The issue is not want of an explanation for the phenomenon, away or otherwise. We have an explanation of the phenomenon, in fact we have several. That’s not the issue. What I’m talking about here is the inherent, not-a-result-of-my-limited-knowledge probabilities that are a part of all explanations of the phenomenon.
Past me apparently insisted on trying to explain this in terminology that works well in collapse or pilot-wave models, but not in many-worlds models. Sorry about that. To try and clear this up, let me go through a “guess the beam-splitter result” game in many-worlds terminology and compare that to a “guess the trillionth digit of pi” game in the same terminology.
Aside: Technically it’s the amplitudes that split in many-worlds models, and somehow these amplitudes are multiplied by their complex conjugates to get you answers to questions about guessing games (no model has an explanation for that part). As is common around these parts, I’m going to ignore this and talk as if it’s the probabilities themselves that split. I guess nobody likes writing “square root” all the time.
Set up a 50⁄50 beam-splitter. Put a detector in one path and block the other. Write your choice of “Detected” or “Not Detected” on a piece of paper. Now fire a single photon. In Everett-speak, half of the yous end up in branches where the photon’s path matches your guess while half of the yous don’t. The 50⁄50 nature of this split remains even if you know the exact quantum state of the photon beforehand. Furthermore, the branching of yous that try to use all your physics knowledge to predict their observations have no larger a proportion of success than the branching of yous that make their predictions by just flipping a coin, always guessing Fire, or employing literally any other strategy that generates valid guesses. The 50⁄50 value of this branching process is completely decoupled from your predictions, no matter what information you use to make those predictions.
Compare this to the process of guessing the trillionth digit of pi. If you make your guess by rolling a quantum die, then 1 out of 10 yous will end up in a branch where your guess matches the actual trillionth digit of pi. If you instead use those algorithms you know to calculate a guess, and you code/run them correctly, then basically all of the yous end up in a branch where your guess is correct.
We now see the fundamental difference. Changing your guessing strategy results in different correct/incorrect branching ratios for the “guess the trillionth digit of pi” game but not for the “guess the beam-splitter result” game. This is the Everett-speak version of saying that the beam-splitter’s 50⁄50 odds is a property of the universe while the trillionth digit of pi’s 1⁄10 odds is a function of our (current) ignorance. You can opt to replace “odds” with “branching ratios” and declare that there is no probability of any kind, but that just seems like semantics to me. In particular the example of the ten trillionth digit of pi should not be what prompts this decision. Even in the many-worlds model there’s still a fundamental difference between that and the quantum processes that physicists cite as intrinsically random.
The issue is not want of an explanation for the phenomenon, away or otherwise. We have an explanation of the phenomenon, in fact we have several. That’s not the issue. What I’m talking about here is the inherent, not-a-result-of-my-limited-knowledge probabilities that are a part of all explanations of the phenomenon.
Past me apparently insisted on trying to explain this in terminology that works well in collapse or pilot-wave models, but not in many-worlds models. Sorry about that. To try and clear this up, let me go through a “guess the beam-splitter result” game in many-worlds terminology and compare that to a “guess the trillionth digit of pi” game in the same terminology.
Aside: Technically it’s the amplitudes that split in many-worlds models, and somehow these amplitudes are multiplied by their complex conjugates to get you answers to questions about guessing games (no model has an explanation for that part). As is common around these parts, I’m going to ignore this and talk as if it’s the probabilities themselves that split. I guess nobody likes writing “square root” all the time.
Set up a 50⁄50 beam-splitter. Put a detector in one path and block the other. Write your choice of “Detected” or “Not Detected” on a piece of paper. Now fire a single photon. In Everett-speak, half of the yous end up in branches where the photon’s path matches your guess while half of the yous don’t. The 50⁄50 nature of this split remains even if you know the exact quantum state of the photon beforehand. Furthermore, the branching of yous that try to use all your physics knowledge to predict their observations have no larger a proportion of success than the branching of yous that make their predictions by just flipping a coin, always guessing Fire, or employing literally any other strategy that generates valid guesses. The 50⁄50 value of this branching process is completely decoupled from your predictions, no matter what information you use to make those predictions.
Compare this to the process of guessing the trillionth digit of pi. If you make your guess by rolling a quantum die, then 1 out of 10 yous will end up in a branch where your guess matches the actual trillionth digit of pi. If you instead use those algorithms you know to calculate a guess, and you code/run them correctly, then basically all of the yous end up in a branch where your guess is correct.
We now see the fundamental difference. Changing your guessing strategy results in different correct/incorrect branching ratios for the “guess the trillionth digit of pi” game but not for the “guess the beam-splitter result” game. This is the Everett-speak version of saying that the beam-splitter’s 50⁄50 odds is a property of the universe while the trillionth digit of pi’s 1⁄10 odds is a function of our (current) ignorance. You can opt to replace “odds” with “branching ratios” and declare that there is no probability of any kind, but that just seems like semantics to me. In particular the example of the ten trillionth digit of pi should not be what prompts this decision. Even in the many-worlds model there’s still a fundamental difference between that and the quantum processes that physicists cite as intrinsically random.