At the dawn of the 20th century, physicists were partaking in a scientific revolution the likes of which have not been seen before or since. At the heart of this revolution is the physics of light. People were discovering that light was not behaving at all like they expected.
First of all there was Maxwell’s theory of electromagnetism according to which light is an electromagnetic wave, propagating through space and time at a constant velocity for all observers. This was profoundly confusing back then and it took the likes of Einstein --- who had to rearrange our notions of space and time --- to make sense of this behaviour. At the same time Max Planck was grappling with the ultraviolet catastrophe, a consequences of the theory that light is a classical wave. Planck’s solution to this problem (or perhaps more accurately: Einstein’s realist interpretation of Planck’s solution) was to propose that light is made out of particles; it was the beginning a profound and intricate theory now known as quantum mechanics.
The remarkable story of the discovery of special relativity and quantum mechanics has always inspired a deep sense of awe in me; everything that I love about physics can be found here: the initial, profound shock resulting from discovering that seemingly obvious theories are completely wrong, the genuine --- ever so human--- creative effort to grapple with these new problems, the proposition of many new explanations and finally the relieve at discovering one explanation which neatly solves all of the old problems.
However, the story of quantum mechanics and special relativity both have profoundly different endings. On the one hand there is special relativity (as well as general relativity), which is taken seriously on its own terms. Space-time is, nowadays, considered as real as the computer I am writing this on; it is not seen as pure metaphysics or a simple collection of mathematical tricks for producing predictions. Physicists consider spacetime to be a real, malleable physical entity.
Quantum mechanics, on the other hand, does not enjoy these same privileges. Its most straight forward ‘interpretation’ is not even excepted by a majority of physicists today. I use the word interpretation in scare qoutes here because the idea that quantum mechanics needs to be interpreted has been uniquely damaging to the growth of knowledge. It suggests that quantum mechanics needs to be treated differently from other scientific theories; it is seen as unwieldy, weird and even upsetting in a way that is perhaps only rivaled by the theory of Darwinian evolution (to which the creationists also still apply the label ‘interpretation’). All of this is not true, quantum theory should not cause upset.
Contrary to what is often claimed, quantum mechanics is at heart a theory of multiple universes interacting through interference phenomena. This means that every second there are a great many copies of you, me and the rest of the universe branching of into separate histories. These copies of us go on to live different but slightly similar lives in their respective slices of the multiverse. Although we will never interact with them again these copies of us really exist because we need those copies to explain what happens in our slice of the multiverse.
My claim is that ---contrary to what you may have been told --- quantum mechanics is a fully comprehensible theory. The absurdities that it presents us with are no stranger than is the fact we all live on a globe, half of us living upside down, all while we are gliding through orbit around a huge ball of glowing, nuclear fire. I will back this claim up by actually explaining the multiverse theory of quantum mechanics (most of these topics are still under construction, but I hope to have them out soon).
Books The Beginning of Infinity by David Deutsch The Fabric of Reality by David Deutsch The Many-Worlds Interpretation of Quantum Mechanics by Bryce DeWitt & Niell Graham The Global Approach to Quantum Field Theory: Volume 1 by Bryce DeWitt (chapters 9 & 12) The Emergent Multiverse by David Wallace Quantum Mechanics: The Theoretical Minimum by Leonard Susskind & Art Friedman* Papers The Theory of the Universal Wave Function by Hugh Everett, III (here) The Logic of Experimental Tests, Particularly of Everettian Quantum Theory by David Deutsch (here) Quantum Theory of Probability and Decisions by David Deutsch (here) Many Worlds, the Born Rule, and Self-Locating Uncertainty by Sean Carroll (here) Probabilities and Shannon's Entropy in the Everett Many-Worlds Theory by Andreas Wichert & Catarina Moreira