On this date in 1856, English physicist Joseph J. Thomson was born. He ended up discovering the electron.
And on this date in 1926, American physicist Gilbert N. Lewis coined the word photon for a “particle” or bundle of light energy.
Electrons and photons are called elementary particles because (at least as far as we know) they are not made up of smaller particles. Really, really tiny things like cells are made of scads of tinier units called molecules, which are in turn made up of atoms. A human body is made up of trillions of cells, and each one of those cells is made up of quadrillions of atoms. But atoms are made of even smaller particles: protons, neutrons, and electrons. Protons and neutrons are made up of quarks held together by strong forces called gluons.
Quarks and electrons seem to be fundamental particles—not made up of smaller parts. The forces, including gluons and photons, seem to be fundamental as well.
Learn more about particle physics at The Particle Adventure. It really isn't so VERY difficult to understand what stuff is made of, although we do have quite a few named items in the list of fundamentals: 16, to be exact. The great scientist Enrico Fermi once said, "Young man, if I could remember the names of these particles, I would have been a botanist!"
Another easy-to-understand website is Etacude.
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