Earth's rotation takes how many hours to complete?

Earth's rotation takes how many hours to complete?

• A. 12
• B. 48
• C. 36
• D. 24

Answer: (D)

The key idea is how long it takes Earth to turn once on its axis relative to the Sun, which defines a day. A full solar day—the cycle of day and night—takes about 24 hours. That’s because Earth must rotate a little extra beyond a straight 360-degree turn to bring the Sun back to the same position in our sky as the planet also moves along its orbit around the Sun. If you measure rotation relative to distant stars (a sidereal day), it’s about 23 hours 56 minutes, but the everyday day length we experience is 24 hours. The other options don’t match the familiar day length: 12 hours would be half a day, 36 would be longer than a day, and 48 would be two days.

The key idea is how long it takes Earth to turn once on its axis relative to the Sun, which defines a day. A full solar day—the cycle of day and night—takes about 24 hours. That’s because Earth must rotate a little extra beyond a straight 360-degree turn to bring the Sun back to the same position in our sky as the planet also moves along its orbit around the Sun. If you measure rotation relative to distant stars (a sidereal day), it’s about 23 hours 56 minutes, but the everyday day length we experience is 24 hours. The other options don’t match the familiar day length: 12 hours would be half a day, 36 would be longer than a day, and 48 would be two days.