"Today I'm chatting with Adam Brown, who is  a founder and lead of the Blueshift team,   which is cracking math and reasoning  at Google DeepMind, and a theoretical   physicist at Stanford. Adam, welco..."

"is super duper bad news. It's really bad news  because the accelerated expansion of the universe   is dragging away from us lots of distant galaxies.  And we really want to use those galaxies.  We hav..."

"It is not just totally fixed once and for all that  in fact, you have what's called different vacuum,   different regions of parameter space  that you can transition between,   in which the cosmologic..."

"constant. And so what we'd want to do is  engineer that we end up in one of those vacuums.  Sorry, what is a vacuum? Ah, great question. A vacuum is   like a possible, well, what we would perceive as ..."

"and so maybe a good analogy would be water. Water can exist in many phases. It can be steam,   it can be water, it can be ice. And even if  it's in a cloud, let's say it would rather   be water than b..."

"Again, this is speculative, but it's  not super duper crazy. It's a natural   consequence of our best theories, or at least  some of our best theories of quantum gravity,   that they allow for this po..."

"like there was a fission reaction that  naturally happened. It didn't explode,   but it did do the same thing that  happens in our nuclear power plants.  One way you can look at nukes is like, this  t..."

"our understanding of quantum mechanics, if  they're permitted, they must eventually happen.  Furthermore, there are again speculative,  but not wild theories of the early universe   in which this happ..."

"Then do our future descendants have any  constraints in terms of... Because earlier   we were mentioning, as a catastrophe, we found  out about the cosmological constant because it   limits our cosmic..."

"of the universe is exponentially increasing.  So you can imagine a scenario in which there   was a high cosmological constant. You have a bubble universe that has   a lower value of the cosmological  ..."

"It's an active area of research how to combine  quantum mechanics and expanding universes.  On the other hand, it seems pretty natural  when you do combine quantum mechanics and   gravity and try and ..."

"could imagine really adverse laws of physics  in which maybe you could speculatively build   some power plant that just really makes use of  sitting on that edge of instability. And then   each person..."

"I feel like that the most sort of a churchy phrase  physics can occur is "your proposition is not   inconsistent with the known laws of physics." Not this.  If we lived in a world of intelligent desig..."

"all the way to structure at the scale of galaxies. There's interesting structure at all levels. This   is a very interesting fact. Now, some people  think that actually interesting structure is   a ve..."

"in the kind of universe we find ourselves in? I think it's going to depend on what quantity   you're asking me about. So if you ask me, you  know, 99% of the matter in the solar system   lives in the ..."

"existence of these variables scanning over space. Is there some way for the anthropic principle to   exist that doesn't involve these bubble universes? Yes, all you need is that there are different   ..."

"necessary for life as we know it to exist. How confident are we that these different   properties of different universes would  actually be inconsistent with intelligent life?  That's a great question..."

"I think I basically buy that life is quite  adaptable, but whether life is adaptable   enough that a universe with a cosmological  constant that ripped it apart every microsecond,   that seems implaus..."

"So then there's an easy part and a hard part.  The easy part is understanding how if you have   very small inhomogeneities, how they grow into  large inhomogeneities. That's already quite well   under..."

"all the galaxies, you, me, everything else. Is it a meaningful question to ask what   level of structure each individual discrepancy  corresponds to, each individual 1 in 10^5 part?   Is it a galactic..."

"in terms of observational evidence, no strong  observational evidence for those, but those   are a possibility. That's allowed by our theory,  and people think about them and look for them.  What make..."

"What makes General Relativity so beautiful? I think general relativity is really an   extraordinary story. It's pretty unusual  in the history of physics that you,   to first approximation, just have ..."

"And it sometimes gets into a definition game. But this is maybe a good way to test our   intuitions here. The kind of thing that Einstein  was doing, where you start off with some thought   experiment..."

"day, week by week, year by year. Looking at it,  it certainly looks like these LLMs and these AI   systems in some sense are just interpolators,  but the level of abstraction at which they're   interp..."

"will have fully encompassed human intelligence. Will it be of the same character as what Einstein   did? Clearly, there are many disanalogies between  human intelligence in these large language models..."

"problem out of it and solve that problem. Do you think AI mathematicians,   AI physicists will have advantages over  humans just because they can by default   think in terms of weird dimensions and ma..."

""I have this idea, what are some relevant  papers?" They're great at that, and semantically   greater than any other kind of search. The other thing that they're extremely   useful for now that they w..."

"chess players today are much better even when  they're playing across the board without the   benefit of a computer, just having been  able to be tutored by chess machines off   the board. This is the..."

"Yes, they definitely have different strengths and  weaknesses than humans. And obviously one of their   strengths is that they have read way more than  any human will ever read in their entire life.  ..."

"incorrect. So, why do we use this particular  form of quantum light in interferometers   used to discover gravitational waves? The reason that's a good topic is perhaps because   it's an advanced topi..."

"which is definitely a higher grade than I  got. And so I'm already below the waterline.  But you teach a bunch of subjects,  including general relativity at   Stanford. I assume you've been querying t..."

"final exam. That's just in the last couple  of months that these have been doing that.  What is required to ace a test? Obviously,  they probably have read about all the   generality textbooks, but I ..."

"better at another thing across all domains. It is possible to make a model that is really,   really, really good at one very particular thing  that you care about. And then at some stage,   there is s..."

"of... These astronomical observatories  are incredibly expensive. If we can just   have a computer better parse all of the data  from them in a way that no human ever could,   that would be a tremendo..."

"One challenge in that would be, how do you  evaluate whether you had a good theory at   the end? That's going to be the tricky bit. For things that are most easily parallelized   are things in which, ..."

"So it wasn't. Why does one theory replace  another? One reason is obviously that it's   more consistent with the data, but  that's by no means the only theory.  And if you just optimize for being cons..."

"Even if we did someday get superhuman intelligence  that could try to find all the remaining sort   of high-level conceptual breakthroughs, how  much more room is there for that? Basically,   was it j..."

"new ways of understanding the universe. Do you have some hot take about why the   current physics community hasn't—I mean,  cosmology is maybe a very notable exception,   where it does seem like the e..."

"by a lot. So that's just academics pooling  their money. That's an interesting fact.  They got so expensive that it's difficult  to persuade people to buy a new one for   us that's even bigger. It's a..."

"What is the value of seeing these  primordial gravitational waves?  Oh, it gives you hints. You're just examining  the night sky very closely and seeing hints of   what happened at the Big Bang. This ..."

"Most of our confidence about modern cosmology  comes from a number of experiments that,   starting in the '80s but accelerating in  the 2000s, really very carefully measured   that anisotropy and allo..."

"All right, Adam, what are  your tips for hitchhiking?  Oh, good question. So I hitchhiked a bunch around  America and Europe. I've done Oxford to Morocco,   when I moved from Princeton out to Stanford..."

"Any particular examples of the wildest things? Oh, yeah, huge. I mean, it's just   absolutely a fire hose of wild things  happening. I could tell so many stories.  I remember once there was a trucker ..."

"It was quite a high pathos moment. And  then said, uh, this happened before.  And it turned out he'd previously been scammed  in the same way or a similar way through somebody   he'd met through the s..."

"were going along that they were, uh, they had,  they were actually just teenagers and I didn't,   somehow didn't clock that when getting in the car.  And they, they had stolen the family car and were,..."

"In many ways, people will tell you things. Frequently people will say things like, "I've   never told anybody else this in my life before."  That's common, not just the truckers, other   people as wel..."

"Any other tips that somebody should know?  I mean, should they do this anymore,   given that it's largely uncommon and so  uncommon types of people might pick you up?  I think it used to be very commo..."

"another trick. I've never had to deploy that. Oh, I was just about to ask.  No, I've never had to deploy that. Typically,  it's pretty, there's a moment of anxiety in the   first minute. But then afte..."

"library, and I just started reading some books  in the library during deep lockdown. There was   some sort of enigmatic statement in  some book about the history of Japan.  Where do you stay that your..."

"they saw a hole in the clouds. I don't think I  believed them." So that was, I think, one of the   hints. It was maybe reading his autobiography  at some stage, that was one of the big hints.  The oth..."

"Nobody who was on the plane said that  they faked the hole in the cloud story,   but some people who were on the plane said they  were determined to drop the bomb no matter what,   and they were highl..."

"That's right. There's the good kind, where they maybe   should drop the bomb according to their orders  and refuse to, and then there's the other kind.  I also want to ask, so you've had not only one ..."

"to change the world, hopefully for the better, to  such a large degree that that's much bigger than   potentially all the physics papers you ever wrote. That's interesting you say that about,   you fe..."

"Really? Well,   in the narrow domain of high-energy theoretical  physics. There are many more physicists than   that if you include people more generally, but  they're sufficiently specialized. I mean..."

"or many of them. Where we're at now is  the good ideas that look like bad ideas.  So in order to motivate yourself to get over  the hump, get over the barrier, and actually   explore them, you need a ..."

"Another topic I know you studied a lot  is how one might mine a black hole.  Oh yeah, right. I read a  paper about that. Very good.  Tell me about it. Okay, so what do we mean   by "mine a black hole?..."

"Any rope, in fact, that has that, or  an example of a rope that has that,   is a string. So a string is, I mean, a fundamental  string from string theory is an example of a   hypothetical rope that is..."

"Something would be violated that tells  us something important about black holes,   that they can't be mined, and it's deeper  than the tensile strength of the string   that would be required to mine ..."

"and that is what's called the baryon number. So  it's the total number of protons plus the total   number of neutrons. You can transmute protons  into neutrons or vice versa in nuclear processes,   wh..."

"of the entire gas you're putting in. Although, if you consider our cosmic   endowment, we're not exactly lacking for mass. We have a lot of mass. On the other hand, we also   have plans for our future..."

"Well, it turns out that that's been an incredibly  productive line of thought. And it also turns   out that that is the main fact that we're  most confident about about quantum gravity.  So the two gr..."

"mathematically and physically consistent manner. It's tricky, in part because there's very little   experimental guidance because general relativity  tends to make itself felt at large scales,   quant..."

"do with quantum gravity because  it involves both G and H bar.  Is that the only situation in physics where both  of those constants end up being in the same place?  That is not the only situation. No..."

"that that's such a wild answer, and an answer  that's led to all sorts of thought experiments   to do with quantum gravity ever since then, is  that you might naively think that the amount of   inform..."

"will be bigger than the bound that I just said. Therefore, I've ruled out Hawking's, Penrose's,   and Bekenstein's bound. What goes wrong with  that thought experiment is that eventually,   if I make ..."

"Got it. Okay, sorry. I didn't  mean to interrupt. And then you...  So that's the information storage in black  holes. The reason you know that that's also   the information storage bound for anything,..."

"the information storage would scale like the  volume, as we discussed. Whereas in fact,   it scales like the area. Another way to say  that is if you take a three-dimensional,   three-plus-one-dimensi..."

"it in one fewer dimension. And so this led to  Maldacena's ADS/CFT correspondence, the gauge   gravity duality, which was the most  cited paper in high-energy theoretical   physics ever, I think, mayb..."

"don't have gravity than we do on theories that  do have gravity. So, it puts everything on a much   clearer footing to have this non-gravitational  description, because then you can just use the   sta..."

"people have been trying to formulate versions of  it which have a positive cosmological constant.  It's difficult. Part of the difficulty  goes all the way back to Archimedes:   it is easiest to formu..."

"they're perfect simulations of each other. Are you an AdS dreaming you're a CFT,   or a CFT dreaming you're an AdS? I think these  are just two completely different, inequivalent   descriptions of the..."

"real than the other. Things do not need to be  spatially localized. You separately asked, what   would a version of "where is the boundary theory?"  in de Sitter space, since there's no boundary?  Tha..."

"many other universes that are located,  or whose center is located, elsewhere.  Absolutely. A cosmological horizon is very  different from a black hole horizon in   this regard. A black hole horizon  ..."

"Good question. I think I'm going to say yes and  no. I mean, it's clearly, if correct, let's just   take the quantum case, which is perhaps even more  secure than the cosmological multiverse case.  In..."

"Nevertheless, I do kind of understand that you  might have a portfolio theory that seems to be   inconsistent with Born's rule, but is somehow  intuitive, in which somehow it's not just a   linear fun..."

"two populations of some possibly extinct animal. It's also the case that this is a pretty like   Born's rule, narrowly defined, does not  really have anything to say about this how   one should calcul..."

"It's a little bit confusing because in one  context, we're laying out very practical—I   don't know if you can call black hole batteries  practical—but very tangible limitations on the   what future, ..."

"efficiency of batteries and extracting energy. MC squared is the—I'm highly confident that the   most energy you can extract from a given piece  of matter is MC squared, at least until you start   get..."

"One question you might have is: What will be the  nature of not only the things that our descendants   might care about, but what will they be able  to produce domestically? What will they want   to t..."

"you think is just the end result of computations  or confirmation that a computation has been   made? Maybe it's like simulating hedonium that the  other side of the galaxy cares about or something.  ..."