Some may not understand how the Earth is kept rotating around the sun, in its orbit. I am not an astrodynamicist, but here is a simple explanation: The earth is pulled towards the sun at all times by gravity, therefore giving it speed towards the sun. However, the earth is moving sideways so fast that it misses. This is repeated over and over again, with the pull not strong enough to pull it all the way in but the sideways movement not fast enough to allow the earth to escape.