The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family

by Peter Byrne

  And then he recorded and released several albums of songs grieving for his lost family. Engineering the albums in a small recording studio on the other side of a concrete wall from the family archive, he came to terms with sole survivorship by making his story into a work of art for the world. And his career thrived. Eels’ albums were critically acclaimed. He was asked to score songs for “Shrek,” “American Beauty,” and other movies, and his international following grew.

  As Mark aged, he began finding small pieces of his father in his own behaviors, and, finally, some peace. His 2005 album, “Blinking Lights and Other Revelations,” ended with a song of recognition and forgiveness, “Things the Grandchildren Should Know.”

  I’m turning out just like my father

  Though I swore I never would

  Now I can only say that I have love for him

  As I never really understood

  What it must have been like for him

  Living inside his head.

  I feel like he’s here with me now

  Even though he’s dead.

  Everett on cover of Nature, July 2007.

  As part of healing, Mark wrote an autobiography, Things the Grandchildren Should Know. It is mostly about his “long and whacky road surviving the life that led from being his father’s son.”8 As the book was being readied for publication, Scientific American interviewed him for a profile of his father. Mark grinned, “When my rock singer friends tell me they are being interviewed by Rolling Stone, or People, I say, so what, I’m being interviewed by Scientific American!”

  July 2007 marked the 50th anniversary of the publication of Everett’s many worlds theory. Nature put him on the cover, as did several other science magazines. At the University of Oxford, and elsewhere, physicists and philosophers gathered to dissect the influential idea. The BBC filmed Mark traveling around the country talking to his late father’s friends and colleagues—Reisler, Pugh, Misner, Trotter and others—while trying to understand the gist of the many worlds theory. Parallel Worlds, Parallel Lives premiered to great reviews in the United Kingdom. It was picked up in the United States by NOVA and received accolades in publications ranging from The New York Times to Hollywood Reporter. People were captivated by the image of the rock singer searching to forgive his strange, brilliant father.

  Eels used the hour-long film as an opening act during their international tour in 2008. It was a spunky move. Concert halls full of unsuspecting rock fans suddenly found themselves watching a movie about quantum paradoxes and multiple universes punctuated by atomic mushroom clouds. Night after night, when the film ended, E strolled on stage to ask the audience, “What do you want? physics? or rock and roll?” And, despite what you might think, “physics” got a lot of applause (most nights).

  And then he sat down at the piano and sang his heart out—having done his best to give his father a day in the sun.

  Mark Everett performing at Royal Festival Hall.

  BOOK 12

  EVERETT’S LEGACY

  38 Modern Everett

  Today, physics is in crisis. Physical theory is unbelievably successful; it constantly produces new problems, and it solves the old ones as well as the new ones. And part of the present crisis—the almost permanent revolution of its fundamental theories—is, in my opinion, a normal state of any mature science. But there is another aspect of the present crisis: it is also a crisis of understanding. This crisis of understanding is roughly as old as the Copenhagen interpretation of quantum mechanics.

  Karl Popper, 19821

  Fiction and science

  Probability formulas measure uncertainty and entropy, quantify ignorance and information, reduce the need to make wild guesses, and inform our beliefs about reality. Could it be that intelligent decision-making is reducible to the calculation of odds, to betting? The puzzle of probability has flummoxed scientists, philosophers, and novelists ever since humans consciously confronted the nature of choice—the existence of alternatives. The trick, it is thought, to making a rational choice is being able to predict the consequences of a decision before making it by measuring probabilities. Experience provides us with information about possible consequences. Measuring the relative frequency with which an event has occurred in the past allows us to predict the likelihood of it recurring. And the generalization of experiential data allows us to predict chances for events we have yet to experience. For example, the probability that we will pick a white marble out of an urn filled with 99 black marbles, and one white marble, is 0.01 or one percent each time we insert a hand into the urn. Of course, it is not certain that in 100 or 100 million attempts we will snag the white marble!

  Despite having used it on a daily basis for eons, we still do not know what probability is—why the mathematics of probability tracks change in the physical world. What does it mean to say that an event is possible? And, for that matter, what happens to unrealized possibilities? One of the first Western scientists, the Pre-Socratic philosopher, Anaxagoras of Clazomenae, wondered how the ingredients of everything that can possibly happen can all be contained in the same space, the same universe, so to speak. His puzzlement about the operation of probability foreshadowed our modern puzzlement over quantum superposition: how to come to terms with points in an abstract “space” which documents the coincidence of all physical possibilities. Anaxagoras’ solution was to model a universe in which all possibilities, all possible worlds, are somehow manifest, although he could not say how this could be physically so. But he did question why we should assume that there is only one universe, and not many. Twenty-five centuries later, it is even more reasonable to ask whether or not multiple universes exist. Remarkably, the stuff of science is stranger than fiction.2

  Science fiction

  In 1922, H. G. Wells wrote one of the first stories about a parallel universe. “Men Like Gods” treats of a parallel world with “no parliament, no politics, no private wealth, no business competition, no police, no prison, no lunatics.”3 It was a Utopia defined by its differentiation from our world. The Utopians had shared our bloody past until history (inexplicably) branched. Given the contrast between the two worlds, there was little doubt about which world a rational being would choose to live in, although Wells’ characters could not see all possible worlds.

  In the 1934 story Sideways in Time, Murray Leinster’s universe-traversing protagonists must choose,

  between the forks in the road … there is more than one future we can encounter, and with more or less absence of deliberation we choose among them. But the futures we fail to encounter, upon the roads we do not take, are just as real [although] we never see them.4

  Everett was addicted to reading science fiction. The possible existence of parallel universes would have intrigued him long before he wrote his dissertation. And his theory certainly intrigued the world of science fiction. Perhaps the first science fiction story to base itself directly on Everett was “Store,” written by Robert Sheckley in 1959.

  Yes, my friend, though you might not have suspected it, from the moment this battered earth was born out of the sun’s fiery womb, it cast off its alternate-probability worlds. Worlds without end, emanating from events large and small; every Alexander and every amoeba creating worlds, just as a ripple will spread in a pond no matter how big or small the stone you throw.5

  Scheckley’s post-World War III tale of multiple universes appeared in an anthology of such science fiction, Beyond Armageddon. The collection’s editors claimed that it had been inspired by the publication of Everett’s theory two years previous. They probably had no idea what Everett did for a living, but they would have been appalled to find out. They wrote,

  When human extinction (as a result of a decision) is assigned a probability, however small … the statistician and his employer should be detected, apprehended, and led away in straitjackets to the nearest lobotomy ward. Such people are not just running loose in Washington and Moscow, they’re running things.6

  A few years after Everett die
d, Frederik Pohl tapped into the many worlds idea to fictionalize a government research program to travel between parallel worlds. In The Coming of the Quantum Cats, a physicist is testifying to a congressional panel:

  ‘Those parallel universes, created at the rate of millions every microsecond, are just as “real” as the one I’m testifying before you in.’ … A congressman from New Jersey leaned over to whisper in my ear: ‘Do you see any military application in this, Dom?’

  ‘Ask him, Jim,’ I whispered back, and when the congressman did the physicist looked astonished.

  ‘Oh, I do beg your pardon gentlemen,’ he said. ‘And ladies, too, I mean,’ he added, nodding toward Senator Byrne. ‘I thought all that had been made clear. Well. Suppose you want to H-bomb a city, or a military installation, or anything at all, anywhere in the world. You build your bomb. You take it into one of the parallel universes. You fly it to the longitude of Tokyo—I mean of whatever the place is—and you push it back into our world and detonate it. Boom. Whatever it is, it’s gone. If you have ten thousand targets—say, the entire missile capacity of another country—you just build ten thousand bombs and push them all through at once. It can’t be defended against. The other people can’t see it coming. Because, in their world, it isn’t coming … until it’s there.’7

  As the specter of nuclear war insinuated itself into the nightmares of Baby Boomers, a meme of multiple universes began to reproduce itself in Western literature and cinema. It permeates the novels of Andre Norton, Philip K. Dick, Greg Egan, and Neal Stephenson. Jet Li starred in a martial arts film doing kung-fu leaps between parallel worlds. Harry Turtledove makes a living writing alternate history sagas. Philipp Pullman’s trilogy of children’s novels, His Dark Materials, roams through a series of Everett-type worlds.8

  Typical consumers of many worlds fantasia may not realize that their entertainment is mirrored by serious scientific theory. But if you pick up a contemporary book on quantum mechanics—scientific or philosophical—it is likely that “Everett, Hugh III” will be listed in the index.

  Popper speaks

  Philosopher of science, Karl Popper, was drawn toward Everett’s “simple and ingenious” argument.9 In 1982, he published Quantum Theory and the Schism in Physics, a collection of essays attacking the “anti-realism” of positivism, instrumentalism, and the Copenhagen interpretation. Popper found Bohr’s division of the universe into quantum and classical realms to be a “mistaken and even a vicious doctrine.”10 He concocted his own theory of probability to bridge the mysterious gap, using film strips as a metaphor to explain how superpositions decompose into single worlds:

  Since each ‘still’ in the filmstrip attached to a real time slice consists of a whole catalogue of weighted possible states, my proposal really involves that the predictive filmstrips split at any interaction into as many filmstrips as there are possibilities in the catalogue. In this my picture … greatly resembles Everett’s; only that the many worlds remain mere possibilities instead of becoming real.11

  Popper liked Everett’s theory because it,

  is a completely objective discussion of quantum mechanics. In Everett’s approach (as opposed to the Copenhagen interpretation) there is no need, and no occasion, to distinguish between ‘classical’ physical systems, like the measuring apparatus, and quantum mechanical systems, like elementary particles … Instead, all physical systems are regarded as quantum mechanical systems, especially the apparatus used in measurements; and, indeed, the universe.12

  Popper found a use for the universal wave function in his “propensity” interpretation of quantum mechanics, but his main critique of Everett was that, according to Schrödinger’s wave mechanics, the branching universes ought to fuse as well as split. Popper found that prospect to be “clearly absurd,” as the branches would have “no interaction between them before their fusion.”13 Be that as it may, Everett had considered the question of fusion (time reversibility). He did not view it as a problem, as the microscopic superpositions expressed in his universal wave function were time-reversible, whereas the macroscopic splitting process appears to be irreversible in accord with entropy and our experience of the arrow of time.14 And Everett’s argument that the Schrödinger equation applies to the entire universe—micro and macro—gained in credibility after quickly decaying superpositions of molecules were observed in the laboratory.15 (Which is not to say that fusion is impossible.)

  Everett claimed that macroscopic objects—amoebas, cannonballs—can exist in a superposition of states, but we (who are also macroscopic objects) do not see such superpositions because we entangle with each version of the superposed object and our copies embark on different histories. Where he saw branching histories, modern physicists now see an (essentially) irreversible correlation between objects and their environs known as decoherence—a phenomenon amenable to both uniworld and multiworld interpretations.

  Decoherence in a nutshell

  Decoherence theory has emerged from decades of foundational research in quantum mechanics. In the 1920s, Paul Ehrenfest theorized about how quantum superpositions map the world described by classical mechanics. And we have witnessed Mott puzzling over how the environment inside a Wilson cloud chamber caused spherical probability waves to collapse into single tracks. But it is only in recent times that the quantum mechanical formalism has been able to reasonably explain the dynamics of what happens when an object in superposition interacts with its surroundings. Decoherence theory may be more of a heterogeneous collection of techniques than a systematic theory,16 but it goes some distance toward solving the measurement problem. And all of the pioneers in decoherence theory credit Everett with making it possible to even talk about the coherent quantum mechanical space inside which objects and, indeed, entire universes decohere.

  After Bohm and Everett openly rebelled against the monocracy of the Copenhagen interpretation (and the collapse postulate, which many physicists, rightly or wrongly, believed to be a part of Bohr’s complementarity), theorists began looking at the formalism of quantum mechanics in a new light: searching for a way that the wave function could contain the observer without falling into the infinite regression of always having to place the (classical) observer outside the (quantum) system observed. John Bell had strong words for Bohr’s unbridgeable partition:

  From some popular presentations the general public could get the impression that the very existence of the cosmos depends on our being here to observe … So I think it is not right to tell the public that a central role for conscious mind is integrated into modern atomic physics…. The founding fathers of quantum theory decided … that no concepts could possibly be found which would permit direct description of the quantum world…. The ‘Problem’ then is this: how exactly is the world to be divided into speakable apparatus … that we can talk about … and unspeakable quantum system that we cannot talk about? … It is not essential to introduce a vague division of the world of this kind.17

  Decoherence theorists seek to speak the unspeakable by including the apparatus and the observer in the wave function. Decoherence accounts for the loss of interference effects between overlapping wave functions; the loss of coherence between different elements of a superposition in a quantum system; the seeming loss of quantum information as a superposition decomposes into a single state or a collection of non-interfering states.

  For example, the ability of experimentalists to manipulate decoherence rates—the speed at which an atomic superposition decomposes—is part of the technical basis of quantum computation. The longer that a quantum transistor or “qubit” can be sustained in a “coherent,” superposed state without disintegrating (decohering), the longer a quantum computation can run using that qubit.18

  Decoherence occurs when a complex quantum system entangles with its surroundings, thereby appearing to lose information content and becoming “solid,” i.e., behaving classically, macroscopically. But decoherence is not an interpretation of quantum mechanics: It is a mathematical technique f
or describing how microscopic systems of a certain size or complexity segue into macroscopic systems. In it, there is no inexplicable collapse or quantum jump and the transition is governed by the non-collapsing Schrödinger equation. The structure of decoherence does not exclude the measuring apparatus nor the observer from the wave function that includes the object observed. And as a physical phenomenon, it is amenable to explanation by the Everett interpretation, which encompasses—but is not ruled by—the externality central to the Copenhagen interpretation. In this sense, the Everett model is thought to supersede, but not to destroy the Bohr and von Neumann models (which are self-limiting explanations when considering the universe as wholly quantum mechanical). The concept of branching universes can model decoherence; but there is no consensus among those who do so on whether or not the branches are physically real.

  Zeh and Zurek

  In the late 1960s, Dieter Zeh was a young lecturer in nuclear physics at the University of Heidelberg. While exploring the foundational questions in quantum mechanics, he drafted a short paper arguing that quantum mechanics is universally valid, i.e. that the wave function need not collapse.19 Speaking the supposedly unspeakable, Zeh proposed that macroscopic systems exist in superpositions that are not isolated from their surroundings, rather, they are constantly correlating or entangling with the remainder of the universe (which includes observers). He wrote, “It must be concluded that macroscopic systems are always strongly correlated in their microscopic states.”