Postulates of Special Relativity•First Postulate:All laws of nature are the same in all uniformly moving frames of reference–i.e. The behavior of a coin when flipped on a plane that is moving at constant velocity is no different than if flipped while standing still•No experiment confined in the moving reference frame itself can determine whether or not there is uniform motion
Postulates of Special Relativity•Second Postulate:The speed of light, c, in empty space will always have the same value regardless of the motion of the source or observer.
Time Dilation•Light Clock:A flash of light bounces back and forth between parallel mirrors and “ticks” equal intervals of time
Time Dilation•Consider a light clock observed from someone inside a fast-moving space ship–This observer would see the light bouncing vertically up and down•Consider a light clock observed from someone outside a fast-moving space ship–This observer would see the light moving along a diagonal path, which is therefore longer
The Twin Trip•Consider identical twins:–One twin takes a high speed round-trip journey–The other twin stays on Earth•When he returns, the traveling twin will be younger than his stay-at-home twin –i.e.) Traveling at 50% c, 1.15 years will elapse on earth–i.e.) Traveling at 99.5% c, 10 years will elapse on earth