Retroreflectors are immediately useful for improving our understanding of gravity: https://en.wikipedia.org/wiki/Apache_Point_Observatory_Lunar_Laser-ranging_O

Retroreflectors are immediately useful for improving our understanding of gravity: https://en.wikipedia.org/wiki/Apache_Point_Observatory_Lunar_Laser-ranging_Operation https://en.wikipedia.org/wiki/Apache_Point_Observatory_Lunar...