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Earth is the third planet from the sun. You probably already know a lot about the planet Earth
because Earth is the planet where we live! Although it is the largest of the inner planets,
the four rocky planets that orbit nearest the sun, the Earth is far, far smaller than
the four gas giants that circle the outer edges of the solar system. The earth is also the first planet
when traveling out from the sun to have a moon, and the only planet in the solar system
to have only one moon.
The Earth is unique among the planets of the solar system, because Earth is the only planet that
has liquid water on its surface. Other planets are either too hot - causing all their water
to evaporate into gases, or too cold, causing any water they have to freeze into ice.
The earth is about 93 million miles, or 150 million kilometers, away from the sun, which
keeps it at just the right temperature to have liquid water - and the earth has a LOT of water!
More than 70% of the Earth's surface is covered by oceans. That means that the oceans are more than
twice the size of all the land on Earth. Because Earth has so much water on it, it is sometimes
called the 'blue planet.'
Liquid water is what allows life to exist on earth. As far as we know, Earth is the
only place that life exists. Millions of species of plants and animals call the planet earth home, including humans.
Earth's atmosphere is another important feature. The atmosphere is a thick layer of gases that
covers the entire earth. It is mostly made of nitrogen and oxygen. The atmosphere is what
allows us to breathe. It also helps keep the earth warm by acting like a blanket to hold in the sun's
heat. Another way the atmosphere helps us is by protecting the earth from harmful radiation
from the sun, and also from meteors. Anything falling to the earth from space is rubbed against
the gases in the atmosphere until they burn. Most things burn up completely before they reach
the surface, but even anything that makes it through is much smaller by the time it hits the ground.
The earth goes around the sun. The time it takes to go around the sun is called a year.
It takes the earth about 365 days to travel around the sun once: that is why a year is usually
365 days.
The earth also rotates, or spins. The time it takes for the earth to rotate once is called a day.
The earth rotates every 24 hours, and that is why a day is 24 hours long.
The earth does not rotate straight up and down: it is tilted. There is an imaginary line
through the earth from the north pole to the south pole, called the earth's axis, and this axis is tilted
about 23 degrees. Why is it important that the earth is tilted? Well, the tilt of the earth's
axis is what causes the seasons! When a part of the earth is tilted towards the sun, it
will be summer there. When it is tilted away from the sun, it will be winter instead.
The inside of the earth is very different from the outside. If you were to cut the Earth in half,
you could see that it is made up of different layers. The outermost layer, called the crust,
is where we live. The earth's crust is cool and solid. Everything you see - trees, mountains,
rivers, houses, and even the oceans, are sitting on top of the earth's crust. The crust is so
thick that humans have never been able to dig deep enough to break through it, but the
crust is only a thin layer on the surface of the earth.
Underneath the crust is the mantle. The mantle is a thick layer of molten rock, or magma.
It is the thickest layer of the earth. Sometimes magma from the mantle will come up to the surface
through volcanoes. The core is at the very center of the earth, and it is very, very
hot, with a temperature of thousands of degrees. It is made of metal, mostly iron and nickel,
and even though it is very hot it is under so much pressure that it is solid.
The earth is important to us because it is our home. About seven billion people live
on the Earth right now, as well as millions of species of plants and animals. So far, we have not found any
other planet in the entire universe that would make a good home for us, so it is important
that we take care of the planet we have.
I hope you enjoyed learning more about Earth today. Goodbye till next time!