Greg McMann, age 11, of Portland, Maine, for his question:
WHO DISCOVERED THE ATOM?
This remarkable story began with some brilliant guesswork, more than 2,000 years ago. At that time, there were no sophisticated instruments to prove that atoms really exist. The proof had to wait until modern times. So far, about 104 different atoms have been discovered. And, of all things, modern scientists still depend upon educated guesswork to predict the existence of more to come.
The scholars of ancient Greece had no delicate instruments to probe and prove the secrets of nature. Instead, they tried to solve these puzzling problems by logical reasoning. And very often their conclusions came pretty close to the truth, though the proof had to wait for many centuries. For example, the existence of atoms was predicted by the Greek scholar Democritus, who lived in the 5th century B.C.
Democritus was puzzled by the constant changes in nature. He observed the cycles of growth and decay. From this he reasoned that nature must use and reuse the same building materials. Obviously, this modeling and remodeling goes on below the range of human vision. Therefore, the basic building units must be invisibly small.
He assumed that they must be the smallest possible units of matter, too small to be divided into smaller particles and called them atoms, which means indivisible. The universe, he predicted, is empty space occupied by various atoms, which we sense as different colors and textures. Objects are made of groups of atoms, which break apart or decay and regroup to form other objects.
For some 2,000 years, these ideas slept in old books. Then early in the 1800s, they were revived by an English chemist named John Dalton. Suddenly the study of atoms became stylish and one by one they were proved to exist. Most of the ancient Greek reasoning proved correct, but not all of it. For example, we now know that the atom is made of smaller particles that can be split asunder.
Democritus also had some sound ideas about human conduct. He said that happiness does not come from wealth or power. It springs from within, from fairness and kindly good nature. The enemies of happiness are extremes and too much of anything is always too bad.