How in the world could something so spectacular as the Earth's Solar System be created out of nothing? The authors of this Hitchhiker's Guide believe that it was spoken into existence. (Genesis 1:1)

A solar system is defined as a star and other bodies that orbit the star. In this system, the star is the sun and the other bodies are the nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. (My very educated mother just served us nine pizzas.)

All the planets rotate around their own axis as they orbit the Sun. All planets except Mercury and Venus have at least one satellite or moon. The planets can be divided between three groups.

Gravity is the force that holds our solar system together. It pulls particles of matter together to make stars and planets. Gravity holds them together and makes them move around each other in an orbit or revolution.

First, the rocky planets, sometimes called the Inner Planets, are Mercury, Venus, Earth, and Mars. They are closest to the Sun, are inside the asteroid belt, and are mostly rock with metal cores. These planets are smaller than those further away from the Sun. Because they are so close to the Sun, they are also warmer than those farther away.

The second group are referred to as the Gas Giants or the Outer Planets and include Jupiter, Saturn, Uranus, and Neptune. They are further from the Sun than the rocky planets. Their atmospheres are primarily made of gaseous elements mostly of hydrogen. There is a liquid shell under the atmosphere that is made of water, ammonia, and methane. Their center is actually soft rock.

The third group consists only of Pluto and is called the "Tiny Planet." Pluto is made up primarily of ice and differs from the Rocky Planets and the Gas Giants. Visit its page to learn more about this odd little planet.

In preparation for your tours around our solar system, we suggest that you visit the Space Shuttle Launch Simulator.