Thanks, that’s a good explanation. What do you think is silly about “ra-ra-many-worlds”? The Everett interpretation itself, or just the amount of time EY spends making fun of other interpretations?
Also, my memory may be failing me, but I thought the “mangled worlds” stuff was Nick Bostrom, and not in the QM sequence. Am I thinking of something else?
Most of the silliness is just the making fun of other teams / boosting your team stuff. But some of the silliness is in overconfidence (under-caution?) with a dash of ignorance. We still have a whole theory of everything to figure out still, after all. And until there’s a derivation of the Born probabilities, many worlds isn’t necessarily simpler than a model with physical collapse. Many worlds and discontinuous faster than light collapse aren’t the only two options, despite the dichotomous presentation. And cetera.
The “mangled worlds” stuff is Robin Hanson’s idea originally, echoed by Eliezer occasionally in the QM sequence (for example, in the most recent sequence rerun).
And until there’s a derivation of the Born probabilities, many worlds isn’t necessarily simpler than a model with physical collapse.
I find that difficult to believe. Born probabilities are comparable to a law that causes particles to become disentangled, if you ignore the violations of the Tao of physics. In order to get a complete theory, you also have to have a law that causes particles to become entangled, and a law that causes particles to interact without ever becoming entangled.
Am I missing something?
(for example, in the most recent sequence rerun)
Please link when you do that. It’s not going to stay the most recent sequence rerun.
So it’s not hard to get a Born rule—Everett did it nicely in his original paper. But in order to do so, he had to introduce the requirement that the probability measure of different observations should be defined for vectors in the Hilbert space of solutions to the Schroedinger equation. An extra law of physics, basically. Which is fine. But it means that many worlds isn’t necessarily simpler than other stuff.
To meet my challenge, you’d need to require the Born probabilities instead the naive probabilities using only the Schroedinger equation and a Hamiltonian, basically. By “the naive probabilities,” I mean assigning each eigenstate equal probability. Which isn’t what we observe. But if the Schroedinger equation alone isn’t enough, it would make sense that just using it gives us probabilities that aren’t what we would observe.
But in order to do so, he had to introduce the requirement that the probability measure of different observations should be defined for vectors in the Hilbert space of solutions to the Schroedinger equation. An extra law of physics, basically. Which is fine. But it means that many worlds isn’t necessarily simpler than other stuff.
What? No, seriously… what? The extra law of physics you just listed was, ‘The Schrodinger Equation determines physical reality’
Which is to say, it’s entirely redundant with the rest of quantum mechanics. This is not new information, here.
To meet my challenge, you’d need to require the Born probabilities instead the naive probabilities using only the Schroedinger equation and a Hamiltonian, basically. By “the naive probabilities,” I mean assigning each eigenstate equal probability. Which isn’t what we observe.
Did you even read the derivation? How much do you actually know about quantum mechanics anyway? Are you a physicist?
So, let me see if I can restate what you’re saying, building up a bit of the background:
1) Suppose you’ve got a Hamiltonian. Then the SE constrains the world to a specific set of vectors (forming some oddly-shaped manifold) in a Hilbert space on spacetime.
2) Any one of these vectors can be given an equal weight of probability.
There’s more to it, but… I’d like to stop here for a moment anyway. See, these vectors are not instantaneous state vectors. Each vector is the history of a whole many-worlds universe, with all of the quantum branching included. Each vector includes ALL of the branches, all of the weights, everything.
The different vectors, here, are just the cases where different initial conditions (or boundary or other conditions, if you want to really seriously demote time) are taken.
If I’m right about this interpretation, then this isn’t what the Born Probabilities are talking about. Maybe they all are real, with equal weights. No observation we could make would contradict that. Meanwhile, the Born Probabilities are, as you indicated above, highly experimentally testable.
I suppose the main ignorance I mentioned would be about point 3 - discontinuous, faster than light collapse is somewhat of a straw hypothesis when there’s genuine (though not super promising) research being done on continuous, light-speed collapse.
Thanks, that’s a good explanation. What do you think is silly about “ra-ra-many-worlds”? The Everett interpretation itself, or just the amount of time EY spends making fun of other interpretations?
Also, my memory may be failing me, but I thought the “mangled worlds” stuff was Nick Bostrom, and not in the QM sequence. Am I thinking of something else?
Most of the silliness is just the making fun of other teams / boosting your team stuff. But some of the silliness is in overconfidence (under-caution?) with a dash of ignorance. We still have a whole theory of everything to figure out still, after all. And until there’s a derivation of the Born probabilities, many worlds isn’t necessarily simpler than a model with physical collapse. Many worlds and discontinuous faster than light collapse aren’t the only two options, despite the dichotomous presentation. And cetera.
The “mangled worlds” stuff is Robin Hanson’s idea originally, echoed by Eliezer occasionally in the QM sequence (for example, in the most recent sequence rerun).
I find that difficult to believe. Born probabilities are comparable to a law that causes particles to become disentangled, if you ignore the violations of the Tao of physics. In order to get a complete theory, you also have to have a law that causes particles to become entangled, and a law that causes particles to interact without ever becoming entangled.
Am I missing something?
Please link when you do that. It’s not going to stay the most recent sequence rerun.
How’s this?
http://lesswrong.com/lw/8p4/2011_survey_results/5e7e
So it’s not hard to get a Born rule—Everett did it nicely in his original paper. But in order to do so, he had to introduce the requirement that the probability measure of different observations should be defined for vectors in the Hilbert space of solutions to the Schroedinger equation. An extra law of physics, basically. Which is fine. But it means that many worlds isn’t necessarily simpler than other stuff.
To meet my challenge, you’d need to require the Born probabilities instead the naive probabilities using only the Schroedinger equation and a Hamiltonian, basically. By “the naive probabilities,” I mean assigning each eigenstate equal probability. Which isn’t what we observe. But if the Schroedinger equation alone isn’t enough, it would make sense that just using it gives us probabilities that aren’t what we would observe.
What? No, seriously… what? The extra law of physics you just listed was, ‘The Schrodinger Equation determines physical reality’
Which is to say, it’s entirely redundant with the rest of quantum mechanics. This is not new information, here.
Did you even read the derivation? How much do you actually know about quantum mechanics anyway? Are you a physicist?
Well, if you could say that in a way that isn’t also true for the naive probabilities that would be a good avenue to pursue. Yes. A fair bit. Yes.
So, let me see if I can restate what you’re saying, building up a bit of the background:
1) Suppose you’ve got a Hamiltonian. Then the SE constrains the world to a specific set of vectors (forming some oddly-shaped manifold) in a Hilbert space on spacetime.
2) Any one of these vectors can be given an equal weight of probability.
There’s more to it, but… I’d like to stop here for a moment anyway. See, these vectors are not instantaneous state vectors. Each vector is the history of a whole many-worlds universe, with all of the quantum branching included. Each vector includes ALL of the branches, all of the weights, everything.
The different vectors, here, are just the cases where different initial conditions (or boundary or other conditions, if you want to really seriously demote time) are taken.
If I’m right about this interpretation, then this isn’t what the Born Probabilities are talking about. Maybe they all are real, with equal weights. No observation we could make would contradict that. Meanwhile, the Born Probabilities are, as you indicated above, highly experimentally testable.
Could you be specific about this dash of ignorance?
I suppose the main ignorance I mentioned would be about point 3 - discontinuous, faster than light collapse is somewhat of a straw hypothesis when there’s genuine (though not super promising) research being done on continuous, light-speed collapse.
Thanks!