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If Everett's Many-Worlds Theory (MWT) was true, wouldn´t it mean, that each split into two (or n) worlds, would correspond to 2 (or n) equally likely probable outcomes of the currently considered wave function? But real wave functions have probability distributions with very varying probabilities for the outcomes and it does not sound consistent to have the world split into e.g. 0.2 worlds with outcome A and 0.8 worlds with outcome B, right? A split into 1 world with outcome A and 4 worlds with outcome B, would solve this - but for the price of many extra worlds and the impossibility to allow for irrational probabilities.

So is this the final prove, that MWT is nonsense? I don´t believe it can be so easy. So, where´s my mistake?

I´m curious about your thoughts.

Qmechanic
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DataGuy
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2 Answers2

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The problem of the probabilities in the many worlds interpretation is a fascinating and challenging one. Many smart people are working on it, and there have been some interesting advances that, depending on who you ask, may or may not resolve the problem.

You asked where the mistake was in your "final proof". I can see two:

  1. You haven't proved that the "price" you specified is the only way to get probabilities in the many worlds interpretation.

  2. You haven't proved that the "price" is too high.

ReasonMeThis
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One can only measure an observable, e.g. position within the accuracy of the measurment appararus. So if you have a continuous set of states, say position of a particle in 1D, the states get transformed into a new set of discrete states, corresponding to intervals, each with size based upon your apparatus's accuracy (smaller intervals for more accurate devices).

Why do I say this? To help you see that even something as often measured as position need not be binary. The discrete states each correspond some finite measurable interval, and there are a finite number of intervals. And each interval may have an equal chance of being measured.

So you see, from the above you can get all sorts of probablities. 1/1,000,000 if your device can measure 1,000,000 subsets of some length. 3/1,000,000 if you pick 3 positions to choose from with the same device over the same interval instead of choosing just 1. Etc, etc.

That's the easy part. Don't look at MWI as there being n new worlds everytime a measurment occurs where n is the number of finite intervals measured from. Rather, picture yourself as better locating yourself and your measurement somewhere on the universal wave function that was already there now that you have the information of your measurment. It's not that a million new branches spawned because of your 1D position measurment, and you are in one of those million now. Instead, due to superposition prior to measurment, the entire universe of all outcomes, including what you will measure, was always there. Upon measurement, you now better know where you are in this universal wave function. At least that is how some like Sean Carroll put it.

J Kusin
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