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Lesson 1 Spherical Earth

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					    Lesson 1: Spherical Earth
A. Describe Earth

  1. Scientists see the shape of Earth in pictures taken
     by satellites.

  2. These pictures show that Earth is not quite a perfect
      sphere, which has all points on the surface at an
      equal distance from the center.

  3. Instead, Earth looks like a slightly flattened ball, with
      a bulge at the equator.
B. Earth Systems
   1. Earth has four systems that interact with
   each other.

   2. Earth’s outermost system is the
   atmosphere, which is made up of the layer of
   gases surrounding the planet.

   3. Earth’s hydrosphere includes all the water
   found on Earth’s surface, below ground, and
   as a liquid in the atmosphere.
4. As water moves between the air and
Earth’s surface forming raindrops or
evaporating from puddles, the atmosphere
and the hydrosphere interact.

5. Earth’s entire solid body is called the
geosphere.

6. All the living things on Earth form the
biosphere.
C. How did Earth form?

   1. Earth and the rest of the solar system
   formed from a large cloud of dust and
   gas.

   2. Gravity made the material in the cloud
   come together to form the Sun and the
   rest of the Solar system.
3. Gravity is the force that every object exerts
on every other object.

   a. The strength of gravity depends on the
amount of mass in and the distance between the
objects.

    b. The more mass two objects have, the
stronger the force of gravity is between them.
   c. The closer two objects are to one
another, the stronger the force of gravity is
between them.

4. Objects near the Earth’s surface fall to
the ground because Earth’s gravity pulls
objects toward the center of the planet.
D. The Solar Nebula

  1. The solar system formed from a cloud of
     material called a nebula.
  2. Because of the force of gravity, the cloud
     shrank, flattened into a disk, and began to
     rotate.
  3. The material at the center of the rotating
     disk became a star that we call the Sun.
  4. The remaining bit of material around the star
     formed the planets. Including Earth.
E. Early Earth

   1. As Earth grew, it heated up inside. Its
   rocks softened and began to flow.

   2. Gravity pulled surface bumps toward
   Earth’s center. Earth began to look like a
   sphere.
F. The Formation of Earth’s Layers

  1. Thermal heat inside Earth melted some of
     the materials that formed Earth.

  2. These liquid materials were able to move, or
     flow, and form layers.

  3. Earth’s layers formed because of differences
     in density of the materials.

				
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