When the Earth was formed, it was made from a huge cloud of gas and debris circling the sun. All planets formed out of this spinning disk. You can think of it like a whirlpool with the sun at the center. As the planets formed, they kept spinning around the sun, but their momentum like tops kept them spinning in place too. That's why the Earth rotates on its axis how it does. Since all planets orbit the sun in the same direction, and almost all planets rotate in the same direction on their axes, scientists believe this was the same direction the gas cloud was spinning around the sun when planets formed.

There are two exceptions to this. Venus spins the wrong way, and Uranus spins on its side. In 2005, the best explanation for this was discovered. Scientists now think the early solar system was a crazy place with planets and comets running into each other. These collisions disturbed the spins of Venus and Uranus. But the rest of the planets still spin and orbit the same direction as that cloud of gas billions of years ago.