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Ouch My Brain Hurts: Considering Infinite Worlds

Among the insane-but-real ideas in science, I love the fringe idea of quantum physics that says, in short, that every decision point in the Universe breeds another universe. One, we inhabit and, the other, some other "you" that made the alternate...

Among the insane-but-real ideas in science, I love the fringe idea of quantum physics that says, in short, that every decision point in the Universe breeds another universe. One, we inhabit and, the other, some other “you” that made the alternate decision inhabits. This is dubbed the “infinite worlds” or “many-worlds” theory and it is actually a thing that serious physicists talk about.

Think about Schrödinger’s poor cat in his famous thought-experiment. Remember: there’s a cat in a closed, sealed box. In with the cat is a bit of poison. The poison is either distributed to the cat or kept away from the cat according to a random event, like the decay of a radioactive isotope. (Which keeps it in correspondence to quantum probabilities, but don’t think about that if you don’t want to.) We don’t know how the isotope decayed and so we don’t know if the cat is alive or dead, right? According to quantum theory, the cat is neither and both.


Schrodinger’s cat is in what’s called a superposition of alive and dead states, which is a lot like looking at the wavefunction of a subatomic particle. In quantum mechanics, a subatomic particle doesn’t have a known state either. Instead, it’s what’s called a wavefunction, an addition of probabilities of where there particle could be. We can find out exactly where the particle is—open the box—but then we don’t know anymore where the particle was going; we just know exactly where it is at that exact moment.

This is a big problem in physics, the wavefunction collapse. Schrodinger didn’t like the idea of the wavefunction very much, which is what the cat thing is supposed to illustrate. Of course the cat isn’t both alive and dead. Ask the cat.

So that’s the problem. And that’s what this many-worlds idea address. Sure, the cat can be both alive and dead, and the particle can be here and there, because they’re different things in different universes—instead of being two different things in one universe. Every time that wavefunction collapses, every time we pin down a cat or particle to some state, the universe divides again and maybe we’re here with the alive cat and another “me” is off somewhere with a dead cat, poised to go on living in that other Universe and maybe even gather up an entirely different life.

So, this kind of kills the idea of probability, right? Like, if you’re playing blackjack you might ask yourself why the heck am I playing blackjack? ‘Cause you’re just going to win every time. I mean, not just win a hand, but win every hand ever. And not just win every hand. You’re going to get blackjack every hand. Forever. That has to be one of the worlds. This you might not be experiencing it. You most certainly aren’t actually. This you is more likely folding on 16. But within this many-worlds idea, you can relax a bit knowing that there is definitely a “you” that is winning every hand at blackjack ever.


On the other hand, you have also died painfully many, many more times than the above happening. On the other other hand: what if you are actually living in an extremely improbable world. What if you beat some odds of being here? Maybe when you crossed the street this morning there was a 99.9-percent chance of you getting creamed by a semi?

The following comes from the Stanford philosophy encyclopedia, which is a great resource and might help explain this. (MWI is ‘many worlds interpretation.’ Lev is a hypothetical person living in the MWI. Don’t worry about the ‘Lewis 2000.’)

There are claims that a believer in the MWI will behave in an irrational way. One claim is based on the naive argument described in the previous section: a believer who assigns equal probabilities to all different worlds will bet equal bets for the outcomes of quantum experiments that have unequal probabilities.

Another claim, recently discussed by Lewis 2000, is related to the strategy of a believer in the MWI who is offered to play a quantum Russian roulette game. The argument is that I, who would not accept an offer to play a classical Russian roulette, should agree to play the roulette any number of times if the triggering occurs according to the outcome of a quantum experiment. Indeed, at the end, there will be one world in which Lev is a multi-millionaire and all other worlds in which there will be no Lev Vaidman alive. Thus, in the future, Lev will be rich and presumably a happy man.


However, adopting the Probability Postulate leads all believers in the MWI to behave according to the following principle:

Behavior Principle We care about all our successive worlds in proportion to their measures of existence.

So, really, you shouldn’t do anything different. But it’s still fun to think about.

Reach this writer at

Thanks to three main sources:

The Goldilocks Enigma

by Paul Davies;

A Very Short Introduction To Quantum Theory

by John Polkinhorne; and the Stanford website.