Earth Explorers

地球是我們賴以生存的地球。它是從太陽的第三顆行星

Earth is the planet we live on. It is the third planet from the Sun. It is the only planet known to have life on it. The Earth formed around 4.5 billion years ago. It is one of four rocky planets on the inside of the Solar System. The other three are Mercury, Venus, and Mars.

The large mass of the Sun makes the Earth move around it, just as the mass of the Earth makes the Moon move around it. The Earth also turns round in space, so different parts face the Sun at different times. The Earth goes around the Sun once (one "year") for every 365¼ times it turns all the way around (one "day").

The Moon goes around the Earth about every 27⅓ days. As the Earth goes round the Sun at the same time, the changing light of the Moon takes about 29½ days to go from dark to bright to dark again. That is where the idea of "month" came from. However, now most months have 30 or 31 days so they fit into one year.

The Earth is the only planet in our Solar System that has a large amount of liquid water. About 71% of the surface of the Earth is covered by oceans. Because of this, it is sometimes called the "Blue Planet".

Because of its water, the Earth is home to millions of species of plants and animals. The things that live on Earth have changed its surface greatly. For example, early cyanobacteria changed the air and gave it oxygen. The living part of the Earth's surface is called the "biosphere".