Stephen Wolfram

And it was a fluid that kind of was absorbed into substances.

And when one hot thing would transfer heat to a colder thing, that this fluid would flow from the hot thing to the colder thing.

Anyway, then by the 1860s, people had come up with this idea that systematic energy tends to degrade into random heat that could then not be easily turned back into systematic mechanical energy.

And then that quickly became a global principle about how things work.

Question is, why does it happen that way?

So, you know, let's say you have a bunch of molecules in a box and they're arranged, these molecules are arranged in a very nice sort of flotilla of molecules in one corner of the box.

And then what you typically observe is that after a while, these molecules will be kind of randomly arranged in the box.

Question is, why does that happen?

And people for a long, long time tried to figure out, is there, from the laws of mechanics that determine how these molecules, let's say these molecules are like hard spheres bouncing off each other, from the laws of mechanics that describe those molecules, can we explain why it tends to be the case that we see things that are orderly sort of degrade into disorder?

Yeah.

We tend to see things that, you know, you scramble an egg.

You take something that's quite ordered and you disorder it, so to speak.

That's a thing that sort of happens quite regularly.

Or you put some ink into water and it will eventually spread out and fill up the water.

But you don't see those little particles of ink in the water all spontaneously kind of arrange themselves into a big blob

and then jump out of the water or something.

And so the question is, why do things happen in this kind of irreversible way where you go from order to disorder?

Why does it happen that way?

And so throughout in the later part of the 1800s, a lot of work was done on trying to figure out, can one derive this principle, this second law of thermodynamics, this law about the dynamics of heat, so to speak, can one derive this from

from some fundamental principles of mechanics.