Why do we always see the same moon face?
Show answer & explanation
Answer: Tidal locking synchronizes rotation
Moon doesn't rotate at all — Wrong. The moon does rotate—once per orbit (~27.3 days). We see the same face because its rotation period equals its orbital period (tidal locking).
Tidal locking synchronizes rotation ✓ — Correct! Tidal locking (synchronous rotation) means the moon's rotation period equals its orbital period around Earth. Earth's gravity created tidal bulges on the moon long ago. These bulges experienced torque, gradually slowing the moon's rotation until it matched the orbit. Now the same face always points Earthward. Many moons are tidally locked to their planets!
Moon is perfectly spherical — Wrong. Shape doesn't determine this. Tidal locking occurs when gravitational interactions synchronize rotation and orbital periods over time.
More Astronomy & Space questions
- Earth's atmosphere slowly leaks to space. Which gas escapes fastest?
- Why is Earth's day getting slightly longer every century?
- Why was Earth's day stuck at 19.5 hours for 1.5 billion years?
- Why might several small units beat one giant Moon reactor?
- Why is fission likelier than fusion for first Moon bases?
- Why put a lunar reactor away from the habitat?