There’s a short story out there about a device that can actually do this and then let you stay in contact with your alternate self for a while to see how things turn out. Fascinating stuff.
I'll probably remember the title tomorrow, if nobody beats me to it. It was a fairly disturbing story.
Say, fire an electron at a double slit with a detector in one of the slits, and kill yourself if the particle is not detected. Run the experiment 10,000 times, or 100,000,000 times - one copy of you will eventually be satisfied that in any probabilistic interpretation of QM this is not plausible, and all the other copies will be dead.
This works because the MWI predicts that any outcome that has non-0 probability according to the Born rule will be guaranteed to happen (it just "happens less" by some hard to define metric).
Personally I believe the entire notion is absurd, and that this type of thought experiment makes it clear, but still some like to be contrary.
I think MWI is appealing to a lot of people as part of the quiet, but ever-present undercurrent of "how can we make any sort of God totally unnecessary to the universe?" that science has, but if you think about it deeply enough, it becomes clear that MWI, if true, is unbelievably horrible. We'd all better hope it's not the correct interpretation.
Edit: Thanks for the link to the story. I had not read it or seen it before. Same principles for sure. I don't think it's a crazy extrapolation of MWI, I think it's the only logical outcome. I can put that opinion into more firm mathematical language but it's more than I can put into an HN comment, and I haven't typed it out anywhere else either, and it really is just that opinion, in more mathematical language.
Greg Egan also has a number of stories about people who rebelled against a "many worlds" universe by porting human cognition to run on "Quantum Single Processors," which would carefully isolate themselves from the universe until they had made a single decision across every possible timeline. This didn't prevent them from being "branched" by outside factors, but it at least gave them an approximation of free will.
So the main difference between someone like a Buddhist monk and a former US president with a taste for gold is one of choice. The monk acknowledges that all routes to living one's best life are possible so abstains from attaching to outcomes too strongly, while the former president asserts his ego to maximize a certain dimension like personal wealth at the expense of all the others. Too much choice and we risk being ungrounded, too little choice and we end up caught in a web of our own design.
There's a great scene on the show Vikings where Ragnar says:
Power is only given to those who are prepared to lower themselves to pick it up.
Really everything is possible, and we can use our will to sidestep into other realities. But from a framework of reincarnation and the multiverse, our choices can impose on the freedoms of others, so we should be mindful of the impacts of our decisions, because others are aspects of ourselves in another life.
I feel rather strongly that most of the world's problems like wealth inequality and war stem from overexertion of the ego. People constrain themselves into corners and then project their anxieties onto others to the point where it seems like nobody gets to live their best life.
Ain’t that the truth!
That said, Worm was an amazing story let down a bit by the ending.