Disclaimer: I don’t understand QM on a formal level. But here’s what I got out of reading the Sequences and other LW discussions on the subject.
Does this “Many worlds” thing imply that there exists (in some meaningful sense) other worlds alongside us
They exist, in a special sense of the word. Instead of arguing about definitions of existence, measure of reality, etc., let’s talk about the experimental consequences. Which are: you’re not going to interact with them ever again. They exist at most as much as people in our own branch who are outside our Hubble radius.
Should you still grieve for them? That’s for you to decide, but I do make a suggestion: grief is in part a useful adaptation. It may help motivate you to prevent more future grief. If you cannot prevent future grief-causing events (because quantum torture branches will always keep splitting off, and to the extent you cannot influence their measure), then that grief is useless. Eliminating it (not grieving) makes you better off and no-one else worse off, so in such cases I suggest you do not grieve.
Should we try quantum suicide?
Again, there may well be good quantum theoretical arguments against quantum suicide. But here’s a more practical one. Suppose it works. It has been suggested that it in the vast majority of the branches in which you survive, you do not survive unscathed: you survive hurt, reduced, as an invalid, etc. If you rig up a gun to shoot you, there are some branches where it fails to shoot entirely, but there are many more branches where it misses just enough that you live on as a cripple. Quantum suicide is dangerous like an outcome pump.
are there any worlds where the Earth is ruled by Nazi Germany?
In principle, any world whose past evolution does not contradict the laws of physics exists as a branch.
Most people try to avoid the unpleasant implications by assigning significance to the weight of those branches. I find this a bit problematic when applied to branches that are not in our future: the Born probabilities govern the branch we expect to witness, but we don’t understand why or how, so why should we say they govern some “reality measure” of branches we cannot interact with?
Disclaimer: I don’t understand QM on a formal level. But here’s what I got out of reading the Sequences and other LW discussions on the subject.
They exist, in a special sense of the word. Instead of arguing about definitions of existence, measure of reality, etc., let’s talk about the experimental consequences. Which are: you’re not going to interact with them ever again. They exist at most as much as people in our own branch who are outside our Hubble radius.
Should you still grieve for them? That’s for you to decide, but I do make a suggestion: grief is in part a useful adaptation. It may help motivate you to prevent more future grief. If you cannot prevent future grief-causing events (because quantum torture branches will always keep splitting off, and to the extent you cannot influence their measure), then that grief is useless. Eliminating it (not grieving) makes you better off and no-one else worse off, so in such cases I suggest you do not grieve.
Again, there may well be good quantum theoretical arguments against quantum suicide. But here’s a more practical one. Suppose it works. It has been suggested that it in the vast majority of the branches in which you survive, you do not survive unscathed: you survive hurt, reduced, as an invalid, etc. If you rig up a gun to shoot you, there are some branches where it fails to shoot entirely, but there are many more branches where it misses just enough that you live on as a cripple. Quantum suicide is dangerous like an outcome pump.
In principle, any world whose past evolution does not contradict the laws of physics exists as a branch.
Most people try to avoid the unpleasant implications by assigning significance to the weight of those branches. I find this a bit problematic when applied to branches that are not in our future: the Born probabilities govern the branch we expect to witness, but we don’t understand why or how, so why should we say they govern some “reality measure” of branches we cannot interact with?