User:Sílvia M. Correia/TWA/Earth





=Earth= Earth is the third planet from the Sun. It is one of the four terrestrial planets in our Solar System. That means most of its mass is solid. The other three are Mercury, Venus and Mars. Earth is also called Blue Planet, Planet Earth and Earth.

Earth is home to millions of species of plants and animals, including humans.

Earth is the only planet in the galaxy that is known to harbor life. Earth has many places that are suitable for humans to live in; although some areas of the planet may be dangerous to humans or uninhabitable.

Science shows that the Earth formed about 4.5 billion years ago. The organisms that live on Earth have completely changed their air (atmosphere); this is called the biosphere. 71% of the Earth's surface is covered by salt water oceans. Earth is the only place in the Solar System where liquid water is known to exist today. The other 29% are made up of rocky terrain in the form of continents and islands. Earth interacts with other Solar System objects, particularly the Sun and Moon. The Earth orbits the Sun approximately once every 365.25 days. A spin is called a day and an orbit around the Sun is called a year. That's why there are 365 days in a year, but a leap day is added to the calendar once every 4 years.