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As seen from space, Earth's distinguishing characteristics are its blue
waters and white clouds.
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Scientists think the Earth is about 4.5 to 4.6 billion years old.
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The Earth is 93 million miles from the Sun.
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It is 7,926 miles across at the equator.
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The Earth travels around the sun at 66,663 miles per hour.
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The Earth is covered with a blanket of air consisting of 78% nitrogen
and 21% oxygen, and is the only planet in our solar system known to harbor
life at this time.
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The atmosphere has been divided by scientists into five main layers.
The first layer closest to the planet is the troposphere. It is about 10
miles thick, and that is where storms, lightning and thunder occur. The
second layer is the stratosphere, which is about 30 miles thick. Pilots
like to fly their planes here, above the storms. The mesophere is next,
and it is about 50 miles thick and is the coldest part of our atmosphere,
with temperatures about 135 degrees below zero. The ionosphere is next,
and then the last layer, the exosphere, which extends more than 1,000 miles
above the planet.
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The average temperature of the planet is 59 degrees.
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Earth is the only known planet with water in liquid form. (See Europa)
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71% of the Earth's surface is covered with water.
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The Earth has an extensive magnetic field, and when paired with the
atmosphere, shields us from nearly all of the harmful radiation coming
from the sun and other stars.
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Earth is the only planet whose crust is divided into separate plates
which float over a mantel below. There are eight major plates and they
are constantly moving. The movement of these plates causes volcanoes, earthquakes
and the development of islands, like Hawaii.
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The Earth's crust, the rocky surface that covers our planet, even under
the oceans, is 20-40 miles thick. In the deepest parts, it is hot enough
to melt rocks.
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The center of the Earth, the core, is made of melted nickel and iron
and is more than 1,240 miles thick. Hot melted rock deep inside the Earth
is known as magma.
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