# Unit 1 Earths Dimensions

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What IS the shape of the Earth?
 Earth is NOT a
perfect sphere, but it
IS close!
 The true shape of
Earth is an oblate
spheroid.
 This means that
Earth’s equatorial
diameter is slightly
larger than its polar
diameter.
Evidence of Earth’s 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
More on Gravitational Measurements
 Gravity is the force of attraction between any two
objects.
 Newton’s Law of Gravitation – the gravitational force is
proportional to the square of the distance between the
two centers of attracted objects.
• 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!
Where would you weigh the least
on Earth??
Altitude of Polaris (North Star)
 Because of Earth’s spherical
shape, the altitude (height or
observer’s eye and the
observer’s horizon) of
Polaris (Northern Star) is
equal to the observer’s
latitude, but only in the
northern hemisphere.
 Why not in the Southern
Hemisphere?
The Different “Spheres” of Earth
Match the following terms a) Layer of rock forming
with their appropriate      a solid outer shell of
definitions.                Earth’s interior
b) Layer of liquid water
1. Atmosphere
lying between the
atmosphere and
upper layer of Earth’s
2. Hydrosphere                interior
c) Layer of gases
3. Lithosphere                surrounding Earth’s
surface

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 views: 4 posted: 9/9/2012 language: English pages: 6