Teaching Physics with the Physics Suite

Edward F. Redish

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Measuring the speed of light a la Galileo

Galileo tried to measure the speed of light by having two people stand on hills about 5 km apart. Each would hold a shuttered lantern. The first would open his lantern and when the second saw the light, he would open his lantern. The first person would then measure how much time it took between the time he first opened his lantern and when he saw the light returning.

  1. How much time would it take the light to travel between the two hills?
  2. Is this a good way to measure the speed of light? Support your argument with a brief explanation that includes some quantitative discussion of the uncertainty in the measurement.

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Page last modified October 23, 2002: OP01