Tidal force on oceans

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Tidal force on oceans
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Highs and Lows

• Generally- 2 high tides per day, 2 low tides per
  day
• Orbit of moon means next day will move these
  tides to 45 minutes later
• Diagram of tides.swf

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Spring and neap tides
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Extreme tide at Bar Harbor, Maine
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Effect of tides

• Earth rotates faster than the moon orbits, thus
• tidal bulge dragged back towards the moon
• tidal bulge pulls the moon ahead (accelerating
  it)
• Consequences
• Earths rotation period slows currently at
  roughly 0.002 seconds per century (day length
  increases about 1 hour per 200 million years
  currently)- earliest dinosaurs had a 23 hour day
• Moon distance increases 3.5 cm per year