Tides and Tidal Forces
Near Satellites Orbit Faster
What If Satellites Are Tethered?
The Tension Is Real
There are
Two Tidal
Bulges
on Earth
Both Moon and Sun Cause Tides
Tides on the Real Earth
Tidal Friction
Tides
Affect
Earth
and
Moon
Tides and the Earth-Moon System
• Moon retreating at 4 cm/yr
• Day currently lengthening by 2 sec/100,000 yr
• Fossil organisms and some rocks preserve tidal
records
• 600 million years ago
– Day was 22 hours long
– 400 days/year
– Moon 13,000 km closer
– Rate of change not constant
Tides and Planets
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•
•
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All satellites are locked to their parent planets
Large tides can heat planetary interiors
Tidal forces change orbital eccentricity
Most satellites
– Planet rotation slows
– Moon moves outward
– Can “leak” away (Deimos)
• Retrograde Satellites
– Satellite moves inward (Triton)