The moon's distance from Earth is measured very accurately by bouncing a laser beam off of a small mirror left on the surface of the moon. If a laser is fired at the moon and the signal returns in 2.6 seconds, what is the distance to the moon?

Question

Quizplus · Accepted Answer

The total time for the laser to travel to the moon and back is 2.6 seconds, so the one-way trip is 1.3 seconds. The speed of light is approximately 300,000 km/s, so the distance to the moon is 1.3 seconds * 300,000 km/s = 390,000 km.

The Moon's Distance from Earth Is Measured Very Accurately by Bouncing