| |
| | A brief history |
 | | The animated neutral particle, marked N, represents a neutral elementary particle such as a neutrino colliding with one of the nuclei of the atoms in the fluid, producing a cascade of charged particles that then decay into other charged particles. |
 | | Particle physicists have to decode tracks like those above in order to deduce basic information about the observed particles, such as the electric charge, particle spin, mass, lepton number, baryon number, parity and other quantum numbers that turn out to be useful in describing the elementary particle side of Nature. |
 | | Alpha particles are discovered, and later shown to be helium nuclei consisting of two neutrons and two protons. |
| www.superstringtheory.com /experm/exper1.html (651 words) |
|