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The light clock is a simple clock which we can use to understand
relativistic time dilation. The base of the clock emits a pulse of
light up towards a mirror on the top of the clock. The pulse is then
reflected down to the bottom and detected. This is one clock tick.
If the height of the clock is one meter, then since the speed of light is 299 792 458 meters per second, the tick is (1 m +1 m)/(299 792 458 m/s) = 0.000 000 006 67 seconds, or about six and two-thirds nanoseconds. This is the time it takes the light pulse to travel the 2 meter distance up and back down. |