3 ms·

The problem with many-worlds is that there aren't more timelines for probable events. If every outcome occurs in some world, then for some event with two possi

by lg 18y ago

The problem with many-worlds is that there aren't more timelines for probable events. If every outcome occurs in some world, then for some event with two possible outcomes, there ends up being two of you; say, Lefty and Righty, one in each world. So there's no sense in saying "I'll probably end up being Lefty, since his outcome was more reasonable," because you'll end up being both of them.

hhm 18y ago
But I'm conscious of only one of only being Lefty, or not? If that's true, then for me at least, that behaves like a separate timeline of all others. That's what I meant in the post above: we are only conscious on what happens on a very reasonable timeline. Can this be like this?
- lg 18y ago
  right, but Righty is conscious of being Righty, and if his outcome was highly unlikely, then he must be wondering why his world is so unreasonable. And since he's just as much you as Lefty is, post-event, it's not true that you're only conscious of what happens on a reasonable timeline.
  - hhm 18y ago
    But... Righty could ask why his world is unreasonable, but actually, being Righty is very improbable, so if we find the world to be actually very reasonable, it's because it's more probable to be Lefty than to be Right. Whether if Lefty and Righty are the same conscious mind or two different minds, I guess that's more of a philosophycal question.
    - lg 18y ago
      If something is probable, you have to ask what makes it probable. We measure quantum probabilities by the number of times a given experiment yields a given outcome. Say there's an observable and when you measure it, outcome Lefty happens 90% of the time and outcome Righty happens 10% of the time. On MW, both of those happen, and 2 conscious beings result. What makes "being Lefty" more probable? Are there more Lefties than Righties? Or will outcome Lefty happen more often than outcome Righty? The answer to both is no, you get two every time. They're two conscious minds, but both continuous with the old you in the same way.
      - hhm 18y ago
        I'm not sure I understand. Suppose the mind throws a thousand dices. We measure two possible events: if there is at least a dice with a 1 on it, and if all dices have a 1 on it. There are 6^1000 possible conscious minds. We call Lefty to the one that sees the first, very probable event. We call Righty to the one that sees the second, very unprobable event. There is actually only one Righty, but there are many, many Lefties. So it's actually a lot more probable to be a Lefty than to be a Righty. I think this works too with any other kind of event you could imagine (at least in a discrete (meta?)world, I'm not sure how you could have continuous probabilities if there are only discrete amounts of worlds available, or if you can have continuous amounts of worlds instead). How does what you say work in this example? Why would both events have the same probability? I don't know about QM more than the very, very basics, so please excuse me if I'm not understanding something very fundamental here.
        lg 18y ago
        On MW, there are an infinite number of worlds at time t if an infinite number of quantum outcomes has occurred by time t. Anyway, it sounds like you're thinking this: There are an infinite number of worlds. A quantum event happens in many of them. There are more worlds where it happens than where it doesn't. Therefore this event is more likely. But that's not MW. MW says that something happens, and when it happens, you get one world for each outcome. There's a problem here because what these outcomes are depend on the basis you write the wave function in, but that's a different issue. It's certainly not saying that there are an infinite number of worlds, each with a determined series of events, and we have probabilities because some of those worlds are more numerous than others. That's modal realism, as I said in a comment above. By the way, that doesn't just raise its head in the context of quantum mechanics. It only does because it gives us reason to believe that it's physically possible that things could've been different than they actually are. But it seems possible-period that things could've been different, even if physics was deterministic. Even though it might've been physically determined that I went to the grocery store yesterday, it's certainly possible tout court that the whole universe had gone differently, and I could've gone to Fenway to see the Sox game instead. But does that mean that there's an alternate universe where my otherworldly counterpart went to Fenway? Isn't there a simpler explanation for why that's possible? QM has alternatives, like the Bohmian and GRW theories, which are far more plausible as well.
yummyfajitas 18y ago
I think in MW, there are continuously many (macroscopically identical) lefty universes and continuously many righty universes. So one macroscopic state (righty) corresponds to a set of finite volume; the set of all configurations who's macroscopic state (i.e., ignore quantum details humans can't see) looks like righty. So all one can reasonably ask is "what is the probability my universe lives in that volume?" The obvious answer is the integral of |\psi|^2 over that volume, but that is a postulate, not something you can derive from the schrodinger equation.
- lg 18y ago
  I believe that on Everett's approach, when you measure some observable with two possible outcomes, the total number of worlds increases, like a bacterium dividing. But on the version you're suggesting, it sounds like we constantly hop from one already-existing universe to another, because every instant brings with it a different configuration. But it makes little sense for our bodies to hop between worlds, since they're parts of worlds, so is it our 'mind' that does it? But that sounds like many-minds, except with many worlds instead of one, and with a new problem of how we do the hopping. Unless by configuration, you mean that each world is a world-line that contains a set of definite outcomes for all quantum events, and so all the quantum outcomes are predetermined for each world, and we explain probabilities by recourse to the proportion of some worlds to others. That's not really many-worlds, that's modal realism (every possible world exists, and "the actual world" just means "my world"). Which is more David Lewis than Hugh Everett.
  - yummyfajitas 18y ago
    In Everett's approach, I think it is the macroscopic state which splits. But the macroscopic state is a volume of worlds. So I guess think of the interval [0,1] as consisting of a single (macroscopic) world. But [0,1] has infinitely many numbers in it; each one comprises a different "world". Under evolution, [0,1] splits into [-0.5,0] U (0.5,1], two macroscopic states but still infinitely many microscopic ones. Every state in [0,0.5] was turned into a state in [-0.5, 0] and similarly (0.5,1] -> [0.5,1]. (Each real number corresponds to a world configuration.) (note: there are quite a few variants of many worlds, and not everyone realizes they are talking about different theories. I don't know if I'm describing the most common view. ) My (non-mainstream) mental picture of MW is bohmian mechanics, with each possible bohmian trajectory corresponding to a different world history.

by lg 18y ago

hhm 18y ago

But I'm conscious of only one of only being Lefty, or not? If that's true, then for me at least, that behaves like a separate timeline of all others. That's what I meant in the post above: we are only conscious on what happens on a very reasonable timeline. Can this be like this?

lg 18y ago
right, but Righty is conscious of being Righty, and if his outcome was highly unlikely, then he must be wondering why his world is so unreasonable. And since he's just as much you as Lefty is, post-event, it's not true that you're only conscious of what happens on a reasonable timeline.
- hhm 18y ago
  But... Righty could ask why his world is unreasonable, but actually, being Righty is very improbable, so if we find the world to be actually very reasonable, it's because it's more probable to be Lefty than to be Right. Whether if Lefty and Righty are the same conscious mind or two different minds, I guess that's more of a philosophycal question.
  - lg 18y ago
    If something is probable, you have to ask what makes it probable. We measure quantum probabilities by the number of times a given experiment yields a given outcome. Say there's an observable and when you measure it, outcome Lefty happens 90% of the time and outcome Righty happens 10% of the time. On MW, both of those happen, and 2 conscious beings result. What makes "being Lefty" more probable? Are there more Lefties than Righties? Or will outcome Lefty happen more often than outcome Righty? The answer to both is no, you get two every time. They're two conscious minds, but both continuous with the old you in the same way.
    - hhm 18y ago
      I'm not sure I understand. Suppose the mind throws a thousand dices. We measure two possible events: if there is at least a dice with a 1 on it, and if all dices have a 1 on it. There are 6^1000 possible conscious minds. We call Lefty to the one that sees the first, very probable event. We call Righty to the one that sees the second, very unprobable event. There is actually only one Righty, but there are many, many Lefties. So it's actually a lot more probable to be a Lefty than to be a Righty. I think this works too with any other kind of event you could imagine (at least in a discrete (meta?)world, I'm not sure how you could have continuous probabilities if there are only discrete amounts of worlds available, or if you can have continuous amounts of worlds instead). How does what you say work in this example? Why would both events have the same probability? I don't know about QM more than the very, very basics, so please excuse me if I'm not understanding something very fundamental here.
      - lg 18y ago
        On MW, there are an infinite number of worlds at time t if an infinite number of quantum outcomes has occurred by time t. Anyway, it sounds like you're thinking this: There are an infinite number of worlds. A quantum event happens in many of them. There are more worlds where it happens than where it doesn't. Therefore this event is more likely. But that's not MW. MW says that something happens, and when it happens, you get one world for each outcome. There's a problem here because what these outcomes are depend on the basis you write the wave function in, but that's a different issue. It's certainly not saying that there are an infinite number of worlds, each with a determined series of events, and we have probabilities because some of those worlds are more numerous than others. That's modal realism, as I said in a comment above. By the way, that doesn't just raise its head in the context of quantum mechanics. It only does because it gives us reason to believe that it's physically possible that things could've been different than they actually are. But it seems possible-period that things could've been different, even if physics was deterministic. Even though it might've been physically determined that I went to the grocery store yesterday, it's certainly possible tout court that the whole universe had gone differently, and I could've gone to Fenway to see the Sox game instead. But does that mean that there's an alternate universe where my otherworldly counterpart went to Fenway? Isn't there a simpler explanation for why that's possible? QM has alternatives, like the Bohmian and GRW theories, which are far more plausible as well.

yummyfajitas 18y ago

I think in MW, there are continuously many (macroscopically identical) lefty universes and continuously many righty universes. So one macroscopic state (righty) corresponds to a set of finite volume; the set of all configurations who's macroscopic state (i.e., ignore quantum details humans can't see) looks like righty. So all one can reasonably ask is "what is the probability my universe lives in that volume?" The obvious answer is the integral of |\psi|^2 over that volume, but that is a postulate, not something you can derive from the schrodinger equation.

lg 18y ago
I believe that on Everett's approach, when you measure some observable with two possible outcomes, the total number of worlds increases, like a bacterium dividing. But on the version you're suggesting, it sounds like we constantly hop from one already-existing universe to another, because every instant brings with it a different configuration. But it makes little sense for our bodies to hop between worlds, since they're parts of worlds, so is it our 'mind' that does it? But that sounds like many-minds, except with many worlds instead of one, and with a new problem of how we do the hopping. Unless by configuration, you mean that each world is a world-line that contains a set of definite outcomes for all quantum events, and so all the quantum outcomes are predetermined for each world, and we explain probabilities by recourse to the proportion of some worlds to others. That's not really many-worlds, that's modal realism (every possible world exists, and "the actual world" just means "my world"). Which is more David Lewis than Hugh Everett.
- yummyfajitas 18y ago
  In Everett's approach, I think it is the macroscopic state which splits. But the macroscopic state is a volume of worlds. So I guess think of the interval [0,1] as consisting of a single (macroscopic) world. But [0,1] has infinitely many numbers in it; each one comprises a different "world". Under evolution, [0,1] splits into [-0.5,0] U (0.5,1], two macroscopic states but still infinitely many microscopic ones. Every state in [0,0.5] was turned into a state in [-0.5, 0] and similarly (0.5,1] -> [0.5,1]. (Each real number corresponds to a world configuration.) (note: there are quite a few variants of many worlds, and not everyone realizes they are talking about different theories. I don't know if I'm describing the most common view. ) My (non-mainstream) mental picture of MW is bohmian mechanics, with each possible bohmian trajectory corresponding to a different world history.