Can Black Holes Unify General Relativity & Quantum Mechanics?

[@yeahaddigirl]

The devs adding in a firewall plugin to stop dupe exploits is very on brand with our universe

[@thingsiplay]

Hackers will always find a way. No system is perfect.

[@TheGreatSilas]

🤣🤣🤣

[@LuisSierra42]

They thought they could get away with this

[@ZoiusGM]

​@thingsiplay Neo??

[@ex2katana]

Just gotta find an open port and we'll unlock the secrets of the universe.

[@Zaznin]

I like that this basically seems to boil down to, "it's not a crime if you don't get caught." Just on a universal scale.

[@nosuchthing8]

Like he said, that idea already exists in physics. As you know, particles can pop into existence spontaneously as long as they disappear before they can be perceived.

[@palladin9479]

It's the sophistic anthro-centric view of the universe. Something only exists if a human can understand it, anything before or after humanity doesn't exist.

[@archmagusofevil]

@@palladin9479 the theory doesn't rest on the fact that a human observer cannot see both, it rests on the fact that nothing can detect both. As far as abstract point in spacetime outside of black hole is concerned, there was no duplication. As far as abstract point in spacetime inside black hole is concerned, there was no duplication. As far as abstract point in spacetime traveling at or below the speed of light across the event horizon, there was no duplication. If there is nothing in existence where a duplication happened, then there was no duplication and nothing was violated. Whether or not this is what is actually going on is another question entirely.

[@palladin9479]

@@archmagusofevil I'm talking about the core QM concept of "information is never lost", which is demonstrably false due to the information from before the universe being lost. Everyone is coming up with crazy ideas to try to get around the apparent loss of information. If instead they just accept that information is lost anytime we get a singularity, a region of infinite density or where space equals zero, then everything resolves itself.

[@alazarbisrat1978]

@@palladin9479 how would things resolve if we just accept we can never know and stop looking for things? all experiments we've done has the information go somewhere, why give up looking for information on weird things? and the whole issue is that we're trying to learn more about the nature of zero and infinity in the universe and you just say to forget what we know and just accept it? what even is it? there is no resolution like that

[@Paul-A01]

Babies without object permanence: if I can't see it It doesn't exist Physicists: Maybe you're right!

[@FLPhotoCatcher]

Controversially, I'd say: if you can't see the baby, it still exists. Others: if you can't see the baby because it's inside someone, it's not even a baby.

[@Kodiak42]

@@FLPhotoCatcherpolitic

[@w01dnick]

​@@FLPhotoCatcherwell, it's not, it's zygote, embryo or fetus (depending on stage), it becomes baby *only* after birth. That's definition.

[@sivi9741]

@@w01dnick Yes , is human without a brain still a human ? I always trust science over religion for those kind of questions.

[@ThePowerLover]

@@w01dnick Baby is not a technical name for a stage of development unlike zygote, embryo, or fetus; but neonate is.

[@subcitizen2012]

I listened to Susskind's lectures many times. If you put an iPhone into a blender, an iPhone still comes out, even if it's not an iPhone anymore. At least technically speaking, per the math, it's very possible that there's no violations. For our reference frame as observers though, we lose Alice, the qubit, and the iPhone. But we do get to keep the free blender.

[@Giantcrabz]

this seems like a philosophical question about mereology at that point

[@tellesu]

Do not drink the unitarity smoothie it'll rot your brain

[@mikeguilmette776]

Margaritas anyone?

[@donaldbaird7849]

I remember reading a book from Susskind several years ago about the anthropic principle, black holes, many worlds hypothesis, etc. It was a pretty interesting book

[@AndrewBartram-bc8zm]

A screwed-up iPhone has greater entropy. So that's destruction of information...and a stupid waste of money

[@BenWard29]

People are going nuts about Terrance Howard right now. I’ve spent the last 2 hours arguing with people in the comments of his videos about why he’s clueless about physics. He’s brining in a lot of people to gobbledygook with his charisma. I had to watch this video like 4 times to make me feel better again. Thanks Matt! I would love to see a video on pseudoscience or Terryology from you- I know that’s not your game normally but it’s really bad out there right now.

[@serotoninsyndrome]

Is that the actor guy that said he can prove that 1+1 doesn't equal 2 or something like that?

[@AwfulnewsFM]

​@@serotoninsyndrome yeah, that's the guy

[@StefSubZero270]

Yeah Terrance has been cooking for years all his pseudo-scientific mystic stuff and thinks he is like a revolutionary genius and even claimed to have built some new kind of drones making up new words and misinterpreting and misusing old ones. He's really really full of himself and the sad part is that the talk shows he gets invited to are mostly clueless about anything physics (like Joe Regan) and actually end up agreeing with him. He is good at talking and looking smart, i'll give him that, but thats what makes him dangerous

[@DarkPesco]

Poor Alice and Bob! But still...WHAT A WAY TO GO!!!

[@John-jc3ty]

they didnt die. bob got into a blender that turned him into a machine and then reconstructed alice from the hawking radiation after eons passed. then they furiously smashed

[@LuisSierra42]

@@John-jc3ty Interstellar if it was good

[@Khyranleander]

Don't worry about them; like a certain popular 'toon, they die again & again, then are back in the next dilemma. "They killed Alice & Bob. Whoo-hoo, mastered!"

[@beenaplumber8379]

I'm not so keen on being spaghettified. That could take forever in a supermassive black hole. I mean, OW!!!

[@John-jc3ty]

@@beenaplumber8379 i dont think it would hurt much. you would fall so fast that you wouldnt even feel pain

[@bnightm]

This description of black hole complementarity reminded me of superposition. A sort of simultaneous existence that is "allowed" by the impossibility of observing more than one outcome.

[@frun]

Nah, different situations. Complementarity is formed by different views of the very same events, while superposition is constructed from different outcomes and intial conditions.

[@wolfyrine]

Reminds me more of the quantum eraser. The universe similarly "conspires" to prevent the violation of unitarity.

[@juliavixen176]

It's the generalized Stokes-Cartan Theorem (the "Fundamental Theorem of Calculus"). The derivative of volume is the integral of the boundary surface around it.

[@zualapips1638]

I noticed that a lot of quantum physics boils down to the impossibility of observing certain things, so we must make do with probability. Although, not being able to observe where a particle is doesn't necessarily mean it's physically at multiple places at once.

[@anonymes2884]

This is a common misunderstanding of superposition I think (not OP's fault IMO, I mostly blame bad pop-sci explanations). A superposition is just a quantum state that's a linear combination of terms that are each _also_ valid quantum states (this is an aspect of quantum mechanics - or really wave mechanics in general - known as "linearity"). It doesn't make _any_ claims about "existence" in itself (what the equations tell us about "existence" is where _interpretations_ of quantum mechanics come in - "many worlds", DeBroglie-Bohm, Copenhagen etc. - and physicists have been disagreeing on those for about a century). Since superposition is _a_ state (i.e. not a _collection_ OF states) this means It absolutely _doesn't_ tell us for instance that "electrons can be in two places at once" or "the cat is both dead and alive" (though as I say, bad pop-sci has been claiming so for decades) - all we can _actually_ say is "we can describe the electron's/cat's pre-measurement state as a superposition". (I get the various "reminders" BTW but i'd say black-hole complementarity is actually more like e.g. Heisenberg's uncertainty principle - which tells us there are pairs of observables, like position and momentum, where even in principle we can never precisely measure both simultaneously - or wave-particle duality)

[@crystalAegis]

perfect! literally just finished watching the previous episode, went "well DARN I want to learn about this more!" and BAM you upload the next episode! Always lovely for a coincidence like that to happen!! (I even looked up Black Hole Complementarity)

[@ScarecrowB1]

Has it ever been difficult to create the 'space-time' bit at the end of each episode? It's always done so well.

[@feynstein1004]

Nope, it's always been super easy, barely an inconvenience

[@FireHax0rd]

​@@feynstein1004So, you have a new set of thought-provoking insights to better probe the fundamental machinations of reality for me?

[@feynstein1004]

@@FireHax0rd Yes, sir, I do

[@chrismanuel9768]

​@@FireHax0rdYes sir, I do!

[@TinBryn]

Every April 1st I wish he would build up to it, pause, and then say something else and repeat that several times. "It add more mysteries to our ever expanding, ... understanding of the universe with it's fundamentally quantum, ... particles that interact in ways that are sometimes unobservable within our, ... reference frame of"

[@pablolara6186]

I don’t even remember subscribing to this channel, but I’m glad I did. Will pay more attention to it from now on. Funnily enough, today I was listening to Sean Carroll interview Leonard Suskind in his podcast.

[@LuisSierra42]

The backlog of videos goes back for more than 5 years and it's invaluable

[@escanorthelionsinyt884]

Good choice young padawan

[@simonsmith5003]

I always find that I have to really pay attention to it to be able to twist my melon around some of the concepts discussed particularly on quantum theory!

[@umurkaragoz]

I hear you. I've grown to never miss a video from this channel. Also while mentioning channels, there's an up an coming channel named ScienceClick, which I highly recommend as well.

[@eragonawesome]

It seems like Horizons in general represent a much more fundamental mechanism than people give them credit for. Based on the Unruh effect and black hole complementarity, it seems like one could reasonably say that beyond any horizon is effectively not a part of the same universe anymore.

[@WhydoIsuddenlyhaveahandle]

Cool way to describe it!

[@thekaxmax]

That's been said for some time, including hypothesising an actual universe in each black hole

[@ANunes06]

Only trouble with this interpretation is Hawking Radiation. But for practical understanding, this is probably the best way to think of the weirdness.

[@RichardGeresGerbil]

I would take it with a grain of salt black hole theory is beyond theoretical and even if we manage to send a probe or someone in we likely will never get any information back

[@RaveYoda]

I made a comment trying to articulate this point too. It's like two extremes meeting and the horizon a kind of transitional intermediary.

[@glennscott8622]

This one will have to get watched multiple times. Appreciate your work and keeping this a higher level discourse. 🙏

[@mello1016]

always must be

[@GentleReader01]

Move around some and see if the episode changes any. :)

[@supernatural_forces]

From Theological perspective I would prefer 'What was God doing before Creation ?' from channel Rational Believer. Its interesting to see that its zero for the Creator, i.e. not passing.

[@hassassinator8858]

​@@supernatural_forces Interesting

[@disastergarage4261]

Dont bother.. its incorrect

[@liamlieblein6375]

This contradiction actually sounds surprisingly similar to Godel's incompleteness theorem for arithmetic. The idea there was that a sufficiently complex system, such as arithmetic, cannot be both fully provable using that same system and also self-consistent. In other words, one had to choose either self-consistency (assumed by Godel to be non-negotiable) or full provability (also called completeness, hence the incompleteness theorem). The reason why there was such a contradiction between provability and consistency was the existence of arithmetic statements whose interpreted meaning within the system is "I am unprovable". To prove it means to prove its meaning to be true, namely that it is unprovable, a contradiction that destroys self-consistency. Failure to prove these statements leads to a lack of complete provability, since these true arithmetic statements cannot be proven within the laws of arithmetic. Translating this to the context of the video, it seems that the complex system we are analyzing is the universe itself, and the proving method is that of observation (or interaction). Qbits that enter a black hole form Liars paradox statements within the universe, i.e. they are interpreted as "I am unprovable", which in turn would be interpreted as "I am unobservable". To avoid the lack of self-consistency, we must therefore affirm that such statements are in fact unprovable, unobservable. This helps to show how strange such an idea is, since it seems that, by affirming that such statements are in fact unprovable/unobservable, their meaning is actually true - its just that we can never prove that truth without that proof leading to contradiction.

[@Graycy808]

Spacetime was the first channel I subscribed to on utube and actually watched daily till I'd binged all the vids. I look forward to every release and still binge on the old stuff in between. I think if I listen enough I'll have no choice but to understand quantum physics having learned by pure absorption and exposure lol!

[@Josecannoli1209]

Time to take a hit of pot and watch another great video Edit: to all the dweebs who apparently are to cool to say pot. smoke a doobie, toke a fatty, roast a blunt, spark a grinch finger, bogart a billy, let the dogs chase a skunk but only after I get a whiff, Fly Mexican Airlines, harvest some broccoli, get ill from the chronic… I can do this all day choose what ever you prefer… the point is these videos are 🔥 and I love them for making this grade A content that’s perfect for laying down some of Larry’s lettuce

[@freshtoast3879]

Howd it go??

[@lironadir35]

Doing the same here, cheers!

[@Jack_Redview]

Hit of pot, I’ve never heard somebody say it in such a awkward way lol anyway, let me go have one marijuana and then watch

[@MrWizardGG]

​@Jackiee_Chann thats cuz he's a gentleman unlike you 😊

[@Nosirrbro]

@@Jack_Redviewgive him a break he’s 35

[@lilpixie25]

It feels like I can never get enough of this series. It is so beautiful, our universe and our capacity to grapple with its mysteries. Just can’t get enough! ❤

[@nithinsuku]

Just as I was rewatching PBS Space-Time videos, you dropped a new one! 😊

[@richardmcbroom102]

In an idiocracy something is considered "explained" when that explanation becomes so convoluted as to become sufficiently opaque to all logical inquiry.

[@fhvisuals479]

Alice and Bob, the favorite guinea pigs in theoretical physics.

[@Paul-A01]

Forever separated by traveling past each other at the speed of light

[@nobody.of.importance]

Alice and Bob are quite popular in cryptography, too!

[@Ethrel1024]

Alice and Bob are popular anywhere where you need 2 theoretical people. Followed closely by Charlie if you need a 3rd.

[@nobody.of.importance]

@@Ethrel1024 Can you name another field where they pop up frequently? I've only seen them in these two contexts.

[@FLPhotoCatcher]

@@Ethrel1024 Dan if you need a 4th?

[@DruNature]

okay I am not missing this merch drop, finally a Tshirt I really like from one of my favorite creators!! never ordered something so fast! I got the astronaut one, killer graphic! Thank you Matt and PBS Space Time!

[@WhydoIsuddenlyhaveahandle]

That scene in Spaceballs with Colonel Sanders and Dark Helmet about "Now" was always hilarious to me. The more I learn about Relativity, I realize that scene is actually scientific haha

[@poppedweasel]

But when will then be now?

[@paulmichaelfreedman8334]

@@poppedweasel Now. Where? You just missed it. When? Just now.

[@poppedweasel]

@@paulmichaelfreedman8334 Soon.

[@paulmichaelfreedman8334]

@reson8q Forget my children, that scene will be the last thing I ever think of when I die 😂

[@randrothify]

@@poppedweaselSoon!

[@n0tthemessiah]

It feels like the explanation of BHC implies it wouldn't only apply to black holes and the spaces outside them, but also to any regions of space which can no longer be causally linked. For instance, two galaxies that drift so far apart the light from one would never reach the other. There doesn't appear to be any functional difference between these pictures. Am I missing something? Because the implications of this are kind of wacky.

[@Appletank8]

There's indeed a theory that our observable universe is functionally inside a gargantuan black hole, Kurzegast did a video on it a few days ago. Light we emit can functionally never leave the edges, it is retreating form us faster than light.

[@zualapips1638]

​@@Appletank8But black holes don't grow exponentially. It's like making gravity and dark energy equivalent in some weird way. Also, wouldn't our universe have a singularity somewhere in there that everything is headed towards?

[@koenvandamme6901]

@@zualapips1638 They actually touch on that in the video, including how the singularity could lead to a new Big Bang, creating bouncing universes. Of course, the entire theory can't be falsified, but it's a pretty cool thought experiment.

[@YandiBanyu]

But is that thinking wrong tho? The math is always there. It always state that there is always a disconnected region of space that is not linked causally no matter where/when you are. PBS even did an episode that cover this to calculate how many of the universe we can "see". What is the difference between causal disconnection from falling into a black hole and being so far apart? Note that I don't know the answer myself but your question indeed makes me ponder that

[@onebronx]

@@zualapips1638 in this model, the apparent expansion of the universe is equiavlent to us falling deeper and deeper inside the BH and watching its horizon getting more and more distant.

[@bash_maxwell]

3:27: Oh yeah, Lines of Fixed Location, I love this album!

[@thechickenduck8377]

I love how the music turns serious at 10:38 😜. And, amazing animations as always. Thank you.

[@NewMessage]

Alice and Bob are built different, man.

[@serversurfer6169]

Gotta trust the science! 🤓

[@herbertkeithmiller]

They must be up to something, why all those secret messages?

[@Supermitsuba]

Thanks, PBS Space Time! Got some shirts!

[@cipcervantes15]

That firewall is interesting. We gotta exploit that

[@thekaxmax]

The reason it exists is also how and why it's inaccessible.

[@o1-preview]

_firewall: cmp byte [particle], 1 jne .terminate_particle; 01011001 01101111 01110101 00100111 01110110 01100101 00100000 01100010 01100101 01100101 01101110 00100000 01100010 01100001 01101110 01101110 01100101 01100100 00100000 01100110 01110010 01101111 01101101 00100000 01110100 01101000 01100101 00100000 01110011 01100101 01110010 01110110 01100101 01110010 00100000 01110101 01101110 01110100 01101001 01101100 00100000 01110100 01101000 01100101 00100000 01101110 01100101 01111000 01110100 00100000 01101001 01101111 01101110 00100001

[@whateverrandomnumber]

I see what you guys did there.

[@Merennulli]

I'm still working on the privilege escalation attack using the buffer overflow error on the singularity.

[@o1-preview]

@@Merennulli same

[@Endofnames]

What ever happened to comment reads/responses? That was one of my favorite parts.

[@thebundroid]

Seconded, I'm missing the comments replies a lot.

[@LuisSierra42]

@@Nope-w3c Don't you think that's kind of an exaggeration? They were only doing it in just a few videos anyway because Matt was busy

[@BethAlpaca]

​@@Nope-w3cthen you will miss a lot of otherwise free content.

[@andoletube]

@@LuisSierra42 True, people seem to be forgetting that Matt is actually a proper working physicist - if he spent all his time on KZbin comments, he wouldn't be making the videos or doing proper physics.

[@fameus4423]

@@Nope-w3c God, you people are so entitled.

[@nigeldepledge3790]

My . . . brain . . . hurts . . .

[@Dr.Akakia]

It is good sign actually

[@gregp7980]

PBS Space Time is genius in getting lots of views. The complex material forces everyone like me who doesn’t get it to watch every video over and over and over and over…

[@SailingSVPipedream]

Cool, Matt curing my insomnia every night! Thanks

[@Surgical02]

Are you saying that this video put you to sleep? What an odd thing to say...

[@beea314]

​​@@Surgical02 I also love this channel and fall asleep to the videos. They're relaxing

[@o1-preview]

I got the opposite effect, it gives me more energy and inspiration.. can't believe people fall asleep to this, it makes my brain more active if anything...

[@SailingSVPipedream]

@@Surgical02 well I am an odd kind of guy! I do enjoy the videos though. I find them really fascinating, but just cannot stay awake…

[@SailingSVPipedream]

@@beea314 yep, I watch one every night and rarely get past ten minutes. Which is in some ways annoying as I never get to the conclusion. Although sometimes I fall asleep and wake up again halfway through or near end and then fall asleep again.

[@YaofuZhou]

5:25. This is the coolest animation of blackhole formation I have ever seen!

[@grewech]

I miss the old intro. But as always, awesome video 👍🏻

[@fpoggesi]

The old intro had a nice vibe to it. Like it was a show that could get magnitude of the sun's effect on tides wrong or mispronounce the name of one of Saturn's best-known moons. This into says the show is a professional operation. I liked the old one better too.

[@frun]

I miss astronauts from the old intro. They were the best.

[@renatobergallo6321]

Veritasium has just made a video about Black Holes with a lot of Penrose Diagram examples and thinking exercises. It was really fulfilling watching the two videos in such a short SPACE-TIME

[@davejones542]

which just goes to show things can be in two places at once

[@nuckyducky]

This is one of the first times the channel really attempts to claim that reality might really be nonlocal. 'Different descriptions of one quantum system', 'extreme relativity', so close to quantum gravity. I feel like this channel is going to accidentally stumble on quantum gravity just from the sheer brute force of the topics it covers. Amazing channel. Amazing video.

[@Giantcrabz]

what? they've done multiple episodes on these topics

[@nuckyducky]

@@Giantcrabz This time they said the quiet part out loud. To me, this was a definitive moment where before it was more playful hypothesis.

[@anonymes2884]

@@nuckyducky No, it's _still_ a "playful hypothesis". ER = EPR is _highly_ speculative at the moment, the video isn't stating what _is_ it's merely presenting what _might_ be. (the description for instance refers to black-hole complementarity as "a proposed solution")

[@armagetronfasttrack9808]

Everything they cover is stuff that has already been discussed in research papers for several years, so it makes no sense that the show itself would figure out anything new merely by covering the topics when researchers have already been considering these things, in far more detail/nuance, for much longer than the show.

[@nuckyducky]

@@anonymes2884 I entirely agree. I think I misrepresented my claim in the ambiguity of language. I'm not suggesting this is truth nor knowledge, I'm rather saying that this level of analysis is quite deep in the rabbit hole of 'relativity' and I like that. It's nice to see bold claims being made because they stir my wonder of the universe. I wish my teachers had taught me that reality 'could' be this wacky, because as I get older, I find the world becoming more magical, not less. I don't think we can go into wormholes, but I'm delighted that there's a way to interpret reality in which we 'possibly could'. TL;DR: thanks for reinvigorating my imagination again, PBS.

[@sevenstarsofthedipper1047]

This is one of the few PBS spacetime videos I really understood.

[@user-Tenebrea]

Make a video about the d-0 branes that create spacetime itself in string theory

[@o1-preview]

Hello fellow simulated being, your request has been rejected but an alternative simulation had a script for the video I just so happened to grab it. Hey everyone, before we get to the episode, remember we have the new merch in the store, link in the description. In string theory, D-branes (short for Dirichlet-branes) are objects upon which open strings can end. These objects can have various dimensionalities, denoted as Dp-branes, where "p" indicates the spatial dimensionality of the brane. For example, a D0-brane is a point-like object, a D1-brane is a string, and a D2-brane is a membrane, and so forth. A D0-brane is a zero-dimensional object, meaning it is a point in space. In string theory, D0-branes are especially interesting because they are considered to be the fundamental building blocks from which higher-dimensional branes and spacetime itself can emerge. Here’s how they are related to the creation of spacetime: D0-branes carry mass and can be electrically charged under the Ramond-Ramond (RR) fields in type II string theory. This mass is typically proportional to the string tension and inversely proportional to the string coupling constant, making them heavy in weak coupling regimes. D0-branes can interact and form bound states. These bound states can aggregate to form higher-dimensional objects, such as Dp-branes. The dynamics of multiple D0-branes can be described by a gauge theory, specifically a U(N) gauge theory for N D0-branes. In the context of M-theory (a proposed unification of the various string theories), D0-branes are interpreted as the quantum mechanical degrees of freedom of the theory. Matrix theory, proposed by Tom Banks, Willy Fischler, Stephen Shenker, and Leonard Susskind, suggests that the dynamics of a large number of D0-branes can describe M-theory in the infinite momentum frame, where the eleven-dimensional spacetime emerges from the collective dynamics of these branes. The idea that D0-branes can create spacetime comes from several theoretical constructs: In the matrix model of M-theory, the positions of D0-branes are represented as the eigenvalues of large matrices. The spacetime coordinates themselves become dynamical quantities emerging from the D0-brane interactions. Essentially, the geometry of spacetime can be seen as an emergent phenomenon from the underlying matrix model. In the AdS/CFT correspondence, which posits a duality between a gravity theory in Anti-de Sitter (AdS) space and a conformal field theory (CFT) on its boundary, D-branes play a crucial role. D0-branes in this context can be used to construct black hole solutions in string theory, and their dynamics can provide insights into the nature of spacetime and gravity. The non-commutative geometry arising from D0-brane interactions suggests that at very small scales, spacetime coordinates do not commute, leading to a "fuzzy" or quantized structure of spacetime. This is a departure from the classical continuous geometry and hints at the fundamental quantum nature of spacetime itself. D0-branes are fundamental point-like objects in string theory that carry mass and can form bound states, interacting via gauge theories. The collective dynamics of many D0-branes can give rise to higher-dimensional branes and spacetime. This emergent perspective on spacetime suggests that what we perceive as smooth, continuous spacetime is actually a macroscopic manifestation of the underlying quantum interactions of these fundamental objects. In matrix theory and related frameworks, spacetime is not a fixed backdrop but rather a dynamic entity shaped by the behavior of D0-branes. Thank you to all of our Patrions, considered joining us there for extra content. I hope you've enjoyed, see you in the next PBS space time episode.

[@jamesmorseman3180]

Space time is one of the only channels that I immediately like the video before I watch the first second

[@Surgical02]

Why did you stop doing a comments section every couple of shows?

[@ingoseiler]

It took a lot of time to do and people skipped it, which was bad in the eyes of the almighty algo

[@BethKjos]

@@ingoseiler People only skipped it because it came after the ad read close to the end of the video.

[@bobjackson6669]

Loved the show and sent it to my grandkids to view. Thank you PBS.

[@I3endoubles]

So the core of this seems to be that fact that hawking can’t emit information for the first half of the black holes life. I’d really like more detail about why we can ignore the radiation for the half of the black holes life. Also isn’t there some information in that initial hawking radiation? Where is that coming from?

[@RWMAirgunsmithing]

Has to do with the background temperature of space itself, something about the temperature being lower then that of the black hole for it to evaporate.

[@user-sl6gn1ss8p]

@@RWMAirgunsmithing and that always comes around to half of the lifespan?

[@RWMAirgunsmithing]

@@user-sl6gn1ss8p it probably isn't exactly half but when we are talking trillions of years I think it is safe to approximate xD. 99% sure this info is in my brain because of this channel (might be a Sean Carroll podcast) so I'd suggest searching the PBS video library for hawking radiation and checking those out before you quote me xD but this is the gist of it hehe.

[@user-sl6gn1ss8p]

@@RWMAirgunsmithing thanks for the pointers : ) And yeah, I get that these things are often order of magnitude, but the explanation in the video made it sound like it would result in a very near miss. But maybe the point was more like "if you time it optimally it will still be a near miss", rather than "if you time it a half the lifespan it will still be a near miss".

[@RWMAirgunsmithing]

​@@user-sl6gn1ss8pI was wrong, matt was not colloquially approximating time scales. I wasn't wrong about the hawking radiation but that is just the tip of the iceberg. The physicists he mentions are debating the actual properties of the radiation and it would appear that in the (roughly) first half of the evaporating black hole the radiation is too diffuse or mangled to be actually measured as information, only after that mid point does the radiation become identifiable as information. Thanks for sending me down the rabbit hole lol

[@crayvun2196]

Super cool episode! I find the idea of the holographic concept of the information in a blackhole really tantalizing. Made me imagine it as sort of a mirage, or reflection being cast. Honestly feels like we're getting closer to figuring out just how the event horizon might work. Well, not me, but you wonderful people anyway! Thanks for sharing science with us, you're the best!

[@jounik]

The postulate of the unobservability of a macroscopic object crossing the event horizon bothers me greatly. One would assume that an astronaut crossing the event horizon feet first would notice not getting any information from their feet anymore, for starters.

[@tymoteuszdomeradzki6645]

If the astronaut is falling then they are still getting information from their feet, but instead of the information travelling up to meet them they sort of fall on it (the information is falling in slower because it is trying to climb up). As was discussed in the previous video, you won't notice anything near you change when you fall freely through the event horizon. If you're instead trying to hover just above the horizon and dip your feet in then they will get ripped off, which you would probably notice indeed. Standing on the Earth instead of free-falling you experience constant 1 g acceleration, trying to 'stand' on a black hole will feel like a lot of g's.

[@jounik]

@@tymoteuszdomeradzki6645 I don't think so, the topology doesn't add up. Once the horizon is crossed, any events happening at the feet would no longer be anywhere within the future _head's_ past light cone, after all. As far as I can tell the 3+1 spacetime geometry itself becomes fully degenerate at the event horizon since one of the spatial dimensions ("inwards") can no longer be considered separable from the time dimension ("future") at all, let alone orthogonal to it even locally. For all practical purposes involving spacetime the black hole then _is_ its event horizon.

[@mzaite]

That is because it is a functional simplification. The “alice” or “you” is simply a point source observer in these descriptions. The “you” is just an artifact to help describe the stuff around “you” it’s not really an analysis of the physiological effect of crossing an event horizon. “You don’t notice” really means, there’s no sudden change of acceleration, space etc..

[@Howtheheckarehandleswit]

It always takes time for information to reach your brain about different parts of your body. In the case of the feet, it takes about 80 milliseconds for a signal to reach the brain. For that 80 milliseconds after your feet cross the event horizon, you notice nothing, because the signal has not reached your head. If you're freefalling, you still notice nothing wrong after more than 80 milliseconds, because you fall onto the information just as fast as it would normally climb up towards your brain. If you somehow manage to massively accelerate the rest of you enough to escape the black hole immediately after your feet dip in, you feel your feet being ripped off faster than a signal can reach your head from your toes, which is in fact the uh... "normal" experience of having one's feet ripped off, it's always faster than a signal about it can travel, the pain comes from whatever's left.

[@darthrainbows]

As you fall into the black hole, you would catch up to the signals that were emitted by your feet before they crossed the event horizon. If it was possible to hover at the event horizon, you would notice that the signals from your feet are arriving slower and slower (essentially redshifted, but not quite, as they are electrochemical signals, not photons). Hovering at the event horizon isn't possible, though - you'd either fall in or have your feet torn off accelerating away.

[@aldo8547]

please dont ever stop making videos

[@binbots]

General relativity and quantum mechanics will never be combined until we realize that each individual observer is observing them both at different moments in time. Because causality has a speed limit (c) every point in space where one observes it from will be the closest to the present moment. When one looks out into the universe they see the past which is made of particles (GR). When one tries to look at smaller and smaller sizes and distances, they are actually looking closer and closer to the present moment (QM). The wave property of particles appears when we start trying to predict the future of that particle. It is a probability wave because the future is probabilistic. Wave function collapse is what we perceive as the present moment and is what divides the past from the future. GR is making measurements in the observed past and therefore, predictable. It can predict the future but only from information collected from the past. QM is attempting to make measurements of the unobserved future and therefore, unpredictable. Only once a particle interacts with the present moment does it become predictable. This is an observational interpretation of the mathematics we currently use based on the limited perspective we have with the experiments we choose to observe the universe with.

[@AgneDei]

This sounds very reasonable

[@bengoodwin2141]

This doesn't solve anything

[@binbots]

@@bengoodwin2141 I never claimed it did.

[@bengoodwin2141]

@@binbots oh, I guess it just sounded like you did to me, sorry

[@anonymes2884]

This is plausible sounding incoherent gibberish unfortunately. ALL measurements are of events that have, by necessity, already happened (events in the future can't produce physical changes in a measurement apparatus in the present, that would break causality). Quantum measurements are no different (no, not even those involving entanglement). Similarly, ALL predictions, whether those made using QM or GR, are of the future (by definition). It's true that QM's predictions are probabilistic (as far as we know this is because that's just how reality works though it's _possible_ there 's some deeper underlying theory that's entirely deterministic) but they're _also_ "from information collected from the past" since the Schrodinger equation (arguably _the_ central mathematical tool of QM) evolves entirely predictably and deterministically from the past to the future, just like the equations of classical physics (after solving it you then apply the Born rule to the resulting complex wavefunction and _that_ step yields a probabilistic prediction but everything before that is standard deterministic physics, again, just as with General Relativity). (you're perhaps getting wrapped up in the fairly trivial notion that since light takes a finite time to travel everything we observe is in our past. While true this is irrelevant because it's just as true of quantum mechanics as it is of general relativity)

[@paulthomas709]

Matt is the best host ever. Great visual aids too! I think that learning abstract concepts require visualization and unfortunately without it, learning becomes extremely boring. This is why our educational system is failing and more people think that watching a youtube video is the same as gaining an education.

[@chadwcmichael]

12:33 “We live in a computer simulation” I’m not so sure... “Here’s a firewall”

[@Bob-of-Zoid]

Hi I'm Bob!! Thanks for putting me and my freind Alice (no I wasn't the one who gave her the acid) on the Penrose diagrams and launching us all over space and time! I loved the transitions between universes, and space sex is something else, although the dimensional reconfigurations do a real job on my hair! Who would have known that passing cosmic horizons was such a thrilling ride!

[@CRIMELAB357]

Lord, this channel leaves me more confused than ever.

[@Josecannoli1209]

Commenting this before you even saw the video? Trying to farm likes for your comment or somthing?

[@CRIMELAB357]

​@Josecannoli1209 your burning desire and need to reply to my comment. 👏

[@Namedonelettere]

Even the experts are confused

[@marinosoric1117]

A very simple idea actually, looking forward to testing it with one of my own cubits

[@AdrianBoyko]

Existence is overrated

[@AwfulnewsFM]

You sound like the type that would be into femboys

[@erdngtn9942]

Love the new black hole opening graphic.

[@Numba003]

This one was difficult. The black hole does provide such a wonderful area to speculate on the nature of reality. What an incredible time to be alive and investigating such things! Thank you for another fascinating episode. God be with you out there, everybody. ✝️ :)

[@markolson4660]

Nice. I'm glad you described this fascinating speculation with clarity about how much of this is speculation!

[@ScalarInfluon]

You know it's gonna be an enlightening day when pbs space-time posts

[@POLICECAMERA6688]

"Wow, this video is amazing! I've always been fascinated by questions about the connection between general relativity and quantum mechanics.

[@AndromedatheBasshead]

Thank you for yet another great episode. The Space Time team is one for the books!

[@TheShawnMower]

Im loving how we keep building on previous episodes lately. Seems more intentional

[@eucariote79]

it is here where I learn. Thank you, guys, from Space Time.

[@novailoveyou]

Maan this literally blew my mind. Almost as if there is whole bigger world underneath our limited perception

[@casnimot]

That part where you drew "simultaneous" lines in the Penrose diagram highlighted the projection/holographic part of this pretty well. That sort of thing keeps showing up in other combos of time-velocity-distance, e.g., most of the universe we see today ending up as a red-shifted holographic memory/projection.

[@QuantumLeapResearch]

Excellent work PBS Space Time

[@kingstoler]

Matt is such a great communicator about complex topics. Also your beard is getting gray.

[@alonhaviv6755]

2:17: When the Qbit escapes as Hawking Radiation it should follow that the internal quantum state of the black hole changed, and so the Qbit doesn't exist anymore inside it -> Unitarity preserved. BTW it also happens to the mass of the black hole, that is reduced by the Hawking Radiation which contains information about it (its temperature correlates to the mass).

[@blijebij]

yes, When a qubit escapes as Hawking Radiation, it implies that the internal quantum state of the black hole has changed, and thus the qubit no longer exists inside it. This preserves unitarity. According to the holographic principle, this loss of a qubit necessitates a corresponding reduction in the surface area of the black hole. Regarding the holographic principle, the two-dimensional surface (one Planck scale per bit of information) of the black hole shrinks. A potential conditioning factor is that we project a three dimensional volume inside or behind the surface. Therefore, what we are doing-conditioned by our human scale and surroundings-is projecting locality onto the inside as if it were spacetime. That could be totally wrong.

[@chrism3562]

I find Penrose diagrams so damn facinating.

[@redbeard499]

Scary I actually understood this concept lol thanks for the great vids team!

[@Stinger-rq4gy]

Thank you for teaching me.

[@YandiBanyu]

I think if we do have theory of everything, it makes sense that both fundamental assumption about GR and QM holds true. Since no information can travel faster than C, it also makes sense that the horizontal line on penrose holds no meaning for the observer since the observer is not causaly connected

[@MrTripcore]

OFC it can travel faster than C. C is just the limit to 3D space. In the early universe there was literally no light. This is a fact

[@petepanteraman]

Great job and loving the graphics 👍👍

[@pierfrancescopeperoni]

Since we are approaching this kind of spirit, an episode about relational quantum mechanics would be interesting.

[@Falcury]

This is great, looking forward to the firewall episode! My gut feeling: a black hole acts like an event that got delayed for as long as QM permits it. Below the outermost part of the horizon you encounter consecutively older versions of the event horizon, frozen in time until the outer layers are peeled off like an onion. Matter is destined to get radiated back out near the outside, and never actually 'enters' as the interior is not a place that physically exists. Also, the outgoing Hawking radiation would fry you as you try to enter.

[@jo_crespo11235]

Excellent video Matt and team, keep the hard work.

[@RobinMaddock]

PBS Space Time is so good (TY). So many of the arbitrary limits, contradictions and weird rules closely resemble the trade offs you make when doing software engineering simulations for open world video games. eg. You must limit the speed of information or your computation goes infinite. You should avoid computation until it is useful (cat). Use a simpler simulation to capture a larger experience (holographic)

[@zacharywong483]

Absolutely superb video, as always!

[@jmcsquared18]

The ER=EPR conjecture is one of the most incredible dualities proposed yet. Quantum gravity and the quantum measurement problem are almost certainly related.

[@robertsutherland7378]

The 1973 paper Ether flow through a drainhole: A particle model in general relativity by H. G. Ellis Journal of Mathematical Physics. 14 (1): 104-118 mathematically finished what Einstein started. The solution Ellis discovered is singularity-free, devoid of one-way event horizons, and geodesically complete. The Ether in the title is the Ether of Einstein's general theory of relativity he discussed at Leiden in 1920. euclid.colorado.edu/~ellis/EtFlThDrPaMoGeRe.html and en.wikipedia.org/wiki/Ellis_drainhole.

[@Krystaltho]

What about for rotating black holes ~0.95c? How does Black Hole Complementary behave then? Do Penrose Diagrams work with rotating Black Holes?

[@AndreiFierbinteanu]

Hawking radiation is sometimes explained as a matter-antimatter pair being created at the horizon, with the matter escaping, and the antimatter falling in the black hole and annihilating some matter there (at the singularity). But antimatter is also sometimes described as matter going backwards through tine. So can we not think of the qubit falling in, reaching the horizon, "turning around in time", travelling as an anti-qubit out of the blackhole, and, at the event horizon "turning around in time" again to exit as hawking radiation? Basically a clasic Feynman diagram of a pair creation, followed by a pair annihilation, with the creation happening at the event horizon, and the annihilation at the singularity, but treating that as a single particle (qubit) going forward -> backwards -> forward in time. That way it's not a problem, as it is a single qubit, just at different "times" in it's life.

[@ruudvdlinden]

It seems to be all about information in some way. Would love a deep dive episode on this.

[@redandblue1013]

Really enjoying this series

[@flanger001]

I know they’ve been mentioned a few times but I’d love a deeper dive into Planck Stars. I feel like that solution to the black hole information paradox is the closest to being actually physical without any singularity stuff.

[@Zamicol]

This is a solid argument that there's something wrong with the diagram due to it's production of an apparent paradox. This is an excellent thought experiment because it succinctly demonstrates this problem.

[@georgeburdell517]

Anyway... great episode! My week is now complete!

[@VideoGamingSociety]

I understand about 30% of everything said in these videos, although I constantly read and watch Cosmos and Quantum physics stuff. Amazing! 😂

[@ConnoisseurOfExistence]

Can't help with money, but I absolutely love this channel!

[@quentinbricard]

Thank you for this video!

[@branemarkmoriarty]

Seems like a good way to conserve energy/compute in the simulated universe. Things only come into existence when observed, instead of having to exist at all times. It's like a video game that only shows the part of a map visible on the screen, instead of loading the entire world.

[@TheMarrethiel]

The beauty of this theory is that it seems to link the quantum and classic universes.

[@objective_psychology]

Going into this I was certain that complementarity made the most sense intuitively: why should what are effectively two separate “universes” care about each other? But the more I think about it, the less it makes sense why spacetime would link those two regions without some kind of continuity of the same laws; after all, there are still continuous symmetries that apply across the event horizon. So now I'm thinking: doesn't the qbit's wave function exist on both sides of the horizon? Isn't it entangled with both sides? Is there absolutely zero chance of it tunneling back out of the black hole once it crosses, in which case its wave function does has an absolute horizon, or can tunneling break the speed of light, as recent experiments suggest? Is there some deeper connection between quantum probability and the existence of the speed of light?

[@eonasjohn]

Thank you for the video.

[@Lleanlleawrg]

I've been thinking for a few months that if you take the mathematical formalisms of quantum mechanics and general relativity, you can envision a model where you have a multiverse governed by quantum mechanics, where every outcome is equally real. They are distributed by probability across an infinite series of static, unchanging block universes. If accurate, it would mean we'll never find a quantum theory of gravity, because gravity is an emergent phenomena of universes, and isn't directly in quantum mechanics. A bit like trying to apply psychology to an atom. So, gravity isn't really a fundamental force in that scenario, because it emerges at more of a macro scale. In this interpretation, black holes would be through-holes in spacetime, leading out into the greater multiverse where the rules of the universe do not apply. So that would explain singularities at the big bang, and in black holes. It becomes like trying to describe the ingredients for the hole in the donut. You're trying to apply something to an area where it doesn't have anything to say. That would give us a mechanism for information "loss". It's not really destroyed, it's just left our universe, but still exists in this multiverse model, inaccessible to us. It could also tell us part of the reason for our universe expanding faster than C. Simply, it indicates that C might be a constant for this universe block, and not necessarily be applicable outside it. We're also given a more intuitive understanding of why time dilation occurs. We're moving at a constant C-velocity in four dimensions. So an increase in spatial velocity has to mean a decrease in temporal velocity, giving rise to time dilation. This should be intuitive to gamers who who remember moving diagonally was faster than forwards or sideways, but now it's usually fixed in games. We also get a potential insight that maybe we got the relationship between mass and inertia backwards. We usually think of mass giving rise to inertia, but maybe it's the other way around. Maybe particles interacting with the higgs field are resisted, by the higgs somehow counteracting the energy you put in, meaning if you want to go faster, you need to put in more energy. This scales scales infinitely. So it's almost like a non-newtonian liquid in my view. The harder you slap it the more solid it seems. Thinking about inertia-first can also perhaps tell us something about why we'd follow curves of spacetime to begin with, and how space can form. We know mass deforms spacetime, and we know black holes do so with such strength it creates an inescapable pit. Well, it sort of indicates that the "rubber sheet" metaphor for the universe is quite apt. Massive objects warp the sheet, because the sheet is flexible, but it has mass of it's own. It resists movement. If it didn't, then surely every mass should be a black hole. There wouldn't be anything to curve, presumably. Everything would fall straight through. So it indicates there is something resisting movement, something with it's own inertia, able to balance out the mass and inertia of planets and things, but that with enough mass in a dense enough configuration, you're going to rip a hole in spacetime, and you can peek out into the multiverse. By placing quantum mechanics at a more fundamental level than gravity, we're also hinting at a potential way to explain the faster than light action in quantum entanglement. It indicates there is a kind of... substrate of quantum information that is more fundamental than spacetime, and so there could be aspects of quantum information that are not governed by the emergent properties of spacetime. Probably just gibberish. I'm not scientifically trained at all, and I thought this up in a literal armchair in like four hours one evening, so it's doomed to be wrong, but I'd like some feedback on it, whether some of it is plausible or if it's all nonsense.

[@quietfox157]

This reminds me of the episode about the thought experiment with the train going through a house (or something similar) at such a high speed that it fits entirely into that house or not depending on the reference frame. That already lead me to the idea that reality could differ drastically depending on the reference frame. If that's true then wouldn't every person live in their own kind of parallel universe? Then every person we see around us is kind of a "copy" that exists only for us. I even wonder if one person could even influence the reality of another person or if they only influence that one "copy". So, I imagine something like this, assumed realities can be drastically different: Universe 1: [Real me] [Copy of A for me] [B doesn't exist] Universe 2: [Real person A] [Copy of me for A] [Copy of B for A] Universe 3: [Real person B] [I don't exist] [Copy of A for B] Universe 4: There's no earth Does a thought experiment like this exist maybe?

[@hindigente]

This interpretation seems so sensible, so reasonable, in its simplicity, that it's almost self-evident. I can hardly comprehend its mainstream rejection if its most damming objection amounts to "non-causal simultaneous duplication of information" (in lack of a -catchier- better term).

[@MrTripcore]

There is no duplicate. Only thing that changed is the speed of time passing for observer entering bh

[@hindigente]

Well said, ​@@MrTripcore!

[@frun]

Interpretation 1 makes sense, it appears. Riemann tensor encodes a phase of a qubit and each observer sees it differently. QM doesn't allow to find out the value of the phase exactly, because measurement alters it. I do understand the explaintion overall, but it's hard to grasp the details.

[@Pfhorrest]

I still think that the simplest solution is just that nothing ever finishes falling into a black hole because it would take forever to do so. The route that outside observers see qbits taking is the one route that they really take. There is nothing inside of an event horizon, everything that ever "fell in" is just taking an extremely long time to eventually escape the traffic jam of particles that got way too close together, and the slow escape of those particles just is the Hawking radiation.

[@MrTripcore]

Lol no such thing as nothing. Try again

[@erdemmemisyazici3950]

Cool. It was really interesting to know that someone actually thought about what would happen if Bob also decided to get spaghettified (infinity does make math difficult) by floating into the event horizon and tried to break the complimentary nature, the qubit would still be just out of reach. It does appear that the very nature of an observer simply requires an unknown to exist at all.

[@arturskirhners2025]

I used to watch PBS videos to fall asleep, now once I turn one video before sleep, I end up at 4am 10 videos deep.

[@gruvhagen]

Amazing like always

[@jovetj]

Except for the "singularities"...

[@astrocoastz]

Hey Matt, after hearing that BHC mentioned that there is no contradiction, I had the idea that brought me around to Schrödinger's cat. Even though the cat can observe itself, relatively, to us the cat is both alive and dead. Could that be what's happening here? Such as bob and alice both observing their own relative universe, in which the waveform collapses. But for the other observer, the waveform hasn't decohered, meaning quantum physics still holds up, and relatively bob and alice's universes are following relativity.

[@NeilCrouse99]

Your first description made it sound like if there's no one that can visualize/utilize a certain perspective, then it doesn't exist.

[@thekaxmax]

A perspective requires a perceiver, therefore this is correct.

[@some-say-gregms]

Great episode, I enjoyed it a lot. Interpretation 2 makes sense but I would hesitate to jump right to the holographic principle. A holographic universe might work, but I wouldn't want to overlook the possibility that there is some other unknown way that the interior and exterior descriptions of the quantum information reflect the same underlying system.