"In the entire history of civilization, there are a small number of intellectual leaps that stand out as the crowning achievements of the race. An example is Newton's astounding revelation that the laws governing the motions of planets are the same as those that cause apples to fall from trees. In the twentieth century, we were blessed with two such feats of imagination.
The first is Einstein's General Theory of Relativity, which probably ranks as the biggest of them all because it dared to put forth postulates that were completely counter-intuitive: who would believe that things get bigger and heavier as they go faster, or that time itself slows down in the presence of a gravitational field, or that the very concept of 'simultaneous' events is illusory? Einstein's great contribution wasn't the theory itself, but the invitation to others to think outside the boundaries of empiricism and take nothing for granted, including a goodly number of our most grounded notions.
This license to ignore common sense in evolving strange concepts from seemingly innocuous first principles underlies the second great intellectual revolution of this century, that of the development of quantum physics. One of Einstein's innocuous first principles was that the speed of light is constant regardless of the motion of the observer. This gave rise to insane-sounding conjectures, such that gravity bends light, every one of which has thus far proven true in experiment.
The innocuous first principle of quantum physics is that the universe at its most basic is not smoothly continuous but granular. Everything ultimately boils down to something which can no longer be subdivided. There is a smallest allowable length, mass, even the tiniest unit of time that can possibly exist. (First principles again: the reason that the speed of light is the speed limit of the universe is because it is the rate at which light travels over the smallest unit of distance in the smallest unit of time).
That doesn't sound too difficult to deal with, but when you work forward from this simple supposition, things start to get so weird that Einstein himself denied them to his dying day … and he was one of the founders of quantum theory. The most axiomatic concept we possess, for example, is that cause precedes effect. Something happens, and this causes something else to happen. I drop an egg - then it breaks. But in the quantum world, this concept is abandoned. Sometimes, things happen now because of something else that hasn't happened yet, but will soon. Other times, things happen for absolutely no reason at all".