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Nitpick: even for quantum mechanical effects. The equations have no randomness in them. As far as we know, the laws of physics are deterministic. It's just t

Nitpick: even for quantum mechanical effects. The equations have no randomness in them. As far as we know, the laws of physics are deterministic. It's just that we can't know in advance which Everett branch we will subjectively experience. We could (in principle) compute what proportion of Everett branches lead to what outcome, though. Probability is still in the mind. Not in the territory. http://lesswrong.com/lw/oj/probability_is_in_the_mind/ http://lesswrong.com/lw/oj/probability_is_in_the_mind/ (In case you didn't already spot me.)

jules 14y ago
In a sense that's true, but Bell's inequalities show that there is something qualitatively different about quantum mechanical randomness. Bar some technicalities, they show that there isn't some hidden internal state that determines what outcome we experience, unlike with elections and baseball (assuming QM effects don't play a significant role in those). In this sense, QM is "truly random". That said, even though there is good experimental evidence for this, it is not 100% certain that the world actually works this way. http://en.wikipedia.org/wiki/Bells_theorem http://en.wikipedia.org/wiki/Bells_theorem
- loup-vaillant 14y ago
  Nothing is 100% sure :-) http://lesswrong.com/lw/mp/0_and_1_are_not_probabilities/ http://lesswrong.com/lw/mp/0_and_1_are_not_probabilities/ But yeah, as long as we didn't find complete laws of physics, we're bound to ignore something.
  - jules 14y ago
    Not sure if you got what I'm saying...in case I didn't explain it clearly enough: Bell's inequalities show that quantum randomness CANNOT be explained by an underlying deterministic law of physics that we're ignoring. With ordinary probability you can never find out whether it's truly random or whether there is some underlying deterministic process that you just don't have knowledge about. Turns out with quantum mechanics, which works with probability amplitudes instead of just probabilities, you can rule out such an underlying deterministic process (again modulo technicalities). This is one of the most striking results of physics, and Einstein himself didn't believe it at first.
    - loup-vaillant 14y ago
      Disclaimer: I have read http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ cover to cover. Let's see with an example. A half sievered mirror, a photon going through (or bouncing), and 2 detectors. You say there is no hidden variable that would allow us to predict which detector we will see go off. I agree. It doesn't mean however that the laws of physics have true randomness in them. Under the Everett interpretation, two "worlds" (blobs of amplitude) are created: one in which detector 1 goes off, and one in which detector 2 goes off. from the outside, this is purely deterministic. The only randomness lies in our subjective experience. The only question remaining is why do we experience the Born statistics (based on square moduli), rather than something else (like, based on moduli)? We would have true randomness at the fundamental level if some form of the Copenhagen interpretation where true. But believing the blob of amplitude we don't see would mysteriously disappear, violating the equations in the process? That's just nuts. If this idea appeared after the Everett interpretation, it would have been ridiculed.
      - jules 14y ago
        Many Worlds vs Copenhagen is a largely irrelevant debate. It doesn't make any observable difference whatsoever, so it's metaphysics. By analogy to classical probability, Copenhagen is like looking at the sampling of a random variable, and Many Worlds is like looking a weighted list of possible outcomes. It's just a different perspective on the same thing. I say largely irrelevant because there is a minority of people (including, if I'm not mistaken, Nobel prize winner 't Hooft) who say that neither Many Worlds nor Copenhagen is right, because there are hidden assumptions in EPR that are overlooked. Since you seem to be a fan of lesswrong.com, this should appeal to you ;-). I think for the rest we are in agreement, I misinterpreted "as long as we didn't find complete laws of physics, we're bound to ignore something" and "Probability is still in the mind. Not in the territory.". The latter statement becomes rather tautological and its meaning rather weak if you include QM randomness though. In the context of the frequentist vs Bayesian debate it means something far stronger.
        loup-vaillant 14y ago

jules 14y ago

In a sense that's true, but Bell's inequalities show that there is something qualitatively different about quantum mechanical randomness. Bar some technicalities, they show that there isn't some hidden internal state that determines what outcome we experience, unlike with elections and baseball (assuming QM effects don't play a significant role in those). In this sense, QM is "truly random". That said, even though there is good experimental evidence for this, it is not 100% certain that the world actually works this way. http://en.wikipedia.org/wiki/Bells_theorem http://en.wikipedia.org/wiki/Bells_theorem

loup-vaillant 14y ago
Nothing is 100% sure :-) http://lesswrong.com/lw/mp/0_and_1_are_not_probabilities/ http://lesswrong.com/lw/mp/0_and_1_are_not_probabilities/ But yeah, as long as we didn't find complete laws of physics, we're bound to ignore something.
- jules 14y ago
  Not sure if you got what I'm saying...in case I didn't explain it clearly enough: Bell's inequalities show that quantum randomness CANNOT be explained by an underlying deterministic law of physics that we're ignoring. With ordinary probability you can never find out whether it's truly random or whether there is some underlying deterministic process that you just don't have knowledge about. Turns out with quantum mechanics, which works with probability amplitudes instead of just probabilities, you can rule out such an underlying deterministic process (again modulo technicalities). This is one of the most striking results of physics, and Einstein himself didn't believe it at first.
  - loup-vaillant 14y ago
    Disclaimer: I have read http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ cover to cover. Let's see with an example. A half sievered mirror, a photon going through (or bouncing), and 2 detectors. You say there is no hidden variable that would allow us to predict which detector we will see go off. I agree. It doesn't mean however that the laws of physics have true randomness in them. Under the Everett interpretation, two "worlds" (blobs of amplitude) are created: one in which detector 1 goes off, and one in which detector 2 goes off. from the outside, this is purely deterministic. The only randomness lies in our subjective experience. The only question remaining is why do we experience the Born statistics (based on square moduli), rather than something else (like, based on moduli)? We would have true randomness at the fundamental level if some form of the Copenhagen interpretation where true. But believing the blob of amplitude we don't see would mysteriously disappear, violating the equations in the process? That's just nuts. If this idea appeared after the Everett interpretation, it would have been ridiculed.
    - jules 14y ago
      Many Worlds vs Copenhagen is a largely irrelevant debate. It doesn't make any observable difference whatsoever, so it's metaphysics. By analogy to classical probability, Copenhagen is like looking at the sampling of a random variable, and Many Worlds is like looking a weighted list of possible outcomes. It's just a different perspective on the same thing. I say largely irrelevant because there is a minority of people (including, if I'm not mistaken, Nobel prize winner 't Hooft) who say that neither Many Worlds nor Copenhagen is right, because there are hidden assumptions in EPR that are overlooked. Since you seem to be a fan of lesswrong.com, this should appeal to you ;-). I think for the rest we are in agreement, I misinterpreted "as long as we didn't find complete laws of physics, we're bound to ignore something" and "Probability is still in the mind. Not in the territory.". The latter statement becomes rather tautological and its meaning rather weak if you include QM randomness though. In the context of the frequentist vs Bayesian debate it means something far stronger.
      - loup-vaillant 14y ago