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Earth's Days Lengthen: From 5 Hours to 24

4/7/2025

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Summary

Story summary

Earth's days are gradually stretching, lengthening by 1.7 milliseconds each century as it drifts 3.78 cm away from the Moon. Using retroreflectors from the Apollo missions, scientists reveal that early Earth had just five-hour days, a transformation driven by the Moon's gravitational pull over 4.5 billion years, resulting in our current 24-hour cycle.

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Story summary

Earth's days are gradually stretching, lengthening by 1.7 milliseconds each century as it drifts 3.78 cm away from the Moon. Using retroreflectors from the Apollo missions, scientists reveal that early Earth had just five-hour days, a transformation driven by the Moon's gravitational pull over 4.5 billion years, resulting in our current 24-hour cycle.