This is how corner reflectors work. A signal sent from *any* direction gets reflected back toward the sender. Simple maths with great applications. We even put some on the Moon!

Gif by @panlepan

The maths behind this is nice and simple. Multiply reflections through 3 pairwise perpendicular planes and you get minus the identity. So every vector gets reversed.

An everyday use for corner reflectors is the safety reflectors on bikes. If you arrange these cube corners in a nice hexagonal pattern, you get one of these.

Back to the Moon, the reflectors left there by Neil Armstrong and Buzz Aldrin were used to measured the Moon& #39;s motion with millimetre precision.

https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment">https://en.wikipedia.org/wiki/Luna...

*measure