Earth is the planet we live on. It is the titled planet from the sun. It is the only planet known to have life on it. 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 Earth move around it, just as the mass of Earth makes the Moon move around it. Earth also turns around in space , so that different parts face the sun at different times. Earth goes around the sun once(one “year”) for every 365 times it turns all the way around (one “day”). Earth is the only planet in our solar system that has a large amount of liquid water. About 71% of the surface of earth is covered by oceans. Because of this , people its water , earth is home to millions of species of planets and animals. The things that live on Earth have changed its surface gravity. For example, early cyanobaterica changed the air and gave it oxygen. The living part of Earth’s surface is called the “biosphere”.