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Space Science

A Skeptical Look At The Multiverse 139

sjanich writes "The NY Times has a short, interesting article on multiverse theory. The author, Paul Davies, writes: 'This idea of multiple universes, or multiple realities, has been around in philosophical circles for centuries. The scientific justification for it, however, is new.' It is quite an interesting read. The author is a Physicist and pretty good science writer." Davies is not kind to the multiverse theory.
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A Skeptical Look At The Multiverse

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  • The Multiverse FAQ (Score:5, Interesting)

    by Anonymous Coward on Saturday April 12, 2003 @04:13PM (#5717140)
  • Taking the multiverse theory at face value, therefore, means accepting that virtual worlds are more numerous than "real" ones. There is no reason to expect our world -- the one in which you are reading this right now -- to be real as opposed to a simulation.

    I mean, what's the problem with this? Until we find evidence to the contrary, it remains a distinct possibility. And it borders on the realm of so-what. Is the knowledge that you're actually a participant in a very large simulation going to change how you live your life?

    I mean, are you annoyed that when you fall, you accelerate at exactly 9.8 m/s^2 (in a vacuum) towards the center of the earth, without fail? Those unimaginative programmers...

    • You're absolutely correct. Davies reasons as follows -- see if you can spot the false (implicit) premise:

      (1) If the multiverse theory is correct, there are a lot of "universes" that are the product of simulations run by intelligent beings.

      (2) If (1) is true, then our "universe" might be the product of a siumulation run by intelligent beings.

      (3) I do not believe that it is possible that I live in a universe that is the product of a siumlation run by intelligent beings.

      (4) The nature of the universe corr

      • #6 does not follow from #5 unless we could prove that #1 is "all" universes rather than "a lot of" universes.

        Plus he's saying "I do not believe" and "beliefs about nature of reality". Believe is not proof, simply opinion.

        I could probably pick it apart further but I'll stop there.

        SB
      • Actually I think it's more on the following line. He assumes that the reasoning behind the mutiverse theory is as follows:

        P1) There is no god
        H1) There exist multiple universes
        H2) Some of these multiple universes have capacity to simulate more universes
        H3) These simulated universes thus have a "creator" or "god" which is in conflict with the original premise
        Thus RAA: there are no multiple universes

        Only, AFAIK if you get an RAA you can only safely reject your /latest/ hypothesis. So his reasoning would main
        • Only, AFAIK if you get an RAA you can only safely reject your /latest/ hypothesis. So his reasoning would mainly reject the idea that given P1 H3 is not possible. (That's what I've learned from my introductions to logics class at any rate.)

          You're correct re RAAs. I was actually structuring the argument slightly differently, and leaving out a few steps.

          Ahh, for the good ole days of undergrad logic classes.
        • Only, AFAIK if you get an RAA you can only safely reject your /latest/ hypothesis. So his reasoning would mainly reject the idea that given P1 H3 is not possible. (That's what I've learned from my introductions to logics class at any rate.)

          No. That's stupid. Go research Currying and the commutativity of conjunction.

          Cliff notes: RAA is based on reducing a /set/ of assumptions to a contradiction. Then, you find the assumptions that are neither provable nor consequences of assumptions you've stated at t

    • and one I had not heard before.

      I think the real point is, not that he finds the idea of us living in a "simulation" abhorrent or impossible, but that any theory from which such a conclusion logically follows is something that cannot be considered scientific - such a theory is exactly equivalent to a religious doctrine in which unexplained events are attributed to the supernatural (unexplained "miraculous" events in our universe could be just defects in the simulation, or even deliberate effects caused by t
  • by obtuse ( 79208 ) on Saturday April 12, 2003 @04:32PM (#5717215) Journal
    Davies refers to, but never explicitly states one particular point: Most of the multiverse theories are inherently untestable, because we're completely isolated from the other universes. These are theories that don't predict or even suggest anything. How meaningless can you get?

    This is a good general point. Solipsism is uninteresting. Subjectivism & deconstructivism are often taken to similar absurd extremes by stupid people, including respected critics.

    He makes the analogy between theology & these scientific non-explanations. Religion is personally very meaningful, but metaphysics isn't science. Consequently a classic metaphysical question, "How many angels can dance on the head of a pin?" is the canonical meaningless question.

    The word that springs to mind is sophomoric. It reminds me of High School, when one friend asked another "What if you're really insane & just dreaming all of this?" The answer was of course, "So what? You've gotta pretty much live your life the same way anyway."
    • Oh but they are not unfalsifiable in principle,
      only in current practice. This is a crucial
      distinction between a physical and a metaphysical
      theory. The Higgs boson, when postulated, was
      an hypothesis unfalsifiable in practice. But
      clearly it is a physical, rather than a metaphysical,
      hypothesis.

      Now suppose that someone, let's call him Zweistein,
      proposes a theory of multiple universes which
      is incapable of producing a falsifiable prediction.
      We may say that the good Zweistein's theory is a
      metaphysical theory.
      • No dice. Appeals to the future don't get you out of that bind. We can't evaluate future theories, we can only evaluate current theories, because "somebody might figure it out in the future!" goes for everything.

        I might also add that "somebody might figure it out in the future!", as a theory, is also untestable, except by waiting for said theory, at which point we can just evaluate the theory directly, so "somebody might figure it out in the future!" is not useful.
        • I think you misunderstood him. He's not making an appeal to the future as justification for a present claim. He's just saying that while it may be a useful heuristic to presently relegate theories-without-predictions to the proverbial "corner", it is the height of folly to forget old speculations altogether.

          Put differently, it's like burning all sci-fi books that don't make falsifiable claims. The smart thing to do is to look at some of the dreams and see if you can make them happen.

          -l
    • I would take Davies's article with a large dose of salt.

      There is actually evidence FOR multiverses.

      Consider the twin slit experiment. You shine single photons through the slits, and they arrive in a single photon in a well defined location.

      And yet there are places where it never arrives. These places suggest that single photon has somehow travelled through BOTH slits and destructively interfered on arrival. Essentially all generally accepted interpretations of QM say that this is what happened in fact

      • A small point of order: if I'm not mistaken "Many Worlds" and "Many Histories" are just two names for the same QM interpretation - the one originally postulated by Everett, which places the different potential outcomes of a quantum event as *actual* outcomes in different universes which share a common past.

        The alternative (and more mainstream) QM interpretation which explains the appearance of a just one single result from the quantum event as being due to the collapse of the wave function - that one is kn
        • No, Many Worlds and Many Histories are distinct.

          Many Histories says we got here by many prior paths that coallesced. That much is essentially certain. Many Worlds says that here isn't the only point- there are many other parallel universes out there too that we can't reach.

          Most top physicists agree with Many Histories; it's more or less a consensus position. Many Worlds is a bit more controversial.

        • I understand it lets you get away with not having to treat the observer of the quantum event as seperate and somehow special.

          This seems less arbitrary to me... Copenhagen's interpretation makes a big assumption about the role of the observer.
      • by Alsee ( 515537 ) on Saturday April 12, 2003 @09:16PM (#5718534) Homepage
        Actually the article is about a seperate of multiverse theory, though they are compatible. You described quantum multiverse where every event that can happen does happen. The article discusses big-bang multiverse where there are many (or infinite) big-bangs. Each big-bang would create a seperate universe with it's own random variation on the laws of physics.

        -
    • The correct answer to "What if you people are all a dream of mine?" is to smack the questioner in the side of the head. What's he going to do, get mad at one of his dreams?
      • Doh. What makes that the correct answer?

        Killing/torturing you may be one of the questioner's favorite fantasies.

        Maybe that's potentially the correct answer and result for you. But I wouldn't assume that for everyone. Not even you - I'd more likely assume you're mistaken.
  • Why is nature so ingeniously, one might even say suspiciously, friendly to life?

    Well, this is one to ponder, granted that you consider life to be basically an earthbound form or entity. It always amuses me that there is talk about whether this place or that could support life. Just because we, as earthbound beings, rely on certain conditions to live, who is to say that other lifeforms would live in something that we'd consider completely destructive to our own very nature. How do we know that there are
    • by ralphclark ( 11346 ) on Saturday April 12, 2003 @07:00PM (#5717930) Journal
      This isn't a case of anthropomorphism or earth-centrism or anything like that. It's an outcome of basic physics (it does take into account that physics may be different in other universes, though).

      To take a simple example at the grossest level: imagine a universe in which symmetry broke in such a way that instead of three macroscopic spatial dimensions resulting, there were only two. A two-dimensional universe would be incapable of hosting structures of very significant complexity such as multicellular lifeforms. There would be strict limitations on size becaues a 2-D lifeform cannot possess any kind of internal transport system for alimentation or circulation - it would simply fall apart (try drawing one and see how internal channels effectively divide the creature into pieces).

      Four dimensional universes (and higher order dimensional spaces) also have topological problems which would make life difficult though you'll have to look those up for yourself.

      Even in three dimensional universes, very slight modifications to the relative strength of the four fundamental post-symmetry-breaking forces would make the universe appear very different.

      There will be universes composed entirely of radiation - but radiation does not interact well enough to form structures spontaneously.

      There will be universes where stars shine but never explode, thus elements heavier than helium are never released from their cores - and you can't get interesting chemical reactions from just hydrogen and helium.

      There will be many dark universes where star-sized agglomerations of matter simply do not ignite at all, thus energy cannot be concentrated sufficiently enough in any one place to fuel a biosphere.

      Even if you had hot stars and an interesting array of elements it may still be devoid of life if there was no possible *simple* (and thus common) combination of those elements available to provide a molecule like water - slightly more than weakly polar, which remains liquid at a range of useful temperatures (warm enough to enable chemical reaction at a significant rate, cool enough to allow stable reaction products).

      It's all very well to postulate "energy beings" or Horta-style silicon-based lifeforms but basic physics just doesn't make these very likely. There are strong practical reasons why all life on Earth is based on water and carbon compounds. There may be other constellations of physical laws which could generate a universe complex enough to support life, but there are far, far more that couldn't, no matter how good your imagination is.
      • Four dimensional universes (and higher order dimensional spaces) also have topological problems which would make life difficult though you'll have to look those up for yourself.
        More specifically, IIRC there was a statement in The Elegant Universe that said life (among other things) would be impossible in even-dimensional universes, due to something about how waves propagate through space.
      • This isn't a case of anthropomorphism or earth-centrism or anything like that.

        Yes it is. You made a ludacris number of false statements and assumptions.

        Two-dimensional organisms for starters: Just because you can't have a conventional mouth-alimentary_canal-anus is no evidence that you cannot have a complex multicellular organism. (Not that life needs to be multi cellular, or even cellular at all). Even if we take the silly assumption that life requires a "conventional" digestive system it could still u
        • Two-dimensional organisms for starters: Just because you can't have a conventional mouth-alimentary_canal-anus is no evidence that you cannot have a complex multicellular organism. (Not that life needs to be multi cellular, or even cellular at all). Even if we take the silly assumption that life requires a "conventional" digestive system it could still use an adsorption type system, a vacuole type system, or a two-way digestive system like hydras have - one opening acts as both mouth and anus.

          [...]

          Well a

          • Of the more outlandish sytems you envisage the best one can say is that they are not absolutely impossible.

            You claimed to give reasons 2-d life was impossible. I proved that claim false with counter examples. I never claimed that those are the systems 2-d life would actually use. The point is that there are a wide variety of ways life could overcome each of your objections. Life is far more "creative" at problem solving than I am and it would probably come up with far better systems than I described.

            But
            • You have not proven that you cannot have a mass collection at some distance from a star in 4-d. I can conceive at least 5 mechanisms by which it could occur.

              Five? I'd genuinely like to hear the details of these mechanisms. If you can model processes in five-dimensional spacetime in your head you must be the cleverest person on this planet. Either that or not actually from this planet.

              Consider that a 4-d sun would have a 3-d "surface".

              OK, I follow you...

              Our entire universe could conceivably be a limited

              • Yikes, this post got kind of long and wordy. I'm too tired to trim it down. Sorry, chuckle.

                I'd genuinely like to hear the details of these mechanisms. [mass at some distance from a star in 4-d]

                Unstable orbits can be maintained as a stable orbit when an aditional force enters the picture. Some of these "unstable" orbits can be maintained with an amazingly small small additional force. For example in 3-d there are five lagrange points. Three of them are "unstable" points of exactly this type. It only takes
                • I'm afraid I was disappointed by your examples of how to maintain stable orbits in 4-space.

                  Sure, extra forces can be applied on purpose to rectify the orbit but there is no way for those forces to just handily appear all by themselves and give a little push at just the right point in spacetime with just the right vector.

                  The many-body example fails precisely because of the lack of stable orbits it is meant to address. The particles in Saturn's rings each have a stable orbit of their own to go to; in 4-spac

                  • Akk! Netscape crashed mid-post and I have to start from scratch. Grrr.

                    I'm afraid I was disappointed by your examples... no way for those forces to just handily appear all by themselves

                    I don't think you understood what I meant. Maybe I didn't explain it well enough. I was talking about forces that would in fact be inherent in the system. We were talking about a sun/planet type system. Radiation pressure is part of that system. Solar wind is part of the system. Bodies in that system will aquire a charge
                    • Akk! Netscape crashed mid-post and I have to start from scratch. Grrr.

                      That used to happen to me a lot back in my Netscape 4 days. Current Mozilla (since at least 1.2) is a hell of a lot more stable.

                      [orbital mechanics with various forces propitiously balancing 4d gravity etc.]

                      Now I do see what you mean. But the inverse cube law for gravity in 4-space means that everything would have to be a lot closer. Don't know what this would mean for orbital angular momentum - everything whizzing about madly? I

                    • I moved this to the top because I think it may bring a crucial insight:
                      is it physically possible to make a replicator out of waves

                      You're still being blinded by assumptions based on human experience. I'm sure you're familiar with the basic concepts of quantum mechanics, there is no difference between particles and waves. Light behaves like a particle. Electrons behave like waves. "Waves" are a high level emergent phenomena. They don't exist! :D

                      Quantum mechanics and relativity are "hard" and "confusing" e
                    • Quantum mechanics [...]

                      I'm well aware of all that but I don't draw the same conclusions, obviously.

                      Also you kind of glossed over the answer to my question about whether waves could be used to make replicators. I see nothing proven about this.

                      Your speculations about mass,energy,space,time etc are only half right. For starters, mass != energy. There is an equivalence but not an equality. Otherwise there would be no distinction. If your mass were to suddenly become indistinguishable from energy we'd all be

                    • Also you kind of glossed over the answer to my question about whether waves could be used to make replicators. I see nothing proven about this.

                      You're pretty knowledgable about science, I guess I assumed you were more familiar with the "oddities" of quantum mechanics.

                      Two "waves" of light that can in fact interact. We don't see this effect in everyday life because visible is far too low in energy to equal even the lightest stable mass. Two high energy photons can collide resulting in matter and antimatter
                    • *sigh* Mozilla crashed and ate my detailed reply. I haven't the heart to type it all in again. So here's the shorthand blockquote-free version (my apologies if it appears a bit curt, it's late and I have to get to bed :o\ ):

                      Your arguments, where they attempt to rely on physics, are strictly pop-sci, littered with implausible and incorrect layman-friendly analogies and accompanied by several diversionary straw men. (I'm trying not to say 'barely sophomoric', but you do tend to labour the most basic points w
                    • Finally as regards your claim that QM is bizarre - actually I find QM quite rational and satisfying

                      Ahh, that explains the problem.

                      "Anyone who is not shocked by quantum theory has not understood it." - Niels Bohr
                      "I think I can safely say that nobody understands Quantum Mechanics" - Richard P. Feynman

                      quantum mechanics bizzare [google.com] 8910 hits. If you don't think QM is bizarre then you're only familiar with simplified and erroneous pop-sci explanations of QM.

                      Your arguments, where they attempt to rely on physic
                    • The Bohr and Feynman quotations were broadly true (and esoterically funny) when they were spoken decades ago. But we've all had a long time to mull over what QM means since then. Secondly, for your patronizing remark to mean anything we'd have to agree on what "understand" means. Since hardly any two people can actually agree on what "mean" means where QM is concerned, that is going to be difficult. But what this argument seems to be increasingly about is who understands QM better, you or me. If your quotat
                    • Apropos of something we were talking about earlier (Permutation City) I found this [higgo.com] tonight - quite amusing...
                    • Chuckle. I'd rather have two of me with £10,000 pensions than one of me with a £12,500 pension :)

                      -
                    • your patronizing remark
                      I hate being patronized more than almost anything else.


                      My comment was intentional minor dig, you were far more patronizing to me in your previous post. I understand you were frustrated having to re-write the post from scratch, but you did let it slip in.

                      Sorry if I over did it with the "basic physics" and links, you accused me of "attempting" to be based on physics, "pop-sci", "implausible and incorrect layman-friendly analogies". You thought I wasn't talking valid science so I atte
            • I do not want to comment too much, except for

              a) Life in a 2D universe has to expend much more energy to function due to all the constraints put on it that 3D life does not have. For instance the comlicated set of valves and thingies that one poster envisioned simply takes more effort, and therefore energy, to develop and to operate inside the lifeform. This may not preclude life but it may preclude very complicated life and would at the least make it more difficult to develop. Just as there is more life in
              • a) Life in a 2D universe has to expend much more energy to function due to all the constraints put on it that 3D life does not have.

                You are carrying in many assumptions based on human-centric view of life and physics.

                Lets look at the energy levels available to run human life processeses. We run off of the chemical energy available from food, a couple of joules per gram.

                But the available chemical energy is only a small fraction of the thermal energy enviornment. Thermal energy at room temperature is a co
      • There may be other constellations of physical laws which could generate a universe complex enough to support life, but there are far, far more that couldn't, no matter how good your imagination is.

        Since my imagination can think of an infinite number of variations on any set of physical laws, how do you quantify "more"?
        • Re:One question (Score:3, Insightful)

          by ralphclark ( 11346 )
          Mathematicians say that some infinite sets can contain more members than other infinites sets, eg the set of real numbers is more highly populated than the set of natural numbers (effectively integers). This holds wherever one infinite set can be mapped onto a subset of another infinite set. Also in that particular case the set of real numbers that can't be mapped is larger than the set that can. So it's meaningful to postulate, on statistical grounds, that the number of sterile potential universes is large
          • They don't seem to in many other branches of physics. If a meteor hits the Earth, there are as many points for it to land on in Luxemborg as there are in the Pacific Ocean, but because those points don't cover as much area, the odds are greater that the ocean will be hit. How do you measure the "area" spanned by a set of possible potential universes?

            What makes the situation worse is that "the set of all possible universes" doesn't look to me like something that can be constructed with the axioms of set t
    • by Black Parrot ( 19622 ) on Saturday April 12, 2003 @07:07PM (#5717976)


      > > Why is nature so ingeniously, one might even say suspiciously, friendly to life?

      > Well, this is one to ponder, granted that you consider life to be basically an earthbound form or entity. It always amuses me that there is talk about whether this place or that could support life. Just because we, as earthbound beings, rely on certain conditions to live, who is to say that other lifeforms would live in something that we'd consider completely destructive to our own very nature. How do we know that there aren't life forms out there that don't depend on breathing molten gold in the same way we need to breathe oxygen? Or to take it even farther, who says they need to breath at all?

      Also, when people start arguing that the universe is uniquely suited for life it is useful to ask them what percentage of the universe is actually hospitable to life AWKI.

      A thin crust at the surface of a few planets, out of the entire volume of the universe? It looks to me like the universe was "designed" for something else altogether, and life found a few rare, small cracks to hide in. As well to say that the lobby of a fine hotel was designed to harbor dust particles.

      • A thin crust at the surface of a few planets, out of the entire volume of the universe? It looks to me like the universe was "designed" for something else altogether, and life found a few rare, small cracks to hide in. As well to say that the lobby of a fine hotel was designed to harbor dust particles.

        Run for you lives! The maid is coming!

        Sorry. Just couldn't resist.

        -- MG

  • How ridiculous, (Score:5, Interesting)

    by rritterson ( 588983 ) on Saturday April 12, 2003 @05:08PM (#5717385)
    Everywhere he says life could not exist in any other universal properties and constants should be modified to state "life as we know it."

    quote:
    Life would probably be impossible with more (or less) than three dimensions to work with, so our seeing three is then no surprise. Similar arguments apply to other supposedly fixed properties of the cosmos, such as the strengths of the fundamental forces or the masses of the various subatomic particles.

    Why exactly is life impossible with more than 3 dimensions? He subscribes to the fundenmental flaw that all science fiction writers subscribe to: all alien life forms breath, walk on legs, and "see" through eyes. Sure, it's hard to change a human actor on a movie screen by too much, but the world of books and pages ought to be able to create something better.

    I also agree with the other post that says, paraphrased, if we live in a giant simulation, does that make existance different? If you can't get out of, or control the simulation, what difference does it make? I, for one, am not worried about hyperintelligence alien giants looking at me showered naked, and the like.

    Along those same lines, if we can eventually create computer simulations with sentiant beings, why can we not create a universe with different parameters and force life to exist within it?
    Lastly, if we can't get out of this universe into another one, what difference does it make? And if we somehow break the barrier and jump universes, the link between them makes them one universe with localized properties doesn't it?
    • He subscribes to the fundenmental flaw that all science fiction writers subscribe to: all alien life forms breath, walk on legs, and "see" through eyes.

      You need to read better science fiction.
      • Can you recommend something?
        • Authors: Niven (lots of aliens, the closest to anthropomorphic is the K'zinti, a warrier cat race, and quite a few very non-human races, such as the Outsiders (apparently a living form of liquid helium) and the Pierson's Puppeteers [larryniven.org]), Vinge's "A Fire in the Sky" (incredible handling of sentient communal mind organisms (!)) and "A Deepness in the Sky" (cool but somewhat less incredible handling of spider-like aliens in a very unusual environment, complete with cultural implications). You might be surprised bu
          • Heh. Yeah, actually I work in a used bookstore with a SF/F section that's as large as a small bookstore, so I have quite a selection to choose from. :-)

            I haven't read any Niven (I've been meaning to, it's on the list, somewhere), but the other books you mention all involve species that breathe, walk on legs, etc. The communal-mind creatures in _A Fire Upon the Deep_ were basically normal wolves with intelligence and ultrasound telepathy. Pretty much all SF I've read, especially hard SF, sticks to three co
        • You can go back to really old space operas like E.E.Smith's Lensman stories. Smith proposes several life forms that exist only partially in this 3-D existence of ours. Then, A.E.Merritt's dweller in the Moon Pool (1919) was both artificial and not bound by 3-space and neither were its makers. Many Scifi authors do seem to shrink from going to far into the unknown.

          • Awesome, thanks :-)
            • Another really interesting story was called "The Children's Hour." The action takes place probably right after WW II. The authors were Henry Kuttner and C. L. Moore. The story cast a very different light on certain myths and suggested that some "human" adults are really still children in a much vaster scheme of things.

    • Why exactly is life impossible...see my other comment [slashdot.org]
    • Along those same lines, if we can eventually create computer simulations with sentiant beings, why can we not create a universe with different parameters and force life to exist within it?

      Wouldn't such a simulation actually be a universe? After all, the universe is generally described as everything which is observable. If you created sentient computer programs in a virtual evironment, would this not be a universe in its own right? If you were ambitious and the computer had sufficient power you could ev
    • Lastly, if we can't get out of this universe into another one, what difference does it make?

      You have some interesting thoughts on the subject, many of which I have also been thinking from time to time. The more I think about it the more I start wondering. What is existence actually? It seems to me there must be different definitions of existence. In physics existence means it exists in our universe. In mathematics it means aproximately that it can be described and is not inconsistent with itself. The two
  • by aminorex ( 141494 ) on Saturday April 12, 2003 @05:14PM (#5717421) Homepage Journal
    It is worthwhile to point out that cosmological
    diversity is only one kind of "multiverse" theory.
    In it, all of the various universes are embedded
    in a larger space. Such theories are not therefore
    unscientific, in the sense of being intrinsically
    unfalsifiable, or unverifiable: Because the various
    universes have topological relation to one another,
    there is a continuum of existence connecting them,
    and they may interact in yet unforseen ways. Our
    current inability to design experiments to detect
    such interactions is merely an artifact of
    ignorance.

    But there are many other forms of ontological
    multiplicity which do not involve topological
    continuum. The outstanding example is the
    Everett interpretation of quantum mechanics.
    In that theory, rather than the actual state of
    affairs in the universe being the sole real
    instantiation of the phi wavefunction, created
    by the act of observation (as in the classical
    Copenhagen interpretation of Bohr et al), the
    quantum wave function is considered to be a
    representation of the distribution of an infinite
    multiplicity of alternatives, all equally "real".

    I find the Everett interpretation to be much
    preferrable, on several grounds, not the least
    of which is that it is consistent with the
    mathematical concept of probability distribution
    in a way which the Copenhagen interpretation is
    not, but others disdain
    it because it implies the real existence of
    entities which are not, so they say, in principle,
    detectable. Again, this complaint fails because
    it is an argument from ignorance: The current
    inability, at a given level of human understanding
    and technology, to design a verifying or falsifying
    experiment, does not relate to the truth or falsity
    of the hypothesis. Cophenhagenists are quite
    comfortable supposing that unseen cats are undead,
    and any truth not currently known is not yet true.
    I think this is a much larger leap of faith than
    is needed to create a working understanding.

    • Nice one! Have you read Schrodinger's Kittens? It goes through the various ways to look at quantum weirdness, and proposes a novel idea: that light paths actually allow "choices" to be made by particles in a non-temporal way.

      That is, any space-time event will be sensitive to future events, and will "choose" its quantum state based on information that flows BACKWARDS in time to it via photons. This allows for a continuous-probability universe that is nonetheless "discrete" and "real".

      Or something like that
  • by C21 ( 643569 )
    this is neat, especially when you look at some more current work on virtual particles, and virtual particle clusters. Then when you apply time dialation and distortion to a virtual particle cluster its amazing what happens. Well, that can be 20 billion years in the blink of an eye as compared to the actual particles surrounding the virtual universe.
  • This article annoyed me, because it felt like the author reasoned backwards from his own prejudice. It seemes as if he has an actual abhorence of the very idea of multiple universes, perhaps because that would make our own little universe less than special.

    He claims multiverse theories are all by nature unverifiable. Hogwash. Off the top of my head, I can think of at least one type of multiverse theory that would be. Scientists now speculate that we may live on a higher-dimensional 'sheet' or brane, as
  • The existence of intelligent life does require the universe to be large and complex. The multiverse interpretation demonstrates a related point: the probability of intelligent life arising in this universe might be low, or even very low. You don't need the multiverse interpretation to work this out, but it does make it a lot clearer. The ET searchers often express the assumption that our existence shows that intelligent life is likely to have a probability greater than one (because here we are). The fallacy
  • by Christopher Thomas ( 11717 ) on Saturday April 12, 2003 @07:00PM (#5717932)
    This seems to be Parallel Universe Month.

    The May issue of Scientific American contains a much more in-depth article on parallel universes, which has enough points in common that it might have inspired the op-ed piece.

    Teaser for the article is here [sciam.com]. To get the whole thing, you either have to have a subscription or wait until next month.

    The gist of it is as follows:
    • The first type of "parallel universe" is just another part of this universe. Because the universe appears to be infinitely large, any configuration of matter - be it Earth, our galaxy, or our entire currently-observable universe - must be duplicated somewhere out there. Back-of-the-envelope statistics math is used to figure out how far away (hint: really, really far).

      In principle, these other "universes" can interact with our own, but in practice they're far enough away that it doesn't matter. Physical laws are likely similar.

      Re. an infinite universe, the article states that a finite universe would leave artifacts in the cosmic microwave background that weren't seen.

    • The second type of parallel universe is other post-inflationary regions in the still-infationary space that holds our own universe. These universes would have different physical laws, and possibly different numbers of uncurled/macroscopic dimensions, some or all of which are set by symmetry breaking as the expanding universe cools.

      These parallel universes are utterly unreachable, as the space between them a) exists in a different coordinate system that puts it in our past from our point of view, and b) is expanding exponentially quickly, dragging other universes away from ours at mind-boggling speed.

    • The third type of parallel universe scenario is the familiar "multiple histories" interpretation of quantum mechanics - the idea that all possible outcomes to any event occur, in their own universes.

      As far as I understand it, interaction between these universes wouldn't be possible without violating some of the ground rules involved (the history tree could be thought of as a state transition diagram for all possible states of a closed system; if it's closed, it can't interact with anything else).

    • The fourth type of parallel universe discussed is, as far as I can tell, imaginary universes. The idea is to consider an arbitrary mathematical description of an object a spacetime diagram, and to consider the result of interpretation of this diagram to be a universe.

      If you call this a "real" universe, then Everquest and the reality hosting the United Federation of Planets are also real universes. It depends on your point of view (and what you mean by "real" in this context).


    The existance of "universes" of the first type is certain if the universe is infinite, from information theory arguments. The infinite or non-infinite nature of the universe is something that can be empirically tested (though the final test - waiting for every part of it to come within our observation horizon - is impractical).

    The existance of the second type of universe hinges on the nature of the scalar fields proposed in the various inflationary models. In principle, this is testable, either by recreating the energies required or by observing distant parts of the universe that are undergoing inflation.

    The existance of the third type of universe is not testable, due to the requirement for closed systems. So it's pretty much a moot point.

    The existance of the fourth type of universe is a metaphysical question, whose answer depends on what you mean by "exist".

    The full article has a lot of additional discussion, and pretty pictures. By all means pick up a copy, if the topic interests you.
    • > The May issue of Scientific American contains a much more in-depth article on parallel universes

      Just finished it. (Love that day every month when I drop everything and browse the new issue!)

      > The first type of "parallel universe" is just another part of this universe. Because the universe appears to be infinitely large, any configuration of matter - be it Earth, our galaxy, or our entire currently-observable universe - must be duplicated somewhere out there.

      I didn't get his calculations. He gi

      • I didn't get his calculations. He gives the number of protons that could fit into our observable universe ("Hubble space") and then calculates the permutations of present/absent for each to get the total number of possible configurations. But wouldn't there be more configurations than a present/absent calculation would account for? Such as variants arising from the momentum and quantum state of each proton?

        And from the fact that the universe consists of more than just protons, yes. I think (or at least ho
  • by etymxris ( 121288 ) on Saturday April 12, 2003 @07:17PM (#5718027)
    Paul Davies is a religious person. And so when there are two competing theories, one of which includes his ideals of religion, and one which does not, he will choose the first if there is no other evidence given. The reason that the multiverse theory is postulated is to give a kind of evolutionary account of the cosmology of the universe. Who knows if there are other universes, or if they are anything like our own? We certainly will never know.

    But Davies' favored alternative is a much less viable option. To explain away the existence of our world with something that's even more complicated, such as God, is no explanation at all. Explanations reduce complex things to simple things. And if God can create something as complex as the universe, he must clearly have at least that much complexity within Himself.

    We've seen this conflict before. Look at these well designed humans! How could they have possibly arrived upon this Earth? Surely only a being as complex as God could have accomplished such a wonderful feat! This was the great argument of the last two centuries, and the consensus is that evolution and natural selection form a much better explanation than divine creation.

    And I guess not much has changed since then. Look at this well designed universe! If things were only slightly different, no life could have been formed at all. Surely there is a divine influence at work! But whenever you drop something like God into your explanation, you've only made your job harder. Now instead of explaining life or the universe, you have to explain the existence of this vastly powerful and mysterious creature that made it all take place.

    The other possibilities, though possessing many flaws, are much more plausible. It's much more plausible to think that many universes were created, and that only those suitable for life actually developed life, than it is to think that there is only one universe, whose existence can only be explained though divine creation.

    • by Black Parrot ( 19622 ) on Saturday April 12, 2003 @08:09PM (#5718235)


      > Paul Davies is a religious person.

      Some may find it useful to google for "paul davies" creationism.

      > But whenever you drop something like God into your explanation, you've only made your job harder. Now instead of explaining life or the universe, you have to explain the existence of this vastly powerful and mysterious creature that made it all take place.

      Moreover, the existence of an all-powerful agent that acts on its whim of the day is compatible with any observation, and thus is absolutely useless as an explanation for anything. One universe exists? God wanted it that way! An infinite number of universes exist? God wanted it that way!

      The only things incompatible with the "theory" of creation by a willful omnipotent agent are the things the believers in that agent don't choose to believe (such as biological evolution, in much of the USA).

    • The bottom line is that we don't know.

      A creator is certainly a valid theory, although it does not simplify things because a creator is also a complex thing with an unknown origin. If God always existed, then it is also possible that the "seed" for the Big Bang also existed, but did not fire until 15 billion years ago. Similarly, God waited for some reason also to create this universe if we go that route.

      I think cosmologists are relunctant to add a creator(s) to the list of possibilities because it opens u
    • It's much more plausible to think that many universes were created, and that only those suitable for life actually developed life, than it is to think that there is only one universe, whose existence can only be explained though divine creation.

      Would this not also imply that in one of those universes there must be a being who created a smaller sub-universe which contains other beings debating about whether a being could exist outside of their universe and could be responsible for its creation?

      If there ar
    • I'm sorry; I don't follow this. It's more plausible to believe in many, many universes than in one God? Why?
  • A Brief History of the Multiverse
    By PAUL DAVIES
    New York Times, April 12, 2003
    http://www.nytimes.com/2003/04/12/opinion/12DAVI. h tml?pagewanted=print&position=top [nytimes.com]

    SYDNEY
    Imagine you can play God and fiddle with the settings of the great cosmic machine. Turn this knob and make electrons a bit heavier; twiddle that one and make gravitation a trifle weaker. What would be the effect? The universe would look very different -- so different, in fact, that there wouldn't be anyone around to see the result
  • ... those socks that vanish every time I do laundry have to go somewhere.

  • I wonder what the timecube guy [timecube.com] has to say about multiverses?
  • If you buy into the "Schroedinger's Cat" thought experiment, then you pretty much have to accept that there are multiverses.

    In Schroedinger's experiment, there is a cat in a box that is either killed or not killed depending on the result of some test of quantum superposition. The cat remains in this hybrid state of being dead or not dead until someone opens the box to 'observe' the event. I think most scientists believe this - and it's being demonstrated right now in things like Quantum Computers.

    That's
    • That would all be valid and intriguing - but for the little fact that the universe does not change its state just because a human makes an observation. We're caught in the dangerous lands of antropo-centrism here.
      The cat of course does not exist in an unresolved state just because there is no human around to know whether it's currently dead or alive.
      Likewise the universe is not pending resolutions to human observation and be in a kind of "unresolved" state before humans observe something. Because: the unive
  • Imagine that your car begins making a strange knocking sound when you brake. You take your car into the autoshop to find out what's causing the problem. Without even looking under the hood, the mechanic explains that the reason your car is making the sound is because there are infinitely many universes with different versions of you and your car, and you just happen to live in the universe where the car began making a knocking sound. Odds are, you'd look for another mechanic. The multiverse theory essentia
  • My 'twin' is probably using this [nytimes.com] link.
  • Is this not old news? I mean, I complete believe after watching The One [imdb.com].

  • The idea of parallel universes gives me some sense of hope, simply because in one of them I must be smart enough to understand parallel universes.

    I just happen to live in the one in which the wave functions collapsed into a solution of cant-do-hard-math. That sucks for this one of me.

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