The Moon completes one orbit around Earth in approximately how many days?

The Moon completes one orbit around Earth in approximately how many days?

• A. 24 days
• B. 27 days
• C. 28 days
• D. 30 days

Answer: (B)

The Moon’s orbital period around Earth is about 27.3 days when measured against distant stars, called the sidereal month. This is the time it takes the Moon to complete one full revolution around Earth, independent of the Sun’s position. Because Earth is moving around the Sun, the Moon also has a roughly 29.5-day cycle from new moon to new moon, known as the synodic month, which is longer than the actual orbit. Among the options, 27 days is the closest to the true sidereal period, making it the best match. The 28-day figure is a reasonable rough estimate but slightly longer; 30 days aligns more with the synodic month, and 24 days is too short.

The Moon’s orbital period around Earth is about 27.3 days when measured against distant stars, called the sidereal month. This is the time it takes the Moon to complete one full revolution around Earth, independent of the Sun’s position. Because Earth is moving around the Sun, the Moon also has a roughly 29.5-day cycle from new moon to new moon, known as the synodic month, which is longer than the actual orbit.

Among the options, 27 days is the closest to the true sidereal period, making it the best match. The 28-day figure is a reasonable rough estimate but slightly longer; 30 days aligns more with the synodic month, and 24 days is too short.