Hacker News new | ask | show | jobs
by snowwrestler 1486 days ago
The classical way to think about entropy is a relationship between scales. There are a lot of ways for matter and energy to arrange as a “cloud of smoke.” There far fewer ways for matter and energy to arrange as you. You have lower entropy than a cloud of smoke.

Just before the Big Bang (again, if it occurred), there would have been a perfect 1:1 relationship. There was only one possible way to be, and everything was that way. Zero entropy.

It is basically a definition, not empirical. Entropy only increases; the universe has a definite and specific history; therefore the beginning of things must have been only possible exactly one way, the lowest-entropy way.

If this sounds weird and non-scientific, it is! Scientists don’t know if the Big Bang occurred. We have basically no evidence to support any theory of what things were like before inflation.
1 comments
zmgsabst 1486 days ago
> There was only one possible way to be, and everything was that way. Zero entropy.

The issue I’m having is this:

There are a lot of states that initial singularity could have been in, leading to a whole diversity of universes.

How is it different than your smoke example?

link
snowwrestler 1486 days ago
There are a lot of possible singularities that could have existed, but only one did. (Again: if it did.)

At least, in the context of this universe. But that is the entire and only context available to us.

Whereas all sorts of different clouds of smoke exist, some probably even right this second just here on Earth.

link
zmgsabst 1485 days ago
> At least, in the context of this universe. But that is the entire and only context available to us.

But we know things take “multiple paths” — why does that not apply to the original singularity diverging into multiple universes?

> Whereas all sorts of different clouds of smoke exist, some probably even right this second just here on Earth.

But only a particular cloud exists — the one that comes out of your fire. You go from one log as it exists to one cloud as it exists… one state to one state.

We normally explain that as “there’s more potential ways to be a cloud than potential ways to be a log”, but that brings us back to my question…

Why do the potential other smoke clouds count as entropy in the case of smoke clouds but not potential other universes in the case of universes?

link