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Instant Physics
You must realize that to the Greeks and their successors, the concept of atom was an abstract hypothesis that might explain certain phenomena. But at the time there could be no experimental evidence to support it. And there would be no evidence for a thousand years.
If this seems like a strange statement in this age when we take atoms for granted, ask yourself: how do you know atoms exist? Yes, you. Probably you read about them in grade school. But what experiment can you propose to give evidence of their existence? Your Ginsu knife may slice and dice, but it's not going to cut a brick into atoms. To most people there's little difference between atoms and magic.
To illuminate the difficulties more sharply, pretend you are a scientist in the sixteenth or seventeenth century. The villain Aristotle had rejected atoms and instead embraced Empedocle's notion of four elements - earth, air, fire, and water. All remaining substances on the Earth arose from combinations of these elements. As a follower of Aristotle, it is difficult for you to conceive of anything more fundamental. But the result, for scientists trying to prove this theory, was centuries of blood, sweat and tears. Thanks, Ari.
Moreover, the Master held that once a new substance is formed, all traces of its ingredients are erased. To take a modern example, we know that limestone (chalk to laycreatures) is composed of calcium, carbon, and oxygen. But as an Aristotelian, you scoff at this. Limestone is an entirely different substance; once it has formed, the calcium, carbon, and oxygen vanish. Along with the fact that everything is ultimately made of earth, air, fire, and water, you are convinced that it is a waste of time to search for more basic units of construction.
The next great obstacle to an understanding of atoms is that you lack the modern concept of a chemical element - a basic substance that cannot be transformed by any chemical reaction into another substance. Following the Aristotelian quest for perfection, you have attempted to make the perfect metal - gold - in your alchemy laboratory. This seems a perfectly reasonable endeavor. During your years in the laboratory you added zinc to copper, which is yellowish, and thereby transmuted copper into the more yellow brass. Why cannot brass be transmuted into something even more yellow - gold? Without the idea of an element, there is no reason to think this can't be done.
The chemical situation at the start of the seventeenth century was even worse than this. Chemical ideas were mixed with astrological ideas (the behavior of iron was governed by the red planet Mars; followers of Jean Dixon have evidently stopped thinking in the seventeenth century). And because Aristotle taught that things follow their nature, some chemicals reacted because they felt "sympathy" for each other, and others refused to react because they "abhorred" each other. Indeed, by the seventeenth century, chemistry had become the Yugoslavia of science. How could such a mess be sorted out? The answer lay in atoms, but to prove it took another three hundred years of false starts, missed opportunities, and inspired guesses.
Tony Rothman
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