User:John Carter/Tachyon

From Wikipedia, the free encyclopedia

Tachyon (pronunciation characters I can't find), a hypothetical subatomic particle that travels faster than the speed of light, which is about 300,000 kilometers per second (186,000 mph) in free space. Its name is derived from the Greek word tachys, meaning "swift". While it has often beens tated that the special theory of relativity implies that nothing can travel faster than light, in reality that theory rules out only the possibility of accelerating a particle from a speed below that of light to a speed greater than that of light. Such acceleration is not required in the theory of tachyons, which is consistent with relativity, because these particles always travel faster than light and hence need not be accelerated through the "light barrier".

If tachyons were indeed to exist, their energy and momentum would be real quantities and could be measured by their interactions with ordinary objects. One unusual property that tachyons would have is that their kinetic energy would decrease as their speed increased. Thus a tachyon that radiated away some energy would speed up, eventually reaching infinite speed as its energy approached zero. On the other hand, a tachyon that gained energy from some outside source would slow down, and its speed would come closer to the speed of light but never go below it.

Several experiments have been performed in an effort to create and detect tachyons. Such experiments are based on the hypothesis that if tachyons exist, then, as is the case with other subatomic particles, it should be possible to create them in reactions between known particles, even if no tachyons are present at the beginning of the experiment. As of the early 1990s no experiment had succeeded in creating and detecting tachyons. Whether this means that tachyons do not in fact exist, or whether future experiments of a different type will reveal them, remains uncertain.

Gerald Feinberg, Columbia University