Dimensions of reality beyond spacetime | Janna Levin and Lex Fridman

What this episode is about

In this conversation, physicist Janna Levin and Lex Fridman explore whether extra spatial dimensions beyond our familiar three might exist, perhaps tightly curled up like origami or as a three-dimensional membrane floating through a higher-dimensional "bulk." They examine why only three dimensions appear to have "unraveled," how string theory and multiverse ideas fit in, and whether other universes or even other civilizations could exist on neighboring membranes. It's a thought-provoking tour of the frontier where speculative mathematics meets fundamental questions about why our universe looks the way it does.

Key takeaways

• Extra spatial dimensions may be tightly rolled up like origami, and string theory needs them to make sense.
• Maybe we're stuck to a 3D membrane, and the extra dimensions aren't small at all, just out of our reach.
• Why three spatial dimensions got big while the rest stayed small remains one of physics' best unanswered questions.
• Gravity is the only thing that can travel through the 'bulk,' making gravitational waves the hypothetical cosmic mailbox.
• If nature can try something mathematically possible, it probably has, which hints at a multiverse full of other universes.

What is discussed, and when

1. 0:00 – 3:00: Big Bang, Dark Energy, String Theory
2. 3:00 – 6:00: Multiverse
3. 6:00 – 9:00: Exoplanets, Milky Way Galaxy
4. 9:00 – 12:00: Jellyfish, Dinosaurs
5. 12:00 – 15:00: Entropy, Multiverse
6. 15:00 – 18:00: Big Bang, Carbon, Sulfur

Notable quotes from "Dimensions of reality beyond spacetime | Janna Levin and Lex Fridman"

• Quantum exitations that look a lot like dark matter. It's kind of an interesting idea that in the Big Bang, the universe was born with lots of these dimensions.

  about Big Bang · at 1:12

• Try it out. Yeah. which is how people get into the strange territory of talking about a multiverse.

  about Multiverse · at 3:07

• Happening right now in the past 30 years in astronomy looking at real objects is that the number of planets, exoplanets outside our solar system has absolutely proliferated.…

  about Exoplanets · at 7:06

• Because that's a pretty big bar. So if you look at the just to say for a comparison dinosaurs you know 250 million years I mean maybe not very bright didn't invent but fire didn't write sonnets they didn't contemplate the.

  about Dinosaurs · at 10:38

• Very long lived, very longived. and have very different states of consciousness. They have the jellyfish does not even have a localized brain.

  about Jellyfish · at 11:26

• It does something interesting in quotes with information. I think there are arguments like that. how entropy is changing from the beginning of the universe to today. How life…

  about Entropy · at 13:40

• Earth, but it's probably even more complicated elsewhere where the chemistry could be anything. Carbon is really cool and really useful because it finds a lot. It's nice. It finds a lot of ways to combine with other things.

  about Carbon · at 17:37

Who and what is mentioned in this episode?

Concepts & topics

• Entropy — Concept · 4 mentions · first at 13:46
• Big Bang — Concept · 2 mentions · first at 1:18
• Multiverse — Concept · 2 mentions · first at 3:12
• Jellyfish — Concept · 2 mentions · first at 11:32
• String Theory — Concept · 1 mention · first at 0:36
  Tightly rolled up dimensions. not all of them, not all the models require that they're small, but most do. String theory requires extra dimensions to make sense. But even if…
• Dark Energy — Concept · 1 mention · first at 1:00
  Dimensions. And we think that they can trap little quantum energies in such a way that might align with the dark energy. And the numerology is not perfect. It's a little bit…
• Exoplanets — Concept · 1 mention · first at 7:12
• Dinosaurs — Concept · 1 mention · first at 10:43
• Carbon — Concept · 1 mention · first at 17:39
• Sulfur — Concept · 1 mention · first at 17:57
  Can't have a very simple linear chain and expect to get life. But I don't know, maybe sulfur would do okay.
• Electroweak Theory — Concept · 1 mention

Places & events

• Milky Way Galaxy — Place · 1 mention · first at 7:20
  Outside our solar system has absolutely proliferated. There are probably more planets in the Milky Way galaxy than there are stars. And now we have a real quandry. Not I don't think it's quandry.

Full transcript with timestamps

0:02 So when you mentioned discovering extra dimensions, what do you mean? What could that possibly mean? Well, we we know that there are three spatial dimensions. We like to talk about time as a dimension. We can argue about whether that's the right thing to do, but we don't know why there are only three. It very well could be that there are extra spatial dimensions that there's like a little origami of these tightly rolled up dimensions. Um, not all of them, not all the models require that they're small, but most do. String theory requires extra dimensions to make sense. But even if you uh feel very um hostile towards string theory, there are lot there are lots of reasons to consider the viability of extra dimensions. And we think that they can trap little quantum energies in such a way that might align with the dark energy. And the numerology is not perfect. It's a little bit subtle. it's

1:07 hard to stabilize them. Um, it's possible that there are these kind of quantum exitations that look a lot like dark matter. It's kind of an interesting idea that in the Big Bang, the universe was born with lots of these dimensions. They were all kind of wrapped up in the early universe. And what we're really trying to understand is why did three get so big and and why did the others stay so small? Is it possible to have some kind of natural selection of dimensions kind of situation? There is actually and people have worked on that. Is there a reason why it's uh easier to unravel three? Some people think about strings and brains wrapping up in the extra dimensions causing a kind of constriction but preferentially loosening up in three. Um, sometimes we look at exactly models like that which have to do with the origami uh being resistant to change in a certain way that only allows three to unravel and

2:07 keeps the others really taught. But then there are other ideas that we're actually living on a three-dimensional membrane that moves through these higher dimensions. And so the reason we don't notice them isn't because they're small. Maybe they're not small at all. But it's because we're stuck to this membrane. So, we're unaware of these extra directions. Is it possible that there's other intelligent alien civilizations out there that are operating on a different membrane? Is is this a bit of an out there question? But I I ask it more kind of seriously like is it possible do you think from a physics perspective to exist on a slice of uh what the universe is capable of? I think it is certainly mathematically possible on paper to imagine a higher dimensional universe with more than one membrane.

3:03 And if things are mathematically possible, I often wonder if nature will try it out. Yeah. Um, which is how people get into the the strange territory of talking about a multiverse. Because if you start to say one of the aspirations was in the same way that we identified the law of electroeak theory of matter that it was a single description and exactly um landed on the description that matched observations. People were hoping the same thing would happen for a kind of theory that also incorporated gravity. there would be this one beautiful law, but instead they got a proliferation, all of which did okay or did equally badly. Um, they suddenly had trouble finding not only finding a single one, but sort of that would just beg a new question, which is, well, why that one? And if if nature can do something, won't she do anything she can try? And so maybe we really are just one example in an infinite sea of

4:05 possible universes with slightly different laws of physics. So if I can do some of these things on paper, like imagine a higher dimensional space in which I'm confined to a brain and there's another brain or maybe a whole array of them. Maybe nature's tried that out somewhere. Maybe that's been tried out here. Um, and then yes, is it possible that there's life and civilizations on those other brains? Yeah, but we can't communicate with them. They'd be like in a shadow space. Can you seriously say we can't communicate with them? No, that's fair.

4:39 I there I'm limited in my communication cuz I'm glued to the brain. But some things can move. We call the bulk through the bulk. Gravity for instance, a gravitational wave. So I could design a gravitational communicator communication system and I could send gravitational waves through the bulk and how STEI is doing with light into space. I could um send signals into the bulk nice telling them where we are and what we do and of course singing songs. Sending gravitational waves is very expensive. We don't know how to very expensive very hard to localize. They tend to be long wavelength and very hard to do. lot of energy moving around. A lot of energy. Uh, so is it possible that the membranes are quote unquote hairy in other ways like some kind of weird? It is possible that there's other things that live in the bulk. I mean, last night I was calculating away looking at something that lives in the

5:33 bulk. Okay, this is fascinating. So, I mean, okay, can we take a little bit more seriously about the the whole when I look out there at the stars? Mhm. I from a basic intuition cannot possibly imagine there's not just alien civilizations everywhere. Yeah. Life is so damn good. Like you said, nature tries stuff out. Yeah. Nature is an experimentter. And I just can't just basic sort of uh observation life uh you said somewhere that you like extreopiles life just figures out. It just finds a way to survive. Now there could be something magical about the origin of life, the first spark, but like I can't even see that it's over and over and over. I bet actually once once the story is fully told and figured out, life originated on Earth almost right away and did that so like billions of times uh in multiple places just over and over and over and over. Uh that seems to be the thing that just whatever is the life

6:43 force behind this whole thing seems to uh seems to create life seems to be a creator of different sorts. Yeah. the the the very from the very original primordial soup of things. It just creates stuff. So, I just can't imagine, but we don't see the aliens. So, right. Yeah. We don't even have to go to something as crazy as extra dimensions and brain worlds and all of that. What's happening right now in the past 30 years in astronomy looking at real objects is that the number of planets, exoplanets outside our solar system has absolutely proliferated. There are probably more planets in the Milky Way galaxy than there are stars. And now we have a real quandry. Not I don't think it's quandry.

7:27 I think it's really exciting. It becomes impossible. What you just said, I totally agree with. It becomes impossible to imagine that life was not sparked somewhere else in our Milky Way galaxy and maybe even in our local neighborhood of the Milky Way galaxy, maybe within a few hundred lighty years of the Milky of of of our solar system. So my my my gut says like some crazy amount of uh solar systems have life bacterial life somewhere at some point in their history had some bacterial type of life something like bacterial maybe it's totally different kinds of life so then I'm just facing with a question it's like why have we not clearly seen alien civilizations and there the answer I I just I I don't find any great filter answer convincing. There's just no way I can imagine an advanced alien civilization not avoiding its own destruction. I can see a lot of them getting into trouble. I could see how we

8:29 humans are really like 50/50 here. Well, isn't that kind of appalling? I mean, just take that statement. We've only been around for like I mean couple hundred thousand years tops, you know? Um, that is not very long and we're at a 50/50. I mean, that's unbelievable. I mean, it's indisputable that we have created the means at least potentially for our own destruction. Will we learn from our mistakes? Will we avert course and save ourselves? One hopes so, right? But but even the concept that it's conceivable whales have not invented a way to kill themselves to wipe out all whales and earth and life on earth.

9:12 That's one way to see it. But I I actually see it as a feature not a bug when you look at the entirety of the universe because uh it does seem that the mechanism of evolution constantly creates you want to operate on the verge of destruction. It seems like I mean the predator and prey dynamic is really effective at creating a at accelerating evolution and development. It seems like us being able to destroy ourselves is a really powerful way to give us a chance to really get our together and to flourish to develop to innovate to to uh go out amongst the stars or 50/50 destroy ourselves. But like, which I think me as a human is a horrible thing.

9:56 But if there's a lot of other alien civilizations, that's a pretty cool thing. You want to give everybody nuclear weapons, half of them will figure it out, half of them won't. And the on everyone all these civilizations, all these civilizations, and then the ones that figure it out will figure out some incredible technologies about how to expand, how to develop, and all that kind of stuff, right? You could use a kind of evolutionary Darwinian natural selection on that where in survival isn't just in a harsh naturally induced climate change but is because of a nuclear holocaust and so but and then and then something will will be created that is now impervious to that that now knows how to survive. Yep. Exactly. So why haven't we seen them? Right. Well because that's a pretty big bar. So if you look at the just to say for a comparison dinosaurs you know 250 million years I mean maybe not very bright

10:52 um didn't invent but fire didn't write sonnets they didn't contemplate the origin of the universe but they they lived and um in a benign situation without confronting their own demise at their own hands pause um so It's just a sheer numbers game. That's a long time, 250 million years. I do think though that life can flourish without wanting to manipulate its environment. And that we do see many examples of species on Earth that are very long lived, very very longived. Um, and have very different states of consciousness. They have the jellyfish does not even have a localized brain.

11:37 Um, I don't think they have a heart or blood. I mean, they're really different from us. Okay? And that's what I think we have to start thinking about when we think about aliens. Those, uh, species have lived for a very, very long time. They even show some evidence of immortality. You can wound one badly, and there are certain jellyfish that will go back into a kind of pre-state and start over. So, I think we're very attached to imagining creatures like us that manipulate technology. Um, and um, and I think we have to be way more imaginative uh, if we're going to really take seriously life in the universe. Yeah.

12:15 They might not prioritize conquest and expansion. They might not be violent. Mhm. They might not be violent like us humans. They might be solitary. They might not be social. They might not move in groups. They might not want to leave records. Um, uh, they might again not have a localized brain or have a completely different kind of nervous system. I think all we can say about life is it has something to do with moving electrons around and um, like neurologically we move electrons through our nervous system. Our brain has electrical configurations. We metabolize food and that has to do with uh getting energy, electrical energy in some sense out of um what we're eating. You know, we have organisms on the earth that can eat rocks. It's quite amazing. Minerals. I mean, talk about extreophiles. They can metabolize things that I would have thought uh were impossible to metabolize. And so, again, I think we we

13:15 have to kind of open our minds to how strange that could be um and how different from us. And we are the only example even here on earth that that does manipulate its environment in that extreme way. I mean can you think of life as cuz you said electrons is is there some degree of information processing required? So like it does something interesting in quotes with information. I think there are arguments like that. um how entropy is changing from the beginning of the universe to today. How life uh lowers entropy by organizing things but it costs more as a whole system. So the whole entropy of the whole system goes up. But um but of course I I organized things today and reduced the entropy of certain things in order to get up and get here. um and even having this conversation organizing thoughts um out of the cloud of information but it comes at the cost of the entire system increasing um entropy. So I do think

14:23 there's probably a very interesting way to talk about life in this way. I'm sure somebody has. Yeah. Yeah. It creates local pockets of low entropy. And then the kind of mechanism, the kind of object, the kind of life form that could do that probably can take arbitrary forms. And you could think now if you could reduce it all to information now, you could start to think about physics. And in the realm of physics with with the multiverse and all this kind of stuff, you could start to think about, okay, how do I detect those pockets of low entropy? Mhm. Yeah. I mean, people have tried to make arguments like that. Like, can I look for entropic arguments that might suggest we've done this before? The big bang has happened before. So, is it possible that there's some kind of physics explanation why we haven't seen the aliens? Like we said, membranes. I don't think membranes is going to explain why we don't see them

15:21 in the Milky Way. I think that is just a problem we're stuck with. whether or not there are extra dimensions or whether or not there's life in another membrane. Um I think we know that even just in our galaxy which is a very small part of the universe um 300 billion stars something like that a whole kind of variety of possibilities to be explored by nature in the same way that we're describing. And I think you're absolutely right when when life was kicked off first sparked here on Earth it was voracious. Now, it took a really long time though to get to multisellularity. I think that's interesting. That's weird. It's weird.

15:59 It took a really really long time to become multisellular. But it it did not take long just to start. Yeah. What do you think is the hardest thing on the chain of leaps that got to humans? I would say multisellularity, which is strictly an energy problem. I I think again it's just like can electrons flow the right way? Uh and is it energetically favorable for multisellularity to exist? Because if it's energetically expensive, it's not going to succeed. And if it's energetically favorable, it's going to take off. It's really just and that's why I also think that going from inanimate um to animate is probably gray. Like the transition is gray. At what point we call something fully alive? Famously, it's hard to make a nice list of bullet points that need to be met in order to declare something alive. Is a virus alive? I mean, I don't know. Is a pron alive? Those are They seem to do some things, but they kind of rely on

17:16 stealing other DNA and replicating. And I don't know. I guess they're not alive. But I mean, the point is is that it really at the end of the day, I really think it's just You asked if it's just physics. I mean, I think it's just this these rules of energetics. And the gray area between the non-living and the living is way simpler just on Earth. And you said it's already complicated on Earth, but it's probably even more complicated elsewhere where the chemistry could be anything. Carbon is really cool and really useful because it finds a lot. It's nice. It finds a lot of ways to combine with other things.

17:49 And that's complexity. And complexity is the kind of thing you need for life. You can't have a very simple linear chain and expect to get life. But I don't know, maybe sulfur would do okay.

Questions about this episode

What is "Dimensions of reality beyond spacetime | Janna Levin and Lex Fridman" about?

In this conversation, physicist Janna Levin and Lex Fridman explore whether extra spatial dimensions beyond our familiar three might exist, perhaps tightly curled up like origami or as a three-dimensional membrane floating through a higher-dimensional "bulk." They examine why only three dimensions appear to have "unraveled," how string theory and multiverse ideas fit in, and whether other…

What is mentioned in this Lex Clips episode?

12 people, works and ideas are mentioned, including Entropy, Big Bang, Multiverse, Jellyfish, String Theory, Dark Energy. Each one on this page links to its own page with every episode that mentions it.

How long is "Dimensions of reality beyond spacetime | Janna Levin and Lex Fridman"?

The episode runs 18 min; the transcript is about 2,922 words in 21 timestamped sections.

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