THE EARTH and MOON

 Earth is a small, rocky planet which supports a variety of life! As far as
we know, Earth is unique from all other planets in this respect.
Temperatures at the Earth's center (called the "core") may be as high as
7500 K - That's hotter than the surface of the Sun!
The Earth is the densest major body in the solar system. This means that it's
the most "compact" of all the planets.  For example, you have two loaves of
bread, both of the same amount. You smash one loaf of bread flat. Even though both loaves are of the same amount, the smashed bread is *denser* because
it is more compact.  The Earth is 4.5 to 4.6 billion years old, but the oldest
known rocks are less than 4 billion years old. Rocks older than 3 billion
years are rare. The oldest fossils of living organisms are less than 3.9 billion
years old! The Earth is orbited by one moon.

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