Around and around the sun

The Earth doesn't just spin-it also moves through space.

Right this very moment, the earth is rushing through space at tremendous speed-more than 66,000 miles straight line, though. It's whirling around and around the sun, in a kind of stretched-out circle. This circle the earth makes around the sun is called an orbit.

What makes the earth keep moving around and around the sun ? Why doesn't it just fly off into space ?

Everything in space pulls at everything else. This pull is called gravitation. The bigger a thing is, the stronger its pull. The sun is more than a million times bigger than the earth, so it tugs hard at the earth. It is this strong tug that keeps the earth in orbit. If you fasten some string to a ball, you can whirl the ball around and around, to show the way the earth goes around the sun. The string is like the pull of the sun's gravity-it holds onto the ball. Even though the ball is moving, it can only move in a circle.

The time it takes the earth to go all the way around the sun is a little more than 365 days. This is what we call a year