Which planet has the shortest days?

Which planet has the shortest days?

• A. Mercury
• B. Neptune
• C. Jupiter
• D. Earth

Answer: (C)

Day length is determined by how fast a planet spins on its axis—the faster the spin, the shorter the day. Jupiter rotates the quickest among the planets, so its day is the shortest. Mercury, by contrast, turns very slowly, giving it a long day. Earth’s day is longer than Jupiter’s, and while Neptune and Uranus also spin relatively fast, their days are still longer than Jupiter’s because their rotation isn’t as rapid as Jupiter’s.

Day length is determined by how fast a planet spins on its axis—the faster the spin, the shorter the day. Jupiter rotates the quickest among the planets, so its day is the shortest. Mercury, by contrast, turns very slowly, giving it a long day. Earth’s day is longer than Jupiter’s, and while Neptune and Uranus also spin relatively fast, their days are still longer than Jupiter’s because their rotation isn’t as rapid as Jupiter’s.