(And) we started out with understanding that matter is made out of atoms (at distances of the order of angstroms or ten to the minus six centimeters or some.) And then with better microscopes and better tools we discovered that atoms were actually made out of little nuclei and electrons. So there were nuclei like the protons, and electrons. (That was at distances of ten to the minus eight centimeters.)
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And in the twentieth century, we explored the property of nuclei and discovered that the nucleus was built out of little smaller point-like quarks, (in addition to the leptons.) And that required microscopes that have taken us to something like 10-17 cm of precision. And that's more or less where experiments stop today.
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And on the basis of those experiments we have constructed, what's sometimes called the standard model, which is a remarkably successful theory of these constituents of matter, of the stuff that makes ordinary matter, and of the forces that hold these particles together.
(The forces that hold quarks together are called gluons. They are the glue that binds quarks inside the proton. The forces that act on electrons, leptons, are called electromagnetism and the particles of electromagnetism are photons. So we now have a very comprehensive theory which describes the matter and the forces between these particles.)
And this theory has been developed over many years now and has been tested at great precision with our present experiments, our present day accelerators. And it works.
