Democritus

Democritus

The first hint, the whiff, of the existence of atoms, proposed by Empedocles, was carried much further by a man named Democritus, who came from the Ionian colony of Abdera in northern Greece. Abdera was a kind of joke town. If in 430 B.C. you told a story about someone from Abdera, you were guaranteed a laugh. It was in a way the Brooklyn of its time. For Democritus all of life was to be enjoyed and understood; understanding and enjoyment were the same thing. He said that “a life without festivity is a long road without an inn”. Democritus may have come from Abdera, but he was no dummy. He believed that a large number of worlds had formed spontaneously out of diffuse matter in space, evolved and then decayed.

At a time when no one knew about impact craters, Democritus thought that worlds on occasion collide; he believed that some worlds wandered alone through the darkness of space, while others were accompanied by several suns and moons; that some worlds were inhabited, while others had no plants or animals or even water; that the simplest forms of life arose from a kind of primeval ooze. He taught that perception – the reason, say, we think there is a pen in our hand – was a purely physical and mechanistic process; that thinking and feeling were attributes of matter put together in a sufficiently fine and complex way and not due to some spirit infused into matter by the gods.

Democritus vision. Photo by Elena

Democritus invented the word atom, Greek for “unable to be cut”. Atoms were the ultimate particles, forever frustrating our attempts to break them into smaller pieces. Everything, Democritus said, is a collection of atoms, intricately assembled. Even we. “Nothing exists”, he said, “but the atoms and the void”.

When we cut an apple or a pumpkin, the knife must pass through empty spaces between the atoms, Democritus argued. If there were no such empty spaces, no void, the knife would encounter the impenetrable atoms, and the apple could not be cut. Having cut a slice from a cone, say, let us compare the cross sections of the two pieces. Are the exposed areas equal? No, said Democritus. The slope of the cone forces one side of the slice to have a slightly smaller cross section than the other. If the two areas were exactly equal, we would have a cylinder, not a cone. No matter how sharp the knife, the two pieces have unequal cross sections. Why? Because, on the scale of the very small, matter exhibits some irreducible roughness. This f fine scale of roughness Democritus identified with the world of atoms. His arguments were not those we use today, but they were subtle and elegant, derived from everyday life. And his conclusions were fundamentally correct.

A pumpkin. Illustration by Elena