MEPX
Chapter 5 of 12All chapters
  1. 1The scale of things
  2. 2The Sun
  3. 3The rocky planets
  4. 4The giant planets
  5. 5Moons
  6. 6Asteroids and comets
  7. 7Gravity and orbits
  8. 8Light and distance
  9. 9Stars and their lives
  10. 10Galaxies
  11. 11The expanding universe
  12. 12Observing for yourself

Chapter 5 of 12

Moons

Worlds of their own.

Ours

The Moon is about a quarter of Earth's width and keeps one face towards us because its rotation matches its orbit. It drives the tides and steadies the tilt that gives us stable seasons.

  • The phases come from the angle of sunlight, not from Earth's shadow.
  • An eclipse needs the three bodies in a line, which is why they are rare.

Elsewhere

Jupiter and Saturn have dozens each. Europa and Enceladus hide liquid water under ice, and Titan has a thick atmosphere and lakes of methane, which makes them the most interesting places to look for life.