Death Comes (and Comes and Comes) to the Quantum Physicist

I. A Resurrection of Cats

In 1957, a physics graduate student at Princeton, Hugh Everett III, proposed a ­cryptic and seductive solution to the central paradox of quantum mechanics. He argued that the paradox—roughly stated, that the Schrödinger equation perfectly predicts an electron’s behavior in every quantum mechanical experiment ever imagined but also entails some sort of nonsense about an unobserved cat being simultaneously alive and dead—is in fact no paradox at all. Everett made a case for reading the Schrödinger equation literally. The cat is both dead and alive: dead in one world, and still alive in another. One consequence of Everett’s idea is that the universe consists of infinite worlds, embodying every possibility, such that, for example, in one world I die of rheumatic fever in childhood, in another I’m writing a slightly different version of this article, in most I do not exist at all, and, in a few, you and I are in love. Everett’s argument, originally set out in the rather prosaically titled “The Theory of the Universal Wave Function,” re­ceived virtually no attention, after which the dispirited young Everett left academia forever. Applying his mathematical innovations to private and government de­fense analysis projects, he became a heavy-drinking, chain-smoking millionaire; his em­ployees say he avoided mention of his physics background altogether.

Thirteen years later, in 1970, the physicist Bryce DeWitt published in Physics Today a short ­article, “Quantum Mechanics and Reality.” DeWitt, one of the few academics who had noticed Ever­ett’s work, began:

Despite its enormous practical success, quantum theory is so contrary to intuition that, even after 45 years, the experts themselves still do not all agree what to make of it. The area of disagreement centers primarily around the problem of describing observations… Of the three main proposals for solving this di­lemma, I shall focus on one that pictures the universe as continually splitting into a multiplicity of mu­tually unobservable but equal­ly real worlds… Although this proposal leads to a bizarre world view, it may be the most satisfying answer advanced yet.

DeWitt’s flatly sincere, hand-holding article, which led to the catchy “Many Worlds” moniker for Everett’s long-ignored idea, elicited an enormous response from the physics community. Physics Today ran a follow-up article half a year later, with six (handsomely photograph­ed) physicists responding at some length to DeWitt, and DeWitt responding more in kind. Many Worlds was thus officially sexy, and by 1973 Everett’s dormant thesis work was finally, through DeWitt’s arrangement, published. Seemingly aloof to the renewed interest in his hypothesis, Everett claimed he couldn’t be bothered to write an introduction. So DeWitt wrote one instead. As epigraphs he used quotes from Borges and William James.

...