Apollo astronauts left mirrors on the Moon. By bouncing lasers off them, scientists measure that it moves about 3.8 cm further away each year. Earth's days are slowly getting longer as a result.
Truth label: Established. Strong evidence and broad agreement among experts.
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Tidal tug
The Moon's pull raises tides, and the friction drags on Earth's spin while giving the Moon a push outward.
Ancient long nights
Hundreds of millions of years ago, a day lasted less than 22 hours.
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- Still working. The Apollo mirrors placed over 50 years ago are still used today.
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How do we measure the Moon's distance so precisely?
Lasers and mirrors. Lasers bounce off mirrors left by Apollo crews.
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