Can Quantum Fluctuations Create a New Universe?

Quantum fluctuations happen everywhere, all the time, and in principle they can become arbitrarily large. So if we wait long enough at the end of the universe, brains can spontaneously assemble. Those are the so-called "Boltzmann Brains". And eventually, even an entire universe might be born. Seriously? Well, it depends on exactly how the laws of nature work.

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#physics #philosophy

[dantescalona]

As a Boltzmann brain myself, I approve of this video.

[MoranM]

I also find it remarkable that despite being surrounded by a vacuum at close to zero Kelvin my Boltzmann brain sustains itself for quite some time and doesn't crystallise or disperse into the void. Indeed, a period of time that is a lot more consistent with the theory that I am not a Boltzmann brain after all.

[markamos-geek]

I'm just wondering what would happen if Boltzmann Zombies also occurred at the same time as Boltzmann brains. It could get messy...

[frankcl]

Caroll's argument actually makes sense from a bayesian perspective : observing the universe being large is very surprising under the recurrence hypothesis, since most of the time the universe is observed it is much smaller under this hypothesis. Therefore, to consider the recurrence hypothesis likely despite this observation you would have to give it a very strong prior.

[Substance]

An idea for telephone call: phone rings, Sabine picks up, listens for a while, then says "Wrong number" a puts down the phone. :-)

[emalee]

This is the kind of content I began following for. Glad to see it.

[loicthierry]

What I find disturbing with this is that I'd expect therefore that a very very long time after I die my consciousness should be generated somewhere as some kind of Boltzmann Brain and replicate the memory state I had when I died (or any other moment of my life). This would mean conscicousness never really stops from ones point of view, nevermind the gooplex years one had to wait for such event to occur as without being conscient it's like a continum.

[cassianogunji]

Your closing joke in this video was the best I heard from you to date!!!

[ilialvov]

Hi Sabine, thanks a lot for addressing the topic!

As a long time follower of both your and Sean Carroll's work, I wanted to mention that I'm not sure you related the up-to-date version of Sean's reasoning, as expressed in Carroll 2020 "Why Boltzmann Brains Are Bad".

I believe his argument goes something as follows: when selecting your priors regarding the theory of cosmology, it is rational to put very low priors to the cosmologies that predict Boltzmann brains. Indeed, otherwise, you would necessarily have to conclude that with an overwhelming probability you yourself are a Boltzmann brain, and all your experiences and memories are just random fluctuations. But if you are a Boltzmann brain and all you think you "know" is in fact just a fluctuation, you have no access to understanding what the reality is, what the law of physics are, and whether those laws of physics allow for Boltzmann brains in the first place. So it's what Sean calls a "cognitively unstable" position. It's not an argument from probability (well, probability is involved, but it's not the main focus), it's an argument from *choosing to believe* something that allows you to make scientific progress :).

[dellseasandoval]

Half the reason I watch your channel is for the humour. You’re just as funny as you are smart.

[esra_erimez]

Why did the Boltzmann brain refuse to attend the physics conference? Because it was worried it might spontaneously reorganize into a coffee machine during the keynote speech.

[orionspur]

The issue with recurrence is that while quantum states of single particles are perhaps enumerable, and thus doomed to repeat if contained, it may well be that direction of motion is (essentially) real valued, and thus will never repeat. Evidence for this is that we can image distinct photons that left distant galaxies 14 billion years ago. The *angle* between those photons is on the order of 10^-36 radians, with no hint of any limit. So the precision of vector direction in space may in fact be combinatorial (cumulative), with complexity always increasing over time. In that scenario, the probability of any complex system repeating, ever, is effectively zero, even if the universe has infinite size and duration.

[MuhaiminKhan-pgtf]

I have a question about these boltzman brains.

If structures can spontaneously and randomly appear, i think its much more likely for those structures to be a cloud of hydrogen rather than the really really specific configuration of particles required to create a brain.

Doesnt that mean that stars are more likely than brains?

If the probabilities work out, it could be that you are indeed more likely to get a galaxy than a brain because there are many configurations of particles that form galaxies than configurations that form brains.

After we get galaxies, we don't need to rely on entropy to randomly create brains. Instead, we can rely on the four fundamental interactions (which we know to tend to give rise to organized structures on small scales).

I say "If the probabilities work out" because it could be that it's actually more likely to get brains rather than a galaxy simply because brains have much less particles than galaxies. The size of galaxies might make their probability if appearing much much lower.

Is this a valid argument against boltzman brains?

[nebula_M]

When everything is possible then nothing is possible. You can't work under the basis that everything will eventually happen

[booJay]

If a Boltzman brain (or universe) fluctuated into existence, would it just immediately disappear after it formed? To me, this wouldn't violate what we currently know, assuming the block universe exists, because every moment is already happening and regardless of what order events come into being, in the moment of coming into existence we'd always interpret it as being in its proper place and time.

[Psychx_]

Somewhere out there, Ludwig Boltzmann's very own brain will also rematerialize. Oh boy, he'll be so pissed that he got re-alived.

[peppipeppi]

In some way this resembles the many worlds theory, only with the difference that one is a parallel solution, where all the worlds and possibilities exist at the same time, and the other ist linear in time, where also everything ist possible but not at the same time.

[notbusy]

That's what I tell my wife . . . . . I'll eventually get up and clean the mess, but if you wait long enough, I mean really really long enough, the mess will cleanup itself . . . . eventually. She doesn't buy that argument.

[Nogill]

The recurrence time could be a function of the size of whatever constitutes "the universe". If you have a finite collection of bits in equilibrium, there's also a constraint on what you can expect to assemble. But assume unbounded time and enough stuff to make the observable universe. Then assume twice as much stuff, and so on. Given infinite stuff, the recurrence time, as long as it is finite, seems to give you a universe somewhere, in some form, at all times. The recurrence time loses meaning. You also get many many more Boltzmann Brains, but experientially, you'd never be able to discriminate, so that point is moot.

[helicalactual]

i don't deny Boltzmann brains. i absolutely believe we come back for judgement as Boltzmann brains. this is where we are either allowed out of the universe, sent to another universe or stuck in the thermal equilibrated space depending on if you can be stasis based or not.
i digress.
what does Prof Doc Sabine think about Boltzmann brains personally?
sad how Boltzmann himself died, suicide because he couldn't tell if he was a Boltzmann brain and so killed himself.