Inertia as Brute Fact

When I posted about brute facts there was a little salmon of doubt gnawing away (which I mentioned in the post). It was a counterargument from a [fictional] religionist:

I’m claiming that the rationality of the world (and its existence) requires God as an explanation. And here you say that these might be brute facts, requiring no explanation at all. But the history of science is filled with us learning to demand explanations for things that we used to take for granted — never the other way around. The human mind demands an explanation for the universe, what hope is there of reprieve?

But now an example came in a vision: inertia! According to Aristotle there’s no inertia: you must keep applying force to an object to keep it moving. A cannonball’s natural place is the earth so that’s where it wants to go. But then you shoot it, applying force. This briefly gives it its “unnatural” upward motion. However once its out of the cannon the force ceases. So the ball stops and falls to its natural place (straight down, mind you). To an Aristotelian the concept of inertia needed extra explanation — why would a stone you throw keep moving?

Fast forward to today’s view: when you shoot the cannonball it sets off on an eternal path of motion. It’s only because the earth applies gravitational force to it continuously that it slows down, stops and falls. To a person who knows something of Newtonian mechanics (probably anyone in a western or urban society) the question would be — why wouldn’t a cannonball you shoot keep moving? The answer is gravity but the reason the ball stops needs explanation.

Our framework’s changed. What requires explanation has reversed. Eternal linear motion is the default. Sure, there are physicists working on the deeper reasons behind inertia. But if ever there was a basic law that can be accepted as a brute fact, here it is.

I think the origin of the universe is similar. Today the question on the lips of religious apologists is why is there something rather than nothing? (The answer of course being a 3 letter word). But according to standard ideas in physics, this question might also be reversed. I wouldn’t be surprised if in 100 years nothing requires more explanation to scientist & layperson than something. Yet another gap is in the process of closing forever.