8 ms·

Any randomness could in principle be predetermined. God could have rolled the dice ahead of time.

justinpombrio 9y ago
Amazingly, we have an experiment that shows that this is not the case, if you make some pretty reasonable assumptions. It's based on Bell's theorem. Your statement is very intuitive, and the fact that it may be wrong is very surprising. https://en.m.wikipedia.org/wiki/Bell%27s_theorem#Bell_inequalities_are_violated_by_quantum_mechanical_predictions https://en.m.wikipedia.org/wiki/Bell%27s_theorem#Bell_inequa... EDIT: tone.
- guskel 9y ago
  https://en.wikipedia.org/wiki/Superdeterminism https://en.wikipedia.org/wiki/Superdeterminism
- Xcelerate 9y ago
  > if you make some reasonable assumptions Not everyone agrees on what is "reasonable". I have no problem giving up locality, but "true" randomness (i.e., information generated without an algorithm) seems like a philosophical cop out. Note that something can also be globally deterministic but indeterministic from the perspective of a subsystem. In this sense, the universe would appear random as far as we're concerned, but not random to whoever is simulating the universe (this is often called superdeterminism, but I think that's a silly word—the universe is either deterministic or it isn't).
  - justinpombrio 9y ago
    The probability of an event depends on your knowledge. Whether something is deterministic is a question of probability. Hence whether something is deterministic can depend on your knowledge. If the universe is deterministic to its simulator but random to us, I would call it random. Besides this difference in terminology, I think we agree.
    - jamesrcole 9y ago
      Your knowledge of something can't change or determine whether it is deterministic or not.
      - justinpombrio 9y ago
        Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?
        cool_shit 9y ago
        You are right, according to quantum mechanics. If you have a pair of electrons in a product state and measure the spin of one of them, you instantly know what the "other particle's" spin is going to be (if you knew what the initial state was). When you "peek at a card", you "make a measurement" and alter the system. For anything that exists outside of a light-cone around the first electron, a measurement of the second electron will be truly random from the measurer's perspective.
        jamesrcole 9y ago
        There's two kinds of probability in question. One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledge is independent of whether it is probabalistic or not. The other is whether the universe contains fundamental randomness, such that you could say it is literally "probabalistic". And in this case whether that is true or not is independent of our knowledge of the probabilities.
        justinpombrio 9y ago
Houshalter 9y ago
It can also be explained by branching. Run a simulation of a universe, and every time a random bit is required, fork into two separate processes. One where the "random" bit is 1 and another where the bit is 0. From the inside, it would seem indistinguishable from true randomness. But the system as a whole is purely deterministic.
- hasenj 9y ago
  How would forking occur? Forking requires copying data. Does the universe get cloned infinitely many copies all the time? That's quite an extraordinary claim.
  - deleted 9y ago
    [deleted]
  - quickben 9y ago
    You have to consider his concept as an analogy. Infinity is a thing inside this universe, it may not be outside.
    - hasenj 9y ago
      The problem is not with infinity per se. If the universe gets cloned one time every second that would still be a huge claim. A million times every nanosecond is even a bigger claim. Now imagine how many states the universe can be in, and how many times a second can be meaningfully divided. If you can solve the "one clone every second" then I would be satisfied.
      - virgil_disgr4ce 9y ago
        What is the problem, though? Who says the uni/multiverse has a finite memory capacity? For more in this vein: http://www.preposterousuniverse.com/blog/2014/06/30/why-the-many-worlds-formulation-of-quantum-mechanics-is-probably-correct/ http://www.preposterousuniverse.com/blog/2014/06/30/why-the-...

Amazingly, we have an experiment that shows that this is not the case, if you make some pretty reasonable assumptions. It's based on Bell's theorem. Your statement is very intuitive, and the fact that it may be wrong is very surprising. https://en.m.wikipedia.org/wiki/Bell%27s_theorem#Bell_inequalities_are_violated_by_quantum_mechanical_predictions https://en.m.wikipedia.org/wiki/Bell%27s_theorem#Bell_inequa... EDIT: tone.

guskel 9y ago
https://en.wikipedia.org/wiki/Superdeterminism https://en.wikipedia.org/wiki/Superdeterminism
Xcelerate 9y ago
> if you make some reasonable assumptions Not everyone agrees on what is "reasonable". I have no problem giving up locality, but "true" randomness (i.e., information generated without an algorithm) seems like a philosophical cop out. Note that something can also be globally deterministic but indeterministic from the perspective of a subsystem. In this sense, the universe would appear random as far as we're concerned, but not random to whoever is simulating the universe (this is often called superdeterminism, but I think that's a silly word—the universe is either deterministic or it isn't).
- justinpombrio 9y ago
  The probability of an event depends on your knowledge. Whether something is deterministic is a question of probability. Hence whether something is deterministic can depend on your knowledge. If the universe is deterministic to its simulator but random to us, I would call it random. Besides this difference in terminology, I think we agree.
  - jamesrcole 9y ago
    Your knowledge of something can't change or determine whether it is deterministic or not.
    - justinpombrio 9y ago
      Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?
      - cool_shit 9y ago
        You are right, according to quantum mechanics. If you have a pair of electrons in a product state and measure the spin of one of them, you instantly know what the "other particle's" spin is going to be (if you knew what the initial state was). When you "peek at a card", you "make a measurement" and alter the system. For anything that exists outside of a light-cone around the first electron, a measurement of the second electron will be truly random from the measurer's perspective.
      - jamesrcole 9y ago
        There's two kinds of probability in question. One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledge is independent of whether it is probabalistic or not. The other is whether the universe contains fundamental randomness, such that you could say it is literally "probabalistic". And in this case whether that is true or not is independent of our knowledge of the probabilities.
        justinpombrio 9y ago

Houshalter 9y ago

It can also be explained by branching. Run a simulation of a universe, and every time a random bit is required, fork into two separate processes. One where the "random" bit is 1 and another where the bit is 0. From the inside, it would seem indistinguishable from true randomness. But the system as a whole is purely deterministic.

hasenj 9y ago
How would forking occur? Forking requires copying data. Does the universe get cloned infinitely many copies all the time? That's quite an extraordinary claim.
- deleted 9y ago
  [deleted]
- quickben 9y ago
  You have to consider his concept as an analogy. Infinity is a thing inside this universe, it may not be outside.
  - hasenj 9y ago
    The problem is not with infinity per se. If the universe gets cloned one time every second that would still be a huge claim. A million times every nanosecond is even a bigger claim. Now imagine how many states the universe can be in, and how many times a second can be meaningfully divided. If you can solve the "one clone every second" then I would be satisfied.
    - virgil_disgr4ce 9y ago
      What is the problem, though? Who says the uni/multiverse has a finite memory capacity? For more in this vein: http://www.preposterousuniverse.com/blog/2014/06/30/why-the-many-worlds-formulation-of-quantum-mechanics-is-probably-correct/ http://www.preposterousuniverse.com/blog/2014/06/30/why-the-...