Newton's Apple

The story of Newton and the apple feels comfortable – until you think about it. The great man watches an apple fall to the ground, has a flash of inspiration, and comes up with the theory of gravity.

Newton, though, isn’t really explaining what happens with the apple. He is dreaming up a theory which is consistent with things falling to the ground, but also has other, less intuitive implications. The latter are just hidden from us because they don’t make any difference on a human scale – we exist in one little corner of physics, out of the way of most of the implications of gravity.

So, just as the earth pulls the apple down, the apple pulls the earth upwards. We just don’t see it, because the apple is too small. And as the apple gets closer to the earth, the force of gravity increases, and the apple accelerates. We just don’t see it, because the height of the tree is nothing compared to the distance to the center of the earth.

Even with 300 years of hindsight, I find it hard to get my head round how you can look at something falling and imagine gravity. I assume Newton only managed it because half his mind was on celestial mechanics, where gravity’s non-intuitive predictions become more relevant.

It’s nonetheless a comforting story for the more straightforward-minded among us, and one Newton presumably told as such. As a bible crank he presumably also had an eye on Genesis – though as a bible crank he also knew that the forbidden fruit only became an apple because of a Latin pun. But discovering one of the hidden forces on the universe is the best opportunity you could ever get to insert yourself into a cosmic narrative of forbidden knowledge, so why let a good story go to waste?

Written on March 25, 2021