the thought experiment goes: ‘Hey, suppose we have a radioactive particle that enters a superposition of decaying and not decaying. Then the particle interacts with a sensor, and the sensor goes into a superposition of going off and not going off. The sensor interacts with an explosive, that goes into a superposition of exploding and not exploding; which interacts with the cat, so the cat goes into a superposition of being alive and dead. Then a human looks at the cat,’ and at this point Schrödinger stops, and goes, ‘gee, I just can’t imagine what could happen next.’ So Schrödinger shows this to everyone else, and they’re also like ‘Wow, I got no idea what could happen at this point, what an amazing paradox’. Until finally you hear about it, and you’re like, ‘hey, maybe at that point half of the superposition just vanishes, at random, faster than light’, and everyone else is like, ‘Wow, what a great idea!’”
Obviously this is a parody and Eliezer is making an argument for many worlds. However, this isn’t that far from how the thought experiment is presented in introductory books and even popularizations. Why, then, don’t more people realize that many worlds is correct? Why aren’t tons of bright middle-school children who read science fiction and popular science spontaneously rediscovering many worlds?
Why, then, don’t more people realize that many worlds is correct?
Note that you are using Eliezer!correct, not Physics!correct. The former is based on Bayesian reasoning among models with equivalent predictive power, the latter requires different predictive power to discriminate between theories. The problem with the former reasoning is that without experimental validation it is hard to agree on the priors and other assumptions going into the Bayesian calculation for MWI correctness. Additionally, proclaiming MWI “correct” is not instrumentally useful unless one can use it to advance physical knowledge.
‘hey, maybe at that point half of the superposition just vanishes, at random, faster than light’
It’s worse than that, actually. In some frames it means not just FTL but also back in time. But given that this is unmeasurable, it matters not in the slightest if you adopt the Physics!correct definition.
Note that the OP wasn’t asking about physicists, but people… explicitly “bright middle school children” for example. It’s certainly possible that the lack of differential predictive power or experimental validation for MWI explains that, but I’m inclined to doubt it.
Good point, I missed it in my original reading. Certainly “bright middle school children” are unlikely to spontaneously discover the definition of correctness which matches either Eliezer!correct or Physics!correct. Certainly it’s still an open issue for adult professionals.
Why, then, don’t more people realize that many worlds is correct?
I am going to try and provide short answer, as I see it. (Fighting urge to write about different levels of “physical reality”.)
Many Words is an Interpretation. An interpretation should translate from mathematical formalism towards practical algorithms, but MWI does not go all the way. Namely, it does not specify the quantum state an Agent should use for computation. One possible state agrees with “Schroedinger’s experiment was definitely set up and started”, another state implies “cat definitely turned out to be alive”, but those certainties cannot occur simultaneously.
Bayesian inference in non-quantum physics also changes (probabilistic) state, but we can interpret it as a mere change of our beliefs, and not a change in the physical system. But in quantum mechanics, upon observation, the “objective” state fitting our knowledge changes. MWI says “fitting our knowledge” is not a good criterion of choosing quantum state to compute with (because no state can be fitting enough, as example with Shroedinger’s cat shows) and we should compute with superposition of Agents. MWI may be more “objectively correct”, but it does not seem to be more “practical” than Copenhagen interpretation. So physicists do like to cautiously agree with MWI, then wave hands, proclaim “Decoherence!” and at the end use Copenhagen interpretation as before.
Introductory books emphasize experiments, and experimental results do not come in form of superpositioned bits. So before student gets familiar enough with mathematical formalism to think about detectors in superposition, Copenhagen is already occupying slot for Interpretation.
From If Many-Worlds had Come First:
Obviously this is a parody and Eliezer is making an argument for many worlds. However, this isn’t that far from how the thought experiment is presented in introductory books and even popularizations. Why, then, don’t more people realize that many worlds is correct? Why aren’t tons of bright middle-school children who read science fiction and popular science spontaneously rediscovering many worlds?
Note that you are using Eliezer!correct, not Physics!correct. The former is based on Bayesian reasoning among models with equivalent predictive power, the latter requires different predictive power to discriminate between theories. The problem with the former reasoning is that without experimental validation it is hard to agree on the priors and other assumptions going into the Bayesian calculation for MWI correctness. Additionally, proclaiming MWI “correct” is not instrumentally useful unless one can use it to advance physical knowledge.
It’s worse than that, actually. In some frames it means not just FTL but also back in time. But given that this is unmeasurable, it matters not in the slightest if you adopt the Physics!correct definition.
Note that the OP wasn’t asking about physicists, but people… explicitly “bright middle school children” for example.
It’s certainly possible that the lack of differential predictive power or experimental validation for MWI explains that, but I’m inclined to doubt it.
Good point, I missed it in my original reading. Certainly “bright middle school children” are unlikely to spontaneously discover the definition of correctness which matches either Eliezer!correct or Physics!correct. Certainly it’s still an open issue for adult professionals.
I am going to try and provide short answer, as I see it. (Fighting urge to write about different levels of “physical reality”.)
Many Words is an Interpretation. An interpretation should translate from mathematical formalism towards practical algorithms, but MWI does not go all the way. Namely, it does not specify the quantum state an Agent should use for computation. One possible state agrees with “Schroedinger’s experiment was definitely set up and started”, another state implies “cat definitely turned out to be alive”, but those certainties cannot occur simultaneously.
Bayesian inference in non-quantum physics also changes (probabilistic) state, but we can interpret it as a mere change of our beliefs, and not a change in the physical system. But in quantum mechanics, upon observation, the “objective” state fitting our knowledge changes. MWI says “fitting our knowledge” is not a good criterion of choosing quantum state to compute with (because no state can be fitting enough, as example with Shroedinger’s cat shows) and we should compute with superposition of Agents. MWI may be more “objectively correct”, but it does not seem to be more “practical” than Copenhagen interpretation. So physicists do like to cautiously agree with MWI, then wave hands, proclaim “Decoherence!” and at the end use Copenhagen interpretation as before.
Introductory books emphasize experiments, and experimental results do not come in form of superpositioned bits. So before student gets familiar enough with mathematical formalism to think about detectors in superposition, Copenhagen is already occupying slot for Interpretation.