Anyone who has taken a course on quantum mechanics and learned the dominant Copenhagen interpretation of it has encountered the so-called measurement problem that says that systems can exist simultaneously in a superposition of mutually exclusive states until an actual measurement is made, at which point the superposition collapses in ways that are unknown to the observer and the system is found in just one of the possible states. What happened to all the other states? No one knows. They are assumed to just cease to exist. The most famous example of this is Schrodinger’s cat which, while still in the unopened box is both alive and dead, but when the box is opened is found either alive or dead.
The process by which the system collapses, that requires treating the observer as a classical system and the observed as a quantum mechanical one, has never been explicated in a consistent mathematical form and is one of the unsatisfying features of this interpretation. In his doctoral dissertation in physics, Hugh Everett came up with a bold solution to this problem but at what seems like an extravagant cost.
In pursuing this endeavor, Everett boldly tackled the notorious measurement problem in quantum mechanics, which had bedeviled physicists since the 1920s. In a nutshell, the problem arises from a contradiction between how elementary particles (such as electrons and photons) interact at the microscopic, quantum level of reality and what happens when the particles are measured from the macroscopic, classical level. In the quantum world, an elementary particle, or a collection of such particles, can exist in a superposition of two or more possible states of being. An electron, for example, can be in a superposition of different locations, velocities and orientations of its spin. Yet anytime scientists measure one of these properties with precision, they see a definite result—just one of the elements of the superposition, not a combination of them. Nor do we ever see macroscopic objects in superpositions. The measurement problem boils down to this question: How and why does the unique world of our experience emerge from the multiplicities of alternatives available in the superposed quantum world?
The Schrödinger equation delineates how a quantum system’s wave function will change through time, an evolution that it predicts will be smooth and deterministic (that is, with no randomness). But that elegant mathematics seems to contradict what happens when humans observe a quantum system, such as an electron, with a scientific instrument (which itself may be regarded as a quantum-mechanical system). For at the moment of measurement, the wave function describing the superposition of alternatives appears to collapse into one member of the superposition, thereby interrupting the smooth evolution of the wave function and introducing discontinuity. A single measurement outcome emerges, banishing all the other possibilities from classically described reality. Which alternative is produced at the moment of measurement appears to be arbitrary; its selection does not evolve logically from the information- packed wave function of the electron before measurement. Nor does the mathematics of collapse emerge from the seamless flow of the Schrödinger equation. In fact, collapse has to be added as a postulate, as an additional process that seems to violate the equation.
Everett’s radical new idea was to ask, What if the continuous evolution of a wave function is not interrupted by acts of measurement? What if the Schrödinger equation always applies and applies to everything—objects and observers alike? What if no elements of superpositions are ever banished from reality? What would such a world appear like to us?
Everett saw that under those assumptions, the wave function of an observer would, in effect, bifurcate at each interaction of the observer with a superposed object. The universal wave function would contain branches for every alternative making up the object’s superposition. Each branch has its own copy of the observer, a copy that perceived one of those alternatives as the outcome. According to a fundamental mathematical property of the Schrödinger equation, once formed, the branches do not influence one another. Thus, each branch embarks on a different future, independently of the others.
The idea of the universe on each measurement splitting into other universes corresponding to all the possible superposition states ‘solves’ the measurement problem but seems extravagant though hard to refute. Most people just try to forget about the problem.
String theorist Juan Maldacena of the Institute for Advanced Study in Princeton, N.J., reflects a common attitude among his colleagues: “When I think about the Everett theory quantum mechanically, it is the most reasonable thing to believe. In everyday life, I do not believe it.”
I had not thought about this for a while but came across a surprising reference to it in an article on false memories and something called the ‘Mandela effect’ in which many people share the same false memory.
Would you trust a memory that felt as real as all your other memories, and if other people confirmed that they remembered it too? What if the memory turned out to be false? This scenario was named the ‘Mandela effect’ by the self-described ‘paranormal consultant’ Fiona Broome after she discovered that other people shared her (false) memory of the South African civil rights leader Nelson Mandela dying in prison in the 1980s.
Is a shared false memory really due to a so-called ‘glitch in the matrix’, or is there some other explanation for what’s happening? Broome attributes the disparity to the many-worlds or ‘multiverse’ interpretation of quantum mechanics.
It’s important to keep in mind that the many-worlds interpretation was developed to explain the results of physics experiments and not the Mandela effect. Nonetheless, Broome believes that her shared memory isn’t actually false, and that she and others who remember a different past were actually in a parallel reality with a different timeline that somehow got crossed with our current one.
While the many-worlds interpretation of Everett is extravagant, suggesting that shared false memories are a possible example of that is even more extravagant. False memories are more likely to be due to a plausible but wrong idea being spread rapidly through social interactions.
Back to Everett, I did not know much about him other than this one idea of his and the biographical article says that his idea did not gain much headway, at least initially, in the world of physics and he left physics research after getting his PhD and had a successful career working for the Pentagon on nuclear war scenarios and then starting his own consulting company.
But he had an unhappy personal life.
Despite all these successes, Everett’s life was blighted in many ways. He had a reputation for drinking, and friends say the problem seemed only to grow with time. According to Reisler, his partner usually enjoyed a three-martini lunch, sleeping it off in his office—although he still managed to be productive.
Yet his hedonism did not reflect a relaxed, playful attitude toward life. “He was not a sympathetic person,” Reisler says. “He brought a cold, brutal logic to the study of things. Civil-rights entitlements made no sense to him.”
Everett was egocentric. “Hugh liked to espouse a form of extreme solipsism,” says Elaine Tsiang, a former employee at DBS. “Although he took pains to distance his [many-worlds] theory from any theory of mind or consciousness, obviously we all owed our existence relative to the world he had brought into being.”
And he barely knew his children, Elizabeth and Mark.
Everett died in bed on July 19, 1982. He was just 51. His son, Mark, then a teenager, remembers finding his father’s lifeless body that morning. Feeling the cold body, Mark realized he had no memory of ever touching his dad before. “I did not know how to feel about the fact that my father just died,” he told me. “I didn’t really have any relationship with him.”
Mark’s sister, Elizabeth, made the first of many suicide attempts in June 1982, only a month before Everett died. Mark discovered her unconscious on the bathroom floor and got her to the hospital just in time. When he returned home later that night, he recalled, his father “looked up from his newspaper and said, ‘I didn’t know she was that sad.’” In 1996 Elizabeth killed herself with an overdose of sleeping pills, leaving a note in her purse saying she was going to join her father in another universe.