But, if an object could reach the speed of light, it's length would shrink to nothing. As length becomes shorter for a moving object, its mass increases and time slows down. Relativity forced a reexamination of the physical properties of energy and momentum. From this new understanding, scientists realized that enormous amounts of energy could be released from a very small amount of matter. This made possible atomic bombs, and the use of nuclear fission for producing useful energy.
Light experiences red and blue shifts as a light's source moves.
The speed of light is constant regardless of how the source moves, but the motion can cause the light's spectrum the range of its colors to shift up blue shift or down red shift. It appears that galaxies are moving away from us in every direction, because their light is red shifted. So, relativity implies that the universe is expanding. Copyright 2000 - Byrd and Block Communications, Inc.