Physics P1- The Earth in the Universe: Information

There are eight planets orbiting the sun in almost circular paths (ellipses.)
Closest to the sun are the inner planets- Mercury, Venus, Earth and Mars.
Then we have the asteroid belt.
Then, the outer planets, which are much further away from the sun; Jupiter, Saturn, Uranus, and Neptune.

You can see some planets with the naked eye. They look like stars, but they're totally different.
Stars are huge (the Sun's diameter is over 100 times bigger than than the Earth's), very hot, and very far away. They give out lots of light- which is why you can see them even though they're far away.

The solar system is about 5 thousand million years old.
The solar system was formed over a very long period of time from big clouds of dust and gas.
For some reason, one cloud started to get squeezed slightly.

When the temperature got high enough, a process called fusion started- hydrogen nuclei joined together to make helium.
Fusion gives out massive heat and light, so a star, our sun, was born. (The sun and other stars' energy comes from the fusion of hydrogen nuclei.)

The oldest rock on earth is actually meteorites (rocks from space that crashed into earth- we think they were formed not long after the birth of the solar system).
They are about 4500 million years old- so we know that the solar system is at least that old.

Comets are balls of rock, dust, and ice which orbit the sun in very elongated ellipses, often in different planes from the planets. The sun is near one end of the orbit.

We're in the milky way galaxy. Our sun is one of thousands of millions of stars which form the milky way galaxy- about 1 in 100 000 000 000 (or 10 to the power of 11) if you had to write it out.
The sun is about half way along one of the spiral arms of the milky way.