Transcription
There is another f way of thinking that says no spacetime is fundamental, you know. Relativity is fundamental. Um, so I'm saying that because there's debate. It's not, it's not mo, I think most physicists would say quantum mechanics is the underlying theory, some kind of quantum description of nature, that emerges.
It's on a roll for how successful it has been in accounting for everything, right? I mean, so why doubt it at this point? Yeah. So we maybe we don't know enough to start. So, so you, I, he, I think I'm not misrepresenting him. He would, he would question whether you really need to have a quantum theory of gravity in the coming from quantum mechanics. I think he would question that. So the, the reason I'm saying that is to say it's an open question. We don't know.
So what about the fabric of spacetime? Is that emergent? Well, so the recent work in the study of black holes, which is the, the tiny bit of research I still do, I had a PhD student and postto working on this. It's called emergent spacetime.
Yeah. What is that? So it's the idea that space and time are not fundamental. So spacetime is not fundamental. There's a, let's say, a deeper description which is basically a network of cubits to put to do the shorthand, the shorthand version. So cubits, quantum bits. So essentially, it looks like a quantum computer. Not absolutely not to say that we live in a simulation, right? No one's going.
There's a little different. Have you noticed that these sounded? I don't really mean that. I, well, I don't know whether we live in a simulation. Nobody does. But I'm just saying it's not, it's not evidence for that.
Right. But it's beginning to look like you can say, well, a, no, let's say, a notion of distance can emerge from a network, an underlying network which doesn't have the notion of distance or geometry in it. So that's the.
That's you just described subspace from Star Trek. [laughter] Kind of possibly. Yeah. It's like this underlying substrate where the laws of physics aren't necessarily in play, which is why you can go faster than the speed of light.
Well, information goes faster. Information goes faster. So, you communicate in subspace in a, in a, in a with witty reparte. Exactly. Even though they're.
Even though they're a half a galaxy apart. Right? Yeah.
It's interesting. I, I was thinking about this in another context actually, because I, so, there would be laws of physics, by the way, that the, there'd be underlying laws. Right? And then our laws would emerge from them.
Please [clears throat] forgive my inelegant description. We call them effective theories, right? So it's an effective theory, right? Which is, which works in the regimes we observe things. But.
Effective theory. But I was thinking about this and I have no evidence for this at all. So I, I might cause lots of people to write in. But I think that that note causality, for example, cause and effect, which is what you're saying, when things, if things can go faster than light, then you can essentially build a time machine and go into the past. You can send messages back into the past if you can go faster than the speed of light, basically. My guess is that that's absolutely fundamental. Um, and so that, so you wouldn't just because you can skip, if you could skip beneath relativity, so to a deeper picture of spacetime, I still guess that causality will be there.
Will still be there. I will be now. I, I'm not aware of any anyone who's really who's proved that or I'm not aware of any any other anyone's opinion on it. It is my opinion. Yeah. I don't have any, I don't think I have any evidence for that other than Stephen Hawking.
How is that different from Stephen Hawking's time travel conjecture? Yeah, the chronology protection.
Protection conjecture. Sorry. So, it's called a conjecture because he conjectured it. Conjecture. It [laughter] was conjecture and that was his conjecture. You're right. He said that whatever the underlying laws of physics are, they prevent time travel into the past, which is to say that causality.
Protecting. Right. Exactly. But I think we're absolutely miles away. We're miles away. This might not be right. This idea of spacetime emerging, although it's quite a popular research field.
It is interesting because quantum mechanics can seem to violate the spirit of that. So we, you probably discussed before on the show, quantum entanglement. Yeah. Everybody wants to know about quantum entangle, spooky action at a distance, he called it. Right. So he didn't like the idea that you can have these widely separated things that can appear to be correlated in such a way that something happens instantly. Now, we know John Bell and others showed, and it's been experimentally tested, that information can't travel faster than the speed of light.
But still, the idea that some kind of, call it configuration, that the quantum state can change instantly seems to violate that somehow, doesn't it? So this is again.
I heard from the other Brian. Brian. Brian. So I was having lunch with him and I just, he said something that just blew my mind. The, what might be fundamental in spacetime is this sea of entangled virtual particles where the particles are entangled via what are essentially wormholes.
Yeah. Because a wormhole has instantaneous contact from one side to the other. And the wormholes then are the stitching of the fabric of space time.
It's called ER equals EPR, which is Einstein Rosen equals Einstein Podolsky Rosen. So EPR is the spooky action at a distance paper and ER is Einstein Rosen, which is 1935, I think.
Where, where they showed that the, the, uh, swatch geometric, the eternal swatch geometric, which is the description of a, the, a non-spinning black hole, which discovered very early in relativity, um, has in it, if you extend it as far as you can, a wormhole geometry. So that was Einstein and Rosen. So it's called, I think Lennon Susskin and coined the term ER equals EPR.
So what does that mean to you as a thinker in this space? Can, can wormholes be the fabric of anything? Yeah, it's part of the answer, one of the answers for how information might get out of a black hole. So is it what called the black hole information paradigm?
Okay, that's that's very cool. Go ahead. Yeah. Well, one of the, one of the pictures people have for that, very handwavy picture, is that wormholes somehow connect the interior of the black hole to the external universe.
But all the other virtual particles that fill the vacuum of space. Yeah. Those are particle pairs that come in and out of existence. Yeah, they're entangled.
Why wouldn't they be? They're entangled. Why wouldn't that also be in this wormhole discussion? Yeah, it, yeah. So that's it. That's. So, so it seems there's some sense of a, a link. The, the reason it's, it came in, in, in the black hole context is the math people did very complicated mathematical calculations about what happens to the Hawking radiation. So this [clears throat] is the, the, the radiation that is emitted from a black hole, from the, and it's really one way to think about it is it's the event horizon of a black hole is disrupting these particles that you talked about, these entangled particles that that are really the structure of the vacuum of space, right? And it kind of disrupts them. And so people were calculating how that radiation, which is entangled with the black hole, how everything behaves as the black hole shrinks. Because, because if you think about this black hole is glowing. It has a temperature, losing energy.
Through Hawking radiation. Through the Hawking radiation. So not at the moment, because they're much colder than the cosmic microwave background. So the cold things at the moment, but eventually in the universe, they'll be, there'll be hot things and they'll start, they'll shrink.
Be hotter than the background. Yeah. So they'll be net, net flow of energy is out. Yeah. Hot is, I mean, we're talking about 0.0 whatever Kelvin it.
But eventually they'll shrink. They're entangled with the Hawking radiation because of what you said, because of these pairs that are coming out of the vacuum. And so you get to a point where you get a crisis, really, where the entanglement can't be supported. It's one way of thinking about one of the problems with the black hole information paradox. So it's all to do with entanglement and what happens and, um, so from that research, some calculations were done which are just mathematical, that say that ultimately the Hawking radiation ends up essentially entangled with itself again, right? Is one way to think about it. Um, be, because, so, so you don't lose information. But those, those calculations can be pictured with handwaving as representing wormholes. Wormholes. Some sort of wormholes. They're not the Einstein Rosen wormholes, actually. So it gets very complicated and, and, and people aren't clear on the interpretation, but that's where the modern resurgence in this idea has come from. I think it's coming from these really very technical calculations about black holes and how information behaves in the, in the presence of black holes and wormhole like structures appear to be one interpretation of what's happening. But I sh, I'm choosing my words carefully because it really isn't fully fleshed out by a long way.
It's interesting, isn't it? Is it really about like this is how the, it's like an information tunnel just for that for the purposes of getting it out?
Yeah. Yeah. And then [laughter] you go, why? And even, you know, you see the language, except for the purposes of why is it that information is conserved?
That looks quite basic. So it looks like another of these basic ideas. Information is not destroyed, right?
It becomes massively scrambled. So you can't, in any conceivable future, read the stuff, but it's, you know, the example that's often given is if you, if you burn, but it's the iPad. Let's say you set fire to the iPad. You might say, "Well, surely I destroy the memory." But the, the idea is that you don't. If you could measure everything that came off somehow, all the photons and the whole thing, then in there, scrambled up, the, you could reconstruct would be the iPad, even though you set it on fire and all those atoms, like, and every particle that was in there, if you could get them all together, use, you would be able to say, "Oh, that was the iPad."
Yeah. And you'd have that, your photos in there, or whatever it is, you know, you could, in very principle, but really in principle, not practice, reconstruct. So you don't destroy information.
You don't destroy information. It's also determinism. It's also.
It's called unitary evolution in our [laughter] language, right? Really, you don't, you don't destroy information.
Gotcha. So energy and information, conservation of energy, conservation of information, is, is can we think about them like that, or is it not, is that a wrong way to think about it?
Well, it's less about information more about entropy, right? I mean, entropy you can move from one place to another and then there's a, then you can measure that or think about it as an entity, whereas.
Okay, I get a point. We're raising before, obviously, if I send a molecule that has structure, a DNA molecule, into a black hole and it gets ripped apart and then it comes out as separate atoms, I lost all that DNA information. However, that DNA became DNA at the expense of the sun or whatever other input.
The energy that went into it. That's correct. Gotcha.
Right. So that, so a, a, you draw a sphere around all the action.
Somebody get me some weed. [laughter] This is awesome. I should be high right now, man. [laughter]
So then you could talk about sort of entropy moving, right? You know, without having to to inventory the shape of the DNA molecule.
Right. Because the, the DNA molecule is a result of the energy taking energy from another system, from another source that put it in there. Correct.
Oh, wow. Okay. This is great. [laughter] You're right. You're right though. I mean, it is, it's it's so fascinating that this work on on black holes, black hole information paradox, emergent spacetime. Yes. But it's, it's such an early stage that I don't think there are popular articles that really, you know, the language isn't there yet. It's just mathematically.
Mathematics. Difficult. Wow, man. [music] [music] [music] [music] [music]