Solved cryptogram
The moon drifts a few centimeters farther from Earth each year, and lasers measure the change.
Astronomy Facts, sourced to NASA.
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What it means
The same tidal friction that slows the Earth's spin transfers that momentum to the moon, and a body given more momentum climbs into a wider orbit. Apollo astronauts left reflector panels on the surface, and observatories still bounce laser pulses off them, timing the round trip to within a few centimeters. The retreat has been measured directly for over fifty years.
The claim comes from NASA.
- SourceNASA
- CollectionAstronomy Facts
- Difficultymedium
- Length77 letters, 18 unique
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