The Moon cycle lasts how many days?

• A. 365 days
• B. 29.5 days
• C. 7 days
• D. 12 hours

Answer: (B)

Think about how long it takes for the Moon to go through all its phases and line up with the Sun and Earth in the same way again. That repeating pattern, called the synodic month, is about 29.5 days (roughly 29.53 days). The reason it’s longer than the Moon’s orbital time relative to the stars (about 27.3 days) is that Earth is also moving around the Sun, so the Moon has to travel a bit more to reach the same phase relative to the Sun. The other options describe unrelated timescales: a year, a week, and a half-day. So the Moon cycle lasts about 29.5 days.