HIGH-SPEED PARTICLES

You’ve heard expressions such as electron rest mass, which refers to the mass of an electron when it is not moving relative to an observer. If an electron is observed whizzing by at relativistic speed, it has a mass greater than its rest mass and thus will have momentum and kinetic energy greater than is implied by the formulas used in classical physics. This fact, unlike spatial distortion, is more than mere fodder for “mind experiments.” When electrons move at high enough speed, they attain properties of much more massive particles and acquire some of the properties of x-rays or gamma rays such as are emitted by radioactive substances. There is a name for high-speed electrons that act this way: beta particles.
Physicists take advantage of the relativistic effects on the masses of protons, helium nuclei, neutrons, and other subatomic particles. When these particles are subjected to powerful electrical and magnetic fields in a device called a particle accelerator, they get moving so fast that their mass increases because of relativistic effects. When the particles strike atoms of matter, the nuclei of those target atoms are fractured. When this happens, energy can be released in the form of infrared (IR), visible light, ultraviolet (UV), x-rays, and gamma rays, as well as a potpourri of exotic particles.
If astronauts ever travel long distances through space in ships moving at speeds near the speed of light, relativistic mass increase will be a practical concern. While their own bodies won’t seem to be more massive from their own point of view and the things inside the ship will appear normal to them, the particles whizzing by outside will become more massive in a real and dangerous way. It is scary enough to think about what will happen when a 1-kg meteoroid strikes a space ship traveling at 99.9 percent of the speed of light. However, that 1-kg stone will mass more than 22 kg when u = 0.999. In addition, every atom outside the ship will strike the vessel’s “prow” at relativistic speed, producing deadly radiation of the same sort that occurs in high-energy particle accelerators