Tidal Forces -- Gravity

• Important throughout solar system

  • Earth’s ocean tides v17
  • Synchronous rotation of the Moon v15
  • Synchronous rotation of most planetary satellites
  • Length of day increasing
    • 400 million years ago, day was 22 h long
  • Rings of Saturn

• Ocean tides

  • Forces on Earth from Moon (gravity!) v17
    • Relative to center of Earth
      • creates 2 bulges
        • high tide every 12.4 h
      • Tidal force of Sun ~ 1/2 that of the Moon
        • strongest (“spring”) tides at full or new Moon

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