Sunday, March 14, 2010

A Remarkable Insight

Atomic theory began in Greece almost 2-1/2 millennia ago,in the 5th century BCE. Leukippos is credited with the first proposal of the theory, which was developed and publicised by Demokritos, his pupil and successor.

The logic of the theory is beautifully simple. Nothing comes from nothing - there is no spontaneous generation of matter, and matter is indestructible, as we say now.
But everything changes. Matter is constantly redistributed into different forms.
Therefore matter must be composed of invisible particles, ultimately indivisible [atomos]. There must be different types of atoms, to account for the manifold varieties of matter. Atoms must link together in different ways: rigidly, in solids; loosely, in liquids.

It is a remarkable insight, probably unique: a theory which had to wait more than 2300 years for experimental proof.

Demokritos does not appear to have asked a question which now seems obvious. Are there substances which consist of just one type of atom? In modern terms, are there elements?

Gold would be an immediate candidate for a substance composed of one element only. Silver, copper and tin would be familiar to Demokritos; he might have identified bronze as an example of a new substance formed by mixing two elements, a simple demonstration of the theory.
A bolder step would be to identify carbon as an element -  charcoal the residue after other elements are driven off by heat.

Had Demokritos identified elements, he might then have considered how they mix and combine. He would now be called the father of chemistry.
If by some miracle he had recognized charcoal and diamond as different forms of the same element he might have founded an alternative alchemy.
Unfortunately atomic theory became a topic for philosophers, not experimenters.

It is so easy with 20:20 hindsight.

In 1869 Mendeleev presented the Periodic Table of the Elements; arguably the most significant of all advances in human knowledge.
And Demokritos' logic was finally shown to be correct.

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