by Roger D. Jones
I am writing a new book with my colleague John Casti entitled Eddies in the Stream. It is an arrogant project about what life is. No, I mean really what life is. How did life come about? Is it constrained to be chemistry-based? Can computer programs be alive? Can cities be alive? Is a society of universes possible? That sort of thing.
This series of blogs contains bits and pieces from the book as it is being written. I am writing the blog as a way to decompress. I am also creating paintings on the topics in the book as a way to decompress.
Today we are going to talk about the thought experiment, Newton’s Cannonball. Isaac Newton came up with this thought experiment in order to demonstrate that the mechanism that causes bodies to fall on Earth is the same mechanism that cause the planets to orbit the Sun.He called these mechanism “gravity.”This seems obvious to us now, after the fact, but it was certainly not obvious at the time. Galileo, who died on the day that Newton was born, thought that the two mechanisms were entirely different.
The thought experiment goes like this. Imagine a very tall mountain. In fact the mountain is very much taller than anything found on Earth. Now imagine that a cannon is placed at the top of the mountain. Now imagine that we place a small amount of gunpowder in the cannon along with a standard cannonball. We fire the cannon, and the ball drops to the Earth at point A some distance from the mountain. If we put more gunpowder in the cannon, then the cannonball drops farther from the mountain at point B. As we increase the amount of gunpowder, the cannonball falls farther and farther from the mountain and lands on the backside of the Earth. If we put a sufficient amount of gunpowder in the cannon, and the cannon does not explode, we can drive the cannonball completely around the Earth such that it never lands. This is precisely what the moon does. It travels around the Earth. This suggests that the mechanism that controls orbiting objects is the same as the mechanism that controls terrestrial cannonballs.
I try to organize my thoughts with painting. Here is painting of a modern-day Plato’s Cave. I won’t go into the allegory of Plato’s Cave. I recommend looking it up on Wikipedia.