Hurrah, we come to the end of the module! We started by asking how we can calculate the distance to the Moon very accurately, sitting here on Earth. Though there are many ways of calculating this distance, the most accurate way is by using Laser Ranging.

Laser Ranging is very similar to SONAR, except that laser light is used instead of sound waves. When NASA landed humans on the moon, they placed mirrors there.

So, we can now shoot off a laser ray from the Earth, which gets reflected from the mirror and returns to the Earth. If we know how much time it took the ray to return to the Earth, we can calculate the distance to the Moon, because we know the speed of the laser ray.

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Check out the next module in this series! Why We Fall Ill 1