In All Probability, You Are a Boltzmann Brain

You are a disembodied brain floating, for a brief instant, in the vastness of the universe.

Alan Jones
Jul 23, 2020 · 4 min read
Image Credit: Hubble Heritage Team, ESA, NASA

And in that disembodied brain, your memories and perceptions are the result of the random coming-together of subatomic particles from an enormous sea of stuff that used to be the universe. So, nothing that you see around you is real, nothing you remember really happened.

That is to say, you are a Boltzmann brain.

Because that is more likely than what you believe to be true, that you are an autonomous, independent being living on the third planet from the Sun in one of the spiral arms of our galaxy, the Milky Way. Why? Because there are many more Boltzmann brains than there are real people, so the probability is that you are one.

What is a Boltzmann brain

How do you imagine the end of the universe? Exploding supernovae, planets shattering into pieces, black holes sucking up the remnants of erstwhile galaxies?

Apparently not. The end of the universe will be a formless, lifeless, soup of particles where nothing happens. This is the inevitable consequence of the Second Law of Thermodynamics where, in a closed system (the Universe) entropy must increase over time. Ordered systems such as planets, solar systems or people will become disordered, energy will dissipate until it is at the same level everywhere. The result: a bland mass of particles doing nothing.

But maybe not exactly doing nothing.

Nineteenth century physicist Ludwig Boltzmann argued that the disorder resulting from the Second Law had a random element to it, meaning that the most probable outcome was disorder but that is not the only possible outcome. That leaves the door open to order being created from disorder, meaning that new structures could randomly occur from the unstructured soup — it’s just that it isn’t very probable.

Random fluctuations in the particle soup left over at the end of the Universe will most often just mean a couple of particles getting closer to each other than would be normal. However, the random grouping of particles into some recognizable shape, an atom, say, is not impossible — it’s improbable but not impossible. Indeed, given enough time the highly improbable will happen and given that time is, as far as we know, infinite, atoms will definitely randomly pop into existence now and again.

Anything larger than an atom would of course also be possible but would be much more improbable. But in a long but less than infinite passage of time, we should expect molecules to form, planets, galaxies, people. Highly improbable but these things will occur given enough time (and there’s plenty of that).

Obviously, the more complex the structure that randomly comes together the less likely it is to happen. So, it must be more likely that a disembodied brain will come into being than a whole human being.

It must be the case that over a very long period of time a disembodied brain, complete with memories like yours or mine and with apparent sensory inputs that make it feel that it is living on a planet, in a town, in a house, sitting on a sofa and reading this article — it is certain that these will occur. Many times. Many, many times. In fact so many times that Boltzmann brains will outnumber real brains to such an extent that it is much more likely that you are a Boltzmann brain than a real person.

Perhaps unsurprisingly, theoreticians don’t really like this idea. But they can’t prove it wrong.

Brian Greene, the American theoretical physicist, mathematician, and string theorist has said: “I am confident that I am not a Boltzmann brain. However, we want our theories to similarly concur that we are not Boltzmann brains, but so far it has proved surprisingly difficult for them to do so.”

A slightly less scientific response came from Seth Lloyd, a professor at the Massachusetts Institute of Technology. He has suggested that Boltzmann brains “fail the Monty Python test: Stop that! That’s too silly!” (If you are a fan of Monty Python you will remember that the character, The Colonel, would arrive on the set of a particularly silly sketch and announce those words.)

So, if it really is too silly shouldn’t we be able to prove it wrong? You’d think so, wouldn’t you.

There is one other thing that will eventually happen in a Boltzmann universe. Over a long enough period of time, the random coming together of particles could bring about any possible positions of those particles. Mostly they are distributed but, at some time they will all end up in exactly the same place, a single point at which everything in the Universe is concentrated. The same as the singularity that, according to General Relativity, preceded the Big Bang.

But that is another story — or, rather, the beginning of one.

Originally published at http://mralanjones.blogspot.com.

FutureFile

Things that might just happen

Alan Jones

Written by

Technology, science and programming. Subscribe to my newsletter here: https://technofile.substack.com/ . Web page: https://alanjones.pythonanywhere.com/

FutureFile

Things that might just happen

Alan Jones

Written by

Technology, science and programming. Subscribe to my newsletter here: https://technofile.substack.com/ . Web page: https://alanjones.pythonanywhere.com/

FutureFile

Things that might just happen

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