Hugh Everett saw far beyond one mere universe (Image: Hugh Everett III Manuscripts/University California Irvine)

Hugh Everett’s many-worlds interpretation of quantum mechanics arose from what must have been the most world-changing drinking session of all time. One evening in 1954, in a student hall at Princeton University, grad student Everett was drinking sherry with his friends when he came up with the idea that quantum effects cause the universe to constantly split.

Read more: “Multiverse me: Should I care about my other selves?“

He developed the idea for his PhD thesis – and the theory held up. According to his work, we are living in a multiverse of countless universes, full of copies of each of us. It was sensational.


Max Tegmark of Massachusetts Institute of Technology has said that Everett’s work is as important as Einstein’s work on relativity. But the leading physicists of the Everett’s day, in particular Niels Bohr, one of the fathers of quantum mechanics, couldn’t stomach it. They couldn’t cope with the idea that every decision we make creates new universes, one for all possible outcomes. Everett had to publish a watered-down version of his idea. Thoroughly disgruntled, he left physics.

What he did next fascinates me, in the light of what he had discovered. Everett joined the Pentagon, and worked in a team calculating potential deaths in the event of nuclear war. His job was to calculate how to maximise the death toll for the Soviets while minimising it for Americans by looking at fallout.

If the many-worlds view is right, our actions shape our counterparts’ lives in parallel worlds. What does this mean for how should we behave in this world? It’s a question I explore – with the help of leading physicists, as well as Hugh Everett’s rock star son – in this in-depth article: “Multiverse me: Should I care about my other selves?“.

Mutually assured destruction

But what about Everett himself? Did he consider what working for the Pentagon would mean in parallel worlds? Wasn’t he facilitating nuclear war in the multiverse? We can’t ask him, because he died in 1982, aged only 51. But we can ask those who know his work.

“He wrote arguably the first ever serious report on just how devastating a nuclear war would be for the US,” says Tegmark. It helped devise the concept of mutually assured destruction (MAD). This is a concept appropriately summed up by its acronym – in that we’d be insane to start a nuclear war – but MAD might actually have prevented the cold war from overheating.

“MAD might have in a major way contributed to the extra caution that might explain why we’re still here,” says Tegmark. “My guess is that Everett’s work helped drive home the full horror of war, and this reduced the fraction of the multiverse that saw global nuclear war.”

The work Everett did for the Pentagon, then, arguably had a net positive effect on the multiverse. It’s tempting to speculate that these actions were influenced by his physics work, but we’ll never know.

Unstoppable vs immovable

Everett’s life was fascinating and tragic. Peter Byrne’s book, The Many Worlds of Hugh Everett III provides a detailed account. Many moments stand out, here are a few.

Everett wrote to Einstein when he was 12 – and Einstein replied. Young Hugh was already keen at challenging the very highest figures of physics authority. His letter was an attempt to solve the paradox of what happens when an unstoppable force meets an immovable object.

He was recommended for Princeton by his old professor of mathematics, who wrote, “This is a once-in-a-lifetime recommendation for I think it most unlikely that I shall ever again encounter a student I can give such complete and unreserved support.”

When Everett died of a heart attack, his teenage son Mark discovered the body. Mark recalls that trying to revive his dead father was the first time he could remember ever touching him.

Everett was a keen atheist. Following his instructions his widow, Nancy, threw his ashes out with the garbage.

Everett’s son Mark referenced his father in a 2005 song Things the Grandchildren Should Know:

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.

There is also a comprehensive Everett archive here, and an award-winning BBC documentary on his work called Parallel Worlds, Parallel Lives.