THE PROTON
 

Protons are too small to be observed directly, even with the most powerful microscopes. All protons carry a positive electric charge, and the charge on every proton is the same as the charge on every other. Every proton at rest has the same mass as every other proton at rest. Most scientists accept the proposition that all protons are identical, at least in our part of the universe, although they, like all other particles, gain mass if accelerated to extreme speeds. This increase in mass takes place because of relativistic effects; you’ll learn about this later.
While an individual proton is invisible and not massive enough to make much of an impact all by itself, a high-speed barrage of them can have considerable effects on matter. Protons are incredibly dense. If you could scoop up a level teaspoon of protons the way you scoop up a teaspoon of sugar—with the protons packed tightly together like the sugar crystals— the resulting sample would weigh tons in the Earth’s gravitational field. A stone made of solid protons would fall into the Earth and cut through the crustal rocks like a lead shot falls through the air.