What causes the phases of the Moon?

Start playing free

  1. Earth's shadow covering part of the Moon
  2. Clouds blocking part of the Moon
  3. Seeing more or less of its sunlit half

🔒 The answer is for AhaBulb members. Members see the answer, why it's right and the official sources for every card of Stuff Every CAP Aerospace Cadet Should Know, plus timed practice exams.

The first 50 cards of every test are free to play.

Play the free cards See membership

Like this card?
Play the game

References

  1. NASA Science: Moon Phases science.nasa.gov/moon/moon-phases Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game