Richard FeynmanRichard Feynman won a Nobel Prize for his work on quantum electrodynamics (QED) but he also developed simple yet insightful explanations of quantum mechanics. In his famous Lectures on Physics, some of the more accessible material re-published as Six Easy Pieces, Feynman argued that the most important scientific knowledge - from physics to biology - is the simple fact that all things are made of atoms.
If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied...Feynman is quite right that everything is made up of discrete particles. We might rewrite his advice to the future this way:
The universe consists of discrete, discontinuous, and in some sense "digital," particles. There is no "classical" world, only a quantum world. The "classical" world emerges from the quantum world when a large enough number of particles get together. The continuous space (and time) in which we locate the particles is but a mathematical construct that allows us to describe the world.There are no continuous "fields" in which particles of matter (electrons, atoms, etc.) are thought to be singularities. The continuous, causal "forces" like gravity that we postulate are useful fictions. They are only statistical averages over other types of particles (photons, bosons, gravitons) that look continuous when very many such particles are present. At the microscopic level, quantum events are discontinuous and acausal. The analytic integral and differential equations that we assume deterministically govern the motions of material particles are idealizations only accurate for very large bodies.
The Messenger Lectures at CornellLecture 1 - The Law of Gravitation (video only) Lecture 2 - The Relation of Mathematics to Physics (video only) Lecture 3 - The Great Conservation Principles (video only) Lecture 4 - Symmetry in Physical Law (video only) Lecture 5 - The Distinction of Past and Future (text and video) (video only) Lecture 6 - Probability and Uncertainty (text and video) (video only) Lecture 7 - Seeking New Laws (video only) In his sixth Messenger lecture, Feynman imagined a scenario like that Arthur Holly Compton used as a model for free will based on quantum uncertainty.
...we could cook up — we'd better not, but we could — a scheme by which we set up a photo cell, and one electron to go through, and if we see it behind hole No. 1 we set off the atomic bomb and start World War III, whereas if we see it behind hole No. 2 we make peace feelers and delay the war a little longer.Isn't it strange and somewhat diabolical the kind of examples some physicists come up with? Feynman on the Two-slit Experiment
Probability and Uncertainty - the Quantum Mechanical View of Nature Feynman on Irreversibility
The Distinction of Past and Future