The period of rotation of the Moon on its...

🔍 Key Concepts

• The Moon keeps (roughly) the same face toward the Earth because its rotation period and orbital period are closely related • A day on the Moon (one full spin on its axis) is not the same as an Earth day • Think about the time it takes the Moon to go once around the Earth relative to the distant stars (its sidereal period)

💭 Think About

• If the Moon always shows nearly the same face to Earth, what does that tell you about how long it takes to rotate once on its axis? • Compare the given answer choices to how long it takes the Moon to move from one star background position back to the same position—does that match hours, days, a month, or many years? • Which of the choices sounds like the timescale of the Moon’s orbit around Earth, rather than Earth’s orbit around the Sun or a long eclipse cycle?

✅ Before You Answer

• Eliminate answers that clearly match Earth’s rotation or Earth’s revolution around the Sun, not the Moon’s rotation • Ask: which option is approximately the length of a lunar orbital period (one trip around Earth relative to the stars)? • Make sure the time scale you select is on the order of weeks, not hours or many years

The period of rotation of the Moon on its axis is __________.

24 hours

about 27.3 days

365 days

about 19 years