Which of the following best explains why the Moon's orbital period and rotation period are the same? a. The Moon was once closer to Earth, but the force of gravity got weaker as the Moon moved farther away. b. The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period. c. The equality of the Moon's orbital and rotation periods is an extraordinary astronomical coincidence. d. The law of conservation of angular momentum ensured that the Moon must have the same amount of rotational angular momentum as it has of orbital angular momentum.

Question

Raina Parsons

Physics

4 November, 18:39

Which of the following best explains why the Moon's orbital period and rotation period are the same? a. The Moon was once closer to Earth, but the force of gravity got weaker as the Moon moved farther away. b. The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period. c. The equality of the Moon's orbital and rotation periods is an extraordinary astronomical coincidence. d. The law of conservation of angular momentum ensured that the Moon must have the same amount of rotational angular momentum as it has of orbital angular momentum.

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Answers (1)

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Kathryn Cannon · Answer 1

b. The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period

Explanation:

Almost all moons orbiting large planets still show the same face to the earth for the same fundamental reason. Due to the Earth's effect on the moon, tidal forces are always facing the Earth from the same moon's side. The time of the rotation and the moon's orbit are the same. Earth-bound observers can thus never get to see the "moon's far side."