Daniel and Jorge Explain the UniverseDaniel and Jorge talk about the chance that you could be a brain floating in space.
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Hey Orge, did you ever think about the odds of you existing?
My existence is pretty odd, so one hundred percent.
Well, I'm sure that you exist right now, but you know, go back one hundred years. What are the chances that everything would align to make orge?
Oh, man, I think I'm pretty special, so probably pretty low.
Exactly, so many things had to happen in just the right way for.
You to be here, right, it seems astronomical that I would be.
Here, Yes, and yet you are here. So sometimes unlikely things actually do happen.
Maybe one hundred years from now, you'll be listening to David and Juan explain the universe instead. I am more hamming cartoonists and the creator of PhD comics.
Hi, I'm Daniel. I'm a particle physicist, and I like to think about really unlikely events.
Oh yeah, like us getting a podcast.
Yeah, or two protons colliding to make a Higgs boson, which happens like one in a trillion collisions.
But those are important, right, Like when it happens, it's a pretty big deal.
Exactly when it happens, it's exciting. It teaches us something about the universe and also thinking about these rare things. Thinking about the extremely unlikely events tells us something about like the nature of the universe, what's possible and what's actually zero percent possible?
Does it also sort of teach you a little bit about perseverance, like if you try enough times, you should eventually be able to do anything.
Yeah, and it helps to persevere because our collider operates at like millions of times second, so you don't have to wait that long to get a trillion tries.
Are you saying that your collider this is several million times a second.
No, it makes collisions every time, it's just those collisions are usually boring. Not much exciting happens on your average collision at the LHC.
I see, so it basically it has like a zero point zero zero zero zero zero zero one RBI.
Yeah, exactly. We actually throw away most of the data from the Large Hadron Collider because it's boring.
But anyways, welcome to our Unlikely podcast. Daniel and Jorge Explain the Universe, a collection of iHeartRadio.
In which we focus on that tiny little bit of the universe that's amazing, that's exciting, that's wondrous, that's confusing. We talk about all the things that are out there in the universe that you want to fit into your brain. You'd like to understand how neutron stars work. You want to know how the galaxy form. You want to understand it from particles all the way up to super clusters of galaxies. So you've come to the right place because we take the entire universe and explain all of it to you.
Because it is a pretty huge universe. I mean, it's vast, and it's full stuff in it and energy, and it seems like there are amazing things happening and existing all over the place, and makes you wonder how likely it is for them to be there or not?
Yeah, exactly, And we can't go to all those places, and we can't even see all of those places. So sometimes we're limited to like mental explorations, to take journeys in our mind and wonder, like, is it possible at somewhere out there there's another planet with similar kinds of people on it listening to a even funnier podcast.
I wonder what their names are. But yeah, it's sort of like taking a mental vacation, except you actually do it for work. It's like you take a mental work trip.
Yeah, it's called the thought experiment.
How do you expense that in your accounting?
Fortunately they're mostly free, right, there's no plane tickets, there's no risk of catching a virus. It's a great way to do some work.
Can you fly first class? Though? Is that allowed in your government grant? They have to see it uncomfortably while you have your thought experiments.
No, that's the best part is that it looks exactly like you're taking a nap. So if I rememver caught by my department chair napping on my couch, I'll just say no, No, I was doing thought experiments. I was working.
I was having physics dreams. I guess that counts right. It's work for you, yeah, absolutely.
No, No, it's a real privilege to get to like think about the nature of the universe for your job, so I definitely relish and enjoy that.
Well, it is a crazy universe, which I guess requires some crazy thinking to understand it, explore it, and come up with interesting explanations for it.
Absolutely, we like to do these crazy thought experiments. And you know, I was thinking about the kinds of things we think about happening in the universe, crazy shock waves on all sorts of bizarre stuff. And I got an email from a listener just yesterday who asked me this funny related question. This is dev Kindlewall, and he says, what do you think is the scariest thought in the universe. So I was wondering what you thought about that.
Whoorge, the scariest thought in the universe. Oh, like the one that would shock people the most. Yeah, exactly what did you reply? I said, I would ask Korge next time we record a podcast. Let's see, let's see that the universe would run out of bananas.
A zero banana universe. I don't think that's possible. Quanta mechanically.
Well, there you have it. I can sleep easier at night, or I can take naps much more comfortably.
Now, all right, so there you go, dev you don't have to worry about scary universes. Quantum mechanics protects the number of bananas in the universe.
So we got another interesting question from a listener, this time about a pretty crazy thought experiment.
Yeah, that's right. We're always getting questions from listeners who are thinking themselves about crazy stuff in the universe and wanted to hear us chat about it. So here's a really fun question we got from Roselle, Santos, Hi, Danian.
And Jorge. I have a question about Boltzmann brains. I read that they are hypothetical self aware, disembodied brains floating around in the universe. But why would serious physicists hypothesize about disembodied brains floating around in the universe. It sounds shocking and absurd to me that I'm excited to know more about it. Love the pod. Thank you.
Wow, that was a pretty interesting question. There so much to pokemon app physicists.
I know. I love that she assumes that there are serious physicists out there.
Yeah, there's a difference. Like there's two kinds, right, There's the clowny kind, and then there's this serious kind, you know, the kind that wears bow ties and the kinds that wear both ties with colors in it.
Right, they kind of do actual work, and the kind of just do podcasts with cartoonists.
It's now, those are the seriously cool physicists.
Right, That's why I'm wearing my clown shoes over here.
But thank you Rosell for sending in this question, and thank you to all our listeners who send those questions. So it's cool to get ideas from you.
Absolutely, And this sounds like a ridiculous and absurd idea, but it's actually a very useful and powerful tool in cosmology. Thinking about this question about brains forming in space.
I see, it's a serious question.
It's a serious question about a silly idea.
That's my favorite kind. So to be on the program, we'll be asking the question can a brain spontaneously form out in space? What? What does this even mean? Like a brain just suddenly appears completely out of the blue.
Well, you can't just like violate the laws of physics and just like appear out of nothing. You have to find a way in the laws of physics for a brain to like self assemble out of the stuff that already exists, or for particles to fluctuate out of the vacuum and come together into a brain.
I agree with Roselle, this sounds both shocking and absurd to me. How can you be serious about this?
You can quantify it, right, you can lay down exactly the probability for this to happen or not happen.
All right. So the idea is that I guess to kind of called the Boltzmann brain.
Yeah, it's the Boltzmann brain. It's named after lud Big Boltzmann, who first thought about weird probabilities. Because he was one of the pioneers of statistical mechanics, which thought about entropy in terms of like microscopic little particles.
So it's not his brain. It's like he came up with this idea of a hypothetical brain.
He actually didn't come up with this specific idea of Folks later realized that this is an outcome of some of his arguments. But yet it all goes back to the question of, like, what universe do we live in? Do we understand it is the universe that we're looking at, one that we expect to see, how unlikely is it? And if the universe is unlikely, does that mean that we're totally wrong about what we're actually looking at.
Wow, some pretty big ideas there to be fit into a little brain. So I guess the basic concept is that, you know, the universe is crazy. There are things popping into existence all the time and forming and bumping into each other, and so what are the chances that suddenly things would just form a brain out in space? Right?
That's right, like for.
A long time, for momentarily or does it matter.
Yeah, it would be momentarily, And then the question of you know, how long it survived depends on you know, does it also fluctuate in new existence with the body around it and with a planet around it? Or is it just like literally a brain out in space, which, as you suspect, wouldn't last very long.
It would turn into brincicle pretty quickly there, unless it forms in the middle of the sun.
That would be tragic, roasted toasted brain. Maybe that's the scariest thought in the universe.
Oh man, that your brain, like who exists for second in the sun before you die?
All and that start it's pretty bright.
Actually, well it's a pretty crazy question, pretty serious but crazy question. And we were wondering, as usual, how many people out there had heard of this idea, this hypothetical brain, or even think that it is likely. So, as usual, Daniel went out there into the internet to ask people what are the chances that a brain would spontaneously form in space?
And so, as usual, I'm deeply, deeply grateful to those of you who volunteered to answer random questions and lend your unprepared thoughts to the podcast. If you'd like to volunteer in the future, please I encourage you. You get to hear your own voice on the podcast, and trust me, it's fun. So write to me to questions at Danielandjorge dot com.
There's a whole protocol, right, like you ask people to not read the question, but start recording, and then you ask them to read the question right, and then they have to answer.
Yeah, exactly, no googling. I'm trying to capture the same energy and spirit that we had when I was just walking around campus that you see er run before the world sort of shut down and those folks didn't get like a chance to look on their phone or go think about it or ask their favorite physicists. Because the goal here is just to get a sense for like, hey, what do people know? What do people understand already? Because you know, we're trying to teach this stuff to you guys out there, and we want to get a sense for what level to pitch it at.
Do people run away from you? Also on the internet, do they call campus police?
Also, they don't give me as many weird looks on the internet as they did in real life, which is kind of surprising.
That you know they're probably rolling their eyes. You never know.
Well, I hope they have fun with it at least.
But anyways, think about it for a second. Do you think a brain could spontaneously form out in space? Here's what people had to say.
That's a really interesting question. I think I've heard of it before. It's maybe the Boltzmann brain. My understanding is that if the universe is infinite, then such a brain has to form somewhere at some time. But I still find that really hard to believe.
I don't know how many random atoms if there's like an infinite supply, then well, it also depends on what type of brain. So if it's something less complex like the brain of an ant, I'm guessing maybe one intend to the five. But it's more sophisticated, like a human ruin, maybe one intend to the fifty. I don't have a real basis for these guesses, so.
I think that the chances of a brain spontaneously forming from random atoms is not that low. I could totally see it happening because atoms are the building blocks for matter, So if it didn't happen already, I could definitely see it happening in the future.
Oh my god, Well, I would never say that absolutely, there's no chance for that to happen. But even if it would happen, where would this form and how long would last? But it is interesting. Chances are I don't think it matters to calculate the chances, but push, sure, there are some chances.
I finally got a question and I know the answer to I just finished reading Brian Greens Until the End of Time, and I know that a Boltzman brain could form within ten to the ten to something years, which is at least less than the amount of time left in the universe.
So people are pretty skeptical.
Well, I was surprised a lot of people knew what you were talking about. They're like, oh, yeah, the Boltzman brain. Of course, who doesn't know about the Boltzman brain.
Yeah, Well, we got smart, well educated listeners, and you know, Boltzman brain is a thing that's been sort of bouncing around for quite a few decades.
And people seem pretty open to the idea, right, Like they didn't think like, no way.
Yeah, they're more open to it than you were when you heard about it a minute ago.
I am maybe odd about these odds, all right, So it's a pretty interesting idea. So tell us, Daniel, what are the chances that a brain would spontaneously appear and how would it happen.
Yeah, well, the odds are very very very very very very small, but technically not zero. You know, there is the possibility for particles in space to sort of bump into each other and assemble into atoms, and those atoms could assemble into molecules, which could assemble into cells, which could assemble into a brain. Like, there's nothing in the laws of physics actually preventing that from happening, which means the probability is non zero, but of course very unlikely.
Do you need the atoms to have been formed already, Like do you need carbon atoms or are you talking about particle at the like the quark level, Like quarks suddenly become you know, protons and neutrons just the right you know, ratio, and then those become carbon and potassium and oxygen and suddenly everything like just poofs into existence or do you mean like assembled.
Well, I guess you could actually just poof into existence. That'd be even less likely, right, all that stuff to just like fluctuate out of the vacuum instantaneously. I think it's more likely for you to fluctuate the essential components out of the vacuum. You know, for a photon to turn into a pair of quarks an anti quark, or for a photon to turn into electronic positron and for those particles to assemble into atoms and then molecules and then cells. So I think that's probably more likely than the actual massive quantum fluctuation of a whole brain.
But don't you need like a supernova sometimes to assemble some of these particles or do you mean like they maybe come into existence with that kind of energy.
Yeah, well you can build these things out of anything. Typically they are made in the cores of suns, or in supernovas or in neutron star collisions. But that's not the only way you can make them, right. We can also make them here on Earth in collisions of particles, So yeah, you can make them in other ways. It's no law of physics requiring you to have a supernova in order to make uranium or phosphorus or whatever it is.
So like you're saying, like it's not just a brain, then it could be anything like cow or a perfect diamond. Could you suddenly poof out of existence?
Yeah, exactly, or you know, like a banana the size of a school bus or whatever.
Right, could a million dollars just suddenly appear in my hands? And instead of you know, admitting that I stole it. I could just say that it was a quantum fluctuation. I'm just you know, hypothetically speaking, it's called the bol Boltmann heist.
The Boltzman alibi. I think technically speaking, that's well beyond a reasonable doubt. But it's not impossible. Yes, absolutely, you should try that defense, and then I'll come visit you in prison and bring you some bananas.
But what if I bring a serious physicist with me to testify.
I don't know any so I can't recommend one for you. I only know the podcasting kind.
All right, So let's put my legal troubles aside here. So that's how it would happen. It would happen like you know, particles would appear out of the vacuum or get transformed from light or something, and then they would just happen to assemble into a brain with like thoughts and then personality in it all, or like a blank brain.
With thoughts and a personality and memories, right, because your memories are just a reflection of the sort of physical state of your brain. And so for example, somebody who thinks they are you could assemble out there in space, right, You could make a horehe brain out there which would have thought that it lived your whole life.
It is it like maybe I am a Boltzman brain.
Maybe you are a Boltzman brain exactly, And so we use this as a probe to like think about the likelihood of various cosmological theories of the universe. And one standard is like, does your theory predict that there are more Boltzmann brains than actual real people out there, you know, thinking and breathing. So it sort of is a way for us to think about the origins of the universe and you know what's likely and unlikely to have happened. And you know, we can actually put a number on this probability, the probability to have a brain assemble out there in space.
Really you can quantify this crazy probability.
Well, people have quantified it, you know, they've gone through the argument and thought about how many particles and what are the chances for this to happen and that to happen for them to assemble. And you know the point is you get a number which is really really small. It says that it's just happened about once every ten to the ten to the fifty years. I mean, if you wait a number of years, which is ten with ten to the fifty zeros in front of it. You should get a boltsman brain.
That's insane. It's like ten to the fifty zeros.
Ten to ten with fifty zeros past it.
Wow, that is a really big number and much older than the age of the universe, right, like the age of the universe, it's just ten to the eight or nine.
Yeah, exactly, we're fourteen billion years, so, like you know, ten to the ten.
So basically it's a pretty low probability.
For one to have happened so far in our universe if the universe is only fourteen billion years old, if you believe that, if that's true.
Or if the universe is only going to be fourteen billion years old, but who knows, maybe it will have a long, crazy life exactly.
And so the point is that it's very very unlikely, but it's sort of like a standard like your theory the universe should not predict something like this happening, because that seems pretty absurd and unlikely.
But I guess the point is that the probability is not zero, Like it's possible for a brain to appear out of the blue, even if the probability is small, Like you can roll a pair of snake eyes on a pair of die It's unlikely, but it does. It could happen on your first roll.
Yeah, exactly, and in some way, like everything that is happening was very unlikely, like the chances of me existing are almost zero. In the same way, so many things had to happen just right for me to exist, And yet here I am. I do exist. So some things, even though they're vastly improbable, do actually happen.
All right, Well, let's think about why we think about this crazy scenario and what it has to do with the Big Bang and explaining what happened. But first, let's take a quick break.
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All right, we're talking about Boltwin's brains and big bangs a lot of bees today. Boltsmen sounds like an ad for I don't know a mattress store.
Bye, or space brains. Come on down to Boltzman's.
Brains and your bananas. All right, Well, this is crazy sting there. The idea is that, you know, a brain could spontaneously form out in space out of random particles popping into existence. They could assemble into something that thinks and has the exact same memories as you, and that could maybe, for like a second, think that it is you, right, because this brain would be a lie for you know a little bit of time.
Right, yeah, exactly. The brain would survive for a little bit of time long enough to think, hmm, wow, look I'm a brain. I think I understand the universe, or I'm going to go get a banana or whatever. And you know, if you're living in the moment right now, you don't know that you're not a Boltzman brain. You know, then and about to disintegrate, you.
Could be right, like everything that's happened to you before. It could just be an implanted memory.
Yeah, exactly, nothing that you have thought in the past could be real.
Wow, all right, well this is super highly unlikely to the tune of one in ten to attend to the fifty. But it's not zero the probability, which means that if the universe is infinite, it's happening all the time now right there are brains popping out into existence everywhere.
Yeah, exactly. If the universe is infinite in extent, right, spatially infinite, if it goes on forever with an infinite amount of stuff and totally random initial conditions, and then everything that is possible is happening, even if it's very very unlikely. So that means that's somewhere out there right now, if the universe is infinite and totally random in the initial conditions, there is a boltiman brain appearing and thinking that it's me.
And so this whole wild idea has a lot to do with, as you were saying, thinking about probability in the universe and what are the chances of things happening, and specifically kind of like how you compare that to the Big Bang, because the Big Bang is also pretty unlikely.
The Big Bang is very unlikely exactly. And you know, the current thinking, of course, is that the universe started about fourteen billion years go. And we think that because we look at the expansion of the universe and we track it back and we look at like the oldest things in the universe and they seem to be about that age, and so there seems to have been this special moment early in the universe. But you know, we don't know what comes before the Big Bang. We don't know what caused the Big Bang. So while our universe seems to have come from a very special state fourteen billion years ago, we really know very very little about the origins of that state, what created it, what caused it, if anything, if it even means anything to say this something before the Big Bang. You know, we have lots of different theories, and some of them say that there is nothing before the Big Bang, that's face and time didn't even exist, and other theories that say, you know, maybe there was some before the Big Bang. We talked about Penrose's conformal cosmology that talked about the universe continuing to expand like flower pedals upon flower pedals. So the point is we don't know at all about what happened before the Big Bang, which means that the universe could have existed before it could have gone on basically infinitely into the past, or a very long time into the past.
Or maybe I guess the interesting and alternative is that maybe the universe just popped out of existence out of the blue, just like one of these Boltzmann brains, Right.
That's one idea, and this is sort of the direction that Boltzmann was going when he was thinking about entropy and probability. As he was developing his theories in the late eighteen hundreds, he realized that the second law of thermodynamics that tells you that entropy is always increasing, that things basically tend towards equilibrium, that our universe is sort of tending towards a state where everything's going to be equally spread out, and they call this the heat death of the universe. He realized that if the universe goes on for a very very long time, and this is sort of the eventual end of the universe, that the universe would spend most of its time as the heat death universe, Like eventually you'd get to the equilibrium and then you just stay there forever and ever and ever for the whole life cycle of the universe. And so he realized that it's kind of weird to not be at that point. It's sort of strange and very unlikely, almost vanishingly unlikely, that we're in a moment that's not a maximum entropy, right.
It's like, it's weird that there was so much stuff kind of condensed in one place that would eventually expand and explode into planets and people and bananas.
Yeah, exactly. And so his solution to this sort of paradox to thinking like, hmm, if the universe just trends towards maximum entropy all the time, then it should basically always be at maximum entropy. His solution was like, well, maybe there are fluctuations. Maybe you can get the universe into this like totally smooth state, but then randomly, in some corner of the universe, boom, it fluctuates to a lower entropy situation. And so in his thinking, because entropy was statistical, it's this like property that came out of the motion of the little particles inside it, not absolute that you could get like little deviations, little moments. When you break this second law through a dynamics where things get a little bit lower entropy. So, for example, he imagined, maybe the universe is this vast pool that's in the heat death. That's totally an equilibrium, but then a galaxy fluctuates out of existence, and that's us. So he imagined that our entire existence might be this like fluctuation out of equilibrium of an otherwise like vast universe that's just sort of like smooth and featureless.
Like you're a bubble in your peanut butter or something.
Wow, that's a very humble analogy for our entire galaxy.
But we're not just one galaxy. We can count trillions of galaxies out there. So it's the idea that all of those streelings of galaxies are just like a again, like a bubble in a jar of peanut butter.
Well, Boltzmann was thinking about this before we really understood the context of our universe at all. This is the late eighteen hundreds, before people even understood that there were other galaxies. That wasn't until later when Hubble saw those galaxies and realized, wow, the universe is much bigger than we ever imagined, and it's expanding. So it makes Boltzmann's strategy it's like, well, we could just fluck a galaxy out of equilibrium. Much more difficult because now you have to fluctuate like the whole universe. You have to take like the Big Bang and say this entire Big Bang, this like moment of crazy high density, which led to, as you say, our entire universe with galaxies and superclusters. That whole thing was a fluctuation. And that's when the problem of Boltman brains arose because people realize, you know what, that seems pretty unlikely. It's much more likely to just fluctuate a brain. I mean, now, fluctuating a whole universe out of equilibrium seems much much less likely than just fluctuating one brain, which seems like pretty reasonable.
In comparison, is the idea that, like the universe as we see it now suddenly appeared, or that the Big Bang initially is one of these bubbles in the peanut butter, you know what I mean. Like, is the idea that we sort of like popped into existence the way it is now, with the galaxies moving at just the right speeds and everything moving away from each other coincidentally. Or is the idea that maybe the Big Bang was sort of this bubble forming.
The idea is that the Big Bang was this bubble forming, right. That's the concept of this kind of cosmology. It's not that we're all being fooled and thinking that the universe existed and that it just actually popped into existence right now with this apparent history. It's that the Big Bang itself was a fluctuation. The vaster universe is this ocean of equilibrium, out of which fluctuated this crazy condition, this crazy low entropy state, which was the Big Bang. And then physics sort of rolls forward the way we expected and the way we've observed, and all of our experiments are honest and actually have measured the history of the universe. But this is an argument that's used to criticize that idea. Say that idea is so ridiculous and so absurd and so unlikely that it's more likely that you have this other absurd scenario that we're all just boltspen brains floating in space.
I guess you're saying that the universe is so unlikely that it's more likely than that we are all just all came into existence yesterday.
That's the Boltzmann brain argument exactly. It says that if you believe that, then you should also accept the possibility of Boltzman brains. And in a universe that has lived for a very very long time, there'll be lots of Boltzman brains, and the probability that you're not a Boltzman brain, but like an actual brain, seems very vanishingly small, and so therefore most likely we're all Boltzman brains.
Daniel, are you saying that there's a possibility that the Bible is right and that actually it's more likely than your current theories of physics? Is that what you're saying, Daniel, Can I get to you on the record.
To say that you cannot give me on the record to say that. You know, this is one method that's used to sort of critique this kind of cosmology, this particular idea that the Big Bang was a low entropy fluctuation. It can be criticized by this kind of argument. But you know, as we can dig into it in a minute, there are also criticisms of this argument, like you know, the Boltspin brain argument itself, like does it really hold up as a way to evaluate the likelihood of the Big Bang as a fluctuation? Oh?
I see, we're still in thought experiment mode. It's not that just because the big band is less likely than the idea that we're all just made yesterday, that's not a good argument. We're still in thought mode.
Yeah, we're still in thought mode. And you know, just being unlikely is in devastating. As we said, the unlikely things do happen, and so it certainly is possible that something unlikely happened, and we're here anyway that the reason, for example, that we are here asking questions about why this unlikely thing happened is because the unlikely thing happened, and otherwise they wouldn't be anybody to ask these questions. So that's, for example, one way out of this predicament.
All right, well, let's dig into what is wrong with this argument and why it's maybe not possible for brains to spontaneously form out of the boot, and most important, what does it all mean. But first, let's take another quick break.
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All right, we're talking about spontaneous brains, and sometimes I have spontaneous thoughts. That's not the same thing, Daniel, Right, No.
All your spontaneous thoughts are gold. These bullsman brains are just brain cycles out there in space.
That's right. That's what I'm doing when I'm napping. I'm just making gold. It's called cartoons.
And you know, people out there might be thinking, hold on a second, I'm pretty sure I'm not a Boltzman brain. How can these folks be telling me I'm likely to be a Boltzman brain, because like, you look down and you have arms, right, and legs, and how could that possibly be a Boltzman brain?
But you only have memories and electrical impulses in your brain telling you that you have arms and legs. But maybe those formed out of the blue too.
Yeah, maybe they did. And you know, you can take that direction, you can say, well, you only have memories of them, But you can also go the other direction, and you could say, well, you know, let's just not consider only Boltzman brains. Let's consider Boltzman people. You know, like, if you're going to fluctuate a brain out of the vacuum, and it's basically almost impossibly unlikely, why don't you just go whole hog and make a whole person, you know, with arms and legs and everything.
Well, the full Boltzman think of Boltzman booties exactly, full frontal bolt yeah, and a Boltzman elbows right, yeah.
And you know this is all in comparison to fluctuate in entire universe out of the vacuum, and so compared to that, like everything is basically free. Even if you add like a Boltzman room around your Boltsman body and even a Boltzman town, it's still much more likely than fluctuating the entire universe.
Really, like, and you can expand that to the Earth, like the whole Earth could just propitt existence with photons coming out as in just the right way for us to think that there's a larger universe.
Yes, yes, exactly and.
That's still more likely than the Big Bang.
That's more likely than fluctuating the whole Big Bang. And this was the criticism of Boltzman's arguments. You know, Botzman's like, just fluctuate a galaxy, No big deal, folks, and people like, actually, that is a pretty big deal. Fluctuating brain is unlikely, and that's much more likely. And so, you know, as a way to critique either fluctuating like a Boltzman galaxy out of the vacuum or fluctuating the whole universe, this is just a way to point out that that all seems really really really unlikely.
But I guess the core argument, though, is still valid. Isn't it that it is more likely for us to have suddenly appeared six thousand years ago than through a big bang fourteen billion years ago.
If you think that the Big Bank comes from a low entropy fluctuation. Yeah, And again we're not just talking about like the creation of the universe in general. We're talking about this one idea that the Big Bang is this fluctuation. Right. There are other ideas of how the Big Bang came about or how the universe was formed that are not this one particular cosmology, but this one is susceptible to this criticism of Boltzmann brains.
It's only if you think that the universe itself fluctuated out of the blue. But there's other ideas. Maybe the universe didn't fluctuate out of the blue, maybe it came from something else.
Yeah, exactly. There are lots of other theories for where the universe came from, you know, and like they're all improbable and probably wrong. We talked about them on the podcast before. You know, maybe there was a whole universe before and there was a big crunch, or maybe space just started at that moment and we don't understand how and why and it doesn't even make any sense to ask that question. Or maybe there's an inflating eternal universe where this sort of weird infoton field then decays into the kind of stuff which can create the Big Bang. So, you know, none of these things are like well formed theories that anybody really believes. They're all just sort of still at the level of intellectual playgrounds, because we're at that point where we're like throwing stuff at the wall and see which brains stick to it. You know, which peanut butter makes any sense at all.
Maybe the universe is almond butter, right, or maybe it's got a peanut allergy butter.
Yeah, right, And that's been the problem the whole time.
You know, I guess what you're saying is that there might be other explanations, but for them to be scientific, wouldn't they at the core be sort of random events? Right? Otherwise what else is there besides a random eventAt Sorry?
Are you saying that every idea is just a random event? I mean you can't actually like think hard about things and come up with good ideas.
Well in terms of the origin of the universe, right, Like, maybe the universe came from another universe, but where that units come from? Then at infinitum, and eventually you sort of come to a probability argument, right.
Well it maybe, I mean, you might come to a single possibility. It could be that you discover that the laws of physics can only work in one way, and the universe could have only started in one way and be self consistent. It certainly is possible to reveal that the universe has to be a certain way because the laws only work. For example, if that happens, and that I think is sort of the hope and the goal that we'll get back to the very beginning of stuff and we'll realize, oh, this is the only way that makes sense, and so that must be why it is this way. But we have no guarantee. It could be an infinite ladder of questions leading to questions leading to questions. We have no guarantee we're ever going to make sense of it.
That's making my Boltzman brain hurt a little bit. And that's not just because I'm in the middle of the sun or in space. So I guess then let's get back to this question. Then are we a Boltzman brain? Am I a Boltzman brain? How can I be sure that I'm not?
You can't actually be sure that you're not a Boltzman brain, but you can use your brain to sort of reason your way out of it, right, You can make arguments that convince you that you're probably not a Boltzman brain. And this is, you know, some good arguments out there. One of my favorites comes from Sean Carroll. Right, Sean Carroll thinks about this stuff pretty deeply, and you know, he points out that if you're a Boltzman brain, that means that most of the things you think are not based in reality. They're like false memories that are implanted in your brain when your Boltzman brain assembled. Right, you didn't actually go to that elementary school, you didn't actually marry that person. That's all just fake memories. Right.
Wait wait wait wait, he's saying that we are that or we're not that.
He's saying if you're a Boltzman brain, then all of your memories and all of your thoughts are false. Right, They're just assembled randomly. They're not based on real experiences, real insight into a real universe, and that include the idea of Boltzman brains. So if you're a Boltspan brain, then you shouldn't trust any of your ideas, including the idea of Boltspan brains.
What that's not right? Just because I'm dreaming or because I'm an illusion doesn't mean that there aren't real things that could exist outside of me, right.
That's right. Yeah, but your thought about Boltzmann brains could have not come from a careful analysis of the universe and its likelihood. It could just be like a made up, crazy idea in planting your brain, because you know, it just happened to come that way when the particles assembled themselves out there near alpha centauri.
It could have, but it also could be the opposite. Right. It could be that it is true.
It could be that it's true, right, but you have no basis for believing that it's true just because you're thinking it, right, I mean, he says, if you reason yourself into believing that you live in such universe with Boltsman brains, you have to conclude you have no justification for accepting your own reasoning, because the reasoning in Boltzman brains is by deafen unreliable. They're not doing any reasoning, they just like have ideas.
I think you're saying that The argument against this crazy idea is that if you are like a spontaneous brain that formed with all these crazy thoughts in it, then you can't really say anything about reality. Like maybe all of what you think are the laws of physics could just be some sort of bogus random assembly of molecules in your head.
Yeah, you can't, like, at the same time conclude that you live in like a randomly fluctuating universe creating brains and believe that you have good reason for listening to those brains.
Well, you could, but you just wouldn't be a serious brain.
You'd be a brain cast exactly. So he says that the whole idea is what he calls cognitively unstable, that if you believe in it, that gives you reason to not believe in it. Right, And so he says, the whole thing sort of falls apart.
Well, it doesn't fall apart, it just makes it questionable. Right, but it could still be true.
Right, anything could still be true. That's a low standard. Remember, we're using this idea as a way like probe the likelihood of a cosmological theory of saying, could the universe be this way? And the argument is, if your theory of the universe suggests they're more Boltzmann brains than not, then you're not really going to believe in it. And this is just a way of saying, you know, okay, Boltman brains are bad, but you know, you can be pretty confident that you're not a Boltzman brain if you're forming like well thought out, coherent ideas.
What if Einstein was a Boltzmann brain and he happened to be right?
Yeah, maybe? And you know you have to also wonder like should you listen to your own ideas? Right? If the universe is filled with Boltzmann brains. Probably more of those Boltzmann brains are not very clever than there are Boltzmann brains that are like Einstein, right, which means that you're probably not Einstein, which should you be listening to your own thoughts about the universe. I don't know.
It's the most insulting thing I've heard from you, Daniel. Probably not Einstein.
I mean, Einstein wasn't smart enough to come up with your peanut butter analogy. I got that on MS.
I'm smarter than Einstein, maybe, right, Maybe I'm not Einstein. Maybe I'm better at cartooning than Einstein.
Yeah, I'm sure that's true.
This is part of that counterpoint that you were talking about that you mentioned, is this idea that there could be Boltman brain, but there may not necessarily be smart Boltzman brains.
Yeah, exactly. So we could be a bunch of Boltzman brains sort of fooling ourselves into believing some silly argument about the origin of the universe because we're not.
So we could be Boltzman brains foolishly thinking that Boltzman brains are possible. Is that what you're saying, Yes, yes, exactly, But then we would be right.
If that's true, you might have to be a dumb Boltzman brain to believe the dumb Boltman brain idea.
Doesn't make any sense. You just prove yourself.
Oh man, it's confusing.
Right, Well, then, what's the other alternative? I guess if the universe is not a random fluctuation.
Well, you know, there are sort of two other alternatives. One is to accept that maybe the universe was a really unusual, unlikely fluctuation, and then just to say that's okay, Like, sometimes really rare things do happen, even like unfathomably rare, like an entire big bang coming into existence out of thermal equilibrium. Sometimes they do happen. And this is what we were talking about before. It's the anthropic principle. It says that it's okay for unlikely things to happen if they're necessary for you to be here to ask questions about how unlikely they are. Maybe the universe is infinite, and this kind of stuff almost never happens. But in the places where it's not happening, there's nobody noticing. There's nobody asking like, hey, how come we didn't get a big bang over here? It's only in the places where you do have a big bang, and then people to ask these questions that you ask these questions. So it's like me saying, what's the probability of me existing? I can't rule out my own existence by arguing that I'm unlikely because I did happen.
Right. It's like you're a pair of snake eyes on a pair of die right, Like you're two ones and you're thinking, like, oh my my god, what that's crazy that I exist? But you don't know if the universe, you know, through the pair of dyes of Brazilian times before you existed.
Yeah, exactly. And I don't really like that argument that much. It feels to me like sort of a cop out. It says there's no answer. Stop asking questions. You know, there's no reason for this very unlikely thing. And in science it might be true. But in science we've made a lot of good progress by looking at weird stuff and going, hmm, that's weird. I wonder if there's more to the story, And that's usually the way we pull on threads and unravel something deep and true and interesting about the universe. So can't disprove the anthropic argument. But it's sort of like it doesn't give you anywhere else to go. There's nothing deeper you can do after you answer a question that way, so it's not really very satisfying. I like to keep digging.
Well, you could keep asking like who through the die right? Or like how does the die throwing work? That would explain and it'd be interesting to look into.
Yeah. Absolutely, But it doesn't answer the question of like, why are seemingly impossibly unlikely universe exists? It says, well, it just kind of does. Well.
I think that's a perfectly good reason. I mean, I'd tell it to my kids all the time. Yeah, just because why can't you watch more TV?
Just because because Daddy needs you to go to bed?
Because my Boltzmann brain says so, my Boaltman red is tired. I guess the it is that maybe our universe did come out of this super crazy unlikely event, But that doesn't mean that within it you can have these crazy Boltzman brains floating in it.
Yeah, And I think the other sort of category of answers is to say, all right, you're right, Boltzmann brains suggest that the universe as a low entropy fluctuation is super unlikely. So let's focus on other cosmologies, other ideas for how the universe started that don't require it to have existed forever and then fluctuate into a big bang things where the universe actually did start fourteen billion years ago, or there's some other mechanism for creating the Big Bang other than it's just like weird random, super low entropy fluctuation.
All right, I guess maybe we just have to keep our fingers crossed.
Then?
Is that kind of the general approach here, that there's a lot we don't know and we don't know what these actual probabilities are.
Yeah, and this is just a fun way to sort of like explore these ideas and to think about the consequences. You know, we have such an incredible lack of knowledge about the early universe and such an incredible variety of kind of bonkers' ideas for how it could have come about that it's useful to like come up with these arguments to evaluate them, because we can't like go back in time and see what actually happened, or journey around the whole universe and gather the daity we need, so until then we just are stuck here on Earth in our brains. Whites and brains or cham brains or boltsmen brains thinking about the origin of the universe and convincing ourselves that maybe we're making progress.
Yeah, that's a good point, David.
You just woke me up from my nap. I was doing some thought experiments nap their way through the universe.
We could replace ourselves and none of the other Bolzman brains would notice the difference.
Maybe our Bolzman listeners would notice.
All right, Well, we hope that gave you as much of a Boltzmann headache and it did for me, and that it maybe helped you think about what's likely out there in the universe and whether or not it's all even real. Thanks for joining us, See you next time.
Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeart Radio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact, but the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste conserve natural resources and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digesters to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
There are children, friends, and families walking, riding on passing the roads every day. Remember they're real people with loved ones who need them to get home safely. Protect our cyclists and pedestrians because they're people too. Go safely California from the California Office of Traffic Safety and Caltrans.
Hey, their fellow globetrotters and destination dreamers. If you're anything like us, you'd note that life's too short for boring toasters and towels. That's why we decided to ditch the traditional wedding registry and went with honeyfund dot Com. Imagine your friends and family chipping in to send you on a dreamy, exotic honeymoon. Practical check, meaningful, double check. Plus, it's fee free and so fun for wedding guests to shop. So why get more stuff when you can have unforgettable experiences. Join the revolution at honey fund dot com and start your adventure today
