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Chapter

Tides

1 pages91 viewsFall 2013

Department
Physics, Engineering Physics and Astronomy
Course Code
ASTR 101
Professor
Prof.

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Tides
Tides arise due to the fact that the gravitational force exerted from a body like Earth
depends on how far away you are from it
The moon influences the tides as it is close to the Earth, producing a "fat cigar"
shape
There are two high tides: the side closest to the moon is stretched into a
bulge, whereas the far side is high due to the Earth being pulled towards
the moon
The sun also influences the tides however the effect is less despite having a stronger
gravitational influence than the moon
This is because the gravity of the sun is so strong that the size of the Earth does
not produce enough variance in the tidal influence
When the sun and the moon are in line with the Earth, the effects are
amplified, producing even higher tides than spring tides (nothing to do
with the season)
When the sun and moon are at 90° to one another, the forces partially
counteract, producing less impressive tides called neap tides
Complications:
The Earth also consists of rocks which are not rigid, so the Earth too is
influenced by tidal forces
Topography of ocean floor also can influence tides
As the water bulges towards the moon, it is attracted by gravity and 'wants' to
stay pointed towards the moon
Results in a force opposing the Earth's rotation, causing the Earth to
gradually slow down
Eventually, the Earth will slow to the point where one face of the Earth is
always facing the moon, just like how the moon has one face always
pointing to the Earth
Conservation of angular momentum causes the slowing Earth to affect
the moon's orbit, thus causing the moon to recede away from Earth at a
rate of 4cm/year
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