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Infinitenight2093
2010-Jun-24, 11:27 PM
According to the Many Worlds Interpretation of quantum mechanics, the universe is constantly "budding" and splitting every time a decision or choice is made. However, if alternate universes are constantly being created to accommodate for every possible outcome, does this mean that these universes are being created without their own big bang? Is the universe just making a slightly different "copy" of its previous self?

am I on the right track, or am I missing something? thanks in advance

01101001
2010-Jun-25, 12:43 AM
[...] does this mean that these universes are being created without their own big bang?

I'm moved to ask if a brother and a sister have their own mother.

What does "own" mean in your question?

Cougar
2010-Jun-25, 01:09 AM
Many Worlds... splitting every time a decision or choice is made... Is the universe just making a slightly different "copy" of its previous self?

It seems ridiculous, and awfully extravagant. That "visualization" may not have even been what Hugh Everett was suggesting. It is more like an analogy of one of those weird quantum features. But when we analogize the cosmic expansion with the surface of an expanding balloon, we do not intend to imply that the universe is actually one unimaginably giant balloon. :)

Ken G
2010-Jun-25, 01:34 AM
Oh I think Everett is quite serious about the "budding" of new universes. Indeed, this view is required, if we stipulate that the universe has a wave function, it is a real attribute of the universe, and it obeys the unitary evolution equations of quantum mechanics. That's because if the universe has a total wave function (a "universal" wave function-- which there isn't any evidence of, but it is a natural though dramatic extrapolation of quantum mechanics), then it is impossible for only a "single outcome" to occur when an experiment is done. Instead, all the outcomes must occur, as "branches" in that total wave function, but for some reason our intelligence is only able to interpret and interact with a single outcome. Or that may be said backward, presumably each such outcome/branch would generate its own uncorrelated intelligences, and we are one of them (out of very very very many). That is what happens when you take quantum mechanics completely seriously-- of course, the alternative is the Copenhagen approach, where we don't take it that seriously, because we see quantum mechanics as a kind of attempt to fit a square peg (the quantum world) into a round hole (our classical approaches to experiments), and the ill-fitting aspects result in some bizarre behaviors we should not interpret too literally. Either approach makes all the right predictions, so the difference is generally viewed as philosophical.

WayneFrancis
2010-Jun-25, 01:44 AM
To the OP, I hope you get a better answer then I can provide.

Lets take our universe at some point in time Tn where there happened to only be 2 possible out comes for a situation, we'll call them a & b. If the universe magically became 2 universes now totally disconnected from each other ... would one of those 2 universes not have its own big bang? How would you determine which universe had its "own big bang" and which one did?

The many worlds interpretation is, at this point, metaphysics and philosophy. Interesting to use in some cases to try to explain what we observe, like a particle spontaneously decaying.

I think pushing it to something like parallel universes like in Sliders is going WAY to far. Great show but if you think about it if the universe did do this then there would be an infinite amount of universes more that have no resemblance to ours beyond the fundamental laws of physics and even that would be questionable. In the end it doesn't provide any really useful answers.

Its an analogy and should be used to get a basic understanding of what is trying to be taught. Just as many analogies are, it is often taken to far or to literally.

WayneFrancis
2010-Jun-25, 01:46 AM
Oh I think Everett is quite serious about the "budding" of new universes. Indeed, this view is required, if we stipulate that the universe has a wave function, it is a real attribute of the universe, and it obeys the unitary evolution equations of quantum mechanics. That's because if the universe has a total wave function (a "universal" wave function-- which there isn't any evidence of, but it is a natural though dramatic extrapolation of quantum mechanics), then it is impossible for only a "single outcome" to occur when an experiment is done. Instead, all the outcomes must occur, as "branches" in that total wave function, but for some reason our intelligence is only able to interpret and interact with a single outcome. Or that may be said backward, presumably each such outcome/branch would generate its own uncorrelated intelligences, and we are one of them (out of very very very many). That is what happens when you take quantum mechanics completely seriously-- of course, the alternative is the Copenhagen approach, where we don't take it that seriously, because we see quantum mechanics as a kind of attempt to fit a square peg (the quantum world) into a round hole (our classical approaches to experiments), and the ill-fitting aspects result in some bizarre behaviors we should not interpret too literally. Either approach makes all the right predictions, so the difference is generally viewed as philosophical.

And there you go....Ken G provided the better answer then I could provide :)

astromark
2010-Jun-25, 02:08 AM
You must admit that a new reality for any choice does seem so foolish as to be silly... this is surly not a real possible answer to a multi universe structure... you would toss a coin and the answer is... not a new reality... Philosophy is for philosophers ... As quantum physics is for people whom might think they know some thing we do not. I will go back to balancing on the fence...

Jens
2010-Jun-25, 03:13 AM
According to the Many Worlds Interpretation of quantum mechanics, the universe is constantly "budding" and splitting every time a decision or choice is made. However, if alternate universes are constantly being created to accommodate for every possible outcome, does this mean that these universes are being created without their own big bang?


I may be wrong, but I think the simple answer to the question is no, that all these alternate universes would be remembering the same big bang, if you will. But I don't really understand that. My own question would be, if the universe splits into a near infinity of new universes each moment, wouldn't that be creating matter out of nothing? Or is there something I'm missing?

Infinitenight2093
2010-Jun-25, 05:49 AM
I'm moved to ask if a brother and a sister have their own mother.

What does "own" mean in your question?

According to the MWI these infinite possibilities are happening simultaneously as other outcomes at the same time. So if the universe is splitting all the time to allow for these infinities to happen at the same time, it would be impossible for each split universe to undergo another big bang. Say that the universe split into two when I flipped a coin; In my universe it landed on heads, but at the same time the universe split to allow for tails. If the split off universe had to undergo another big bang, then by the time the split universe actually caught up to the event when I flipped a coin, my universe would be far far into the future. I hope this makes sense

Infinitenight2093
2010-Jun-25, 05:56 AM
I may be wrong, but I think the simple answer to the question is no, that all these alternate universes would be remembering the same big bang, if you will. But I don't really understand that. My own question would be, if the universe splits into a near infinity of new universes each moment, wouldn't that be creating matter out of nothing? Or is there something I'm missing?

exactly my thoughts. if this is true, then it means that our universe may not have undergone the big bang we hear so much about, but at the same time we resulted from that singularity at some point in the past. As for creating matter out of nothing, I can't even begin to try and answer why. However, who is to say that things outside of our universe even follow our laws of physics

Jens
2010-Jun-25, 06:19 AM
exactly my thoughts. if this is true, then it means that our universe may not have undergone the big bang we hear so much about, but at the same time we resulted from that singularity at some point in the past.

Sorry, but I don't follow you at all. If you want to know whether our universe underwent a big bang or not I think you need to look at the evidence for or against it. And doesn't "undergoing the big bang" and "resulting from a singularity at some point in the past" mean exactly the same thing?

Infinitenight2093
2010-Jun-25, 06:33 AM
Sorry, but I don't follow you at all. If you want to know whether our universe underwent a big bang or not I think you need to look at the evidence for or against it. And doesn't "undergoing the big bang" and "resulting from a singularity at some point in the past" mean exactly the same thing?

I mean that our universe may have split from another universe almost exactly like ours, and may still be splitting. So maybe the universe we exist in today did not actually have a big bang, even though in the distant past there was a universe almost exactly like ours that was created out of a big bang. After that big bang, the universe began to split into alternate universes that eventually split into our universe. This brings me back to the main question, does this splitting of the universe require each split universe to undergo a big bang, or can the universe simply split instantly into a similar copy?

pzkpfw
2010-Jun-25, 06:54 AM
I mean that our universe may have split from another universe almost exactly like ours, and may still be splitting. So maybe the universe we exist in today did not actually have a big bang, even though in the distant past there was a universe almost exactly like ours that was created out of a big bang. After that big bang, the universe began to split into alternate universes that eventually split into our universe. This brings me back to the main question, does this splitting of the universe require each split universe to undergo a big bang, or can the universe simply split instantly into a similar copy?

How would you know which was the "real" (or "original") Universe and which were the ones that "split off"?

It seems to me that (assuming your many worlds interpretation) rather than one "original" Universe being the one that "had" the big bang and all others not - that instead; all the Universes began from a big bang - the same one.

After all, the evidence that led to (the current notion of) the big bang being postulated in the first place, would be present in all those Universes - split off or not. e.g. That evidence is present in our Universe, which you suggest is a "split".

Geo Kaplan
2010-Jun-25, 07:16 AM
I mean that our universe may have split from another universe almost exactly like ours, and may still be splitting. So maybe the universe we exist in today did not actually have a big bang, even though in the distant past there was a universe almost exactly like ours that was created out of a big bang. After that big bang, the universe began to split into alternate universes that eventually split into our universe. This brings me back to the main question, does this splitting of the universe require each split universe to undergo a big bang, or can the universe simply split instantly into a similar copy?

As pzkpfw said, all roads lead back to the same singularity. Each of the many worlds traces its history back to that self-same singularity. So we all "own" a big bang -- the same one.

Infinitenight2093
2010-Jun-25, 07:17 AM
How would you know which was the "real" (or "original") Universe and which were the ones that "split off"?

It seems to me that (assuming your many worlds interpretation) rather than one "original" Universe being the one that "had" the big bang and all others not - that instead; all the Universes began from a big bang - the same one.

[First]. I wouldn't think it's possible to tell which is the split and which is the original because the universe may have split an infinite number of times since it's beginning. [Second] exactly. All possible split universes came from the same big bang (you could theoretically go back in time in all of these universes and see the same big bang) but that still doesn't change the fact that if I stub my toe and the universe splits, the split off universe in which I don't stub my toe is existing at the same time as the universe in which I did stub my toe (which would be impossible if every time the universe splits, the split off universe undergoes another big bang)

Jens
2010-Jun-25, 07:26 AM
[First]. I wouldn't think it's possible to tell which is the split and which is the original ...

This is where I think you're going wrong. There is no original and split. They are all originals, or all splits, depending on how you look at it. Not a real good analogy, but suppose you have a starfish, and it cut it in half and both grow into full starfish. Which is the original and which is the copy?

Geo Kaplan
2010-Jun-25, 07:29 AM
It seems ridiculous, and awfully extravagant. That "visualization" may not have even been what Hugh Everett was suggesting. It is more like an analogy of one of those weird quantum features. But when we analogize the cosmic expansion with the surface of an expanding balloon, we do not intend to imply that the universe is actually one unimaginably giant balloon. :)

As has already been mentioned, Everett was totally serious. You can see for yourself -- his thesis is available online from several sources. Here's one: www.pbs.org/wgbh/nova/manyworlds/pdf/dissertation.pdf

Read and enjoy. It's too bad that he died so young.

Geo Kaplan
2010-Jun-25, 07:30 AM
[First]. I wouldn't think it's possible to tell which is the split and which is the original because the universe may have split an infinite number of times since it's beginning.

No, the real reason is that you can't tell the "split" from "the original" because there is no "original" (or they all are originals).

ETA -- I see Jens beat me to it.

Infinitenight2093
2010-Jun-25, 08:12 AM
I understand that they all came from the same place (i.e. there is no original because they all came from the same BB) but my question remains, does the universe instantly split into many universes to accommodate for every possible outcome of a single event? (I highlight instantly because According to MWI, all possible outcome of a single event have to be coexisting). can it be said that the universe copies itself like the budding process of cells?

snowcelt
2010-Jun-25, 08:52 AM
If the creation of new universes are not instant, a whole new problem presents itself. If there are an infinite number of new universes, any delays, no matter how short in duration would result in a near infinite amount of time passing since the big bang. Am I missing something here?

cosmocrazy
2010-Jun-25, 09:02 AM
Maybe I'm wrong but my interpretation would be that each infinite split would be virtual until the one we experience is observed. If you consider QM and how particles i.e electrons are said to be in every possible position in their orbital cloud until they are observed or interact then surely this would be the function of the split universe theory? So basically each moment in time is the observed set position of the universe's state. Now since time is relative the state of the universe at any "one time" would be subject to the observers opinion and relative reference frame. But where this gets confusing is if this is the case then how does the actual state of the universe become absolute? i.e how does/or does history repeat its self regardless of your relative reference frame?

Argos
2010-Jun-25, 11:59 AM
As pzkpfw said, all roads lead back to the same singularity. Each of the many worlds traces its history back to that self-same singularity. So we all "own" a big bang -- the same one.

Yeah, the many-worlds interpretation can accommodate the idea of a single big-bang for all instances of the universe that are split. The multiverse has a time t=0.

Swift
2010-Jun-25, 12:44 PM
I mean that our universe may have split from another universe almost exactly like ours, and may still be splitting. So maybe the universe we exist in today did not actually have a big bang, even though in the distant past there was a universe almost exactly like ours that was created out of a big bang. After that big bang, the universe began to split into alternate universes that eventually split into our universe. This brings me back to the main question, does this splitting of the universe require each split universe to undergo a big bang, or can the universe simply split instantly into a similar copy?
Infinitenight2093,

This is more some friendly moderator advice, rather than a warning. You are getting fairly close to advocating an Against the Mainstream (ATM) idea. If you do so, this thread will be moved to the ATM forum and you will need to follow ATM rules. As long as you are only asking questions, and not arguing with the mainstream position, you're fine. Thanks for your cooperation.

AriAstronomer
2010-Jun-25, 01:01 PM
I personally view the current QM theory as an approximation for something else that is going on, and the consequences of QM shouldn't be taken too literally. To take QM completely literally is to say that we have finalized the theory, which is obviously incorrect. It is a work in progress, and many of the kinks are still being worked out. Every theory that we have is an approximation, and furthermore, anytime you hear an analogy it's important to remember it's an analogy. The multiverse isn't a collection of soap bubbles, it's only like it. The real thing is most likely something we could not comprehend. I wouldn't rule out the possibility of a multiverse, but I don't think one should also religiously believe it either.

Ken G
2010-Jun-25, 01:31 PM
I personally view the current QM theory as an approximation for something else that is going on, and the consequences of QM shouldn't be taken too literally.Indeed, I think you can replace "QM" with "any physical theory at all" in your statement, and it holds equally well. What's more, this is not a flaw in physics-- it is the purpose of physics to find approximations/idealizations/simplifications of whatever is "going on." Sometimes the approximations are so good we don't even know if they are approximations or not-- but invariably, they do turn out to be so.

The real thing is most likely something we could not comprehend.Yes, that seems spectacularly likely to me-- especially since the "real thing" includes our very brains that are trying to understand the real thing.

I wouldn't rule out the possibility of a multiverse, but I don't think one should also religiously believe it either.Be careful though-- the "multiverse" is something different from "many worlds." The latter would all be playing out within one "universe", the multiverse asserts that there are also other universes, and is generally invoked to avoid having to explain why our universe is the way it is. Personally, I don't think we should beguile ourselves into imagining that science can answer that question in the first place, but those who wish science can address that question hope it will someday be a testable hypothesis.

Cougar
2010-Jun-25, 02:10 PM
As has already been mentioned, Everett was totally serious. You can see for yourself -- his thesis is available online from several sources. Here's one: www.pbs.org/wgbh/nova/manyworlds/pdf/dissertation.pdf

Thanks, Geo. Quite a paper. And yes, a quite serious paper! But serious about what, exactly? I notice "many worlds" appears only in the title, and does not thereafter appear in the entire 139-page dissertation. And how does this extravagant "splitting off" visualization square with his statement (in response to an Einstein 'jab')?






The mouse does not affect the universe - only the mouse is affected.

Everett, p.117

01101001
2010-Jun-25, 02:14 PM
I am still seeking to know what you mean by "own" in the original question.

Everybody has their own mother. That doesn't mean each person has a different mother.


[...] Say that the universe split into two when I flipped a coin; In my universe it landed on heads, but at the same time the universe split to allow for tails. If the split off universe had to undergo another big bang, then by the time the split universe actually caught up to the event when I flipped a coin, my universe would be far far into the future. I hope this makes sense

Why would both of the forks of a split need to undergo a Big Bang? They underwent a Big Bang in their pasts. Each fork has its own Big Bang. That doesn't require that each fork has a different Big Bang.

AriAstronomer
2010-Jun-25, 02:22 PM
I agree with 01101001. You don't need to redo everything that has happened. Once a zygote splits into two cells creating twins, one of the twins doesn't have to be re-fertilized. And which one is the 'original twin'?

Ken G
2010-Jun-25, 03:34 PM
And how does this extravagant "splitting off" visualization square with his statement (in response to an Einstein 'jab')?






The mouse does not affect the universe - only the mouse is affected.
I believe the point there is held in the word "affect"-- when an experiment happens, correlations between various quantum outcomes are destroyed, and the outcomes become uncorrelated, which means they can no longer interfere with each other. This further means they no longer "affect" each other, they will have nothing further to do with each other-- they have become like when a river branches, neither branch cares about anything that happens to the other branch, yet both are from the same river, and both obey the laws of water. A mouse riding a log will go down one branch or the other, and that branch will become the mouse's "universe" from that point onward, yet the mouse did not create the river-- the path the mouse takes matters only to the mouse, not to the river. The presence of the mouse gives meaning to the question "which path does the mouse take"-- that question means nothing without the mouse, you just have a river that splits.

Infinitenight2093
2010-Jun-25, 06:18 PM
Indeed, I think you can replace "QM" with "any physical theory at all" in your statement, and it holds equally well. What's more, this is not a flaw in physics-- it is the purpose of physics to find approximations/idealizations/simplifications of whatever is "going on." Sometimes the approximations are so good we don't even know if they are approximations or not-- but invariably, they do turn out to be so.
Yes, that seems spectacularly likely to me-- especially since the "real thing" includes our very brains that are trying to understand the real thing.
Be careful though-- the "multiverse" is something different from "many worlds." The latter would all be playing out within one "universe", the multiverse asserts that there are also other universes, and is generally invoked to avoid having to explain why our universe is the way it is. Personally, I don't think we should beguile ourselves into imagining that science can answer that question in the first place, but those who wish science can address that question hope it will someday be a testable hypothesis.

would a universe splitting and branching an infinite number of times not be a multiverse? In the MWI, all possibilities are taking place in the "same" universe, but are only similar as much as I am to me in a parallel universe. The many worlds interpretation makes use of a level 3 multiverse (in which there are 4 levels altogether)

Infinitenight2093
2010-Jun-25, 06:21 PM
I wouldn't rule out the possibility of a multiverse, but I don't think one should also religiously believe it either.

religiously how? after all, what is theoretical physics if not blind faith?

cosmocrazy
2010-Jun-25, 06:26 PM
religiously how? after all, what is theoretical physics if not blind faith?

The problem is there's no way to test or observe the theory of a split multi-verse situation.

Len Moran
2010-Jun-25, 06:33 PM
My understanding is that Everett was never very clear on the conceptual riddle of what would be included within the branching. It seems that the idea of universes getting physically multiplied does not even appear in Everett’s original paper (but I have not checked that for myself). He called his theory "relative state theory" and was explicitly aimed at realism, realism in the sense that he felt something "true" could be said about mind independent reality. If it is the case that he was not particularly clear on what was supposed to be included within branching, perhaps it were the case that his emphasis with the paper was more concerned with re-establishing realism at the quantum level. Perhaps it is others after him who have tended to give undeserved attention to the seemingly fantastic permutations of universes being multiplied at an an unimaginable temo.

I think many mathematical physcists (as opposed to science fiction enthusiasts) are attracted to the theory because of its mathematical clarity, and tend to leave the conceptual riddles alone, trusting that the mathematical formalism may lead to major discoveries.

Infinitenight2093
2010-Jun-25, 06:33 PM
The problem is there's no way to test or observe the theory of a split multi-verse situation.

I respectfully disagree. There is no way now to test such a theory, but in the future it seems that massive gravity wave detectors may be able to prove whether or not alternate universes exist. I also believe that if the universe is constantly splitting, there has to be some remnant that it is doing so

trinitree88
2010-Jun-25, 06:48 PM
I respectfully disagree. There is no way now to test such a theory, but in the future it seems that massive gravity wave detectors may be able to prove whether or not alternate universes exist. I also believe that if the universe is constantly splitting, there has to be some remnant that it is doing so

Infinitenight2093. I agree with cosmocrazy. In order for you to conduct a test on something, the very foundation of our physical theories, it must be in our universe, not somewhere else. Stuff outside our physical realm is justifiably called metaphysics, and belongs there. :shifty:It does help nitwits sell books, but produces immense piles of gibberish in physics forums, and nothing for an experimentalist to check out. Try to keep them separate. pete

Geo Kaplan
2010-Jun-25, 10:54 PM
My understanding is that Everett was never very clear on the conceptual riddle of what would be included within the branching. It seems that the idea of universes getting physically multiplied does not even appear in Everett’s original paper (but I have not checked that for myself). He called his theory "relative state theory" and was explicitly aimed at realism, realism in the sense that he felt something "true" could be said about mind independent reality. If it is the case that he was not particularly clear on what was supposed to be included within branching, perhaps it were the case that his emphasis with the paper was more concerned with re-establishing realism at the quantum level. Perhaps it is others after him who have tended to give undeserved attention to the seemingly fantastic permutations of universes being multiplied at an an unimaginable temo.

I think many mathematical physcists (as opposed to science fiction enthusiasts) are attracted to the theory because of its mathematical clarity, and tend to leave the conceptual riddles alone, trusting that the mathematical formalism may lead to major discoveries.

It's been years since I've read his thesis, but now that it's available online, I'll have to give it another go. But my recollection is that his "universal wavefunction" (I don't remember that he used the term "many worlds" anywhere in his thesis) is pretty clear -- it is exactly as it is named. It offers an alternative to the Copenhagen interpretation, with its seemingly ill-formed notion of wavefunction collapse upon an observation. All possible outcomes are "real" -- they all "happen."

His approach is completely consonant with standard QM, because his is an interpretation, not a different formulation. All predictions accessible to experimental verification are the same. Since all of these alternative universes are orthogonal (not "parallel", as is the common language in popularizations of MWI), there's no way to detect them. As such, Everett's formulation is not falsifiable (no more and no less so than Copenhagen), and thus outside of science in that important sense. But it sure gets the neurons a-twitching.

01101001
2010-Jun-25, 11:34 PM
after all, what is theoretical physics if not blind faith?

Something else.

Strange
2010-Jun-25, 11:35 PM
after all, what is theoretical physics if not blind faith?

A set of consistent theories derived from observation and confirmed by experiment? Maybe.

Cougar
2010-Jun-26, 12:52 AM
....there's no way to detect them. As such, Everett's formulation is not falsifiable (no more and no less so than Copenhagen), and thus outside of science in that important sense.

Thanks for making that clear.


But it sure gets the neurons a-twitching.

Ha ha. I'm not sure of the sense you mean, but it seems to fit regardless.


It offers an alternative to the Copenhagen interpretation, with its seemingly ill-formed notion of wavefunction collapse upon an observation. All possible outcomes are "real" -- they all "happen."

Well, until they decohere (http://en.wikipedia.org/wiki/Quantum_decoherence), isn't it? I've got to go with Murray Gell-Mann (http://nobelprize.org/nobel_prizes/physics/laureates/1969/gell-mann-bio.html) on this:







We [Gell-Mann and Hartle] consider Everett's work to be useful and important, but we believe that there is much more to be done. In some cases too, his choice of vocabulary and that of subsequent commentators on his work have created confusion. For example, his interpretation is often described in terms of "many worlds," whereas we believe that "many alternative histories of the universe" is what is really meant. Furthermore, the many worlds are described as being "all equally real," whereas we believe it is less confusing to speak of "many histories, all treated alike by the theory except for their different probabilities." ... it is not necessary to become queasy trying to conceive of many "parallel universes," all equally real.

EDG
2010-Jun-26, 04:21 AM
Infinitenight2093. I agree with cosmocrazy. In order for you to conduct a test on something, the very foundation of our physical theories, it must be in our universe, not somewhere else.

I don't think this is strictly true. In order to conduct a test on something, it must be detectable from within our universe. It doesn't necessarily have to be IN our universe though. What matters is that we have a means to sense it, regardless of where it is.

Ken G
2010-Jun-26, 04:50 AM
would a universe splitting and branching an infinite number of times not be a multiverse?The semantics of it could play out several ways, but it's a very different kind of multiple universe. The branching universe has the same history, and the same laws with the same parameters (c, h, and so on). The multiverse is designed to support universes with different histories, laws, and parameters. It is invoked to "explain" why we have the laws we have, all due to the anthropic principle.

In the MWI, all possibilities are taking place in the "same" universe, but are only similar as much as I am to me in a parallel universe. The many worlds interpretation makes use of a level 3 multiverse (in which there are 4 levels altogether)Yes, Max Tegmark has a hierarchical system for differentiating the various ways of thinking about multiple universes. The problem with a unified approach like that is that it requires if you buy off on one form of many universes, you have to buy off on all of them. That's rather the calling card of alternative thinking about ghosts and ESP and astrology-- they always come in packages like that, where all skepticism is banished.

eburacum45
2010-Jun-26, 03:10 PM
So do (some of) the branching universes come back together when decoherence occurs?

trinitree88
2010-Jun-26, 03:11 PM
The semantics of it could play out several ways, but it's a very different kind of multiple universe. The branching universe has the same history, and the same laws with the same parameters (c, h, and so on). The multiverse is designed to support universes with different histories, laws, and parameters. It is invoked to "explain" why we have the laws we have, all due to the anthropic principle.
Yes, Max Tegmark has a hierarchical system for differentiating the various ways of thinking about multiple universes. The problem with a unified approach like that is that it requires if you buy off on one form of many universes, you have to buy off on all of them. That's rather the calling card of alternative thinking about ghosts and ESP and astrology-- they always come in packages like that, where all skepticism is banished.
KenG. Agreed. While I fancy some edgy ideas at times to see if there is some merit to them, I can't bring myself to ascribe to this stuff at all. Time-wasting. pete

eburacum45
2010-Jun-26, 03:35 PM
Webviewers in Britain might be interested in this
http://www.bbc.co.uk/iplayer/episode/b008d2zj/Parallel_Worlds_Parallel_Lives/

Documentary which tells the story of a rock star and a quantum mechanic. Mark Oliver Everett, better known as E, is the lead singer of cult US band the Eels. What most of his fans don't know is that Mark's father, Hugh Everett III, was one of America's top quantum physicists

Ken G
2010-Jun-26, 03:54 PM
KenG. Agreed. While I fancy some edgy ideas at times to see if there is some merit to them, I can't bring myself to ascribe to this stuff at all. Time-wasting. Yeah, I'm not trying to besmirch Tegmark, he is a top-level physicist and his ideas about multiple universes are brilliant, they just should not be counted in the same body as the rest of physics (and his other work). Call them a philosophical dalliance of considerable pedagogical interest, but not hard science.

Infinitenight2093
2010-Jun-26, 05:33 PM
Yeah, I'm not trying to besmirch Tegmark, he is a top-level physicist and his ideas about multiple universes are brilliant, they just should not be counted in the same body as the rest of physics (and his other work). Call them a philosophical dalliance of considerable pedagogical interest, but not hard science.

The "rest of physics" is incomplete. Maybe it is precisely these "edgy" theories that will finally unify physics? I don't think that such radical ideas should be tossed out. Take the black hole, for example, it was once thought to be an unreal anomaly predicted by Einsteins General Relativity. Physicists thought they were undetectable and could therefore not be proven to actually exist. That all changed after a supermassive black hole was discovered to be directly in the center of our galaxy. I don't see why (in the future) we couldn't prove/ disprove the existence of a multi-verse

Ken G
2010-Jun-26, 05:56 PM
The "rest of physics" is incomplete. Maybe it is precisely these "edgy" theories that will finally unify physics?Maybe yes, maybe no. The point is, if and when these edgy theories inspire real theories, then at that time, and not before, will they become real theories. I have no objection to looking at the philosophical ramifications of existing theories, and I have no objection to using philosophical thinking to inspire new theories. My objection is to calling something a scientific theory that isn't.


I don't think that such radical ideas should be tossed out. Take the black hole, for example, it was once thought to be an unreal anomaly predicted by Einsteins General Relativity. Physicists thought they were undetectable and could therefore not be proven to actually exist. That all changed after a supermassive black hole was discovered to be directly in the center of our galaxy. I don't see why (in the future) we couldn't prove/ disprove the existence of a multi-verseWhy in the future would we not prove/disprove the existence of ghosts, ESP, and UFOs? The issue is not what we may learn in the future, it is what scientific evidence we have right now. Black holes and neutron stars were a prediction-- they involved taking existing theory and extrapolating it outside what was known, so there was no actual "theory of black holes and neutron stars" prior to GR (and the theory of neutron stars is still in its infancy), but there was a prediction that they might exist. Along with that prediction came a host of observable consequences (relativistic accretion disks, high-energy phenomena, large gravity in small spaces), and it was those observable consequences that led to their acceptance. In other words, it was a hypothesis that guided observations. What observations has the multiverse guided? What is the testable hypothesis there? I don't say we know it's wrong, I say at present, it just isn't science at all, though as philosophy, it might someday lead to some science.

Geo Kaplan
2010-Jun-26, 09:05 PM
Maybe yes, maybe no. The point is, if and when these edgy theories inspire real theories, then at that time, and not before, will they become real theories. I have no objection to looking at the philosophical ramifications of existing theories, and I have no objection to using philosophical thinking to inspire new theories. My objection is to calling something a scientific theory that isn't.
Why in the future would we not prove/disprove the existence of ghosts, ESP, and UFOs? The issue is not what we may learn in the future, it is what scientific evidence we have right now. Black holes and neutron stars were a prediction-- they involved taking existing theory and extrapolating it outside what was known, so there was no actual "theory of black holes and neutron stars" prior to GR (and the theory of neutron stars is still in its infancy), but there was a prediction that they might exist. Along with that prediction came a host of observable consequences (relativistic accretion disks, high-energy phenomena, large gravity in small spaces), and it was those observable consequences that led to their acceptance. In other words, it was a hypothesis that guided observations. What observations has the multiverse guided? What is the testable hypothesis there? I don't say we know it's wrong, I say at present, it just isn't science at all, though as philosophy, it might someday lead to some science.

Well put (as usual). Just because one "edgy" idea bore fruit in the past does not automatically confer equal status to all edgy ideas -- that equivalence principle is demonstrably false.

Ken G
2010-Jun-26, 09:30 PM
Right-- "the winners write the history." I'll admit there have been many remarkable instances of basically philosophical ideas getting out ahead and blazing a trail for subsequent physics, but as you say, a few examples of that does not establish every such attempt.