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Name: Virginia
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1993 - 1999
Question:
Dear Newton,

How do you measure the speed of light?

Replies:
Since light moves very fast, you either need to measure its motion over a very long distance, or else you need to be very fast about it. The first measurements (including one based on the orbits of the moons of Jupiter) used the long-distance approach, but with modern very fast clocks and other technolog y it's not that hard to measure the few nanoseconds it takes for light to travel a certain distance. Actually, nobody ever has to measure the speed of light again because it's been established as a constant that is used to define the metric unit of length (the meter) in terms of the unit of time (the second) which we can measure much more precisely.

A Smith


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