Our Moon
Moon dominant celestial object (after sun!)
- Earth’s only natural satellite
- As big as Jupiter and Saturn’s biggest moons
- Jupiter 300 times as massive as the Earth
Moon shines from reflected sunlight
- Also true of all the planets
- planets and moons also emit infrared (heat) radiation
- all heated objects glow
- Hot objects (i.e. Sun) glow in visible (red, green, blue)
- warm objects (planets, people, etc.) glow in infrared
- longer wavelength’s than red (see Chap. 6)
Therefore Moon shows phases
- Exactly 1/2 the Moon is illuminated
- phases from Moon’s orbit around Earth v15