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One big complaint I have with MWI is it seems to throw probability out the window. If every possible result of a quantum calculation actually has physical reali

by eridius 11y ago

One big complaint I have with MWI is it seems to throw probability out the window. If every possible result of a quantum calculation actually has physical reality, then doesn't that make all the states equally likely? The only solution I can think of to that is to have every quantum calculation actually spawn an infinity of worlds, of which a certain percentage of them have a given result that matches the probability of that result in the wavefunction. And that just seems to make MWI incredibly messy. There's a certain conceptual cleanness in saying that the universe splits for every decision such that all possible decisions have their own world, but saying that every possible quantum event results in an infinity of worlds (which also means that for every possible result there's also an infinity of identical worlds for that state) just seems ridiculous.

Houshalter 11y ago
Imagine a ball falling down a peg board. Each time it hits a peg, it has a 50% chance of falling either direction. This creates a Gaussian distribution where it lands. It has a very high probability of landing in the exact center, and slightly less probability of landing to the right, and even less at landing to the far right, etc. See this image: http://ptrow.com/articles/Galton_June_07_files/GaltonBoard2.jpg http://ptrow.com/articles/Galton_June_07_files/GaltonBoard2.... Now imagine instead of probability, you just split universes each time it hits a peg. One universe the ball goes to the left, and in one universe, the ball goes to the right. Each possibility gets it's own universe. Then the same result happens. The majority of universes have the ball land in the middle, and very few universes have it land on the tails. But each possibility does have it's own universe. It's just some things happen more than others. If you pick a random universe, you are more likely to end up in one with the ball in the middle, then on a tail. And this doesn't require an infinite number of universes. It's a completely discrete system.
- eridius 11y ago
  I appreciate the example here, but this only works when every decision has 2 outcomes with a 50/50 probability distribution (or more generally, when every decision has an even weighting between all results). I don't pretend to have a good understanding of quantum mechanics, but my impression is that this model doesn't match how quantum "decisions" actually work.
  - Houshalter 11y ago
    It's my understanding that that's exactly how quantum physics works. E.g. a particle has a fixed number of things it can do each moment. E.g move left or right, or whatever. It's the aggregate combination of all these possibilities that produce the probability distributions we observe. But at some low level, there's just a uniform distribution over some number of possibilities.
    - eridius 11y ago
      But move left/right/whatever by what distance?

by eridius 11y ago

Houshalter 11y ago

Imagine a ball falling down a peg board. Each time it hits a peg, it has a 50% chance of falling either direction. This creates a Gaussian distribution where it lands. It has a very high probability of landing in the exact center, and slightly less probability of landing to the right, and even less at landing to the far right, etc. See this image: http://ptrow.com/articles/Galton_June_07_files/GaltonBoard2.jpg http://ptrow.com/articles/Galton_June_07_files/GaltonBoard2.... Now imagine instead of probability, you just split universes each time it hits a peg. One universe the ball goes to the left, and in one universe, the ball goes to the right. Each possibility gets it's own universe. Then the same result happens. The majority of universes have the ball land in the middle, and very few universes have it land on the tails. But each possibility does have it's own universe. It's just some things happen more than others. If you pick a random universe, you are more likely to end up in one with the ball in the middle, then on a tail. And this doesn't require an infinite number of universes. It's a completely discrete system.

eridius 11y ago
I appreciate the example here, but this only works when every decision has 2 outcomes with a 50/50 probability distribution (or more generally, when every decision has an even weighting between all results). I don't pretend to have a good understanding of quantum mechanics, but my impression is that this model doesn't match how quantum "decisions" actually work.
- Houshalter 11y ago
  It's my understanding that that's exactly how quantum physics works. E.g. a particle has a fixed number of things it can do each moment. E.g move left or right, or whatever. It's the aggregate combination of all these possibilities that produce the probability distributions we observe. But at some low level, there's just a uniform distribution over some number of possibilities.
  - eridius 11y ago
    But move left/right/whatever by what distance?