Einstein’s Special Theory of Relativity shows that both distance and time change with velocity. Einstein reached this conclusion by noting that one must define methods of measuring both distance and time. The result is that as objects move near the speed of light their length (in the direction of motion) shrinks and their internal clocks that measure time run slower. The amount of change is described by a factor called *γ* (gamma), which is always larger than one. Thus the time given by a moving clock is γ*t,* where *t* is the time shown by a fixed clock, and length is given by *lγ,* where *l* is the length of the fixed object. The table below shows *γ* for a variety of velocities (note that *c* is the speed of light):

Velocity |
*γ* |

550 mph |
1 3 x 10^{-11} |

17,500 mph |
1 3 x 10^{-8} |

0.5 *c* |
1.2 |

0.9 *c* |
2.3 |

0.99 *c* |
7.1 |

0.995 *c* |
10.0 |