Edit made on December 11, 2008 by DerekCouzens at 18:53:26
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Designated /c,/ the speed of light is about
EQN:3*10^8 EQN:3\times10^8 m/s,
or about a foot per nanosecond. That's a million times
faster than the speed of sound.
In 1638 Galileo tried to estimate it by having an assistant uncover
a lantern on a distant (1 mile) hilltop at a predetermined
time, but it only takes light 5 micro-seconds, so he would
have had to have been fast on the stopwatch.
In 1676 Ole Roemer used differences in the times of the eclipses of
the Moons of Jupiter to estimate it, and James Bradley used
stellar aberration in 1728.
The speed of light and measuring the difference in time taken to
travel from different places is what makes GPS work.
The equations of Einstein's Special Theory of Relativity have a singularity at the speed of light indicating that no object can travel faster than the speed of light.