Up until the early part of the nineteenth century it was generally thought that the atom was the smallest constituent of matter. The word “atom” comes from the Greek for “uncuttable”. The work of Marie Curie, Joseph Thomson, Ernest Rutherford, Niels Bohr and others led to the discovery of even smaller particles: the electron, proton, and neutron.
The nucleus of the atom contains protons and neutrons, and the electrons surround the nucleus creating the shell. The nucleus is only 1/100,000th the diameter of the atom. Compare the size of a baseball to that of a ball park. Nearly all the mass of the atom is in that tiny nucleus.
A billion atoms in a row would make a line only a few centimeters long. Recent work carried out at the sites of the largest particle accelerators has confirmed that these three atomic particles are themselves composed of combinations of even smaller constituents which we call “quarks.”
Murray Gel Mann took the name quark from the novel Finnegan’s Wake by James Joyce. There are six quarks that combine to make sub-atomic particles. They are named: up, down, charmed, strange, top and bottom. Think of them as flavors in a cosmic ice cream shop. To make a proton shake, you need two scoops of up and a scoop of down. A neutron – 2 scoops of down and a scoop of up.