Earth's Shape

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Earth's Shape
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Aim What is the shape of the Earth?
I. Shape of the Earth
A. The Earth is NOT a perfect sphere, but it is
close!!!!!
B. Oblate spheroid the true shape of earth in
which its equatorial diameter is slightly larger
than its polar diameter.

• Polar Diameter (measured from N.Pole to S. Pole)
  12,714 Km
• Equatorial Diameter 12,757 Km

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N
Polar Diameter
Equatorial Diameter
S
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C. Evidence of Earths Shape
1. Photographs of Earth from outer space show
that Earth is round
2. Years ago, sailors noticed that ships slowly
disappeared or appeared over the horizon.
3. Gravity measurements
a. Gravity is the force of attraction between any
two objects.
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b. The Law of Gravitation the gravitational
force is proportional to the square of the
distance between the two centers of attracted
objects.
Gravitational Force
Distance Between two objects
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c. If Earth was a perfect sphere, then the force
of gravity would be the same anywhere on the
surface. But, the force of gravity is actually
greater at the poles than at the equator. Thus,
the distance from the poles to the center of the
Earth is less than the distance from the equator
to the center of the Earth!!!!!
4. Altitude of Polaris (North Star)
a. The altitude (height or angle made between the
observers eyea and the observers horizon) of
Polaris is equal to the observers latitude (only
in the northern hemisphere).