Might help to have separate options for people who haven't heard of it, people who have but disagree, and people who agree but still don't let it affect their actions

Maybe also a lizardman option for good measure lol

Many worlds doesn't mean “all possible worlds” as in “all imaginable worlds” exist like in scifi but that there’s no wavefunction collapse so there’s a proportional share of worlds where each quantum mechanical outcome exists, hence “all possible worlds” as described by the evolution of the universal wave function. The lottery example only works if there’s alternative configurations from a QM level where you win the lottery, that’s not a given.

There are infinitely many numbers that exist between 1 and 2, but none of them are 3.

So for your example you’d will need a branch where things have evolved along a similar enough path for you to be recognizably you but different enough for either your brain to generate different choices when picking the lottery number or for the lottery winner selection to produce your given number.

One can however couple one’s lottery number directly to outcomes from a series of QM experiments to purposely produce those branches. If one believes in this interpretation, one may wish to do this to generate a winning branch but it will cost every other branch the capital and most future versions of ones self are essentially guaranteed to find themselves in a losing branch.

@LiamZ

most future versions of ones self are essentially guaranteed to find themselves in a losing branch

Hence the idea of having some machine shoot yourself in all those branches, a moment before you can become aware of having lost. The result from your perspective would then become equivalent to winning the lottery magically (at least, under this view of metaphysics).

Regarding the “all possible worlds” vs “all imaginable worlds”: I think it boils down to the same thing in the end, as far as human credulity is concerned. It's physically possible that an hour from now, the molecules in my room will spontaneously arrange themselves into a perfect clone of you, and that we'll continue this same conversation in person. Does MWI predict this event? From my understanding, it does, but my knowledge of the subject is very limited.

The lottery example only works if there’s alternative configurations from a QM level where you win the lottery, that’s not a given.

I think it basically is a given, under all practical circumstances that could be relevant to people answering this poll. But you can help me understand if that's not the case.

@singer it depends a lot on how you define "you" within the wavefunction evolution, which is fairly non-obvious. The strictest and easiest way is to base it on direct branches where you've made the macroscopic outcome very sensitive to the QM microstate, as that guarantees direct evolution. Still, there is an argument for macroscopically similar branches to count, even if they diverge earlier or more drastically. I mention this primarily because I think the idea has reached pop culture saturation with the sci-fi version, leading to some confusion.

There's a fun and accessible conversation between Sean Carrol who advocates the interpretation and the guys who made a recently great scifi movie utilizing many worlds in the scifi sense here: https://open.spotify.com/episode/1VPttPRvhja2wgj4WGpHxX

@LiamZ

Thanks for the podcast suggestion! I've found Sean Carroll's writing very helpful in the past. I hope you still don't mind me asking a few more questions.

If I understand you right, the issue now is mainly a philosophical one, since the examples earlier are true in a physical sense (the lottery example, the suicide example, the example of us talking in person). These branches will certainly exist. But what remains is deciding what branches one ought to care about. Do you think that's right?

it depends a lot on how you define "you" within the wavefunction evolution, which is fairly non-obvious

There's two different ways I can think of that would cause someone to disavow certain future branches as not containing themselves:

1. The physical differences between them and their counterpart have accumulated to such a degree that they no longer recognize themselves.

2. A kind of indexical chauvinism, where only the branch they're observing matters to them, even if they concede that the others are equally real.

The first reason isn't specific to MWI, and not relevant for the short timeframe examples earlier. The second is plausible, but feels more like a denial of MWI itself. Besides those two considerations, I don't see much room for defining "you" in these situations; the options tend to one extreme or the other, either patternism or indexical chauvinism.

Do you think there are any physical facts that could make a difference here? I have to admit, I didn't understand your earlier reference to making the "macroscopic outcome very sensitive to the QM microstate, as that guarantees direct evolution". Is that a distinction not captured in the above?