I've been reading up on the Many Worlds Interpretation of Quantum Mechanics, and there is one thing (among many) that I really don't understand. How many worlds are 'created' by an 'observation' or 'event'?

For example, in the traditional Schrödinger's Cat experiment a cat is put into a box with a poison flask that has a chance of breaking, with the cat dying if it does. But how many worlds are created by this? If the probabilities are even I could understand two worlds being created. But what if the flask has a 70% chance of breaking? Are ten worlds created, in seven of which the cat is dead? Or are an infinite number created, but in 70% of which the cat is dead? Or are just two created, but you somehow have a 70% chance of ending up in the world with the dead cat? Or is it something entirely different?

  • $\begingroup$ One would naturally imagine that exactly the amount of numbers that accomodate ALL possible outcomes for all experiments/observations at all times are being created. In practice, this quickly diverges to infinity. $\endgroup$
    – Danu
    Oct 23, 2013 at 17:41
  • $\begingroup$ But surely that doesn't change anything? Now instead of having two possibilities you have a near infinite number (presumably finite?), but you still have different probabilities of each of those things happening. $\endgroup$
    – Ben Elgar
    Oct 23, 2013 at 19:14
  • 1
    $\begingroup$ possible duplicate of Many-worlds: how often is the split how many are the universes? (And how do you model this mathematically.) $\endgroup$
    – user4552
    Oct 23, 2013 at 23:15
  • $\begingroup$ I did look at that question but decided it didn't answer my question. I suppose I just don't understand the answer well enough to be able to reject it though. My main issue is that the answers seem to favour the Copenhagen interpretation and thus seemed to relate everything to it. $\endgroup$
    – Ben Elgar
    Oct 25, 2013 at 18:04
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    $\begingroup$ I agree that this a different question, and that none of the answers to the linked question address it (in fact none do a great job of addressing that one either). This should be reopened. $\endgroup$
    – orome
    Nov 17, 2014 at 18:34


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