Earth is unique in the solar system in that it is the only planet that has water in solid, liquid, and gas forms. While Earth is almost 5 billion years old, life has only existed on it for 150-200 million years, which is only 5-10% of its lifetime. Earth and Mercury are the densest planets in the solar system. Earth orbits the sun in 365.25 days, requiring a leap day every four years to synchronize calendars with its orbit.

4. http://members.aol.com/bobalien99/earthten.htm Fact One: Earth is the only planet in the Solar System to have water in its three states of matter: as a solid (ice), a liquid (sea, rain, etc.) and as a gas (clouds). These are all shown below. Water is, of course, the most important liquid for life.

5. Fact Two: Earth is almost five billion years old, although life (resembling life as we know it) has only existed on the planet for the last 150 million to 200 million years. This means that life has only been present on Earth for only 5%-10% of its lifetime.

6. Fact Three: Earth and Mercury are the two most dense planets in the Solar System . This means that particles inside the planet are most closely packed together

7. Fact Four: The length of time it takes for Earth to orbit the Sun is 365 and a quarter days. To make up this extra quarter which isn't counted at the end of a year, we have an extra day every four years on 29th February. This year, 2008, is a Leap Year. The next Leap Year will be in 2012.

8. Fact Five: Earth is gradually slowing down. Every few years, an extra second is added to make up for lost time. Millions of years ago, a day on Earth will have been 20 hours long. It is believed that, in millions of years time, a day on Earth will be 27 hours long.

9. Fact Six: The centre of the Earth, its core, is molten. This means that it is liquid rock which sometimes erupts onto the surface through volcanic eruptions. This core is 7,500°c, hotter than the surface of the Sun!

10. Fact Seven: Earth is the only planet in the Solar System not to be named after a mythical God.

11. Fact Eight: Despite being called Earth, only 29% of the surface is actually 'earth.' The rest of the planet's surface (71%) is made up of water.

12. Fact Nine: From a distance, Earth would be the brightest of the 9 planets. This is because sunlight is reflected by the planet's water.

13. Fact Ten: Earth is the only planet in the Solar System known to be geologically active, with Earthquakes and volcanoes forming the landscape, replenishing carbon dioxide into the atmosphere and erasing impact craters from meteors.

14. Revolution

17. Rotation of the Earth

19. The Earth is rotating around an axis (called its rotational axis ). Some objects rotate about a horizontal axis, like a rolling log. Some objects, such as a skater, rotate about a vertical axis. The Earth's axis is tipped over about 23.5° from vertical.