Dalton

John Dalton (1766-1844) was a British scientist who proved that ordinary matter is made up of atoms. It is an old idea that goes back to Democritus and the ancient Greeks. Many believed it to be true, but no one could prove it till Dalton.

The idea is this: take anything and cut it in half. Then cut it in half again and so on. Sooner or later you will get to a piece of it that you cannot cut no matter what. It is not a question of how good your cutting instrument is: the thing you are cutting has to be made of something, however small it might be. If you could go on cutting forever that would mean it was made of nothing, which is impossible.

Those small little bits that the thing is made out of, the bits you cannot cut no matter what, were called atoms by Democritus. Atom is Greek for “uncuttable“.

What Dalton called atoms are cuttable, as it turns out, but no one knew that for a hundred years, so the name stuck.

For a piece of bread, by the way, you would get to the level of Dalton’s atoms after cutting it in half about 80 times.

The Greeks thought atoms were different shapes: water atoms were round, fire atoms were sharp, etc. Dalton said atoms were all alike except for their weight. All gold atoms, for example, have the same weight and no other atom has that weight. It is how you tell them apart. That is what made Dalton’s atoms new and different. And provable.

Dalton noticed that when oxygen and hydrogen are put together to make water, the oxygen that goes to make up the water always has a weight eight times greater than the hydrogen.

And it was not just water. All the substances that scientists knew how to make back then out of elements were the same way. The weights were always the same for a given substance and the numbers were always small and simple, like 3 to 8 or 6 to 1.

Nothing made sense of this but Dalton’s atoms with their different weights. But it took a while for the idea to firmly take hold.

Earlier Dalton had studied the weather and wrote one of the first books about it. He made his own instruments and, like Benjamin Franklin, recorded the weather every day for nearly 60 years.

From studying the weather he became interested in the nature of air. That brought him to the work of Boyle, which in turn brought him to chemistry at age 30. Seven years later, in 1803, he came out with his ideas about atoms. The book followed in 1808.

Most groundbreaking ideas like that come to people when they are in their middle to late 20s, not their late 30s. But Dalton’s case shows that it is not age that matters but how long you have been in the field.

See also:

• Lavoisier
• Britain