4 ms·

I'm not sure what is more far fetched - many worlds or non-locality.

by snarfy 10y ago

VladKovac 10y ago
Why is many worlds far fetched? We observe it in a smaller scale in experiments when you pass light through a half silvered mirror. It's just the logical extrapolation of that observation to the macro scale.
- goodcanadian 10y ago
  You say that observation shows many worlds. I say that the photon interferes with itself. I find the latter far more plausible than invoking multiple universes for the photon to interact with.
  - VladKovac 10y ago
    That's fine until you start talking about a magical collapse process that happens conveniently at sufficiently large scale. IMO postulating additional non-local, non-unitary, ftl, etc. collapse process is strictly more complicated.
    - millstone 10y ago
      Most modern interpretations have "collapse" as only a change in the description level, not a physical process. You're right that postulates such as the projection postulate complicate the theory. But it's not clear how to explain experimental results, like the stochastic nature of measurements or the Born rule, without it. I can make a theory as simple as you like if you don't require it to explain experimental results.
      - btilly 10y ago
        The many-worlds interpretation has no collapse at all. :-)
      - VladKovac 10y ago
        Don't forget that the Copenhagen people also haven't really answered the Born problem, they just lump it into the black box of "collapse".
  - DavidPlumpton 10y ago
    In QM random outcomes occur. By what mechanism are the random values chosen? Many Worlds has a plausible mechanism for this. I'm unaware of any other interpretation claiming the same.
goodcanadian 10y ago
Indeed, I've never found the many worlds (or any other) interpretation to be more compelling than admitting that quantum mechanics is just plain weird.
Houshalter 10y ago
Infinite universes isn't too far fetched. Any interpretation of QM is going to require exponential computing power to simulate all possible states. MW just asks, why assume these other states stop existing when you observe them?
- mikekchar 10y ago
  I may be totally confused, but I don't think the CM has states "stop existing" on collapse. It is not in a state until it collapses. And the "you observe" isn't really "you". Essentially, it doesn't have a state until the state is referenced. Again, I might be wrong, but I think the problem most people have with QM is that they think something must either exist or not exist. From that perspective it's easier to imagine that something exists in all possible states and that we are just observing one of them. However, even logically things can be in an indeterminate state. For example, if I draw a box and then I draw another one that is twice as tall, the first box is short and the second box is tall. If I draw a third box that is 3 times as tall as the second one, then the first 2 boxes are short and the third one is tall. However, if I never drew the second or third box, then the first box is neither tall nor short. The concept doesn't actually make sense without the other boxes. Similarly, imagine a universe with a single particle. What is its position? What is its momentum? Obviously these concepts have no meaning. As soon as I add another particle to the universe, then suddenly position and momentum have meaning. Now imagine that space is not a discrete map of particles with positions, but rather a set of particles which each have a probability of interacting with each other. This probability indicates their position. In such a universe, if a particle does not interact with another particle, then it does not have a position. There is no meaning for position with respect to that particle. As soon as it interacts with another particle, then suddenly position has meaning. It is "created" in the same way that we "created" tall and short by drawing different sized boxes. That is my, very possibly naive, way of thinking about it. Yes... I've read too much Taoist literature... ;-)
  - Houshalter 10y ago
    This is very similar to time travel hypotheticals. If you travel back in time, and totally change the past, did the future you originally observed actually happen? People existed, they lived their lives, etc. And then suddenly you "reset" the universe to a time where that never happened. I would argue they did exist, and that the time travel event actually murdered them. I think of the universe as a computer, and any computation it does actually happens, actually exists in some sense. If the universe does a computation of my entire life, then deletes it, that life still happened. It "exists". I think the same is true of the famous cat experiment. The computation of both possible states of the cat has to be done by the universe. It needs to compute how the cat reacts to the poison gas, it needs to compute the pain it experiences, etc. That's a lot different than a single particle like your example. When you open the box, the universe may "collapse" to the second possibility, where the cat is still alive. But the first possibility still happened, and it may still be out there somewhere in an unobservable branch. In fact that model seems a lot more mathematically elegant, being completely deterministic and not having to deal with the weirdness of "collapse" events.

I'm not sure what is more far fetched - many worlds or non-locality.

by snarfy 10y ago

I'm not sure what is more far fetched - many worlds or non-locality.

Why is many worlds far fetched? We observe it in a smaller scale in experiments when you pass light through a half silvered mirror. It's just the logical extrapolation of that observation to the macro scale.

goodcanadian 10y ago
You say that observation shows many worlds. I say that the photon interferes with itself. I find the latter far more plausible than invoking multiple universes for the photon to interact with.
- VladKovac 10y ago
  That's fine until you start talking about a magical collapse process that happens conveniently at sufficiently large scale. IMO postulating additional non-local, non-unitary, ftl, etc. collapse process is strictly more complicated.
  - millstone 10y ago
    Most modern interpretations have "collapse" as only a change in the description level, not a physical process. You're right that postulates such as the projection postulate complicate the theory. But it's not clear how to explain experimental results, like the stochastic nature of measurements or the Born rule, without it. I can make a theory as simple as you like if you don't require it to explain experimental results.
    - btilly 10y ago
      The many-worlds interpretation has no collapse at all. :-)
    - VladKovac 10y ago
      Don't forget that the Copenhagen people also haven't really answered the Born problem, they just lump it into the black box of "collapse".
- DavidPlumpton 10y ago
  In QM random outcomes occur. By what mechanism are the random values chosen? Many Worlds has a plausible mechanism for this. I'm unaware of any other interpretation claiming the same.

goodcanadian 10y ago

Indeed, I've never found the many worlds (or any other) interpretation to be more compelling than admitting that quantum mechanics is just plain weird.

Houshalter 10y ago

Infinite universes isn't too far fetched. Any interpretation of QM is going to require exponential computing power to simulate all possible states. MW just asks, why assume these other states stop existing when you observe them?

mikekchar 10y ago
I may be totally confused, but I don't think the CM has states "stop existing" on collapse. It is not in a state until it collapses. And the "you observe" isn't really "you". Essentially, it doesn't have a state until the state is referenced. Again, I might be wrong, but I think the problem most people have with QM is that they think something must either exist or not exist. From that perspective it's easier to imagine that something exists in all possible states and that we are just observing one of them. However, even logically things can be in an indeterminate state. For example, if I draw a box and then I draw another one that is twice as tall, the first box is short and the second box is tall. If I draw a third box that is 3 times as tall as the second one, then the first 2 boxes are short and the third one is tall. However, if I never drew the second or third box, then the first box is neither tall nor short. The concept doesn't actually make sense without the other boxes. Similarly, imagine a universe with a single particle. What is its position? What is its momentum? Obviously these concepts have no meaning. As soon as I add another particle to the universe, then suddenly position and momentum have meaning. Now imagine that space is not a discrete map of particles with positions, but rather a set of particles which each have a probability of interacting with each other. This probability indicates their position. In such a universe, if a particle does not interact with another particle, then it does not have a position. There is no meaning for position with respect to that particle. As soon as it interacts with another particle, then suddenly position has meaning. It is "created" in the same way that we "created" tall and short by drawing different sized boxes. That is my, very possibly naive, way of thinking about it. Yes... I've read too much Taoist literature... ;-)
- Houshalter 10y ago
  This is very similar to time travel hypotheticals. If you travel back in time, and totally change the past, did the future you originally observed actually happen? People existed, they lived their lives, etc. And then suddenly you "reset" the universe to a time where that never happened. I would argue they did exist, and that the time travel event actually murdered them. I think of the universe as a computer, and any computation it does actually happens, actually exists in some sense. If the universe does a computation of my entire life, then deletes it, that life still happened. It "exists". I think the same is true of the famous cat experiment. The computation of both possible states of the cat has to be done by the universe. It needs to compute how the cat reacts to the poison gas, it needs to compute the pain it experiences, etc. That's a lot different than a single particle like your example. When you open the box, the universe may "collapse" to the second possibility, where the cat is still alive. But the first possibility still happened, and it may still be out there somewhere in an unobservable branch. In fact that model seems a lot more mathematically elegant, being completely deterministic and not having to deal with the weirdness of "collapse" events.