don’t understand the reasoning which says that it’s more probable that [OBJECTS WHICH I CANNOT SEE OR INTERACT WITH] exist than that they don’t.
I don’t think it says they exist. Or if it does, it is poorly worded.
Existence is not a predicate that applies when dealing with things you can’t interact with. It’s a type error to say they exist or don’t exist.
Look at it this way: beliefs have to pay rent. How are you going to act differently, what different observations do you expect, if you believe that they “exist” vs. believing they don’t?
That’s exactly what I’m saying here. Believing in many worlds doesn’t pay its rent. It also doesn’t match Bayes or Occam’s Razor. I agree that it doesn’t make sense to privilege either their existence or their nonexistence, that’s exactly what I was contending in the grandparent, that is why I said it doesn’t make sense to say that “it’s more probable that [they] exist than that they don’t”.
You’re confusing my position for the one that I am attacking. Now, of course, I might be mistaken about what EY is saying and actually many worlds has other evidence than an appeal to Bayes Theorem or to Occam’s Razor. But I don’t think so. I even believe that one of the quantum mechanics posts explicitly concedes that due to the nature of many worlds theory it is not falsifiable.
Believing in many worlds doesn’t pay its rent. It also doesn’t match Bayes or Occam’s Razor.
To me it seems that neither “many worlds” nor “magical collapse” theory pay their rent, when compared with each other. The only difference is that “magical collapse” theory came first, therefore it was compared with the ancient theories, and in this comparison it paid rent. Under the same circumstances, “many worlds” theory would pay the same rent; we just don’t judge it the same way, because it came later.
Occam’s razor clearly prefers “many worlds” theory, because both theories agree on the part “at a microscopic level, this and this happens, and the equation shows that on larger scales it becomes less visible...”, only the “many worlds” theory continues by saying ”...and that’s the whole story”, while “magical collapse” theory continues by saying ”...and when it becomes really difficult to see the other parts of the equation (and we refuse to say when exactly that happens, which protects us against possible falsifying), they magically disappear”. One theory is strictly a subset of another, the only difference is the additional unfalsifiable magical collapse postulate.
If you disagree with my analysis, feel free to make yours. Please divide these theories into three parts: what both theories say; what the first says and the second doesn’t; what the second says and the first one doesn’t. Intuitively it feels that “many worlds” theory says there are many worlds, while the “magical collapse” theory does not say it—but this is not true! The “magical collapse” theory also, kind of mysteriously, says that there is something mathematically equivalent to many worlds on the microscopic level, it just somehow disappears later… and by a coincidence, it disappears exactly at the moment when it becomes difficult to measure (so if we improve our measurment, the theory will simply say that it disappears even later), so there is no experimental difference between disappearing and not disappearing.
“at a microscopic level, this and this happens, and the equation shows that on larger scales it becomes less visible...”
then I misunderstood what it says. But I don’t think many world says that things become less visible, I think it says that they become inaccessible. That’s a level at which concepts like “existence” don’t make sense. Calling it “many-worlds” seems like a misnomer, in that case, because those words seem to imply that there are many worlds, which implies existence.
Less visible, less accessible, the same thing. In physics, seeing something or touching something is an interaction of particles. (If two spaceships can see each other, they can shoot lasers at each other.)
Yes, “many worlds” is misleading, because it makes us think that there is one set of particles, and another set of particles… but it means that there is one configuration of a set of particles, and another configuration of the same set of particles. Many worlds in not like many planets, but more like many possible futures. It is not possible to travel to a parallel universe, because all your particles are already there, they are just entangled in a different configuration, along with the rest of the universe. It’s almost like saying that a set of equations has two possible solutions, but you can’t mix a part of one solution with a part of another solution.
This analogy is also imprecise (all analogies fail somewhere), because one “world” is not one specific configuration of particles, but more like a set of very similar configurations (having particles in similar places with similar speeds). This set can split—if a particle is flying near another particle, in one part of the set the particles hit, in other part they miss each other, and the futures of these configurations are no longer similar.
The quantum experiments show us that these “worlds” interact, and the interaction is greater if the worlds are more similar (if all their particles have the same position and speed, except for a very few particles). Then probabilities increase and decrease in a ways we would not expect in classical physics, but now we have the equations which describe this. And these equations say that the greater the difference between two “worlds”, the smaller the interaction between them. So if you have a difference greater than 10^10 particles (which is less than a number of particles in one cell, e.g. a neuron), the interaction is almost zero; we are unable to measure it. Therefore in a world A we say: “we can’t measure the world B anymore, so it does not exist; speaking of its existence wouldn’t make sense”, while in a world B we say: “we can’t measure the world A anymore, so it does not exist; speaking of its existence wouldn’t make sense”. Practically speaking, we are right in both worlds; they are separated beyond reach.
In addition to this, the collapse hypothesis says that when the interaction is almost zero, in some unspecified moment the interaction becomes exactly zero (as opposed to staying ever decreasing but non-zero forever, as the equations say). This hypothesis is absolutely unnecessary, it does not predict any experimental outcome, it only serves as a justification for saying (in a world A) that the world B now really really really does not exist… that our seeing of the world A is more than mere saying “in a world A we are in a world A, just like in a world B we are in a world B, and the interaction between these worlds is zero for all practical purposes”… that even a hypothetical non-physical observer outside of our universe would have to agree with us that yes, the world A is real, and the world B is not, because at the moment the interaction dropped to zero, some metaphysical property of the world B was removed, but it wasn’t removed from the world A.
I favor the “shut up and calculate” school, which says any interpretations that don’t make actual predictions are both unnecessary and harmful.
Certainly, if you have to choose an “interpretation” and tell stories about other universes we can’t interact with, MWI is better than collapse, for the reasons Eliezer gives. But I don’t think we should have either of them.
I agree that it doesn’t make sense to privilege either their existence or their nonexistence
It’s not a matter of privileging. Existence is not an applicable predicate. It’s not that we don’t know whether they exist. Just as other universes are neither sweet nor sour, neither happy nor sad, they neither exist nor not-exist.
I don’t think it says they exist. Or if it does, it is poorly worded.
Existence is not a predicate that applies when dealing with things you can’t interact with. It’s a type error to say they exist or don’t exist.
Look at it this way: beliefs have to pay rent. How are you going to act differently, what different observations do you expect, if you believe that they “exist” vs. believing they don’t?
That’s exactly what I’m saying here. Believing in many worlds doesn’t pay its rent. It also doesn’t match Bayes or Occam’s Razor. I agree that it doesn’t make sense to privilege either their existence or their nonexistence, that’s exactly what I was contending in the grandparent, that is why I said it doesn’t make sense to say that “it’s more probable that [they] exist than that they don’t”.
You’re confusing my position for the one that I am attacking. Now, of course, I might be mistaken about what EY is saying and actually many worlds has other evidence than an appeal to Bayes Theorem or to Occam’s Razor. But I don’t think so. I even believe that one of the quantum mechanics posts explicitly concedes that due to the nature of many worlds theory it is not falsifiable.
To me it seems that neither “many worlds” nor “magical collapse” theory pay their rent, when compared with each other. The only difference is that “magical collapse” theory came first, therefore it was compared with the ancient theories, and in this comparison it paid rent. Under the same circumstances, “many worlds” theory would pay the same rent; we just don’t judge it the same way, because it came later.
Occam’s razor clearly prefers “many worlds” theory, because both theories agree on the part “at a microscopic level, this and this happens, and the equation shows that on larger scales it becomes less visible...”, only the “many worlds” theory continues by saying ”...and that’s the whole story”, while “magical collapse” theory continues by saying ”...and when it becomes really difficult to see the other parts of the equation (and we refuse to say when exactly that happens, which protects us against possible falsifying), they magically disappear”. One theory is strictly a subset of another, the only difference is the additional unfalsifiable magical collapse postulate.
If you disagree with my analysis, feel free to make yours. Please divide these theories into three parts: what both theories say; what the first says and the second doesn’t; what the second says and the first one doesn’t. Intuitively it feels that “many worlds” theory says there are many worlds, while the “magical collapse” theory does not say it—but this is not true! The “magical collapse” theory also, kind of mysteriously, says that there is something mathematically equivalent to many worlds on the microscopic level, it just somehow disappears later… and by a coincidence, it disappears exactly at the moment when it becomes difficult to measure (so if we improve our measurment, the theory will simply say that it disappears even later), so there is no experimental difference between disappearing and not disappearing.
If many worlds is only:
then I misunderstood what it says. But I don’t think many world says that things become less visible, I think it says that they become inaccessible. That’s a level at which concepts like “existence” don’t make sense. Calling it “many-worlds” seems like a misnomer, in that case, because those words seem to imply that there are many worlds, which implies existence.
Less visible, less accessible, the same thing. In physics, seeing something or touching something is an interaction of particles. (If two spaceships can see each other, they can shoot lasers at each other.)
Yes, “many worlds” is misleading, because it makes us think that there is one set of particles, and another set of particles… but it means that there is one configuration of a set of particles, and another configuration of the same set of particles. Many worlds in not like many planets, but more like many possible futures. It is not possible to travel to a parallel universe, because all your particles are already there, they are just entangled in a different configuration, along with the rest of the universe. It’s almost like saying that a set of equations has two possible solutions, but you can’t mix a part of one solution with a part of another solution.
This analogy is also imprecise (all analogies fail somewhere), because one “world” is not one specific configuration of particles, but more like a set of very similar configurations (having particles in similar places with similar speeds). This set can split—if a particle is flying near another particle, in one part of the set the particles hit, in other part they miss each other, and the futures of these configurations are no longer similar.
The quantum experiments show us that these “worlds” interact, and the interaction is greater if the worlds are more similar (if all their particles have the same position and speed, except for a very few particles). Then probabilities increase and decrease in a ways we would not expect in classical physics, but now we have the equations which describe this. And these equations say that the greater the difference between two “worlds”, the smaller the interaction between them. So if you have a difference greater than 10^10 particles (which is less than a number of particles in one cell, e.g. a neuron), the interaction is almost zero; we are unable to measure it. Therefore in a world A we say: “we can’t measure the world B anymore, so it does not exist; speaking of its existence wouldn’t make sense”, while in a world B we say: “we can’t measure the world A anymore, so it does not exist; speaking of its existence wouldn’t make sense”. Practically speaking, we are right in both worlds; they are separated beyond reach.
In addition to this, the collapse hypothesis says that when the interaction is almost zero, in some unspecified moment the interaction becomes exactly zero (as opposed to staying ever decreasing but non-zero forever, as the equations say). This hypothesis is absolutely unnecessary, it does not predict any experimental outcome, it only serves as a justification for saying (in a world A) that the world B now really really really does not exist… that our seeing of the world A is more than mere saying “in a world A we are in a world A, just like in a world B we are in a world B, and the interaction between these worlds is zero for all practical purposes”… that even a hypothetical non-physical observer outside of our universe would have to agree with us that yes, the world A is real, and the world B is not, because at the moment the interaction dropped to zero, some metaphysical property of the world B was removed, but it wasn’t removed from the world A.
I favor the “shut up and calculate” school, which says any interpretations that don’t make actual predictions are both unnecessary and harmful.
Certainly, if you have to choose an “interpretation” and tell stories about other universes we can’t interact with, MWI is better than collapse, for the reasons Eliezer gives. But I don’t think we should have either of them.
It’s not a matter of privileging. Existence is not an applicable predicate. It’s not that we don’t know whether they exist. Just as other universes are neither sweet nor sour, neither happy nor sad, they neither exist nor not-exist.
I mean the same things that you do, I’m just using different words to try to express them.
I agree that “existence is not an applicable predicate”, I was just trying to roughly express what my thoughts were.