The idea that the universe constantly splits into alternate realities has had a surprisingly warm reception in science, philosophy and popular literature. But this baroque solution to the unique problems of quantum mechanics is simply not good science. Not only should we resist its strange appeal, it’s time to find another way, writes Philip Ball.
Alternative realities hold an irresistible allure. Whether it’s Dickens’ A Christmas Carol, Frank Capra’s It’s a Wonderful Life, or the quantum-computed parallel universes of Alex Garland’s recent TV series Devs, the possible lives that we can imagine having led but did not lead offer a stage for acting out our fears and fantasies. Like Robert Frost’s traveller confronted with diverging paths in a wood, we often wonder where the road not taken might have borne us.
It is no surprise, then, that the Many Worlds interpretation (MWI) of quantum mechanics seems to hold such attraction. Even though most physicists dismiss or even deride it, it is often eagerly embraced by physics popularizers and their audiences. Yet it can be hard to figure out how seriously some of its advocates really take it. I believe some physicists genuinely see it as an elegant solution to deep conundrums of the notoriously mind-bending quantum theory, and I sympathize with some of their reasoning. But when they start talking about “quantum brothers” (and presumably sisters, though Many Worlds has curiously few female advocates), or using “quantum apps” to make difficult decisions by triggering some quantum measurement in the conviction that they are thereby splitting off a world where they made the other choice, I have to wonder whether, indifferent to the philosophical complications, they are just enjoying the fantasy.
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