Maxwell’s Demon

This was a theory that devised a way the Second Law of Thermodynamics might be circumvented. That law says that heat energy cannot be created, it can only be transferred.

In 1847, James Clerk Maxwell came up with this idea –

Say you had a box with two sides, separated by a gate. A demon would watch over the gate, and when a fast-moving atom would be moving towards it (in a single direction, say left-to-right), he would open the gate to let it through to the right side. When a slower-moving atom was moving from right-to-left, he would let that through to the left side.

Over time, this means that one side of the box (the right side, based on our directions above) would, over time, contain more fast-moving atoms, and the left side would contain more slow-moving atoms. Thus, the right side would be “hotter.”

Essentially, the demon increased order in the universe (reduced entropy) and generated heat energy without actually doing any work. He organized his way to energy.

The significance is that this bridges the gap between physics and information science. In effect, the demon created energy (physics) by increasing organization (information science). One of the criticisms of the theory, in fact, is that determining the speed of the atoms would require the demon to expend energy, which again links the fields of physics and information science.

(And if there’s one thing the scientific community loves, it’s when branches of science come together. This is called “convergence.” I read an entire book about it: Convergence: The Idea at the Heart of Science)

Interestingly, the computing term “daemon” is from Maxwell’s Demon. Maxwell’s version sorted atoms in the background. Computer daemon’s also do information processing in the background, hence the name.

Even more interestingly, Maxwell never used the word “demon.” He first articulated the theory in a 1867 letter to a colleague. There, he referred to the sorter as “a finite being.” The transition to “demon” was added by others after the fact, though sources differ on who changed the word and exactly why they did it.

Why I Looked It Up

I’ve known of this for years, and had a vague understanding of the basic mechanics of it, but never grasped the significance.

Then it was referenced in The Ascent of Information: Books, Bits, Genes, Machines, and Life's Unending Algorithm in a way that helped me understand. They used a parallel analogy of an animal jumping randomly between steps on a staircase. If you put a wall behind it whenever it jumped up, then it could continue to jump up but not down, and would be forced to climb the staircase.

I found this interesting because I’ve always been curious about the spontaneous order of debris on a house floor. When I’m cleaning, I notice that debris – lint, dust, small objects – tend to congregate in corners or off to the side of walkways. I vaguely wondered where this “order” came from.

It came from something like Maxwell’s Demon. If an object is dropped on the floor, it might be dropped directly in a walkway, where it will be kicked or moved by a human during the normal course of daily activity. It it comes to a rest in another walkway, it will get kicked again and again. Until one time, it gets kicked against a wall, so it’s out of the path of human activity. Nothing will disturb it anymore, so there it remains.

You see the same thing on highways. Debris collects in the medians, because it keeps getting knocked around until some point when it doesn’t. And that point happens to be in the median.

This is spontaneous organization at work. The universe is decreasing entropy in a way – it’s creating order accidentally.

Now, I’m neither a physicist or an information scientist, so my theory there might just be nonsensical rambling from a scientific point-of-view. But I always thought it was interesting, and when the idea of Maxwell’s Demon suddenly clicked, I made the connection.