[stevebmark]

The author mentions Boltzman brains and that a human body could theoretically spontaneously form out of particles given a long enough time span. Of course, nothing like this can ever happen. It’s the fallacy of thinking infinite time means infinite possibilities.

[nomel]

> that a human body could theoretically spontaneously form out of particles given a long enough time span.

To be fair, isn't this precisely what happened?

[dilawar]

If you leave out "spontaneously"!

[_carbyau_]

Specifically if you leave it in! It's a matter of viewpoint or scope.

"Spontaneous" can be defined a few different ways: https://www.merriam-webster.com/dictionary/spontaneous

From the link "2: arising from a momentary impulse" you get the implied meaning from the original comment if you assume standard human experience of a "moment" IE a few seconds or less.

However you could argue that human evolution is but a moment in the scope of the universe.

And then with definition "5: developing or occurring without apparent external influence, force, cause, or treatment"

The only way it wouldn't be spontaneous would be if an external actor (Deity of your choice?) directed human evolution somehow. To say this is debatable is an understatement..

And so we have fun in word play and hopefully appreciation of different viewpoints.

:-)

edit: rearranged for better flow

[dj_mc_merlin]

"Oh, that was easy," says Man, and for an encore goes on to prove that black is white and gets himself killed on the next zebra crossing."

[sandgiant]

It's not a fallacy, it's a paradox. One that indicates that our theories of quantum fluctuations in an infinite universe are incomplete.

This podcast episode has a good discussion on the subject: https://universetoday.fireside.fm/745

[stevebmark]

The initial conversation is an entirely false premise, that an infinitely large universe would have "anything that can happen, would happen." An infinitely large universe could be empty, and fit the bill, and there would be nothing like "there are infinite copies of myself that are slightly different than now." It's bad philosophy, not science.

[tempestn]

Perhaps it's actually correct, but our intuitions about ridiculously long periods of time aren't good. Note that heat death is in ~10¹⁰⁰ years, whereas this Boltzman body would take ~10^(10⁶⁹) years. That second time period is literally incomprehensible. So we think, of course a fully formed human body wouldn't appear; in practice, that's not how it actually works; the fact that it appears possible is at best a mathematical artifact, not reality. But we're talking about a timescale that's not just longer than the age of the universe, or than the total lifespan of the universe, not just orders of magnitude longer than those times, but on a completely different scale. Given that, I think we need to toss out those intuitions.

As to the author's last question of whether such a thing even makes sense at all given those time scales, I don't see why not. After all, once the universe reaches heat death, as far as we know nothing from the outside is going to come along and garbage collect it, so why couldn't it last for an arbitrary/infinite number of years? And compared to that, ~10^(10⁶⁹) years, or ~10^(10^(10⁵⁶)) years, or whatever, is nothing.

[ulamia]

I think this more about the arrow than the entropy.

Considering the ‘arrow of time’ a function on each microstate lends itself better to ”can” questions.

I think both the author and you are assuming your definition for the arrow is correct.

It is still unknown if the arrow allows any arbitrary state to become another, or if there is a strict genealogy for the change of the state that can be seeded from an existing state that ensures it will evolve into a specific other under some time scale, or whether either of those permit Boltzmann brains, or even if there is some control the state has over itself (free will?).

[continuational]

Why is it not bound to happen eventually?

[stevebmark]

For the same reason an infinite number of zeroes will never contain a one. Particles still have to follow the laws of how matter behaves, no matter the timescale. Nothing spontaneously forms like the author suggests, regardless of entropy. That’s not how matter works.