Isaac Newton was a great scientist and mathematician who lived more than 300 years ago. He understood and wrote about many of the laws of motion that we see at work every day. To explain how one body can orbit another, he asked his readers to imagine a cannon on top of a very, VERY tall mountain. (Our cannon is on a very tall, imaginary lifter that goes up and down, but it is the same idea.)
The cannon is loaded with gunpowder and fired. The cannonball follows a curve, falling faster and faster as a result of Earth's gravity, and hits the Earth at some distance away.
What if we use more gunpowder? Here's what might happen: (Note that these amounts of gunpowder are just imaginary, not meant to be precise! Also, we are ignoring the fact that the air would cause drag on the cannonball and slow it down.)
|