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.

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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.

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.

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, 2000, is a Leap Year. The next Leap Year will be in 2004.

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.