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9
The History of the Atom
We have already mentioned the atom several times and have seen how it is key in
understanding many things in nature. It is certainly one of the great unifying con-
structs in physics. The idea that all matter is made up of small, solid objects goes
back some 2,500 years to the Greek philosopher Democritus. While we still cer-
tainly believe in the atom, it is quite remarkable that the picture (model) we have of
the atom has changed only in the last 100 years. In this chapter we will concentrate
on how and why that changed view has come about. It is a very nice example of the
methodology in physics.
9.1 THE GREEK MODEL ...