[ExI] THE MANY WORLDS OF HUGH EVERETT

[John Clark]

On Wed, Oct 15, 2025 at 9:57 AM Giulio Prisco via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

That was a great review! I enjoyed it and cited it in my first book

Tales of the Turing Church.
> G.
>

*Thanks  Giulio.*

*John K Clark*



> On Wed, Oct 15, 2025 at 3:29 PM John Clark via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
> >
> > Back in 2010 on this list I posted a review of Peter Byrne's book "THE
> MANY WORLDS OF HUGH EVERETT", this seems like a good time to re-post it:
> >
> > ==
> >
> > I've just finished this book and it's one of the most enjoyable things
> I've read in a long time. Being a staple of science fiction and the only
> interpretation of quantum mechanics to enter the popular imagination it's a
> little surprising that "The Many Worlds of Hugh Everett '' by Peter Byrne
> is the first biography of the originator of that amazing idea. Everett
> certainly had an interesting life, he was a  libertarian and a libertine,
> became a cold warrior who with his top secret clearance was comfortable
> with the idea of megadeth, became wealthy by starting one of the first
> successful software companies until alcoholism drove him and his company
> into the ground. Everett died of heart failure in 1982 at the age of 51, he
> was legally drunk at the time. He requested that his body be cremated and
> his ashes thrown into the garbage. And so he was.
> >
> >
> > Byrne had an advantage other potential biographers did not, the
> cooperation of his son Mark, a successful rock musician and composer whose
> music has been featured in such big budget movies as American Beauty,
> Hellboy, Yes Man, all three of the Shrek movies and many others. Mark gave
> Byrne full access to his garage which was full of his father's papers that
> nobody had looked at in decades.
> >
> >
> > Everett was an atheist all his life, after his death Paul Davies, who
> got 1,000,000 pounds for winning the Templeton religion prize, said that if
> true Many Worlds destroyed the anthropic argument for the existence of God.
> Everett would have been delighted. Nevertheless Everett ended up going to
> Catholic University of America near Washington DC.  Although Byrne doesn't
> tell us exactly what was in it, Everett as a freshman devised a logical
> proof against the existence of God. Apparently it was good enough that one
> of his pious professors became very upset and depressed with "ontological
> horror" when he read it. Everett liked the professor and felt so guilty he
> decided not to use it on a person of faith again. This story is very
> atypical of the man, most of the time Everett seems to care little for the
> feelings of others and although quite brilliant wasn't exactly lovable.
> >
> >
> > Everett wasn't the only one dissatisfied with the Copenhagen
> Interpretation which insisted the measuring device had to be outside the
> wave function, but he was unlike other dissidents such as Bohm or Cramer in
> that Everett saw no need to add new terms to Schrodinger's Equation and
> thought the equation meant exactly what it said. The only reason those
> extra terms were added was to try to rescue the single universe idea, and
> there was no experimental justification for that. Everett was unique in
> thinking that quantum mechanics gave a description of nature that was
> literally true.
> >
> >
> > John Wheeler, Everett's thesis advisor, made him cut out about half the
> stuff in his original 137 page thesis and tone down the language so it
> didn't sound like he thought all those other universes were equally real
> when in fact he did. For example, Wheeler didn't like the word "split" and
> was especially uncomfortable with talk of conscious observers splitting,
> most seriously he made him remove the entire chapter on information and
> probability which today many consider the best part of the work. His long
> thesis was not published until 1973, if that version had been published in
> 1957 instead of the truncated Bowdlerized version things would have been
> different; plenty of people would still have disagreed but he would not
> have been ignored for as long as he was.
> >
> >
> > Byrne writes of Everett's views: "the splitting of observers share an
> identity because they stem from a common ancestor, but they also embark on
> different fates in different universes. They experience different
> lifespans, dissimilar events (such as a nuclear war perhaps) and at some
> point are no longer the same person, even though they share certain memory
> records." Everett says that when an observer splits it is meaningless to
> ask "which of the final observers corresponds to the initial one since each
> possesses the total memory of the first" he says it is as foolish as asking
> which amoeba is the original after it splits into two. Wheeler made him
> remove all such talk of amebas from his published short thesis.
> >
> >
> > Byrne says Everett did not think there were just an astronomically large
> number of other universes but rather an infinite number of them, not only
> that he thought there were a non-denumerable infinite number of other
> worlds. This means that the number of them was larger than the infinite set
> of integers, but Byrne does not make it clear if this means they are as
> numerous as the number of points on a line, or as numerous as an even
> larger infinite set. Neill Graham tried to reformulate the theory so you'd
> only need a countably infinite number of branches and Everett at first
> liked the idea but later rejected it and concluded you couldn't derive
> probability by counting universes. Eventually even Graham seems to have
> agreed and abandoned the idea that the number of universes was so small you
> could count them.
> >
> >
> > Taken as a whole Everett's multiverse, where all things not forbidden by
> quantum mechanics happen, probability is not a useful concept and
> everything is deterministic. However for observers like us trapped in a
> single branch of the multiverse, observers who do not have access to the
> entire wave function and all the information it contains but only a small
> sliver of it, probability is the best we can do. That probability we see is
> not part of the thing itself but is just a subjective measure of our
> ignorance.
> >
> >
> > Infinity can cause problems in figuring out probability but Everett said
> his theory could calculate what the probability any event could be observed
> in any branch of the multiverse, and it turns out to be the Born Rule
> (discovered by Max Born, grandfather of pop singer Olivia Newton John)
> which means the probability of finding a particle at a point is the square
> of the amplitude of the Schrodinger Wave function at that point. The Born
> Rule has been shown experimentally to be true but the Copenhagen
> Interpretation just postulates it, Everett said he could derive it from his
> theory it "emerges naturally as a measure of probability for observers
> confined to a single branch (like our branch)." He proved the mathematical
> consistency of this idea by adding up all the probabilities in all the
> branches of the event happening  and getting exactly 100%. Dieter Zeh said
> Everett may not have rigorously derived the Born Rule but did justify it
> and showed it "as being the only reasonable choice for a probability
> measure if objective reality is represented by the universal wave function
> [Schrodinger's wave equation]". Rigorous proof or not, that's more than any
> other quantum interpretation has managed to do.
> >
> >
> > Everett wrote to his friend Max Jammer:
> >
> > "None of these physicists had grasped what I consider to be the major
> accomplishment of the theory- the "rigorous" deduction of the probability
> interpretation of Quantum Mechanics from wave mechanics alone. This
> deduction is just as "rigorous" as any deductions of classical statistical
> mechanics. [...] What is unique about the choice of measure and why it is
> forced upon one is that in both cases it is the only measure that satisfies
> the law of conservation of probability through the equations of motion.
> Thus logically in both classical statistical mechanics and in quantum
> mechanics, the only possible statistical statements depend upon the
> existence of a unique measure which obeys this conservation principle."
> >
> >
> > Nevertheless some complained that Everett did not use enough rigor in
> his derivation. David Deutsch has helped close that rigor gap. He showed
> that the number of Everett-worlds after a branching is proportional to the
> conventional probability density. He then used Game Theory to show that all
> these are all equally likely to be observed. Everett would likely have been
> delighted as he used Game Theory extensively in his other life as a cold
> warrior. Professor Deutsch gave one of the best quotations in the entire
> book, talking about many worlds as an interpretation of Quantum Mechanics
> "is like talking about dinosaurs as an interpretation of the fossil record".
> >
> >
> > More recently Sean Carroll and others have pointed out the only
> assumption that many worlds makes is that everything evolves according to
> the Schrodinger equation, and Occam's Razor is about an economy of
> assumptions not an economy of results, and all those worlds are not an
> assumption, they are just the result of what happens if you think
> Schrodinger's equation means what it says. However Schrodinger's equation
> is completely deterministic so the real question is not why does the Born
> rule work but why do we need to use probabilities at all?  Carroll says the
> reason is "self location". Many Worlds says that if somebody flips a coin
> then the universe branches, in one branch the coin lands heads and the
> other tales, but until you actually look at the coin you won't know which
> branch you're on so you'd have to resort to probability, in this case 50-50.
> >
> >
> > Everett was disappointed at the poor reception his doctoral dissertation
> received and never published anything on quantum mechanics again for the
> rest of his life; instead he became a Dr. Strangelove type character making
> computer nuclear war games and doing grim operational research for the
> pentagon about armageddon. He was one of the first to point out that any
> defense against intercontinental ballistic missiles would be ineffectual
> and building an anti-ballistic missile system could not be justified except
> for "political or psychological grounds". Byrne makes the case that Everett
> was the first one to convince high military leaders through mathematics and
> no nonsense non sentimental reasoning that a nuclear war could not be won,
> "after an attack by either superpower on the other, the majority of the
> attacked population that survived the initial blasts would be sterilized
> and gradually succumb to leukemia. Livestock would die quickly and
> survivors would be forced to rely on eating grains, potatoes and
> vegetables. Unfortunately the food would be seething with radioactive
> Strontium 90 which seeps into human bone marrow and causes cancer". Chemist
> Linus Pauling credited Evertt by name and quoted from his pessimistic
> report in his Nobel acceptance speech for receiving the 1962 Nobel Peace
> prize.
> >
> >
> > Despite his knowledge of the horrors of a nuclear war Everett, like most
> of his fellow cold warrior colleagues in the 50's and 60's, thought the
> probability of it happening was very high and would likely happen very
> soon. Byrne speculates in a footnote that Everett may have privately used
> anthropic reasoning and thought that the fact we live in a world where such
> a war has not happened (at least not yet), not even in 1962 during the
> Cuban missile crisis where the human race came closer to extinction than it
> ever has before, was more confirmation that his Many Worlds idea was right.
> Incidentally this is one of those very rare books where the footnotes are
> almost as much fun to read as the main text.
> >
> >
> > Hugh's daughter Liz Everett killed herself a few years after her
> father's death, in her suicide note she said "Funeral requests: I prefer no
> church stuff. Please burn and DON'T FILE ME. Please sprinkle me in some
> nice body of water or the garbage, maybe that way I'll end up in the
> correct parallel universe to meet up with Daddy". And so she was.
> >
> >
> >   John K Clark
>
>
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