Time Dilation
Ed and Joe are watching a light clock. (A beam of light bouncing between two mirrors) which is moving along at a very high velocity. The light clock is traveling at nearly the speed of light. Ed is watching the light clock while traveling along with it at nearly the speed of light. Joe is standing in a fixed spot watching the light clock move away from him at nearly the speed of light.
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From Ed's point of view, the light beam travels in a vertical path. |
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From Joe's point of view, the path is much longer. The light beam moves along an angled path. |
| Since the speed of light is always constant, it would take longer for Joe's light beam to go up and come back down again. The effect would be that the clock would slow down, or in other words, time would dilate. | |
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The faster the clock is traveling relative to the observer, the 'slower' the clock seems to tick due to the longer distance that the light must travel. |