3.2.4 Overview of Earth⭐地球概况
Earth is where we all live.
It is our home in the solar system.
There is no other place for us to live.
Earth isn’t just any planet.
It’s a very special place.
It’s special because we depend on it for many things.
Because of its importance, we need to take care of it.
We depend on the Earth for its air, its water and many of its natural resources.
Natural resources such as coal and oil give us energy.
Other natural resources we depend on include forests and soil.
Forests provide clean air and wood for building houses.
Soil is needed to grow plants and keep them healthy.
We need to take care of these resources and not waste them.
The Earth is a large rotating sphere about 4.5 billion years old.
The equator which divides the earth into 2 hemispheres, is about 40,000 kilometers long.
The Earth diameter is 12,756 kilometers.
Its radius is half that, or 6378 kilometers.
The radius is the distance from the Earth’s center to its surface.
Most of the Earth’s surface is covered by water.
The rest of the Earth’s surface is land.
Just above the Earth surface is the atmosphere.
The atmosphere is a layer of gases, about 500 kilometers thick.
These gases include oxygen, nitrogen and carbon dioxide.
This mixture of gases is the air that we breathe.
As we move above the Earth’s surface, the air gets thinner.
At high altitudes, the air is too thin to breathe.
At the edge of the atmosphere is space.
There is no air at all in space.
