arth, our home, is the third planet from the sun. While scientists continue to hunt for clues of life beyond Earth, our home planet remains the only place in the universe where we've ever identified life.
Earth is the fifth-largest planet in the solar system. It's smaller than the four gas giants — Jupiter, Saturn, Uranus and Neptune — but larger than the three other rocky planets, Mercury, Mars and Venus.
Earth has a diameter of roughly 8,000 miles (13,000 kilometers) and is round because gravity pulls matter into a ball. But, it's not perfectly round. Earth is really an "oblate spheroid," because its spin causes it to be squashed at its poles and swollen at the equator.