Bradwardine’s Rule

I love reading about the medieval physics: you can see people struggling against mental traps, often failing, but still putting up a fight. We shouldn’t laugh at them: theoretical physicists may be stuck in their own traps today! Good new ideas often seem obvious in retrospect… but only in retrospect.

For example: Aristotle argued that a vacuum is impossible, because the velocity of an object equals the force on it divided by the resistance of the medium it’s moving through. A vacuum off...