
20221026: Why Did Quantum Entanglement Win the Nobel Prize in Physics?
 18:57: ... that seem to imply alternate universes beyond the singularity  but more likely that’s just an artifact of extending the math too ...


20220622: Is Interstellar Travel Impossible?
 17:31: ... answer is that yes, towards the singularity at the center of a black hole matter should reach arbitrarily high ...


20220504: Space DOES NOT Expand Everywhere
 10:06: ... paths can be traced to the infinite future or past until they hit a singula,rity  the big bang or a black hole. As the universe expands, we don’t have ...


20220330: Could The Universe Be Inside A Black Hole?
 00:28: Both of these involve matter being packed to infinite densities  they are singularities where the mathematics of GR breaks down.
 00:41: ... have led some physicists to believe that the big bang is in fact the singularity of an absurdly gigantic black ...
 01:26: The universe also has a singularity and an event horizon.
 01:30: ... singularity is the Big Bang, which we think of as a point in time at the beginning ...
 02:46: ... obvious difference is that the black hole singularity seems to us to be a point of infinite density in space, while the big ...
 03:01: ... the big bang and black hole singularities do occupy all of space  the difference is that the big bang singularity ...
 04:39: Except at singularities.
 04:41: In fact, in general relativity, singularities are defined as the end points of geodesics.
 04:53: We call the Big Bang a past, spacelike singularity because it occupies all of space  in the past.
 05:01: A black hole contains a future, spacelike singularity.
 05:05: Which means that all geodesics within a black hole spacetime end at the singularity in the future.
 05:19: ... black hole singularity is the allencompassing future for the spacetime that lives beneath the ...
 05:59: The first step is to send that singularity to the past.
 06:13: ... past, spacelike singularity of the white hole is surrounded by an event horizon that is the opposite ...
 06:28: That’s starting to look like our universe  a past, spacelike singularity and an event horizon that can’t be crossed from the outside.
 06:44: The outside that doesn’t share the same singularity origin.
 07:34: The curvature changes dramatically as you approach the singularity.
 08:36: ... matter remains homogeneous and the spacetime is flat until it becomes a singularity. ...
 10:27: ... that case, black holes don’t form singularities, but rather bounce back outward to create a new spacetimes from the ...


20220323: Where Is The Center of The Universe?
 09:04: Geodesic incompleteness is just a fancy way to say “singularity”.
 09:19: ... say that the Big Bang is a past, spacelike singularity  which means it occupies all space at t=0 and is in the past of all ...
 10:34: And that’s the nature of singularities  they are discontinuities in the math we use to describe the universe.
 10:48: By the way, there are close parallels with the singularity of the black hole.


20220216: Is The Wave Function The Building Block of Reality?
 16:00: ... how we can know that a black hole’s mass has time to crush down to the singularity, given that time dilation slows the event down during the collapse. So ...
 16:15: ... frozen time, and you’re right that from that person’s point of view the singularity  in fact the entire event horizon, never quite finishes forming. But ...


20220127: 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 Fact: every black hole singularity is surrounded by ...
 01:01: ... any object that reaches such a density has to collapse to a pointlike singularity of infinite density surrounded by this boundary of no return  the event ...
 03:54: ... around a black hole doesn’t need to know about the mass of the central singularity  it only needs to know what the space next to it is ...
 05:03: Any fish that passes that point will be carried to the singularity  the fall itself.
 05:51: For example, at the black hole singularity.
 07:33: ... gravitons, then those gravitons don’t emerge from the location of the singularity, and they don’t have to travel through the event horizon to do their ...
 11:13: A simplistic view says that it’s at the singularity  but that’s not the mass that you interact with.


20211117: Are Black Holes Actually Fuzzballs?
 00:39: ... matter should contract to a single point of infinite density  the singularity  which is surrounded by a surface from which even light can’t escape  ...
 01:00: At the central singularity, the known laws of physics break down  general relativity comes into irreconcilable conflict with quantum mechanics.
 04:23: The impossibility of the central singularity is the most obvious place where we need a theory of quantum gravity.
 06:01: ... theory immediately solves the problem of the black hole singularity, because instead of collapsing all of a black hole’s mass into a single ...
 12:50: As a side benefit, this eliminates the problem of the gravitational singularity at the center of a black hole.
 12:55: There is no central singularity because there is no center.


20210525: What If (Tiny) Black Holes Are Everywhere?
 10:08: I mentioned this inflation thing earlier  what if at the singularity of a black hole a new inflation is triggered?


20210511: How To Know If It's Aliens
 16:32: ... asks what the difference between super small black holes or naked singularities and WIMPs be. Normally when people talk about wimps they’re referring to ...


20210413: What If Dark Matter Is Just Black Holes?
 11:16: ... speculated that an evaporated black hole might leave behind a tiny naked singularity  a speck of infinite density weighing less than a grain of ...


20201104: Electroweak Theory and the Origin of the Fundamental Forces
 13:32: ... time we talked about Singularity Theorems, and how they show that the singularities at the heart of the ...
 13:57: ... types of infinities, and some are seen as worse than others  the singularity type is considered a bad one  that’s when some property blows up to ...
 14:10: ... the case of the black hole singularity, or the singularity of the big bang, it’s bad because it causes ...
 15:01: Not all of them necessarily converge, but you only need some to get the singularity.


20201027: How The Penrose Singularity Theorem Predicts The End of Space Time
 00:00: ... every black hole contains a place of infinite gravity  a singularity. But the true impact of Penrose’s singularity theorem ...
 01:17: ... to fall inwards towards a central point. At that socalled singularity, the gravitational field becomes infinite. But ...
 02:16: ... dust could collapse into a Schwarzschild black hole, singularity and all. Makes sense  if all particles are falling directly ...
 03:18: ... of infinite gravity is spun out into a ring  but it was a singularity nonetheless. The Kerr solution was still highly ...
 03:38: ... were utterly unavoidable in Einstein’s theory. Penrose’s singularity paper is deceptively short  just a couple of pages in ...
 04:06: ... set out to show that an event horizon and a singularity would form for any distribution of matter, no matter how messy, as ...
 04:35: ... plus a couple of assumptions, black holes must contain singularities. And this is true regardless of how the black hole ...
 08:49: ... curvature  infinite gravity. In other words, singularities. Penrose didn’t actually show what type of singularity would form in ...
 09:31: ... Roger Penrose’s discovery, black holes and the singularities within had to be taken more seriously. But the true utility ...
 10:36: ... in an expanding universe had to truly meet  to form a singularity, which meant they had to terminate. Time itself could not be ...
 11:10: ... is probably the right time to tell you how the singularity theorems must be wrong  or at least point to wrongness. ...


20200824: Can Future Colliders Break the Standard Model?
 14:28: ... be a thin sliver of space in between that is not flowing towards either singularity? ...
 14:44: The key point is that space doesn’t have to flow directly towards the singularity.
 14:49: Think of the case of the rotating black hole  the singularity is a ring, and relatively few geodesics  freefalling paths  hit the singularity.


20200817: How Stars Destroy Each Other
 11:10: Why should the star have crushed down into a pointlike singularity at all?
 11:50: ... think a theory of quantum gravity probably prevents the singularity from really forming  but quantum gravity effects would not kick in soon ...


20200630: Dissolving an Event Horizon
 00:00: Black hole singularities break physics  fortunately, the universe seems to conspire to protect itself from their causalitydestroying madness.
 00:14: Only problem is many physicists think it might be wrong, and that naked singularities may exist after all.
 00:44: ... of this weirdness is the event horizon: the surface around the central singularity where the inward flow of space reaches the speed of light, and time ...
 01:12: Without it, the infinitely dense singularity and its surrounding madness is exposed to the outside universe.
 01:18: We would have what we call a naked singularity.
 01:30: ... Censorship Hypothesis  which basically states that every gravitational singularity must be surrounded by an event ...
 01:59: ... we’re going to look at the astrophysics and see how exactly a naked singularity might be formed in the first place, and how the universe seems to work ...
 02:57: Inside, we found that the rapid rotation has spun the pointlike singularity into a ring of infinite density.
 03:09: The same rotation that f orms the ring also drags the fabric of space into a vortex which counters the inward pull due to the singularity’s mass.
 03:18: The result is that we get this region around the singularity where the fasterthanlight inward flow of space is halted.
 03:51: Instead, there’s a smooth run of normal  albeit rapidly spinning space all the way down to the singularity ring.
 04:00: The NAKED singularity ring.
 04:10: ... presence of electric charge at the central singularity  which pointlike in this case  results in a negative pressure that ...
 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.
 05:14: So that’s how you make an extremal black hole  or even a naked singularity.
 06:25: So naked singularities don’t Hawkingradiate, and extremal black holes radiate only very slowly.
 06:31: ... decay, we may be left with only radiation and these naked, charged singularities. ...
 06:52: So why shouldn’t it be possible to add a little more spin or charge to produce true naked singularities?
 06:58: ... hypothesis tells us that something will always stop a gravitational singularity being stripped of its event horizon  but it doesn’t tell us the ...
 08:49: It’s not yet clear whether we can avoid the naked singularity in this case.
 10:32: Once again, the universe appears to have a mechanism to avoid the naked singularity.
 12:08: ... hole funnel  moving towards the bottom means moving towards the central singularity, and the narrowing of the funnel represents extremely curved ...
 12:25: ... you approach the singularity you end up being wrapped entirely around that shell In the case of the ...


20200615: What Happens After the Universe Ends?
 12:01: ... Tod’s conformal transformation of the Big Bang singularity helped Penrose to demonstrate that the smallness of the entropy at the ...


20200518: Mapping the Multiverse
 04:02: In a regular black hole we’d be crushed by the central singularity pretty quickly.
 04:50: Below you is the black hole singularity  but it looks odd.
 05:14: ... way you came through the inner horizon, or you can plunge through the singularity ...
 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.
 06:43: But those that approach the disk experience an overwhelming antigravitational force from the spinning singularity.
 07:34: For one thing, the ring singularity becomes entirely repulsive  as though it had negative mass.
 07:50: For one thing, the lack of event horizons above you means the ring is a naked singularity, as well as being repulsive.
 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.
 09:39: Extending the Kerr metric from ring singularity into the future leads to something else.
 13:35: They just don’t have the ring singularity leading to the bizarroverse, so Kerr is more fun than ReissnerNordström.


20200511: How Luminiferous Aether Led to Relativity
 14:06: ... size" and "the universe has a finite age" if the universe started from a singularity. How do you go from infinitessimally small to infinitely ...
 15:01: But the singularity happens when you go from a tiny positive age to zero age. Infinity times zero is zero and that's your singularity.


20200422: Will Wormholes Allow Fast Interstellar Travel?
 05:43: ... in between is the inside of a black hole. When that timeslice hits the singularity the wormhole has ...
 11:03: ... with Roger Penrose’ cosmic censorship conjecture, which ensures that all singularities are surrounded by an event horizon, our greatest minds seem convinced ...


20200331: What’s On The Other Side Of A Black Hole?
 00:37: ... merge, and all directions become south. We call these points coordinate singularities. A singularity is where a variable in the equation becomes infinite  and ...
 01:38: ... of the universe in this 4dimensional spacetime also have coordinate singularities  for example around the black ...
 02:56: ... fall through the event horizon. The event horizon is just a coordinate singularity like the earth’s poles, and to make a smooth map through it we need a ...
 03:46: ... scheme was EddingtonFinkelstein coordinates, and they revealed that the singularity of the event horizon was an illusion. Kruskal–Szekeres coordinates ...
 05:00: ... spacetime flapping in the wind. The only place geodesics end is at true singularities, like at the center of the black hole. On our Penrose diagram, we see ...
 07:57: ... have switched roles. These lines represent steps towards the central singularity  it’s the old radial direction, but now flows only in one direction  ...
 08:22: ... behind  those are photons that overtake you heading towards the central singularity. Light can also reach you from below  that’s light from anything that ...
 08:44: ... and get a glimpse of the black hole’s past. You never actually see the singularity  that is manifest as an inevitable crushing future, in which the space ...
 09:00: ... traveling faster than light in that direction doesn’t get you to the singularity more quickly  instead you’re ejected through the parallel horizon into ...


20200324: How Black Holes Spin Space Time
 12:11: ... physicsbreaking phenomena  time travel, universehopping, and naked singularities. And we'll encounter all of these when we drop below the event horizon ...


20200113: How To Capture Black Holes
 13:26: ... spawns. That new universe is birthed in the formation of the black hole singularity. If it grows by some inflationlike expansion into an entirely new ...


20191217: Do Black Holes Create New Universes?
 03:26: ... its mass doesn’t all end up stuck in the central, infinitely dense singularity. ...


20191015: Loop Quantum Gravity Explained
 01:16: ... we think about the extreme densities of the black hole or the big bang singularities. ...
 15:49: ... than a certain amount then the event horizon evaporates, exposing the singularity to the universe  or in the case of a rotating black hole, an infinite ...
 16:02: ... naked singularities are expected to be impossible, and so we expect a maximum rotation rate ...


20190718: Did Time Start at the Big Bang?
 00:25: ... should once have been compacted into an infinitesimally small point  a singularity. It's often said that the universe started with this singularity and the ...
 01:02: And before the Big Bang singularity, well, they say that there was no 'before' because time and space simply didn't exist.
 01:56: ... even at different speeds still leads us towards the T equals zero singularity. I'm going to come back to why we need to forget the idea of this ...
 04:38: ... still infinity Rewinding the universe this way doesn't leave us with a singularity The singularity is when all points are not just next to each other but ...
 05:15: ... point and threedimensional space becomes zero dimensional That's the singularity We say that it didn't happen in any one place because a point is zero ...
 06:02: ... the Big Bang We have to trace a path through space and time back to the singularity We trace a path called a geodesic which in general relativity is the ...
 07:22: ... geodesics end at the Big Bang singularity and their timelines end with them Or they start depending on how you ...
 08:14: ... wrong But it's important because the extreme weirdness of the Big Bang singularity is part of what tells us. It's wrong Any time you encounter a ...
 08:52: ... the crazy densities and temperatures of the Big Bang singularity, and just after, GR comes into terrible conflict with quantum mechanics ...
 09:38: ... first up, cosmic inflation can offer a temporary reprieve from the singularity. ...
 11:36: ... a poetry to that last one. The geodesics approaching the black hole singularity Become the geodesics emerging from the new Big Bang singularity people ...


20190403: The Edge of an Infinite Universe
 05:03: ... these coordinates only defeated the artificial infinity – the coordinate singularity  of the event horizon – also something we’ve discussed (the phantom ...


20180920: Quantum Gravity and the Hardest Problem in Physics
 04:38: ... effects on the smaller scales of space and time, like the central singularity of the black hole or at the instant of the Big ...


20180613: What Survives Inside A Black Hole?
 04:35: ... layer directly above it, continuing the cascade even after the central singularity is lost to all causal ...
 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.


20170920: The Future of Space Telescopes
 13:05: ... and then who knows what as the core continues to collapse towards the singularity. ...


20170913: Neutron Stars Collide in New LIGO Signal?
 14:53: I said that the Big Bang is mathematically similar to a white hole, except that it doesn't possess a singularity.
 15:42: And Hot Fuzz is obviously a reference to black hole singularities in string theory.


20170830: White Holes
 03:41: The singularity no longer occupies a central location.
 03:55: ... the collapse, the future singularity comes into being, and in the past, well, there's just a star, but what ...
 04:14: We find the singularity again lurking infinitely far in the past.
 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.
 05:54: The once vertical contours of space are now timelike and flow inexorably towards the future singularity.
 06:29: The singularity is a past event.
 06:32: ... within is timelike, but instead of flowing towards the singularity, it flows away, and the event horizon is now a barrier to entry, not to ...
 08:11: The past singularity and past event horizon are infinitely far in the past from our point of view.
 10:43: The difference between the Big Bang and a white hole is that the former possesses no singularity.
 11:42: We required that all paths be traceable through infinite past and future space, provided they don't hit the singularity.


20170405: Telescopes on the Moon
 11:33: ... electric field in a charged black hole at the singularity is expected to produce an antigravitational effect through negative ...
 12:46: But they become degenerate close to the singularity.
 12:50: ... means that just before you reach the singularity, perhaps your sideways extent should wrap around and merge with itself, ...


20170329: How Time Becomes Space Inside a Black Hole
 04:26: Space itself is falling inwards faster than the speed of light towards the central singularity.
 07:38: The outside universe exits our future light cone, which now just contains the singularity.
 09:26: But remember that future light cone actually just points towards the singularity.
 10:24: The singularity becomes a future time, not a central place.


20170202: The Geometry of Causality
 11:47: We skipped comments last week because I was at the beach, so today, we're tackling both phantom singularity and quasars.
 12:07: ... way out of the mathematical singularity at the center of black holes is with string theory, which proposes that ...


20170119: The Phantom Singularity
 00:02: The singularity.
 00:09: In mathematics, singularities come in wild and wonderful varieties.
 01:43: ... often use the word singularity to describe the hypothetically infinitely dense core of a black hole, ...
 01:55: Instead of me trying to explain mathematical singularities, how about we get a real mathematician to do this properly.
 02:19: Well, mathematicians use the word singularity pretty broadly.
 02:34: Some singularities come about from your choice of reference frame or coordinate system.
 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.
 02:49: Here on earth, the North and South pole are examples of coordinate singularities.
 03:02: But the gravitational singularity at the center of a black hole is a socalled 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.
 03:29: ... of water to human population growth, mathematics predicts a physical singularity, and we've been forced to reject the corresponding ...
 03:47: Guys, you should check out Kelsey's show "infinite Series," where she goes into much more depth on the nature of singularities.
 04:04: So, does the fact that it includes a singularity mean there's something fundamentally wrong with Newton's law of gravitation?
 04:30: So does general relativity rid us of Newton's pesky singularity?
 04:36: In fact, it gives us even more singularities.
 05:09: Actually, it's really easy to see the singularities in this equation, but let me first walk you through what it tells us.
 06:41: Now the first thing to notice is that the singularity is still present in the Schwarzschild metric.
 07:00: This gives us the same infinite gravitational pull as the Newtonian singularity.
 07:05: And just as with the Newtonian case, this gravitational singularity can only exist if infinite densities are possible.
 07:22: To see how, we need to look at the second singularity in this equation, a singularity that Newton's law does not contain.
 07:45: It's as much a mathematical singularity as the one in the center of the black hole.
 09:54: The act of crossing the event horizon is where this singularity really starts to behave badly.
 10:27: That horizon is a coordinate singularity, just like Kelsey talked about.
 10:36: There are ways to construct our space time axes so this singularity just evaporates.
 11:03: Of course, once inside the event horizon, we still have that central singularity to deal with.
 11:27: The apparent inevitability of this singularity may be evidence that general relativity is incomplete.
 11:45: There, the causal roles of space and time switch places, and the central singularity becomes not so much a location in space but an inevitable future.
 12:13: Cheers to Kelsey Houston Edwards for helping us understand mathematical singularities.
 12:18: Be sure to check out the PBS "Infinite Series" episode dealing with earthly singularities right here.


20170104: How to See Black Holes + Kugelblitz Challenge Answer
 06:46: This is because there are regions of the universe that are doomed to end up in the singularity even before the true event horizon forms.
 08:28: ... spacetime is cascading behind the shell towards the soon to be formed singularity. ...
 08:38: ... that will carry even that light inexorably downwards to form the singularity. ...
 08:51: See, once the event horizon forms, all paths below it lead to that singularity, even outgoing light paths.
 09:01: ... future light cone of everything below the event horizon leading to the singularity, even of the reflected light ...


20161221: Have They Seen Us?
 14:25: If time dilation approaches infinity, do you reach the singularity before the black hole evaporates?
 17:33: So once inside the horizon, avoiding a singularity is like avoiding next Tuesday.


20161214: Escape The Kugelblitz Challenge
 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.
 02:59: ... this otherwise normal space where everything is doomed to fall into the singularity, even though the black hole has not finished ...
 03:09: There's a region where all forward light cones only include the singularity, even before the true event horizon forms.
 05:10: From the inside, Earth has one second in which it notices absolutely nothing wrong before it's consumed in the singularity.


20161208: What Happens at the Event Horizon?
 03:10: It has a point of infinite density, the singularity, and an event horizon a bit further out.
 03:42: Below the event horizon, all possible trajectories lead towards the singularity.
 06:21: Space flows at greater than the speed of light inwards, towards the central singularity.
 06:38: All paths lead to the inevitable singularity.
 06:48: All of them end up at that singularity.
 10:00: All spacetime within the black hole is flowing toward the singularity faster than the speed of light.
 10:21: But even that socalled outgoing light is still moving downwards, doomed to hit the singularity along with the monkey and our rescue mission.


20160323: How Cosmic Inflation Flattened the Universe
 09:53: We don't need to talk about an exploding singularity at all.


20160224: Why the Big Bang Definitely Happened
 02:36: ... observable universe was once compacted into an infinitesimal point, a singularity at time t equals 0, the hypothetical instant of the Big ...
 02:51: Now, that initial singularity is not something that most cosmologists believe in.


20160203: Will Mars or Venus Kill You First?
 10:00: We just don't understand the physics well enough to confidently project the size of the universe to infinitesimal smallness, to a singularity.


20151209: How to Build a Black Hole
 09:03: All paths lead to the central point of infinite curvature, the singularity.
 09:13: All position space collapses towards the singularity.
 10:05: On our clock, the singularity forms infinitely far in the future.


20151028: Is The Alcubierre Warp Drive Possible?
 01:51: ... event horizon of a black hole, spacetime cascades towards the central singularity faster than light, carrying light, matter, monkeys, and everything else ...


20151015: 5 REAL Possibilities for Interstellar Travel
 07:56: ... enough region would bend the fabric of space time enough to produce a singularity, the Kugelblitz, German for ball ...


20150819: Do Events Inside Black Holes Happen?
 09:13: ... into the black hole collapses to an infinitely dense point called the singularity at the center, ...
 10:37: So is the mass a property of the singularity?
 10:41: You see, the singularity also isn't a thing or a place or an event.
