want to check out the course: Black Holes, Tides, and Curved Spacetime: Understanding ...
2019-02-07: Sound Waves from the Beginning of Time
- 13:58: ... 10^(10^25) years for the first quantum tunneling to turn iron stars into black holes, and way, way longer than that for anything ...
2019-01-24: The Crisis in Cosmology
- 16:52: Rishit Vora asks how a T inversion would affect a black hole?
- 16:57: Well, a true time reversal that included the interior of a black hole...
- 17:17: ...frankly, I'm not sure, because we don't know the state of matter in the black hole.
- 17:31: So a rewound black hole shouldn't revert exactly to whatever it formed from.
2018-11-14: Supersymmetric Particle Found?
- 03:52: ... explosions, gamma ray bursts, black hole magnetic fields are all expected to blast high energy particles like ...
2018-11-07: Why String Theory is Right
- 03:01: It doesn't give you tiny black holes when you try to describe gravity on the smaller scales.
- 03:07: ... worth taking a moment to see how stringy gravity avoids the problem of black holes. ...
- 04:15: If you even try to describe very strong gravitational interactions, you get nonsense black holes in the math.
- 04:53: Even the most energetic interactions are smeared out over the string, so you avoid the danger of black hole creating infinities.
- 11:44: ... low-energy limit, which just means not in places like the center of a black hole, then it looks just like the gravitational field in Einstein's ...
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: ... a picture of virtual matter-antimatter pairs being separated by the black hole event horizon, allowing one of the pair to escape to beautiful freedom ...
- 11:40: But without the black hole, the vacuum stays a vacuum.
- 17:02: One star had collapsed into a black hole, which is why you couldn't see it.
2018-10-18: What are the Strings in String Theory?
- 09:10: ... smaller scales, the energies required to interact on that scale produce black holes. ...
- 13:50: ... it would take to compute a universe simulation on the event horizon of a black hole. ...
- 14:39: These black hole computers suck.
- 14:43: A few of you pointed out that a black hole computer couldn't store the information about other black holes, and you're right.
- 14:53: Our supermassive black hole computer is only large enough to contain all information in radiation and matter.
- 14:59: But most of the information in the universe is in black holes, or more accurately, most entropy or hidden information is in black holes.
- 15:07: So our black hole computer can't contain the information hidden in all black holes.
- 15:12: It can't even contain the information from black holes larger than itself.
- 15:57: Like I said, our black hole computer is only simulating particles, not black holes.
2018-10-10: Computing a Universe Simulation
- 03:16: ... was in studying black holes that Jacob Bekenstein realized that they must contain the maximum ...
- 03:27: If you fill a region of the universe with information equal to its Bekenstein bound, it'll immediately become a black hole.
- 04:13: ... bound, essentially, your memory device is the event horizon of a black hole. ...
- 04:21: How large would that black hole need to be to store all of the information about all of the particles in the universe?
- 05:08: That corresponds to a spherical black hole with a radius around 100 kilometers.
- 05:13: ... observable universe of non-radiation particles on the surface area of a black hole the size of ...
- 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.
- 05:35: The mass of a 100 kilometer radius black hole would be 30 times that of our sun.
- 06:05: You'd need a black hole a few million times the mass of the sun and 10 million kilometers in radius.
- 06:11: That's pretty close to the size of the supermassive black hole in the center of the Milky Way.
- 06:20: But remember, we're storing all of the information in the universe on just one of these black holes.
- 08:58: On the other hand, our Switzerland-sized black hole computer is a little slower.
- 09:20: ... the universe is computing its own evolution at maximum speed, our black hole computer would take a factor of 10 to the power of 20 longer or 10 to ...
- 09:38: Our supermassive black hole scale computer does a bit better, taking only 10 to the power of 25 years.
- 10:20: Our small black hole computer could do that in a year and our big one in five minutes.
- 10:26: ... can only read out the simulation results in Hawking radiation as those black holes evaporate, which will take 10 to the power of 70 years minimum-- hell of ...
2018-10-03: How to Detect Extra Dimensions
- 01:22: Unlike merging black holes, which are invisible, merging neutron stars explode spectacularly.
- 09:58: ... to the gravitational wave signal, something that's impossible with black hole ...
- 14:43: ... mechanics are both right, then we should have Planck-length virtual black holes popping into and out of ...
- 14:57: ... and just removing it from the universe, e.g., by dropping it into a black hole, is an interesting philosophical ...
2018-09-20: Quantum Gravity and the Hardest Problem in Physics
- 03:27: Starting with the mild, we have the black hole information paradox.
- 03:33: ... black holes of pure general relativity swallow information in a way that can remove ...
- 03:54: ... 't Hooft and others, it has become clear that information swallowed by black holes can be radiated back out into the universe via their Hawking ...
- 04:38: ... smaller scales of space and time, like the central singularity of the black hole or at the instant of the Big ...
- 05:57: ... energy you would need to put into that region of space would make a tiny black hole with an event horizon one Planck length in ...
- 06:19: That means you make an even larger black hole.
- 06:46: Try to measure any time period shorter than 10 to the power of negative 43 seconds, the Planck time, and boom-- black hole.
- 07:33: Particles whose positions are defined within a Planck length can spontaneously become black holes.
- 07:39: Of course, those black holes don't really happen.
- 11:09: The non-renormalizability of quantized general relativity is connected to the idea that precisely localized particles produce black holes.
- 12:46: ... thanks, we're sending you a box of chocolate-covered Planck-scale black holes. ...
- 13:06: It'll really help us constrain some black hole theory.
- 13:12: Today, we're covering both the black hole entropy enigma and the challenge question episode.
- 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.
- 13:30: When two black holes merge, a lot of energy is pumped into gravitational waves.
- 13:35: There's only one place for that energy to come from, the mass of the black holes.
- 13:39: As a result, the mass of the final merged black hole is smaller than the sum of the masses of the two originals.
- 13:48: And so the radius of the final black hole is smaller than the sum of the radii of the originals.
- 13:54: Note that the final black hole is both more massive and larger than either of the original black holes taken separately.
- 14:03: It's possible to extract energy from a rotating black hole by throwing in objects on near-miss trajectories.
- 14:09: The rotating black hole drags space around with it.
- 14:18: The loss of rotational energy by the black hole also means a loss of mass.
- 14:22: But rotating black holes are slightly squished.
- 16:08: ... is skeptical about the 't Hooft solution to the black hole information paradox and cautions that we don't neglect other interesting ...
- 16:30: We all get to fuzzballs, or better known as the black hole triple hypothesis.
2018-09-12: How Much Information is in the Universe?
- 00:25: ... then there's all the stuff that isn't stars-- the dark matter, black holes, planets, and the particles, and radiation in between the stars and ...
- 01:30: ... holographic principle episode is still coming, but our recent episode on black hole entropy and some of the lead-ups to that might be helpful ...
- 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.
- 06:58: But there's one more source of information-- black holes.
- 07:02: As I mentioned last time, black holes contain most of the entropy in the universe.
- 07:06: The relationship between black hole entropy and information deserves some thought.
- 07:10: ... Black hole entropy in terms of number of bits tells you the information you'd need ...
- 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.
- 07:45: Let's take a supermassive black hole as an example.
- 08:04: So the Milky Way's black hole has as much entropy and hidden information as all of the matter and radiation in the entire rest of the universe.
- 08:14: And there are some hundreds of billions of galaxies in the universe, each with its own supermassive black hole.
- 08:26: Black holes contain, by far, most of the entropy in the universe, and require most information to fully describe.
- 09:05: ... the universe reaches information limit, it would immediately become a black hole with an event horizon as big as the current cosmic ...
- 09:17: The Bekenstein bound does apply equally to engineered information storage as it does to black holes and universes.
- 09:24: It gives the limit of storage capacity within a given volume before the interior collapses into a black hole.
- 09:42: Essentially, they're computing on the surface of a black hole event horizon.
- 09:47: How large a black hole computer would you need in mass and radius to contain enough data to simulate the entire observable universe?
- 09:56: Let's ignore really high entropy stuff like black holes, the cosmic background radiation, and neutrinos.
- 10:21: How long would that black hole computer take to simulate the entire universe?
- 11:30: ... of the universe episodes today, and next week, we'll get to responses to black hole entropy, as well as today's ...
2018-09-05: The Black Hole Entropy Enigma
- 00:07: Black holes seem like they should have no entropy, but in fact they hold most of the entropy in the universe.
- 00:15: [MUSIC PLAYING] At first it seemed that black holes were so simple they should have no entropy.
- 00:34: Black holes are a problem.
- 00:46: That theory is one of the most thoroughly tested in all of physics, which means we should probably believe in black holes.
- 01:01: And yet if black holes exist, which apparently they do, they contradict other theories in physics that are as sacred as general relativity.
- 01:21: It was while pondering that conflict that Jacob Bekenstein realized an incredible connection between black holes and thermodynamics.
- 01:42: But first, you are going to need to know more about why black holes contain most of the universe's entropy.
- 01:50: ... actually rewind back to those episodes where we laid out the black hole information paradox because they're going to be critical to a proper ...
- 01:59: We're also rewinding to the late '60s, early '70s when physicists realized something odd about black holes.
- 02:08: From the point of view of the outside universe, black holes can only have three properties-- mass, spin, and electric charge.
- 02:16: ... suggests that most of the information about anything that falls into a black hole is lost to the outside ...
- 02:30: ... if black holes evaporate, as Hawking discovered and we also covered, this evaporation ...
- 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.
- 04:26: How does this relate to black holes?
- 04:29: Let's make a black hole and see what happens to entropy.
- 04:49: At the instant the star collapses far enough to form an event horizon, it becomes a black hole.
- 05:07: ... region of space in which the black hole formed appears to have gone from high entropy to zero entropy in an ...
- 05:24: If quantum information is stored on the surface of the black hole, can't we store entropy there also?
- 05:49: ... law that got Jacob Bekenstein thinking about the connection between black holes and information in the first ...
- 06:09: So you know how nothing can escape black holes, ignoring Hawking radiation for the moment.
- 06:14: That should mean that black holes can only grow.
- 06:22: If you merge two black holes, some of their mass gets converted to the energy radiated away in gravitational waves.
- 06:29: There's also the Penrose process in which you can extract rotational energy of a spinning black hole.
- 06:40: Gravitational radiation and the Penrose process reduce black-hole mass and radius or the sum of masses and radii of emerging black holes.
- 06:48: But there's one property of black holes that no process other than Hawking radiation can decrease.
- 06:56: Do anything to black holes and their total surface area can only grow or stay constant.
- 07:29: ... can also add the work done when you extract energy from the black hole, and it looks the same as the equation for the work extracted from a ...
- 07:59: Bekenstein estimated the amount of information that would be lost into a black hole as it grew.
- 08:05: Essentially he built a black hole out of idealized elementary particles that each contained a single bit of information.
- 08:14: The information content of a black hole is proportional not to its mass or radius or volume.
- 08:37: ... content by the Boltzmann constant and you have the entropy of a black hole, which is going to be directly proportional to the surface area of the ...
- 09:04: He showed that black holes radiate random particles exactly as though they have a peak glow for a particular temperature that depends on their mass.
- 09:13: So if black holes have a temperature, then they also have entropy.
- 09:26: ... for internal energy and figured out the total entropy contained in a black hole. ...
- 09:42: ... it out from the amount of information that gets trapped building a black hole or the amount of heat that leaks as it evaporates, and it's proportional ...
- 10:01: The second law of thermodynamics is saved because black holes do have entropy.
- 10:06: In fact, they have enormous entropies, the maximum possible, so much that black holes are now believed to contain most of the entropy in the universe.
- 10:25: Bekenstein's formula was derived for black holes, but it also gives the maximum amount of information that can be fit into any volume of space.
2018-08-23: How Will the Universe End?
- 02:32: ... of nothing but stellar remnants, the ultradense neutron stars and black holes from long-extinct massive stars, as well as the white dwarfs left from ...
- 04:15: It's so densely packed that all possible quantum states are completely filled and no further collapse is possible, short of becoming a black hole.
- 05:28: Heavier bodies, mostly neutron stars and black holes, sink towards the center.
- 05:49: Around 10 times longer still, and the entire megagalaxy will either have dispersed or fallen into the massive black hole at the galactic center.
- 06:58: The universe will contain only photons, electrons, and black holes.
- 07:03: And so we would enter the Black Hole Era.
- 07:06: If protons decay, black holes would be the only mass of bodies left in the universe after 10 to the power 40 years.
- 07:13: Some will be the remnant black holes of individual stars that were flung from galaxies long ago.
- 07:18: But most of the black hole mass will be in supermassive black holes.
- 07:38: But all black holes evaporate over time via Hawking radiation, something we've discussed in detail.
- 07:51: The small black holes, say, around 10 times the mass of the sun, completely evaporate in around 10 to the power of 67 years.
- 07:58: The largest supermassive black holes that might ever form will take a little longer, up to 10 to the power of 106, or a million googol, years.
- 08:07: During the long Black Hole Era, there is still energy to be had for an enterprising, super-advanced civilization.
- 08:14: ... Black holes themselves can be used as engines through Hawking radiation, as we've ...
- 08:25: If life manages to master this energy source, then its future history could be as ridiculously long as the Black Hole Era.
- 08:38: ... stellar remnants during the Degenerate Age and, ultimately, end up in black holes. ...
- 08:52: But even black holes must end.
- 08:55: Occasional flashes of gamma rays will light up the darkness as black holes reach that last explosive stage of their evaporation.
- 09:33: Black holes evaporate.
- 10:46: Quantum tunneling may actually bring on the Black Hole Era much earlier.
- 10:50: It depends on how small black holes can really be.
- 10:53: ... small, stable black holes are possible, then quantum tunneling should allow small regions within ...
- 11:07: He figures that the most likely minimum black hole mass is the Planck mass of 20 micrograms.
- 11:14: ... the case, then all matter larger than a dust grain will collapse into a black hole in around 10 to the power of 10 to the power of 26 years, then promptly ...
2018-07-18: The Misunderstood Nature of Entropy
- 01:24: ... different aspects and consequences of entropy, including its role in black hole thermodynamics and how it will lead to the end of our ...
- 08:40: ... we'll need to talk about information entropy, which we'll also need for black hole thermodynamics and will take another ...
2018-07-11: Quantum Invariance & The Origin of The Standard Model
- 12:46: A few of you point out that if you build a wall of lead, one likely, you'd think, to try to stop neutrinos, you would just collapse into a black hole.
2018-07-04: Will A New Neutrino Change The Standard Model?
- 11:33: The statement about the retraceability of the universe doesn't actually care about event horizons, whether cosmic or black hole.
- 11:50: Even a black hole should unravel in that case.
2018-06-20: The Black Hole Information Paradox
- 00:07: Stephen Hawking found a way to vanquish the black hole with his eponymous radiation.
- 00:22: [MUSIC PLAYING] Black holes are engines of destruction that remove from our universe anything that crosses their event horizon.
- 00:37: They add to the mass of the black hole.
- 00:50: But in a way, that same Hawking radiation may be more destructive than the black hole itself.
- 01:27: In recent episodes, we've explored some critical facts about the universe and about black holes.
- 01:54: It states that black holes can only exhibit three properties-- mass, electric charge, and angular momentum.
- 02:01: The inescapable event horizon shields the outside universe from any other influence within the black hole.
- 02:13: If we see a black hole, how can we possibly figure out what particles went in to form it?
- 02:18: ... the no-hair theorem isn't really a problem because even though the black hole swallows information, that information persists inside the black ...
- 02:44: ... causes black holes to evaporate into a perfectly random buzz of radiation that contains ...
- 02:57: The gravitational field of a black hole is expected to distort the surrounding quantum fields.
- 03:02: That distortion looks like particles flowing away from the black hole.
- 03:06: And the energy to create those particles must come from the mass of the black hole itself.
- 03:25: ... Black holes should radiate as though they have a temperature that is inversely ...
- 03:39: The key here is that Hawking radiation doesn't depend at all on what the black hole is made of.
- 03:44: The black hole radiates particles, mostly photons, that contain no information.
- 03:49: Eventually the black hole must completely evaporate into those particles, leaving no clue as to what fell into it in the first place.
- 05:27: ... Einstein-Cartan theory, it's predicted that the formation of a rotating black hole gives birth to an entire new universe accessible by a ...
- 05:40: So what if all of the information lost into the black hole ends up in the new universe?
- 05:55: The competing idea is that the information of everything that falls into the black hole becomes imprinted on the Hawking radiation itself.
- 06:14: For the outside universe, everything that ever fell into the black hole remains frozen in time and smeared flat over that horizon.
- 07:25: From the point of view of an observer falling into the black hole, they aren't frozen at the horizon.
- 07:33: That means their information would radiate back out into the universe and be absorbed into the black hole.
- 07:57: ... fact, because the interior of the black hole doesn't even exist on the same timeline as the external universe, it's ...
- 08:22: Black-hole complementarity argues that the interior and exterior of a black hole are not simultaneously knowable in exactly the same way.
- 09:16: ... the three-dimensional gravitational and quantum-mechanical interior of a black hole could be fully described by interactions on a 2D surface that did not ...
- 09:47: ... mechanism by which information can be stored on the surface of a black hole, it may imply that the entire universe is a ...
- 10:09: ... jumped into that game, suggesting that quantum tunneling from within the black hole could interact with the holographic horizon and carry information back ...
- 10:20: But to enter the game, Hawking had to concede the old bet and admit that information does escape black holes.
- 10:51: ... radiation should be simultaneously entangled with the interior of the black hole and with all past Hawking ...
- 11:22: ... cute little 1974 paper in which the young Stephen Hawking showed that black holes must leak very slightly has led to radical new ideas about the nature of ...
- 11:41: Black holes represent the ultimate victory of gravity.
- 11:50: But the first hint of the existence of black holes appeared long before Einstein.
- 12:01: So, to continue your own mathematical journey into black holes, Newton's gravity is the place to start.
- 12:45: Last week we talked about the no-hair theory of black holes, and you all had some hairy questions.
- 12:52: EpsilonJ asked, what would happen if you fired a continuous beam of electrons at a black hole and how would the charge affect the Penrose diagram?
- 13:03: If you keep injecting charge into a black hole, then it does maintain an electric charge.
- 13:07: That charge only decays if the black hole is left to its own devices.
- 13:11: And it turns out that a charged black hole has a pretty weird Penrose diagram.
- 13:15: The exterior looks pretty similar to a regular black hole, but the inside is very different.
- 13:20: ... electric charge within the black hole produces a negative pressure that actually halts the cascade of space ...
- 13:29: In the mathematics, it looks as though anything falling into a charged black hole is ejected into a separate universe.
- 13:41: ... Blade asks how it can be that the outside of a black hole can feel its electric charge given that the electromagnetic field is ...
- 13:53: ... we talked about a black hole's electric charge in terms of the classical electromagnetic field which ...
- 14:35: ... this picture, virtual particles can escape a black hole to communicate the influence of the charge within, but it's important ...
- 14:44: The electromagnetic field outside the black hole knows about the charge inside the black hole.
2018-06-13: What Survives Inside A Black Hole?
- 00:09: A proton, an electron, and an antineutrino walk into a black hole.
- 00:16: ... PLAYING] We've established by now that black holes are weird, the result of absolute gravitational collapse of a massive ...
- 00:49: These ideas are pretty mind blowing, but as crazy as black holes are, they're also kind of simple.
- 01:00: ... fact, every black hole in the universe, no matter how it formed or what happened to it ...
- 01:21: ... we're get to see why black holes are bold, and in an upcoming episode we'll combined the no-hair ...
- 01:56: Or as Bekenstein put it, black holes have no hairs.
- 02:15: The interior of a black hole is cut off from the external universe.
- 02:28: ... black hole could have formed from a collapsed star or entirely out of antimatter or ...
- 02:50: Perhaps more mysterious are the three exceptions, the three remaining hairs around our otherwise bald black hole.
- 04:20: ... of the event horizon, the outside universe can't see the mass inside the black hole, but that mass is remembered in the gravitational field, the curvature of ...
- 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.
- 07:59: ... the case of the black hole, nothing can get out, but new infalling material will adjust the black ...
- 08:08: By the way, it's worth mentioning that real black holes out there in the universe are never going to have a net electric charge.
- 08:15: ... black hole with nonzero charge will quickly attract particles with the opposite ...
- 08:40: And so if the black hole is spinning or racing past you, you'll see that magnetic field.
- 08:46: In a similar way, you can see a black hole's rotation in its gravitational field.
- 09:09: The frame dragging around a rotating black hole is rather stronger.
- 09:19: ... material with angular momentum falls into a black hole, whether it's a spinning star or a whirlpool of gas, it will either add ...
- 09:30: Its angular momentum is remembered in the frame dragging as though the entire black hole was spinning.
- 09:36: I hope I've given you a sense of why mass, charge, and angular momentum are remembered by the space outside a black hole.
- 09:50: As a result, they are remembered by the fields surrounding the black hole.
- 09:59: If matter with these properties falls into a black hole, information about those properties is lost to the outside universe.
- 10:15: Baryon number is a conserved quantity, but there's no way to know the baryon number of a black hole.
- 10:24: So what if the universe forgets what type of particles a black hole is made of?
- 10:45: Yet Stephen Hawking showed that black holes may break this rule, revealing a conundrum that we now call the information paradox.
- 10:54: The solution to the information paradox is highly speculative, but it may reveal that black holes are more hairy than we thought.
- 13:38: John asks whether the only way to truly erase a hard drive is to throw it into a black hole.
- 13:48: Second, as we'll see next week, even black holes probably preserve information.
2018-05-23: Why Quantum Information is Never Destroyed
- 01:23: In a future episode, we'll see how this law might be broken by black holes.
- 09:50: That's the case of black holes and Hawking radiation.
- 09:54: Stephen Hawking's eponymous radiation appears to destroy quantum information leading to the famous black hole information paradox.
- 10:55: I'm talking black hole thermodynamics and some pretty deep particle physics.
- 13:34: Black hole memory leaks, quantum rounding errors, and it took 10 billion years to compile the first life form.
2018-05-09: How Gaia Changed Astronomy Forever
- 09:44: A popular one seems to be, rotating black holes or harvesting Hawking radiation from black holes.
- 09:52: Super advanced civilizations clustered around black holes, in an utterly dark universe.
2018-05-02: The Star at the End of Time
- 08:55: Last week, we talked about a swarm of black holes recently discovered in the core of the Milky Way.
- 09:17: We'll put a link in the description so you can join the conversation after we finish talking about black hole swarms.
- 09:34: Yeah, dark matter is expected to be more evenly spread through the galaxy than things like stars and black holes.
- 09:54: ... asks how we'd be able to tell that the supermassive black hole in our galaxy center is in itself a dense swarm of smaller black holes ...
- 10:06: Well, the answer is that we can constrain the size of the Milky Way central black hole, Sagittarius A*, because we can see stars in orbit around it.
- 10:15: They get way too close to allow anything but a single black hole to exist in that tiny space.
- 10:21: There certainly couldn't be millions of stellar-mass black holes.
- 10:25: ... close to the event horizon of Sag A*, which confirms it as a single black hole. ...
- 10:34: Lucas James noticed that during minute seven of the "Black Hole Swarms" episode, the plot only shows 12 blue dots, not the 13 that I claimed.
2018-04-25: Black Hole Swarms
- 00:07: It's been conjectured that the center of the Milky Way contains not one, but a vast swarm of black holes, and now, we've actually seen them.
- 00:30: A supermassive black hole-- four million times the mass of our sun-- lurks in the center.
- 00:58: ... years of the Milky Way is thought to contain a vast swarm of smaller black holes that have reigned in from the surrounding ...
- 01:07: ... that our own Milky Way core is packed with hundreds, maybe thousands, of black holes. ...
- 01:28: ... get to how they found these black holes in a minute, but first, I want to ask, why did so many astrophysicists ...
- 01:56: And the densest, stellar objects, like black holes, sink to the centers of galaxies or star clusters.
- 02:01: We think black holes must gradually sink to the center of the Milky Way, although, the exact process is a wee bit more complicated.
- 02:11: Black holes form when the most massive stars end their lives in spectacular supernova explosions.
- 02:16: After blowing off their outer layers, if the remaining stellar core is massive enough, it'll collapse into a black hole.
- 02:26: ... expect the so-called stellar-mass black holes to weigh in at between five and 15 solid amasses, although, the recent ...
- 02:37: Even after blowing off most of their mass in a supernova, these black holes are still heavier than most stars.
- 02:51: As a black hole orbits the galaxy, it tugs on its neighboring stars.
- 02:55: Those stars are accelerated towards the black hole and can gather behind it in a gravitational wake.
- 03:01: That over-density behind the black hole, pulls the black hole backwards reducing its speed.
- 03:07: The black hole can also slingshot stars outwards, losing momentum in that process, too.
- 03:12: The key is that the more massive object-- usually, the black hole-- tends to donate its momentum to the less massive object.
- 03:18: The ultimate result is that the black hole slows down and no longer has the velocity it needs to maintain its circular orbit.
- 03:28: Now, this process takes a really long time for a stellar-mass black hole.
- 03:33: Over a few billion years, we only expect the black holes from the central several light years to have made much progress inwards.
- 03:40: However, there's another process that can really drive a huge number of black holes inwards.
- 04:08: Because globular clusters are much more massive than a single black hole, they reach the galactic center a lot will quickly.
- 04:22: Those globular clusters must have been full of ancient black holes, which would be carried to the core with their parent cluster.
- 04:30: Those black holes would then, sink even further to the center of the galaxy.
- 04:34: ... been calculated that this process should lead to tens of thousands of black holes in the central few light years of the Milky Way's ...
- 04:43: So how did Hailey and team spot these black holes?
- 04:49: Black holes are effectively invisible, but things can be different if a black hole and a companion star are in a binary orbit around each other.
- 04:57: If the companion star gets too close, its outer regions can fall into the gravitational influence of the black hole.
- 05:03: Gas is siphoned off the star into a whirlpool, an accretion disk around the black hole.
- 05:25: By the way, X-ray binaries can also result from a neutron star rather than a black hole cannibalizing its companion.
- 05:32: But today, we're interested in black holes.
- 05:56: Frequently enough that if the galactic core is full of black holes, then it should also contain quiescent X-ray binaries.
- 06:32: Polars are a bit like X-ray binaries, except instead of a black hole or a neutron star, you have a white dwarf with a powerful magnetic field.
- 07:08: ... quiescent X-ray binaries, which appeared to be the type powered by black holes. ...
- 07:18: Now, 13 doesn't sound like a swarm, but remember, only a small fraction of black holes are seen as X-ray binaries.
- 07:25: ... that there would need to be at least hundreds of stellar-mass black holes in the central few light years in order to get these 13 X-ray ...
- 07:35: Now, that's tens of thousands of times the black hole density anywhere else in the galaxy so yeah, it's a swarm of black holes.
- 07:42: If the sun was near the galactic core, the nearest black hole would be inside the solar systems Oort cloud.
- 07:57: Now, we keep seeing these gravitational wave signals from black hole merges, and as I've discussed previously, they're kind of confusing.
- 08:05: ... black holes are so densely packed in the centers of galaxies, then we should ...
- 08:24: ... just one gigantic black hole, but also, a swarm of hundreds, maybe thousands, of smaller black holes, ...
- 08:51: ... if we're talking about black holes, one of the most fun rides on CuriosityStream is brought to you by the ...
2018-04-18: Using Stars to See Gravitational Waves
- 00:46: In its two and a half years of operation, LIGO has observed five certain black hole-black hole mergers.
- 00:55: The black holes in question were enormous.
- 00:58: In three cases, both members of the black hole binary pair were well over 20 times the mass of the sun.
- 01:07: ... if these black holes formed in the deaths of massive stars, which we think they must, then ...
- 01:16: It's hard to imagine black holes forming bigger than this or both of a binary pair growing this large after formation.
- 01:30: Some are trying to adjust stellar evolution models to allow for the formation of more massive black holes.
- 01:36: ... are calculating whether these black holes may have grown inside globular clusters, where the stellar density is so ...
- 01:47: Perhaps we've observed the merging of primordial black holes formed in the instant after the Big Bang.
- 02:04: A more recent paper has a very different explanation for the apparent large black hole masses.
- 03:35: ... to the frequency of the binary orbits just before merger, which for black holes and neutron stars clocks in at a few to maybe 1,000 orbits per second in ...
- 03:49: ... catch the merger of the million to billion solar mass black holes, supermassive black holes that live in the centers of galaxies, we need ...
- 04:34: ... will see those merging supermassive black holes, as well as the faint hum of thousands of binary pairs of white dwarfs, ...
- 05:00: ... buzz from an earlier epoch of the universe in which binary supermassive black holes were common, or from cosmic strings, if they ...
- 07:52: ... of galactic cores if those galaxies also contain binary supermassive black holes that are generating gravitational ...
2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)
- 01:05: Black holes evaporate.
2018-04-04: The Unruh Effect
- 00:00: [GENTLE MUSIC] Are you worried about black holes?
- 00:23: ... same time that Stephen Hawking was demonstrating the existence of the black hole radiation that would bear his name, three other researchers-- Stephen ...
- 06:47: In the case of Hawking radiation, an inertial observer far from the black hole sees the radiation.
- 10:12: ... can get that high, and that's right above the event horizon of a black hole. ...
2018-03-28: The Andromeda-Milky Way Collision
- 00:38: ... 220,000 light years in diameter, and a central bulge that hides a giant black hole that contains the mass of well over 100 million ...
- 06:00: Both galaxies contain a supermassive black hole, which will fall towards the center of the new merged galaxy.
- 06:16: Meanwhile, the black holes lose angular momentum and fall towards the center.
- 06:20: When those black holes are around a light year apart, they'll start losing orbital energy to gravitational waves.
- 06:29: The resulting super supermassive black hole may briefly power a new quasar as it consumes any gas that also ended up in the core.
- 07:49: There's also a small chance that the sun will encounter one of the supermassive black holes as they descend to the core.
2018-03-21: Scientists Have Detected the First Stars
- 02:38: ... a while, the first black holes formed, and started to spew out x-rays, as they gobbled up hydrogen. ...
- 04:03: That period represents the time between the birth of the very first stars to the onset of very active black hole growth.
2018-03-15: Hawking Radiation
- 01:15: ... black holes should exist forever, only growing, never shrinking, or so we thought, ...
- 01:31: ... a new union of quantum mechanics and general relativity to show that black holes should not be so black after ...
- 02:03: ... when this happens near a black hole, sometimes, one of the pair will be swallowed by the event horizon, ...
- 02:15: And so the black hole itself pays the debt by slowly leaking away its mass.
- 04:25: Stephen Hawking knew that black holes with their insane spacetime curvature would wreak havoc on quantum fields in their vicinity.
- 05:10: It passes through the location of a black hole in the instant before it forms.
- 05:21: Hawking imagined a simple quantum field tracing this path, a field that is in a perfect vacuum state before the formation of the black hole.
- 05:28: But he found that the close shave with the black hole disturbs the fundamental vibrational modes that define the fluctuations of the vacuum.
- 05:44: A distant future observer sees radiation coming from the black hole.
- 05:54: ... the state of the vacuum in two regions of flat space far from the black hole, regions where the nature of vacuums, quantum fields, and particles are ...
- 06:06: But to understand the effect of the close encounter with the black hole, he required an uneasy marriage of quantum mechanics and general relativity.
- 06:49: Certain modes of the quantum field are scattered or deflected by the gravitational field of the forming black hole.
- 07:18: Black holes tend to scatter modes with wavelengths similar to their own sizes.
- 07:34: So the more massive the black hole, the longer the wavelength of its radiation.
- 07:47: Black holes should have a heat glow with an apparent temperature that depends on their mass.
- 07:57: Large black holes should appear cold, radiating excruciatingly slowly.
- 08:01: But small black holes should appear hot.
- 08:51: Remember that Hawking radiation has wavelengths the size of the event horizon, the size of the entire black hole.
- 09:06: Hawking radiation must appear to come from the global black hole.
- 10:48: Whichever way you interpret it, it's hard to avoid the conclusion that black holes emit particles.
- 11:23: For example, what happens to the particles or modes trapped by the black hole?
- 11:28: How do they end up reducing the black hole's mass, instead of increasing it?
- 11:44: For now, we must conclude that black holes radiate and in doing so evaporate.
2018-02-21: The Death of the Sun
- 04:20: It'll save the sun from collapsing into a black hole, and it's also currently stopping you from falling through the floor.
2018-01-31: Kronos: Devourer Of Worlds
- 01:49: ... including the numbers of near-invisible stellar objects like black holes and neutron stars, as well as the distribution of gas and dark ...
2018-01-24: The End of the Habitable Zone
- 10:29: In no time at all you'll be coding gravity simulations in Python and calculating the radiation emitted by black holes.
- 11:14: The vacuum state of all fields are redefined in the vicinity of a black hole or for an accelerating observer.
- 11:56: If the event horizon swallows one half of a virtual matter anti-matter pair, then how does the black hole lose mass?
- 12:32: But in short, it involves calculating the state of the vacuum before the black hole formed and then again after it formed.
- 12:44: These are interpreted as radiation from the black hole.
- 12:48: And conservation of energy demands that the black hole give up 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 cosmological horizon that ...
- 01:34: ... fundamental laws of physics shouldn't change if we go near a black hole or if we start accelerating, but enforcing this isn't automatic, and ...
- 03:14: ... observers, be they floating in empty space or accelerating or orbiting a black hole, should agree on the basic result of that interaction-- two photons in, ...
2018-01-10: What Do Stars Sound Like?
- 09:53: In no time at all, you will be coding gravity simulations in Python and calculating the radiation emitted by black holes.
2017-12-22: Space Time VR
- 00:27: Three experiences are out now, and three more covering general relativity, black holes, and the shape of the universe, are on the way for early 2018.
2017-12-20: Extinction by Gamma-Ray Burst
- 01:01: ... the final burning out of the last stars, or the evaporation of the last black hole and decay of the last ...
- 12:16: And some stars will be sling-shotted out of the galaxy by the two supermassive black holes of Andromeda and the Milky Way as they fall together.
2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series
- 13:58: ... of gas ionized by the last burp of energy from an active supermassive black hole in the middle of a spiral galaxy just before it ran out of ...
2017-10-25: The Missing Mass Mystery
- 12:21: ... faster than the speed of light, can't they escape the event horizon of black holes via Hawking ...
2017-10-11: Absolute Cold
- 08:26: ... about the new observation of a potential pair of binary supermassive black holes orbiting only one light year ...
- 08:38: ... asked whether we're going to have to wait billions of years for this black hole binary to spiral together from losing angular momentum to gravitational ...
- 08:54: We know for sure that supermassive black holes do emerge, otherwise, they could never have got so big.
- 09:15: Dylan Burris asks, what besides a supermassive black hole lives in the centers of galaxies?
- 09:31: ... there to be a good number of stellar remnants, like neutron stars and black holes, that have fallen towards the center from the surrounding ...
- 09:47: There it might trigger some quasar activity until it all gets gobbled up by the black hole.
2017-10-04: When Quasars Collide STJC
- 00:15: And stellar mass black holes rip neutron stars to shreds.
- 00:20: But supermassive black holes eat all of the above breakfast.
- 00:24: So what happens when two gigantic black holes tango?
- 00:38: ... to dig into a paper that reports the detection of a pair of supermassive black holes orbiting only one light-year apart from each ...
- 01:07: Studying the dance of these giants should tell us a ton about how black holes grow.
- 01:25: Before we get to this new result, let's talk about supermassive black holes-- SMBHs.
- 01:36: Now, we've he talked about the black hole that form in the deaths of massive stars.
- 01:55: We're still figuring out how supermassive black holes got so big.
- 02:26: In fact, this new observation may turn out to be a pair of supermassive black holes as close to merger as we've ever witnessed.
- 02:34: If so, it's incredibly important for understanding that whole aspect of black hole growth.
- 02:45: When gas from the surrounding galaxy falls into and feeds the central supermassive black hole, you get an active galactic nucleus-- AGN.
- 03:12: Now, the purported binary black holes in this new study were found in a known Seyfert galaxy.
- 03:26: Let's talk a bit about how these binary black holes were found, because it wasn't easy.
- 03:38: The black holes are around one light-year apart in the center of the galaxy.
- 04:39: Those two hot spots are the locations of the possible black holes.
- 04:43: Now, black holes themselves are invisible.
- 04:54: When a black hole feeds, the vortex of infalling plasma-- the accretion disk-- can produce a powerful magnetic field.
- 05:02: That field can accelerate narrow streams of high-energy particles away from the black hole.
- 05:23: Now, this map alone doesn't tell us that there are two black holes.
- 05:46: Here, we can see two bright spots far from the black holes, presumably from a burst of jet activity some time ago.
- 05:54: So how do we know that the hot spots in the core are from two unique black holes instead of a lumpy jet from one black hole?
- 06:21: ... right down near the black hole where the jet begins, we think the matter should be so dense that the ...
- 06:54: The only way this is possible is with two separate black holes, each one powering its own mini quasar.
- 07:01: OK, let's assume the researchers are right, and we've spotted supermassive black holes in a tight binary dance.
- 07:30: Basically, the black holes slingshot stars outwards through gravitational interactions.
- 07:44: You can think of it as a sort of gravitational friction dragging the black holes downwards and towards each other.
- 07:51: However, by the time the black holes are only a few light-years apart, there shouldn't be any stars left in between them.
- 08:04: In fact, we still don't know how supermassive black holes merge once they're within one parsec, or a few light-years, of each other.
- 08:37: Can't gravitational radiation cause supermassive black holes to merge, just like it does with regular stellar mass black holes?
- 09:19: ... may be ways to detect the actual merger of a supermassive black hole binary with a galaxy-sized gravitational wave observatory called a ...
- 09:38: Longer exposure radio observations will pin down the energy distribution to confirm whether these really are jets produced by two black holes.
- 09:54: However, careful observations of the stars in the galaxy can help us figure out the masses of the black holes and look for signs of galaxy mergers.
- 10:08: ... leading us closer to understanding the incredible growth of the largest black holes in all of ...
- 10:44: We will spend it exclusively on animating black holes and quasars, and also pizza.
2017-09-28: Are the Fundamental Constants Changing?
- 06:37: Remember quasars, insanely luminous maelstrom drums of superheated matter surrounding the most massive black holes in the universe?
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.
- 11:11: Kai Whitman would like to know what would happen if a black hole merges with a neutron star.
- 11:16: Well, the black hole would win, for one thing.
- 11:19: The neutron star would be totally disrupted when it got very close to the black hole, producing a blast of observable radiation.
- 11:27: After that, everything that wasn't ejected in the blast would be eaten by the black hole.
- 11:52: Feinstein 100 asks whether a black hole forming in the death of a massive star first goes through a neutron star-like phase.
- 12:42: ... to stop before the core is smaller than its own event horizon, forming a black hole. ...
- 13:29: So yeah, your ring was forged in the death of a star or the birth of a black hole.
2017-09-13: Neutron Stars Collide in New LIGO Signal?
- 00:06: Last year, LIGO announced the detection of gravitational waves from the merger of two black holes.
- 00:37: ... Observatory, LIGO, detected gravitational waves from a pair of merging black holes, an entirely new realm of the universe opened up to ...
- 00:59: Since the first, LIGO has announced the detection of two more black hole mergers.
- 01:04: As the data comes in, we're learning a ton about black holes, how they grow, and the stars that produce them.
- 01:10: But the merger of binary black holes isn't the only game in town.
- 02:00: For the most massive stars, that core will collapse into a black hole.
- 03:38: Any neutron stars or black holes in close orbit with each other will eventually collide as they leave gravitational radiation.
- 03:52: In fact, we expect them to be much more common than black hole binaries.
- 03:56: Well, because the universe makes far more neutron stars than black holes.
- 04:00: See, black holes only form in the deaths of the most massive stars, those over approximately 20 times the Sun's mass.
- 04:18: That means neutron stars should be more common than black holes and neutron star binary systems should merge more often than black whole binaries.
- 04:39: But that's a factor of 10 smaller than the 30 solar mass black holes that merged in the first LIGO detection.
- 05:10: We can see black hole merges across 1,000 times more universe compared to neutron star mergers.
- 05:25: Neutron star mergers do have one advantage over black hole mergers.
- 05:37: ... black holes only hit that range in the final second before merger, while neutron ...
- 05:48: If we did spot a neutron star merger as rumored, we'll have a lot more juicy data to analyze compared to a black hole merger.
- 08:03: We rarely see supernovae from this galaxy type because their most massive stars have long since exploded to leave neutron stars and black holes.
- 08:25: Compare that to the around 1 billion light-year distance of the earlier black hole mergers.
- 09:07: As these stars coalesce, most of their material goes into forming a new black hole.
- 09:59: Black hole mergers are dark, so we have to infer almost everything from the gravitational waves alone.
- 10:35: ... that there were "promising candidates." Probably that means more black hole, black hole mergers in addition to this rumored neutron star ...
- 11:05: ... theorized astrophysical catastrophe, one that may have birthed a new black hole and created half the Earth's mass in ...
- 15:42: And Hot Fuzz is obviously a reference to black hole singularities in string theory.
2017-08-30: White Holes
- 00:05: Lurking in the depths of the mathematics of Einstein's general relativity is an object even stranger than the mysterious black hole.
- 00:14: In fact, it's the black hole's mirror twin-- the white hole.
- 00:28: The astrophysical phenomenon of the black hole has captured the imagination of scientists and science enthusiastic alike for many decades.
- 00:50: ... have since demonstrated that black holes are very real with convincing evidence that quasars, x-ray binaries, ...
- 01:21: A white hole is the opposite of a black hole in a very literal mathematical sense.
- 01:27: In fact, it's a time reversed black hole.
- 01:31: ... black hole is defined as a region of inward flowing space time with a one way ...
- 01:56: Not even light can leave a black hole, hence the whole black thing, but light can only leave a white hole.
- 02:26: White holes first emerged in the very earliest mathematical description of black holes.
- 02:45: ... resulting Schwarzschild metric actually describes a black hole-- the simplest black possible, one without spin, without charge, or ...
- 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.
- 03:16: The time that happens inside a black hole is not part of the past or future history of the outside universe.
- 03:34: Once you fall into the black hole, the Schwarzschild metric tells us that space and time switch their roles.
- 03:49: Now, a real black hole forms from the gravitational collapse of a massive star's core.
- 03:55: ... past, well, there's just a star, but what does this idealized eternal black hole look like in the ...
- 04:20: From the point of view of the outside universe, the eternal black hole singularity exists both in the infinite future and in the infinite past.
- 04:34: To really understand what this eternal black hole looks like, we're going to need to use a tool that we've already played with, that Penrose diagram.
- 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.
- 05:33: In our weird Penrose coordinates, this represents a constant distance from the center of the black hole.
- 05:39: ... horizon, and the region beyond that line represents the interior of the black hole. ...
- 06:04: ... two regions, our universe and the black hole interior, are just the Schwarzschild metric mapped out using Penrose ...
- 06:15: Remember, this is an eternal black hole, so it must exist in the past.
- 06:21: Map into the past, and we see a time reflected version of our future black hole.
- 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.
- 07:20: The light rays from any crossing reach us infinitely far in the future, even if the black hole plunge began far in the past.
- 07:30: ... the past region of the eternal black hole has an event horizon that's a barrier to entry, but also light rays ...
- 07:46: Anything inside the past eternal black hole must be ejected.
- 07:56: The eternal black hole of the past technically is a white hole.
- 08:22: And two, there is no such thing as an eternal black hole.
- 08:27: The universe hasn't existed for eternity, and it didn't even begin with black holes in place.
- 08:49: It really is just a black hole, but viewed backwards in time.
- 10:57: It's been proposed that, when a black hole forms, a white hole forms on the opposite side.
- 11:04: Energy entering the black hole exits the white hole.
- 11:32: The past white hole was revealed when we traced the eternal black hole backwards in time.
- 11:51: But what about light rays entering or leaving our eternal black hole from the opposite side?
- 12:05: ... looks like an identical alternate universe on the other side of the black hole, accessible through what we call an Einstein-Rosen Bridge, better known ...
2017-05-31: The Fate of the First Stars
- 00:13: The resulting swarms of supernova explosions enriched the universe with the first heavy elements and lots of black holes.
- 08:51: These enormous stars are also thought to have left behind enormous black holes when they died.
- 08:57: In fact, it may be that stars greater than around 250 solar masses can collapse directly into a black hole without exploding.
- 09:04: ... of giant stars become clusters of giant black holes, which, in turn, would merge into monsters of thousands or tens of ...
- 09:15: ... these were probably the seeds of the so-called supermassive black holes, with millions to billions of times the mass of the sun, that we find ...
- 09:26: Such black holes power quasars, which themselves, had a huge influence on the later evolution of our universe.
2017-04-26: Are You a Boltzmann Brain?
- 04:26: ... will occasionally converge into a dense environment like a black hole or a galaxy, or into a complex arrangement like a teapot or a box DVD ...
- 05:30: The black holes will evaporate, the last proton will decay, and all of that cool stuff will cease.
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.
- 10:41: Feinstein 100 asks whether energy could be extracted from the flowing space time inside a black hole.
- 10:48: Well, not really from the flow of space time actually inside the black hole.
- 11:20: It's tricky to find a solid surface inside a black hole.
- 11:24: One possibility could be in a Reissner-Nordstrom black hole, so one with electric charge, but no spin.
- 11:31: Here's a weird black hole fact.
- 11:33: ... electric field in a charged black hole at the singularity is expected to produce an antigravitational effect ...
- 11:44: So there should be a point inside such a black hole where this anti-gravity perfectly balances regular gravity, and it's possible to float.
2017-03-29: How Time Becomes Space Inside a Black Hole
- 00:06: ... that occurs in the mathematics when we drop below the event horizon of a black hole. ...
- 00:49: First we'll think about what the flow of time looks like without black holes or even spacetime curvature.
- 02:37: But if we introduce a black hole, we now have a second way to flip the side of the spacetime interval.
- 02:50: Add a non-rotating, uncharged black hole, and the spacetime interval becomes this.
- 02:56: This comes from Karl Schwarzschild's solution to the Einstein field equations, the very first accurate description of a black hole.
- 03:06: This equation assumes no orbital motion, only motion towards or away from the center of the black hole, which is a distance r away.
- 05:07: Let's fall into the black hole one more time, now graphically instead of mathematically.
- 06:12: As you approach the event horizon of a black hole, more and more light rays are turned towards the event horizon.
- 06:18: Your future light cone and your time axis begin to blur together with the inward radial axis of the black hole.
- 06:28: Close to and within the black hole, the Penrose diagram is much more useful.
- 06:52: And light always travels at a 45 degree angle, even inside the black hole.
- 08:00: After that, we have access to the history of the interior of the black hole.
- 08:20: ... might be from the collapsing surface of the star that first formed the black hole, emitted long before we entered the event ...
- 08:54: We can try to move towards either source of light, down towards light from the black hole's past or up towards light from the black hole's future.
- 09:15: ... star-- and future events in the other, everything that fell into the black hole after ...
- 09:39: It's the last mercy granted by the black hole.
2017-02-15: Telescopes of Tomorrow
- 12:31: QED asks, if he gave me a black hole, what would be my first experiments?
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.
- 00:38: Very soon, we'll be dropping below that horizon to peer at the interior of the black hole.
- 10:18: But in the crazy curved space within a black hole, it gets flipped for you.
- 10:50: Janna Levin's "Black Hole Blues" is a wonderful take on the new window that gravitational waves are opening on our universe.
- 11:56: ... Lloyd asks, "Is the calculated infinite density of the core of a black hole an artifact of the limitations of three dimensional mathematics?" Well, ...
- 12:07: ... way out of the mathematical singularity at the center of black holes is with string theory, which proposes that particles that we see in ...
- 13:06: Well, the smallest stable orbit around a black hole is the so-called innermost stable circular orbit.
- 13:12: It's three times the Schwarzschild shield radius for a non-rotating black hole.
- 13:17: Below that, accreting material spirals into the black hole very quickly, and yeah, time dilation would be significant there.
- 13:24: We actually do see the effect of time dilation in some of the x-ray light coming from right near the black hole.
- 13:46: We see that these x-rays are stretched out as they climb out of the black hole's gravitational well.
- 14:32: Bikram Sao asks how large the original star must have been to produce a supermassive black hole.
- 14:47: These giant black holes have been growing since the dawn of time by creating gas and by merging with other black holes.
- 14:54: ... original seed black holes may have been left over by the deaths of an insanely large first ...
- 15:13: "When my dad was in college, he needed one of those easy classes for credit, so he took a class on quasars and black holes in the universe.
2017-01-25: Why Quasars are so Awesome
- 00:16: Let's talk about what happens when the largest black holes in the universe start to feed.
- 01:03: They don't just have a black hole.
- 01:05: They have a supermassive black hole, millions to billions of times the mass of the sun.
- 03:59: Take a black hole of millions to billions of times the mass of the sun.
- 04:16: That gas descends into the waiting black hole's gravitational well and gains incredible speed on the way.
- 04:24: It is swept up into a raging whirlpool around the black hole that we call an accretion disk, where its energy of motion is turned into heat.
- 04:39: Some gas is swallowed, causing the black hole to grow.
- 05:07: This may be due to the magnetic field of a rapidly rotating black hole, but the jury is still out.
- 06:07: ... when a supermassive black hole feeds and blasts energy into the universe, what we see depends on its ...
- 06:21: However, the family name for any type of accreting supermassive black hole is active galactic nucleus.
- 08:20: ... way into the nuclei of galaxies, it encountered there the supermassive black holes that had been growing since the beginning of the ...
- 09:45: ... galaxy and the Milky Way inevitably collide and their supermassive black holes merge, the violence will deliver one last wave of fuel to the combined ...
- 10:35: ... lectures on the nature of time in relativity, and its behavior around black holes. ...
2017-01-19: The Phantom Singularity
- 00:04: The point of infinite density at the core of a black hole, but also so much more.
- 00:14: The black hole itself contains more than one.
- 01:39: And that, of course, would make it a black hole.
- 01:43: ... singularity to describe the hypothetically infinitely dense core of a black hole, but in math the meaning of this word is much more ...
- 02:09: Kelsey, the math for black holes goes to infinity for different properties and in different locations.
- 02:26: Commonly these problematic points are where quantities become bigger and bigger approaching infinity as they do near a black hole.
- 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.
- 03:02: But the gravitational singularity at the center of a black hole is a so-called real singularity, right?
- 03:20: But the reality of the black hole singularity may give reason to doubt the theory that predicts such a thing.
- 04:16: ... the gravitational field is too strong-- say, near a star or a black hole-- Newton's law gives the wrong answers, and we need Einstein's general ...
- 07:45: It's as much a mathematical singularity as the one in the center of the black hole.
- 09:08: An object at the event horizon has to change its distance from the black hole to keep its clock ticking.
2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer
- 00:03: We've been talking a bit about black holes lately and we'll continue to do so.
- 00:27: So to ground us a little bit first, I want to talk about actual real black holes, in particular, how we see these things.
- 00:35: There's been no reasonable doubt about the reality of black holes for some time.
- 00:46: The most spectacular effect is when black holes feed.
- 00:50: ... falling into the extreme gravitational well of a black hole will reach incredible speeds and temperatures, causing the region around ...
- 01:00: This gives us things like quasars, supermassive black holes in galaxy cores that feed on a superheated whirlpool of gas.
- 01:29: This happens when the substance of a visible star is accreting onto a companion neutron star or black hole.
- 01:36: The most famous and the closest is the Cygnus X-1 black hole, 6,000 light years away.
- 01:43: At around 15 times the mass of the sun, the dark object in this system can't be anything but a black hole.
- 01:50: The other famous black hole in the Milky Way, is of course, its own supermassive black hole.
- 02:03: We call our supermassive black hole Sagittarius A star.
- 02:33: ... recent observations of gravitational waves from a pair of merging black holes by LIGO could be considered our first direct detection of black ...
- 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.
- 03:29: This has enabled EHT to map the strange magnetic field structures around the Sag A star black hole.
- 03:55: Interferometry is going to be used to study much smaller black holes in our galaxy, the remnants of dead stars.
- 04:02: These black holes occasionally pass in front of more distant background stars, gravitationally lensing the star's light.
- 04:15: ... or four images as its light passes around the gravitational field of the black hole. ...
- 04:28: ... over the next few years, we'll have mapped the space around black holes in ways that were once thought ...
- 04:41: ... Black holes definitely exist, but these studies will be powerful tests of whether ...
- 04:59: An extremely advanced alien race has decided to destroy the Earth by enveloping it in a giant Kugelblitz, a black hole made entirely of lights.
- 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.
- 06:02: In the challenge question, I showed you the Penrose diagram for a star collapsing into a black hole.
- 06:59: ... surface actually has the crazy spacetime behavior of the interior of a black hole. ...
- 07:38: ... fun thing about black holes made this way is that the interior region-- that sad, doomed little ...
- 09:48: But it's not quite a black hole, and so in principle, the sphere doesn't have to collapse.
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.
- 14:25: If time dilation approaches infinity, do you reach the singularity before the black hole evaporates?
- 14:49: For an eternal non-leaking black hole, there is no last photon.
- 14:55: But real black holes decay.
- 14:57: ... so the final burst of Hawking radiation as a black hole evaporates will be accompanied by all of the remaining light emitted by ...
- 15:16: Its matter became part of the black hole and re-emerges as that Hawking radiation.
- 15:22: Grim Reaper Of Trolls is curious about taking their warp drive into a black hole.
- 15:29: You can escape a black hole by traveling faster than the speed of light.
- 15:44: So you could resist the faster-than-light flow of space within the black hole.
- 16:06: First, let me note that I gave that statement in a list of popular examples of oversimplifications about black holes.
- 16:28: But it's no less accurate near a black hole.
- 16:31: ... event horizon, you need to travel at the speed of light relative to the black hole's stationary frame of reference as recorded by a distant ...
- 17:18: Cornerrecord asks about that thing when you're in a black hole and time becomes space and space becomes time?
2016-12-14: Escape The Kugelblitz Challenge
- 00:00: ... tool for understanding the strange space-time both in and around black holes. ...
- 00:14: ... the one diagram the infinitely stretched space-time in the vicinity of a black hole's event ...
- 00:44: ... diagram to look at the difference between the idealized, theoretical black hole that we discussed in the previous episode versus the real, astrophysical ...
- 01:00: And then we'll use this knowledge to address a very serious, although questionably plausible, scenario involving an alien black hole attack.
- 01:11: The Penrose diagram we looked at represents a Schwarchild black hole-- so no electric charge and no rotation, but also an eternal black hole.
- 01:30: At the very least, even a Schwarchild black hole must have formed at some point.
- 01:35: A black hole forms when the core of a very massive star collapses under its own gravity at the end of a star's life.
- 02:21: Below that horizon, but above the still-shrinking surface of the star, space-time takes on the mad properties of the black hole interior.
- 02:30: Space and time switch places, and the singularity soon forms, with all space within the black hole flowing towards it faster than the speed of light.
- 02:40: Outside the black hole, the event horizon becomes the new edge of the universe on our Penrose diagram.
- 02:47: The shape of space-time outside the horizon warps to make this diagonal line, a line of constant radius, the radius of the new black hole.
- 02:59: ... where everything is doomed to fall into the singularity, even though the black hole has not finished ...
- 03:59: ... we can imagine a scenario in which the black hole is about to fall around you, and yet you are perfectly comfortable all ...
- 04:10: Scenario-- a super-advanced alien civilization decides to build a giant black hole that will engulf the planet Earth.
- 04:23: So these guys plan to destroy the Earth with a kugelblitz, a black hole formed entirely from light.
- 04:53: The Schwarchild radius of a black hole with this mass is about one light second.
- 05:06: At that point, it will look exactly like a black hole from the outside.
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.
- 00:29: Black holes, objects with densities so high that there's this region, the event horizon, where the escape velocity reaches the speed of light.
- 01:07: ... ignoring the complications of Hawking radiation or black hole rotational growth, the simplest black hole of Einstein's general theory ...
- 01:34: It's a tool that will let us easily and so the most common questions about black holes.
- 01:56: And do you see anything at all once you're inside the black hole?
- 03:01: Let's drop a black hole onto our space-time diagram.
- 03:16: ... mass of the black hole stretches space and time so that light rays appear to crawl out of the ...
- 03:29: Now let's throw a monkey into the black hole.
- 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.
- 04:15: It crunches together, or compactifies, the grid lines to fit infinite space-time on one graph-- very useful for black holes.
- 04:42: This is the Penrose diagram for flat space-time with no black holes.
- 05:38: Let's drop a black hole into this space-time.
- 05:44: And because we only have one dimension of space, and any motion to the left brings us closer to the black hole.
- 05:56: The future cosmic horizon on the Penrose diagram is replaced with a plunge into a black hole.
- 06:10: An entirely new Penrose region represents the interior of the black hole.
- 07:01: Now that we've nailed the Penrose diagram, we can use it to do some serious black hole monkey physics.
- 07:14: ... it approaches the black hole, these light rays have further and further to travel through increasingly ...
- 09:56: Once inside the black hole, we could potentially see the monkey below us.
- 10:00: All space-time within the black hole is flowing toward the singularity faster than the speed of light.
- 10:31: All of this describes a non-rotating, uncharged black hole, a Schwarzschild black hole.
- 10:47: ... complete mathematical solution for a Schwarzschild black hole has two additional regions, one corresponding to a parallel universe on ...
- 11:13: We'll also come back to what happens if we set the black hole spinning or add some electric charge.
2016-11-16: Strange Stars
- 00:00: ... PLAYING] As if black holes and neutron stars aren't weird enough, physicists have very good reason ...
- 00:44: The most wonderfully monstrous of these are the remnant corpses of the most massive stars, stellar zombies like neutron stars and black holes.
- 01:08: ... collapse, but ultimately also doom the most massive to collapse into a black hole. ...
- 07:08: And those may provide the final pressure that halts the collapse of some stars into a black hole, at least for another million years or so.
- 09:17: ... dying star shouldn't have been massive enough to leave a black hole, yet astronomers still haven't found the expected neutron star at the ...
- 13:09: ... do that, I'm going to have to go through the black hole information paradox, Hawking radiation, some string theory, the ...
2016-10-19: The First Humans on Mars
- 08:56: ... talked about the incredible, if speculative, possibility that primordial black holes formed in the insanely dense conditions right after the Big Bang and ...
- 09:13: Several of you asked how to tell the difference between a primordial black hole and a black hole formed when a very massive star ends its life.
- 09:21: Well actually, a black hole is a black hole is a black hole, regardless of how it formed or what it formed from.
- 09:29: Even a black hole made entirely from light, a kugelblitz, is the same thing as a black hole formed from regular matter.
- 09:36: Black holes exhibit only three properties-- mass, electric charge, and spin.
- 09:43: You can learn something about the formation of a black hole from those properties.
- 09:47: Mass is one way to identify a primordial black hole from a stellar black hole.
- 09:52: A star's core needs to be more massive than around three times the mass of the sun in order to collapse into a black hole.
- 10:01: However primordial black holes don't form from stars and so aren't subject to this restriction.
- 10:24: A few of you also asked whether the supermassive black holes that we find at the centers of galaxies could be primordial black holes.
- 10:37: Those supermassive black holes started as much smaller seed black holes.
- 10:54: ... like that idea because we see some pretty gigantic supermassive black holes in the early universe, and it's quite tricky to explain how they got ...
- 11:07: Very large primordial black holes may help explain this, but there's no evidence for this idea.
2016-10-12: Black Holes from the Dawn of Time
- 00:03: In the very first instant after the Big Bang, the density of matter was so great everywhere that vast numbers of black holes may have formed.
- 00:12: These primordial black holes may still be with us.
- 00:15: [MUSIC PLAYING] There's no longer any question that black holes exist.
- 00:25: LIGO's recent observation of gravitational waves from merging black holes is a stunning confirmation of this fact.
- 00:35: As long as a volume of space contains a high enough density of mass or energy, general relativity tells us that a black hole will form.
- 01:11: So why didn't all the matter in the universe become black holes then?
- 01:15: Well, actually, some of it may have formed what we call primordial black holes, and they may still be around today.
- 01:24: In order to make a black hole, extremely high density isn't enough.
- 01:50: That means most of it avoided collapsing into black holes.
- 02:19: These density fluctuations were enough to kick-start the formation of galaxies, but certainly not enough to immediately collapse into black holes.
- 03:00: ... intense enough to resist the local expansion of the universe and form a black hole. ...
- 03:16: Some highly speculative Big Bang physics also predicts primordial black holes.
- 03:29: Now, these models can predict a huge range of possible masses for primordial black holes-- PBHs, as we like to call them in the biz.
- 04:05: We need to hunt for these black holes or their influence in the modern universe.
- 04:10: First of all, we aren't going to find primordial black holes less than around a billion tons, or the mass of a small asteroid.
- 04:25: Black holes larger than this should still be around, but they'd be very difficult to spot, being so black and all.
- 04:43: Could primordial black holes be dark matter?
- 04:48: This is a slightly terrifying possibility that 80% of the mass in the universe is in the form of countless, swarming black holes.
- 04:59: That's a lot of primordial black holes, and so we expect them to leave their mark on the universe in different ways.
- 05:39: There's also the fact that swarms of black holes would mess up their surroundings.
- 05:53: The smallest should fall into neutron stars, causing them to either explode or become black holes themselves.
- 06:07: These arguments let us rule out all but a very narrow set of mass ranges for primordial black holes as an explanation for dark matter.
- 06:38: ... think that the voracious feeding of lots of really big primordial black holes would have left their mark on the cosmic microwave ...
- 06:48: However, others argue that the recent LIGO detection of the merging of two approximately 30-solar-mass black holes is evidence in favor of this idea.
- 07:07: ... too long, we'll either spot the signature of primordial black holes at these masses, or discover that PBHs are actually very rare, and that ...
- 07:24: ... course, primordial black holes that have already evaporated due to Hawking radiation definitely are not ...
- 07:58: It wouldn't be right to end a discussion on primordial black holes without talking about what would happen if one passed through the Solar System.
- 08:07: Even a close encounter with a black hole as massive as the Sun or higher would be pretty catastrophic.
- 08:30: Of course, regular black holes from supernovae can, and perhaps have, done that.
- 08:36: Having high mass primordial black holes just makes it more likely.
- 09:11: ... if primordial black holes have approximately the minimum possible mass to not have evaporated-- ...
- 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.
- 09:49: In fact, perhaps geologists will be the first to discover the primordial black holes.
- 10:31: I found some amazing insights into the nature of black holes in Benjamin Schumacher of course Understanding Gravity.
2016-09-14: Self-Replicating Robots and Galactic Domination
- 00:47: Even the unusual denizens of the galaxy like pulsars and black holes just do what they do.
2016-08-24: Should We Build a Dyson Sphere?
- 07:15: Perhaps we can do better there, but there are also other options, for example, black hole engines.
- 07:22: ... can be harvested from a black hole, either from the Hawking radiation, from heat generated from infalling ...
- 07:43: ... the Hawking radiation from an artificial black hole is appealing, because once formed, we could perhaps sustain it from ...
- 08:47: Of course, the trick is making the black holes in the first place.
2016-08-10: How the Quantum Eraser Rewrites the Past
- 10:48: Mircea Kitsune asks, what if a black hole was headed towards the Earth?
- 10:58: Long answer-- depends on the type of black hole and how close it gets.
- 11:02: The only black holes that we know for sure are buzzing around our galaxy are stellar remnant black holes.
- 11:28: However, there's a theoretical type of black hole, so-called primordial black holes, which may have formed in the first instance after the Big Bang.
- 11:49: In fact, impact by a primordial black hole was one of the hypotheses that Seveneves scientists proposed for the moon's inexplicable destruction.
2016-08-03: Can We Survive the Destruction of the Earth? ft. Neal Stephenson
- 08:58: ... supernova, the resulting collapse of the core into a neutron star, or black hole, can produce these insanely powerful jets of high-energy radiation, ...
2016-07-20: The Future of Gravitational Waves
- 00:14: ... LIGO, detected the gravitational waves from the merger of two black holes. ...
- 00:43: These oscillations echoed the final 1/10 of a second of the end spiral and merger of a pair of black holes, each around 30 times the mass of the Sun.
- 01:09: On December 26, LIGO again observed the merger of two different black holes.
- 01:30: ... arm lengths that increased in both amplitude and frequency as the black holes approached before dying away again after the ...
- 02:41: That's due to the fact that the smaller black holes took longer to coalesce as they became very close.
- 03:51: If it were real, it would also be from merging black holes.
- 04:14: We now have more confidence in our understanding of the space-time around black holes.
- 04:20: We also now know that our estimates of the number of binary black holes in the universe and their masses are at least in the right ballpark.
- 04:28: This is good because it means we're going to see a lot more black hole mergers.
- 04:33: As we do so, we'll start to nail down the astrophysics of black hole formation and growth.
- 04:43: So far, we've only seen black holes merging.
- 04:54: We should eventually see mergers between two neutron stars or a neutron star and a black hole, as well as supernova explosions.
2016-06-15: The Strange Universe of Gravitational Lensing
- 04:51: This is the Einstein Cross, an extremely luminous distant quasar powered by a supermassive black hole feeding on its surroundings.
- 05:33: The quasar is a vortex of superheated matter falling into a black hole.
- 06:35: We can read this flickering to map regions near the black hole many orders of magnitude smaller than any telescope could resolve.
- 07:20: ... stellar bodies-- black holes, neutron stars, and brown dwarves-- occasionally pass in front of other ...
- 07:50: Of course, the most extreme gravitational bending of light results in the most awesome of all astrophysical objects, the black hole itself.
- 08:07: This gives us the black in black hole.
- 08:29: This is a region where light paths are so strongly curved that photons can actually orbit the black hole, forming a shell of light.
- 08:38: There are no stable orbits this close to a black hole.
- 08:46: ... any surrounding whirlpool of hot plasma to form a bright ring around the black hole. ...
- 09:03: But real lensing simulations show us what black holes should look like up close.
- 09:07: Both the black hole and the wormhole from the movie "Interstellar" are amazing examples.
2016-06-08: New Fundamental Particle Discovered?? + Challenge Winners!
- 12:47: ... with your address, US T-shirt size, and let us know if you want a black hole orbit or an I'll sign to anything I want ...
2016-06-01: Is Quantum Tunneling Faster than Light?
- 10:15: Throw in some string theory and black holes and a really unique writing style and it's a very insightful Pop Sci book.
2016-05-04: Will Starshot's Insterstellar Journey Succeed?
- 10:06: The universe expands exponentially forever and eventually the stars die out, the black holes evaporate, and the universe undergoes heat death.
2016-04-06: We Are Star Stuff
- 09:40: When they collide, most of their mass gets sucked into a newly born black hole.
- 12:44: It's happening below the event horizon of black holes.
2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!
- 01:11: ... colliding stellar remnants, supernovae, neutron stars collapsing into black holes, crazy stuff like ...
- 08:46: And also let us know whether you'd prefer a I'll Science Anything I Want t-shirt or a Black Hole Orbits T-shirt?
2016-03-23: How Cosmic Inflation Flattened the Universe
- 12:29: A couple of you asked about the shape of a black hole and its accretion disk based on the spin of the black hole.
- 12:37: So first, the accretion disk that forms around the black hole can either be very flat or fatter, but probably more toroidal than spherical.
- 12:47: Yet that doesn't have much to do with the spin of the black hole itself.
- 13:00: Although the magnetic field of a spinning black hole can also play a part here.
- 13:05: However, the shape of the event horizon of the black hole itself does depend on spin.
- 13:11: ... indeed, a rapidly-rotating Kerr black hole is flattened-- it's an oblate spheroid-- while a non-rotating ...
2016-03-16: Why is the Earth Round and the Milky Way Flat?
- 11:12: Felix Ironfist asks, "why didn't the universe collapse into a black hole, if it was so dense and massive?" This is a classic question.
- 11:21: In order to make a black hole you don't just need a high density, you need a high density relative to the surrounding regions.
- 11:56: Therefore, no universe-sized black hole.
2016-02-24: Why the Big Bang Definitely Happened
- 09:41: ... on just in time to catch the gravitational waves from the merger of black holes. ...
- 09:54: That almost as soon as LIGO became sensitive enough to spot black hole mergers, it spotted one.
- 10:51: ... Proctor points out that the date cited for the discovery of this black hole merger is September 14, and yet the official turn on date for Advanced ...
2016-02-17: Planet X Discovered?? + Challenge Winners!
- 08:02: Also, let us know if you prefer an I'll Science Any Question I Want t-shirt or a Black Hole Orbits t-shirt.
2016-02-11: LIGO's First Detection of Gravitational Waves!
- 00:10: The Advanced LIGO Observatory has seen the spacetime ripples caused by black holes at the moment of merger.
- 01:35: Since then, ripples from mergers of black hole pairs in distant galaxies have changed the shape of spacetime here on Earth.
- 02:06: Now, LIGO is sensitive to pairs of stellar mass black holes and/or neutron stars.
- 03:22: ... those few minutes, the merging black holes or neutron stars produce such strong ripples in the fabric of spacetime ...
- 03:33: In the case of merging black holes, to five billion light years.
- 03:44: It's expected that an observable merger of two black holes will happen only once every 10,000 years in any given galaxy.
- 03:56: Advanced LIGO can feel the ripples produced by merging black holes through a volume of space equal to about 0.1% of the observable universe.
- 04:31: ... of stretches and squeezes per second, that matches the rate at which the black holes were orbiting each other just before ...
- 04:46: So we saw some black holes merge.
- 05:42: These observations are going to tell us a ton about how black holes grow and about the physics of black holes themselves.
- 06:13: ... is sensitive to gravitational waves at frequencies produced by merging black holes and neutron stars, as well as the formation of neutron stars and ...
- 06:48: ... as well as the final dance of pairs of truly gigantic, supermassive black holes just before they merge in the cores of ...
2015-12-16: The Higgs Mechanism Explained
- 07:33: ... In the last episode, we told you how to build a real astrophysical black hole. ...
- 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.
- 08:06: ... an outside observer sees does grow because anything falling into the black hole adds to its effective mass as seen by a distant observer even before it ...
- 08:35: Any object that gets crushed down below its own Schwarzscihld radius becomes a black hole.
- 09:05: ... stars near the core of a galaxy with merging super massive black holes should have temperatures raised by an observable amount by the ...
2015-12-09: How to Build a Black Hole
- 00:00: [MUSIC PLAYING] Black holes are one of the strangest objects in our universe.
- 00:13: [MUSIC PLAYING] In a previous episode, we discussed the true nature of black holes.
- 00:37: And really, black holes were, at first, just a strange construction of general relativity.
- 00:48: So are black holes real?
- 00:51: Black holes are astrophysical realities that we have ample evidence for.
- 00:56: Yet, to actually form a black hole, Einstein's descriptions of mass energy and space time are not enough.
- 01:06: If you're up for it, let's build a black hole.
- 02:44: It's also a different quantum phenomenon that will let us push it over the edge, creating a black hole.
- 05:01: We want to build a black hole.
- 06:01: But for now, we have a black hole to make.
- 08:35: We've finally created our black hole.
- 08:54: When the black hole first forms, the material inside must resemble the stuff of the original neutron star.
- 09:42: The black hole forms.
- 10:13: So this is how a real astrophysical black hole is made.
- 10:16: The mass of the stellar core becomes the apparent mass of the black hole.
- 10:24: The black hole retains mass, electric charge, and spin.
- 10:34: Of course, a real black hole is not the static creature that we sometimes describe in theory.
- 10:43: ... get to what this means, for black holes and for the universe, in another episode of "Space Time." In a previous ...
2015-11-25: 100 Years of Relativity + Challenge Winners!
- 01:24: On December 9, we'll delve deeper than ever into the weirdness of black holes, after which we'll start exploring the nature of matter and time.
- 07:47: And be sure to join us in two weeks because we're going to learn how to build a black hole on the next episode of "Space Time." [THEME MUSIC]
2015-11-05: Why Haven't We Found Alien Life?
- 00:43: ... by a nuclear war, environmental catastrophe, accidentally making a black hole that swallows the planet, et ...
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 faster than light, ...
- 02:03: ... the spacetime around and within a black hole is predicted by solving Einstein's field equations around a point of ...
- 06:49: Even the Kugelblitz engine, the black hole drive, has fewer physics hurdles than the warp drive.
2015-10-22: Have Gravitational Waves Been Discovered?!?
- 03:16: ... most insane gravitational phenomena in the universe-- neutron stars or black holes in-spiraling just before merger, or gravitational catastrophes like ...
- 04:42: ... if we could actually see g-waves, we'd be able to study black holes, neutron stars, even the extremely early universe in ways never before ...
- 06:51: LIGO really just scratched the minimum sensitivity needed to spot merging neutron stars and black holes in relatively nearby galaxies.
- 08:50: A little birdie told me that it's the signal of two black holes in-spiralling towards each other.
2015-10-15: 5 REAL Possibilities for Interstellar Travel
- 07:47: This is an engine powered by an artificial black hole and is one of the fastest options for subluminal travel.
- 07:52: This is a black hole made not from mass but from light.
- 08:07: A black hole of the right size radiates Hawking radiation like crazy.
- 08:11: The smaller the black hole, the more radiation, and this radiation could drive our starship.
- 08:16: The sweet spot is a black hole of around 600 billion kilograms or two Empire State buildings, which would be roughly the size of a single proton.
- 08:24: Such a black hole would radiate nearly 160 petawatts, which is roughly the equivalent of 10,000 times the world power consumption.
- 08:38: Larger and it radiates too weakly and becomes too massive to feasibly accelerate the ship and the black hole.
- 08:45: ... to a significant fraction of the speed of light in the lifespan of the black hole. ...
- 09:04: The only drawback is that the lasers creating the black hole would need to be vastly more powerful than even the black hole they created.
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 information because ...
- 09:06: MrLewooz asks if we can please stop throwing monkeys into black holes?
2015-09-23: Does Dark Matter BREAK Physics?
- 02:37: And they're basically crunched down, compact, dead or failed stars, black holes, neutron stars, brown dwarfs, Macaulay Culkin, et cetera.
- 02:53: But when, say, a black hole passes between us and a more distant star, we sometimes see a brightening of that star.
- 07:36: ... next episode of "SpaceTime." Last time on "SpaceTime," we talked about black holes. ...
- 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 ...
- 08:53: Agen0000, and others, pointed out that Hawking radiation will eventually cause a black hole to evaporate.
- 08:59: ... on the event horizon with respect to a distant observer, shouldn't the black hole evaporate beneath ...
- 09:36: In fact, in the vicinity of the black hole, this radiation is poorly localized, having a wavelength of all of the Schwarzschild radius.
- 09:48: But is the monkey saved at the last moment as the black hole evaporates way beneath it?
- 10:03: The monkey's horizon crossing corresponds to a time when the black hole exists.
- 10:07: The distant observer does witness the instance that the black hole evaporates, with a huge burst of Hawking radiation.
- 10:21: It never even happens in the distant observer's universe, either before or after the black hole's evaporation.
2015-08-19: Do Events Inside Black Holes Happen?
- 00:00: [MUSIC PLAYING] I'm sure you've read, seen, and heard a lot about black holes.
- 00:07: Well, today, I'm going to try to make you rethink all of them, down to what the term "black hole" even means.
- 00:13: [THEME MUSIC] Today's episode, we'll only talk about black holes from the perspective of classical general relativity.
- 00:32: Now, it's a lot harder to say what I want to say about black holes if I make this video self-contained.
- 00:56: ... need you to put your preconceptions about black holes aside and for the next few minutes, become tabula rasa and let me tell ...
- 01:06: Suppose that I'm very far from a black hole and there's a pony orbiting the black hole.
- 01:40: Now suppose that I send a tumbling monkey falling radially toward the black hole.
- 01:54: ... is, until he gets really close to the black hole-- see, eventually, the monkey will cross the black hole's edge without him ...
- 02:05: I see him weirdly slow down his progress until he's floating right outside the black hole's edge.
- 02:20: So does another pony that's using powerful rockets to hover much closer to the black hole's edge.
- 02:24: In fact, so would any observer, inertial or otherwise, who is always outside the black hole's edge.
- 02:52: The monkey is saying that certain events happen, but everyone else outside the black hole says that those events never happen, ever.
- 03:01: ... be assigned a "when." From our frame of reference outside the black hole, those events just don't occur, even if we wait an infinite amount of ...
- 03:19: Here's the thing-- a black hole is that set of events.
- 03:33: But the blob, the black hole, is not just a set of locations.
- 03:44: The black hole is not a region of concurrent happenings with the outside world that the pony and I are just unable to see.
- 03:53: Instead, the black hole is the collection of happenings that we say don't happen at all.
- 04:13: ... the way, for every particle that enters the black hole, some event on its world line is always the last event that makes it into ...
- 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.
- 04:41: ... the last events to which you can even assign a "when." So if a black hole is a bunch of events, then why do we talk about it as if it's an ...
- 05:05: ... if I replace the Sun with a spherical black hole that's around six kilometers across-- and I'll tell you later how I got ...
- 05:19: So as far as Earth is concerned, that black hole generates the same spacetime geometry out here that the Sun does.
- 05:27: In that respect, the black hole certainly behaves like an object, an object with the Sun's mass.
- 05:32: So we associate one solar mass with the black hole itself.
- 05:36: ... fact, if I give you a spherical object of any mass M, a spherical black hole with this special radius, called the Schwarzschild radius, will leave ...
- 05:48: A black hole that mimics the Sun has a Schwarzschild radius of 3 kilometers.
- 05:56: A black hole is a bunch of events.
- 06:05: Hold that thought, because first, I want to debunk a few black hole misconceptions and then we'll come back to this question.
- 06:10: Misconception one, that black holes suck stuff in-- they don't do that.
- 06:18: I think this idea of suckage is rooted in a misunderstanding of the region that used to be inside the Sun but is still outside the black hole.
- 06:54: Misconception two-- black holes are black because not even light can escape their gravitational pull.
- 07:15: If a planet's radius equals the Schwarzschild radius of the equivalent-mass black hole, it turns out that the escape velocity is the speed of light.
- 07:28: ... even though it's true that everything inside a black hole, including a photon, will always move radially inward, it's not being ...
- 07:50: Now, that's really freaky, but it's not the reason black holes are black.
- 07:57: A laser pointer carried by the monkey never enters the black hole, as far as we're concerned.
- 08:20: That means that to external observers, black holes are black because light that gets emitted just outside the horizon is redshifted into invisibility.
- 08:37: ... three, that all black holes are super dense-- this kind of depends on what you mean by "density." If ...
- 08:47: More massive black holes can have very low density.
- 08:50: For instance, the 4 million solar mass black hole at the center of the Milky Way is about as dense as water.
- 09:00: By the way, bigger black holes also have smaller tidal effects near their horizons.
- 09:05: ... even though a solar mass black hole would spaghettify you from pretty far away, you could enter a billion ...
- 09:13: ... maybe that's not what you mean by "density." Maybe you mean that all black holes are infinitely dense because all the stuff that goes into the black hole ...
- 09:33: ... a black hole can form when a sufficiently massive object, typically a very heavy ...
- 09:42: In this situation, the mass of the precursor star and the associated mass of the black hole will indeed be the same.
- 10:01: To us, it's not inside the black hole.
- 10:05: ... Einstein equations also allow for an empty universe that has an eternal black hole that didn't form from anything, a spacetime that has an event horizon ...
- 10:18: ... is the prototypical Schwarzschild black hole and I've always felt that whatever we're going to say a black hole's ...
- 10:30: And in this circumstance, what are we supposed to assign the black hole's mass to?
- 11:05: ... some of the philosophical subtleties associated with thinking about black holes as "things." Of course, I've only scratched the surface of black ...
- 11:17: ... rotating black holes, charged black holes, black hole evaporation, what goes on around black ...
2015-04-08: Could You Fart Your Way to the Moon?
- 05:58: ... Last week I considered whether the moon in Majora's Mask might harbor a black hole. ...
- 06:43: ... why the shell of the moon wouldn't collapse and get sucked into the black hole. ...
- 06:52: The short answer is that black holes don't suck.
- 06:54: ... since the horizon is sub-millimeter sized, the fact that there's a black hole in play becomes kind of ...
- 07:02: ... a shell that just sits there around pretty much anything, including a black hole. ...
- 07:29: Raphael Hviding and Daniel Jenkins asked, wouldn't a black hole as small as the one I'm claiming evaporate quickly?
2015-04-01: Is the Moon in Majora’s Mask a Black Hole?
- 00:09: But what if I told you that the so-called moon is really a black hole?
- 00:50: ... that punches a major hole in their conclusions-- and by hole, I mean black hole. ...
- 01:05: Today I'm going to argue that the moon in "Majora's Mask" is not a moon at all, but instead of a rocky shell surrounding a miniature black hole.
- 01:38: And it gives us a chance to talk about miniature black holes, which I'm super pumped to have discovered lurking in a "Zelda" game.
- 05:58: OK, what about condensing some of the necessary mass into a black hole?
- 06:02: That black hole would end up having a radius less than a millimeter.
- 06:09: How could you ever make such a tiny black hole?
- 06:13: You could start with a more massive and larger black hole and just let it evaporate slowly.
- 06:20: And about a gazillion years later, poof-- moon-ish mass, submillimeter-size black hole.
- 06:27: The moon in "Majora's Mask" is basically some super-dense crust with teeth and with a mini black hole in the middle.
2015-03-18: Can A Starfox Barrel Roll Work In Space?
- 08:42: Likewise, people ask whether rogue planets or rogue black holes, streaking through the Milky Way, could come in and collide with Earth.
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