On 9/13/2024 1:11 AM, Stathis Papaioannou wrote:
On Fri, 13 Sept 2024 at 17:30, Bruce Kellett <[email protected]> wrote:On Fri, Sep 13, 2024 at 5:23 PM Stathis Papaioannou <[email protected]> wrote: On Fri, 13 Sept 2024 at 15:08, Bruce Kellett <[email protected]> wrote: On Fri, Sep 13, 2024 at 1:07 PM Liz R <[email protected]> wrote: I don't think that works. The idea often put forward is something along the lines of self-locating uncertainty -- out of all the branches, which one am I on? But that is only apparent randomness, and to get such an idea to work, you need to be able to make a random choice between branches. Such randomness will be intrinsic in that It doesn't come from anywhere else (it is not already part of the theory). So in order to generate such apparent randomness you actually need an independent source of intrinsic randomness (to be able to make your self-locating choice.) The intrinsic randomness arises from the fact that it is impossible to predict which branch you will end up in, even for an omniscient being. That is just a restatement of the traditional measurement problem. Self-locating uncertainty is not intrinsic randomness. What is it that selects which branch you are actually on? You need some means of random selection which is not included in the underlying theory. You have to add, by hand, some additional principle of randomness, such as the Born Rule. Nothing selects which branch you will be on, since with certainty a version of you will end up in each branch. If the omniscient being predicts that you will end up in branch A, the prediction is wrong for the version of you in branch B, and if the omniscient being predicts that you will end up in branch B the prediction is wrong for the version of you in branch A. It is logically impossible to make an accurate prediction. It is unfortunate, therefore, that all real experiments result in just one answer, which is the nub of the measurement problem. Which answer is unpredictable, but that does not mean that there can be some omniscient being that can predict your result. It is a matter of an intrinsic probability -- /viz/. the Born Rule.The branching makes the outcome fundamentally unpredictable, which is what randomness is. It results from the branching and nothing else. It is not specific to QM or MWI: it results from any process where the observer branches.
Remember MWI is just a theory. There are no known processes in which any observer (or even a non-observer) branches; which is one reason to doubt MWI.
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