Many readers have heard that lasers can now be fired from Earth to the Moon and reflected back. By calculating the round-trip time of the light, the distance between the Earth and the Moon can be measured. The question now is: what kind of mirror can reflect light coming from different angles back in the same direction? Mirrors designed for this purpose are known as “multi-angle reflectors” (retroreflectors).
Do not think that this requires very difficult physics knowledge. It can be achieved using just two (or three, when considering 3D space) mirrors that are mutually perpendicular to each other. Please see the figures below (blue represents the mirrors, orange represents the light rays).
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