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Therefore, are these many worlds constrained by what is physically possible, or by what is sensibly possible?
jamest wrote:... Firstly, assuming that there are many worlds like this that exist at the same space & time, it should be acknowledged that these worlds cannot be comprised of the same matter, for if one (the same) set of matter exists at one (the same) set of space & time, then we only have one world, not many. That is, the MWI requires that different matter/bodies exist at the same space & time. But, how can more than one body exist at the same space & time? That is illogical. (Problem 1)
UndercoverElephant wrote:
Therefore, are these many worlds constrained by what is physically possible, or by what is sensibly possible?
The former. In some branch of an MWI multiverse, somebody is in the Guinness Book of Records for rolling 100,000 consecutive sixes without cheating....
Is MWI sensible? Depends what non-sensible things you are trying to get rid of.
jamest wrote:UndercoverElephant wrote:
Therefore, are these many worlds constrained by what is physically possible, or by what is sensibly possible?
The former. In some branch of an MWI multiverse, somebody is in the Guinness Book of Records for rolling 100,000 consecutive sixes without cheating....
Is MWI sensible? Depends what non-sensible things you are trying to get rid of.
You seem to have overlooked the first two problems, focusing instead upon addressing the 3rd problem, lightly.
When you send me a cheque for £10,000, I will take heed of your response to the 3rd problem.
Zwaarddijk wrote:It's interesting how terrible your arguments are. They don't stand up to any scrutiny. (And I reject MWI just as you do - I just find your arguments to be very worthless.)
Paul Almond wrote:jamest wrote:... Firstly, assuming that there are many worlds like this that exist at the same space & time, it should be acknowledged that these worlds cannot be comprised of the same matter, for if one (the same) set of matter exists at one (the same) set of space & time, then we only have one world, not many. That is, the MWI requires that different matter/bodies exist at the same space & time. But, how can more than one body exist at the same space & time? That is illogical. (Problem 1)
MWI does not propose that that "more than one body exists at the same time" in any fundamental way. To put it simply, it proposes that the basis for "reality as we know it" is the quantum wave function, and that this has real existence. Parts of the quantum wave function become "decoherent" from other parts, meaning that they cease to interact in any way worth talking about. This gives the appearance of separate worlds, with separate objects. Suppose a ball exists in my world, and I can interact with it. Another ball exists in someone else's world, and I can't interact with that. The two balls don't interact with each other - even though that might be in the same space. The underlying explanation of this isn't that "two bodies occupy the same space". It is that a single wave function occupies the same space, and parts of it don't interact with other parts - and yes, the two parts can overlap. However, the idea that waves can overlap is hardly radical.
A (very crude and open to misuse) analogy might be radio transmissions. Someone might ask how radio transmissions of two separate radio shows can pass through the same space at the same time. Doesn't this require two things to occupy the same space? This is dealt with when we see that nothing really passes through the space except radio waves - and a single description can be made of the radio waves passing through the system. Likewise, you could step back from the many-worlds of MWI and describe everything in terms of just "one world" with the wave function - and parts of that wave function ceasing to interact with other parts explain the appearance of separate worlds. The different worlds in MWI aren't really separate in any ontologically "profound" way but merely by lack of interaction and limited human perception due to our status as observers embedded in the system.
In a way, the concept of matter as we know it is no longer fundamental in MWI anyway. It makes little sense to object to a ball in one world being "the same matter" as the ball in another world. Looked at closely enough it is all just waves anyway.
Even thinking of this in terms of "bodies" existing in different worlds suggests a problem to me, so I have doubts about whether it is worthwhile getting into the other questions right now. I will say that MWI makes no claim that the results of quantum mechanics experiments should be predictable by humans.
jamest wrote:Okay, thanks for the explanation. It appears that I've taken this 'many worlds' conception too literally. Anyway, if there are problems with the MWI I need to rethink them.
Paul Almond wrote:jamest wrote:Okay, thanks for the explanation. It appears that I've taken this 'many worlds' conception too literally. Anyway, if there are problems with the MWI I need to rethink them.
It depends what you mean by "too literally". What is important is that the "splitting" doesn't happen in any kind of (I don't even know what vocabulary I should use here) "ontologically profound" way. However, the theory does propose that these worlds do exist as far as we are concerned. If MWI is true, there will indeed be worlds in which the Nazis won World War II and a statue of Adolf Hitler is standing in London: the proportion of such worlds might be large or small depending on how lucky or not you think you Britain was during World War II. However, the only thing that makes these "other worlds" is the lack of interaction. To some being able to take a "Godseye" view of this, there would just be the wave function. This is the sense in which MWI is supposed to get rid of randomness. Randomness is still apparent to the inhabitants of a single world, but from the "Godseye" perspective, there is just the wave function, developing deterministically over time. To you, the randomness comes from having multiple futures at any time and continually being split as an observer.
Incidentally, a test for MWI was proposed, but I don't advise doing it.
Paul Almond wrote:To put it simply, it proposes that the basis for "reality as we know it" is the quantum wave function, and that this has real existence.
andrewk wrote:I find every-world hypotheses, whether in the quantum-mechanics based form or any other, somewhat morally disheartening. If whenever faced with a moral decision I believe that, regardless of what choice I make, there will always be just as many worlds in which I make the immoral decision, it seems to make it pointless to weigh up ethical choices. In short, there is nothing I can do to make the totality of all worlds any better.
Teuton wrote:Paul Almond wrote:To put it simply, it proposes that the basis for "reality as we know it" is the quantum wave function, and that this has real existence.
Functions are abstract mathematical entities, so the quantum wave function cannot be the basis of physical reality, which must itself be a concrete physical entity (a quantum field?). It can at most represent that basis mathematically.
Paul Almond wrote:In any event, I am not suggesting that anyone should do this.
Paul Almond wrote:Teuton wrote:
Functions are abstract mathematical entities, so the quantum wave function cannot be the basis of physical reality, which must itself be a concrete physical entity (a quantum field?). It can at most represent that basis mathematically.
That sounds like a semantics issue to me, really …
Paul Almond wrote:…- about whether we can use the word "function" or whether we are being lazy with semantics and ontology: what is being claimed by MWI is that "something" exists and that the "something" is described by the quantum wave function, and that that "something" can explain both quantum mechanics and the appearance of separate events to us.
Paul Almond wrote:
The term "quantum wave function" is used by both advocates and detractors of MWI without too much issue - and I think they all understand what they mean.
Yes my terminology was a bit loose there. I was aware of that as I wrote it, but couldn't be bothered doing the extra typing to state the thought more clearly - and got called out on it!Paul Almond wrote:andrewk wrote:I find every-world hypotheses, whether in the quantum-mechanics based form or any other, somewhat morally disheartening. If whenever faced with a moral decision I believe that, regardless of what choice I make, there will always be just as many worlds in which I make the immoral decision, it seems to make it pointless to weigh up ethical choices. In short, there is nothing I can do to make the totality of all worlds any better.
But it doesn't actually say that - some things would occur in more worlds than others.
I don't follow this point. Can you expand on it? Are you referring to the conceptual problems surrounding the concept of free will?Another point - this moral issue, if it is one, is still there if MWI is not true
Teuton wrote:Paul Almond wrote:To put it simply, it proposes that the basis for "reality as we know it" is the quantum wave function, and that this has real existence.
Functions are abstract mathematical entities, so the quantum wave function cannot be the basis of physical reality, which must itself be a concrete physical entity (a quantum field?). It can at most represent that basis mathematically.
Paul Almond wrote: Another point - this moral issue, if it is one, is still there if MWI is not true! It just has a purely probabilistic nature without the "many worlds" issue.
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