Approximately how many days does the Moon take to revolve around the Earth?

Approximately how many days does the Moon take to revolve around the Earth?

• A. 1 year
• B. 30 days
• C. 27 days
• D. 29.5 days

Answer: (C)

The Moon’s motion around Earth is best described by its sidereal month, which is about 27.3 days. This is the time it takes for the Moon to return to the same position relative to distant stars. The longer ~29.5-day cycle you might have heard of is the synodic month, the cycle of the Moon’s phases, because Earth is moving around the Sun as the Moon orbits, so it takes a bit longer to catch up in the Sun-Earth-Moon alignment. So, approximately 27 days is the orbital period around Earth. The other options don’t reflect the actual orbital period.

The Moon’s motion around Earth is best described by its sidereal month, which is about 27.3 days. This is the time it takes for the Moon to return to the same position relative to distant stars. The longer ~29.5-day cycle you might have heard of is the synodic month, the cycle of the Moon’s phases, because Earth is moving around the Sun as the Moon orbits, so it takes a bit longer to catch up in the Sun-Earth-Moon alignment. So, approximately 27 days is the orbital period around Earth. The other options don’t reflect the actual orbital period.