proton
In physics, a positively charged elementary particle, a constituent of the nucleus of all atoms. It belongs to the baryon group of hadrons and is composed of two up quarks and one down quark. A proton is extremely long-lived, with a lifespan of at least 1032 years. It carries a unit positive charge equal to the negative charge of an electron. Its mass is almost 1,836 times that of an electron, or 1.673 × 10−24 g. The number of protons in the atom of an element is equal to the atomic number of that element.
| In January 2001, scientists at the Kamioka Observatory, Tokyo, Japan, proposed plans for a US$326 million project to study whether protons decay over time. The experiment would involve setting up a tank containing one million tons of water, that would show up decaying protons as faint flashes. Protons are believed by many scientists to have a half-life 20 times the age of the universe. |
