11 August 2010

Atomism – Getting Physics Right Accidentally

More right than he knew.

Start the Wayback Machine

It's time to drop some straight physics on you all. No, wait. Time to drop some history. Oh, hold on. Get ready for some history of physics! All the way back to 5th century BC Greece. This story starts with the metaphysical philosopher Leucippus.

Without going too deep into Greek philosophy, which is at the same time interesting and incomprehensible, Leucippus was trying to resolve an argument. One side argued that the universe was static and eternal where motion and changes were just an illusion, while the other spoke of a universe where the concept of change was the only thing that truly existed. Leucippus tried to make peace by hypothesizing that everything is made of some indivisible building block, but that these fundamental pieces could experience motion and constructed and that exists. Leucippus and his student Democritus named these particles atomos, or atoms; literally Greek for "uncuttable." For 2,400 years Leucippus' and Democritus' theory of Atomism was more correct than they probably ever imagined.

It would take thousands of years to figure out what exactly these "Atoms" were, but now we know there are, in fact, tiny particles that make up the entire physical world around us, not counting light and radio waves. Atoms of different types (elements) create the different materials and objects we see. 

A Common Idea, Lost

Let me step back for a moment. It would be irresponsible to omit the fact that Leucippus was not the first to propose this idea. Similar theories were included in Jainism of ancient India about a century earlier, though the teachings were not tied as directly to science as Atomism would eventually be. Before that would happen, in the western world the thought was abandoned for centuries. About two hundred years after Leucippus, Aristotle argued, incorrectly, that water, air, and other things were continuous and not made of individual pieces. Eventually, Aristotle's teaching dominated thinking, and Atomism was quiet until it made a magnificent return starting with hypotheses by Galileo and others (1650's), concluding at the turn of the 19th century with John Dalton's list of atomic weights.

Now, Atomism teachings were not all correct. The same logic dictated that nothing more advanced than atoms existed; that trees and people were just illusions created from atoms and not more complex objects. Also, in the early 20th century, scientists figured out that atoms were made of smaller pieces, protons, and neutrons, which are in turn are made from quarks. But the concept of a indivisible unit remains. We have no evidence now that quarks can be split, so they gain the status of the indivisible unit Leucippus was talking about, despite a different name.

Leucippus arrived at his ideas without experiments and scientific process, just a challenge in thinking. Whether or not the reasoning was stumbled upon by accident, the basic idea of a fundamental building block, be it atoms or quarks, is a cornerstone of science today, tracing roots back two and a half millennia.

Additional Links

Atomism at Wikipedia

Atomic Theory at Wikipedia

Atom at Wikipedia
Atoms, Compounds, and Minerals at IU

How Stuff Works: Atom


  1. Lucky guess, I say:)

    Also, have you looked at string theory at all?

  2. I have looked at string theory a little bit, but can't say I am familiar with the whole thing. It is very interesting and might do some more reading. One thing I would like to do on this blog would be to explain some physics ideas that are not common knowledge in an easy to understand way. String theory is probably too complex for me to try describing simply, but if I think there are enough people reading this that might be interested, I might take a shot at explaining parts of relativity, electricity, or, my favorite, the double-slit experiment.