# Parallel Universe Theory -- Did I Understand This Correctly? **URL:** \ **Category:** Factual Questions\ **Created:** [December 3, 2008, 10:02pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577 "2008-12-03T22:02:18Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [December 4, 2008, 3:33am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/21 "2008-12-04T03:33:39Z")
> [@Indistinguishable](#): > > I took the OP to merely be saying something like “Every possible 1 meter cube is realized somewhere within the universe”, which cannot be defeated by cardinality arguments. Well, rather, “Every possible n meter cube is realized somewhere within the universe” for all finite values of n. ---
**Author:** ![Darryl\_Lict](https://avatars.discourse-cdn.com/v4/letter/d/7cd45c/32.png) [@Darryl\_Lict](https://boards.straightdope.com/u/Darryl_Lict)\ **Post date:** [December 4, 2008, 3:37am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/22 "2008-12-04T03:37:52Z")
The whole multi-universe theory infuriates me. Is this not just philosophy? It is absolute conjecture, and has no relevance in science, as far as I can tell. If there are multiple parallel universes that we will never see, it has no meaning whatsoever. If one of these universes intrudes upon our observable space, well then all bets are off and there will be radical changes in physics understanding. This will never happen in my lifetime, and I suspect, it never will. When I am proven wrong, I’ll be more than happy to come back and admit that I was wrong. ---
**Author:** ![AllWalker](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@AllWalker](https://boards.straightdope.com/u/AllWalker)\ **Post date:** [December 4, 2008, 6:11am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/23 "2008-12-04T06:11:35Z")
Slight sidetrack, but here is a fun thought experiment 1. Assume infinite number of universes, as with the many worlds interpretation 2. Assume travel between universes is possible - not even likely, just not outright impossible 3. So therefore, any scenario you can imagine occurs in some of the universes - like in the OP, we have Rhode Sea universes, or universes with life but no planets. In infinite Creation, it is all inevitable. 4. So therefore, in a different universe, a giant lizard opens a portal to our universe, comes through and declares underpants illegal. I imagined it, so it is possible, nay, inevitable. Now, don’t argue over 1) and 2), indulge me for a moment and assume they are true. Even so, what is wrong with the logic of steps 3) and 4)? I’m pretty sure I know the answer, but it’s fun to think about. **Darryl Lict** , you are right, this is mostly just conjecture based on one interpretation of quantum mechanics. But, the latest thinking out of M-theory is that gravity bleeds across between the universes, so there is some interaction. This hypothesis explains the weak strength of gravity plus the existence of dark matter, so it’s not all baseless spectulation. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 4, 2008, 6:36am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/24 "2008-12-04T06:36:23Z")
Quoth **Darryl Lict** : > [@](#): > > If there are multiple parallel universes that we will never see, it has no meaning whatsoever. Hence my question. If you start from the assumption that things we can never see have no meaning whatsoever, then such parallel universes as the OP describes are meaningless. This is a perfectly sensible view to take, and I’m not about to say that it’s wrong. Then again, I’m also not about to say it’s right, either: Even arguing that is a bit too philosophical for me. Quoth **AllWalker** : > [@](#): > > Now, don’t argue over 1) and 2), indulge me for a moment and assume they are true. As a great computer once said, I’m sorry Dave, I can’t do that. “As with the Many Worlds interpretation” means that we’re utterly rejecting the possibility of communication between the worlds: Any such communication is simply not compatible with the model. And M-theory, incidentally, has nothing whatsoever to do with the Many Worlds model. While M-theory does open up the possibility of spacetimes or branes parallel to our own, it doesn’t say anything about how many of them there might be. Ours could be the only one, and parallel to nothing but itself, or there could be exactly one other, or there could be ten million others. But those other spacetimes can’t be the many worlds of the Many Worlds interpretation, because new worlds must branch off at every decision point, and M-theory doesn’t allow for any mechanism for the number of branes (whatever it is) to change. ---
**Author:** ![nivlac](https://avatars.discourse-cdn.com/v4/letter/n/3bc359/32.png) [@nivlac](https://boards.straightdope.com/u/nivlac)\ **Post date:** [December 4, 2008, 6:41am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/25 "2008-12-04T06:41:50Z")
> [@Der\_Trihs](#): > > Sure. Think of it this way; imagine that there is indeed another universe, with intelligent life, that can never affect us. Now, imagine that some creature in that universe asks the same question you have. Clearly, the answer is yes - we are here, regardless of the opinion of an extrauniversal alien. And by the same token, they exist whether or not we will ever know of them or believe in them. This is silly. Replace “another universe with intelligent life” in your statement with “a tooth fairy”. So you are saying that tooth fairies exist because they can ask themselves if we exist? That’s nuts. As to parallel universes, I find them great sci-fi reading, and only that. [Here’s](http://discovermagazine.com/2008/jul/16-is-the-universe-actually-made-of-math) an interview with Max Tegmark, a leading proponent of parallel universes. Interesting reading, but his ideas are too speculative for me. I don’t quite buy his idea that “mathematical formulas create reality”. Mathematics can create a model that explains observations and makes predictions, but is that the same as reality? ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 4, 2008, 12:33pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/26 "2008-12-04T12:33:30Z")
> [@Indistinguishable](#): > > Well, rather, “Every possible n meter cube is realized somewhere within the universe” for all finite values of n. I think one problem with this sort of idea is that it doesnt take into consideration physical laws of operations and how particles/whatever interact/evolve. Can I imagine a twin earth that evolved far far far far away (get a really good travel agent) and the only difference is Everest is a millimeter higher? Sure. Sure, the I think the argument then becomes about discrete versus continous states versus which infinities are bigger and what infinity actually means and if infinity is a physical reality and whether it could even be a physical reality. A place where Hitlers head exists in the core of our twin sun? One possible state of a cubic meter for sure…but how you GET to that state in first place? ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [December 4, 2008, 12:46pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/27 "2008-12-04T12:46:52Z")
Interesting thread, full of misconceptions. The argument is independent of quatum mechanics and has nothing to do with Zeno. And even of the cardinality of the set of points on a line. It is based on the hypothesis (which doesn’t seem to have any chance of being proved or disporved) that the universe is infinite, even though only a finite part of it is visible, even in theory. Now choose a volume, say of a sphere 14.3 billion light years in radius. And suppose nothing smaller than the Planck length is discernible even in theory. By a Planck volume I will mean a sphere of diameter equal to a Planck length. Now how many Planck volumes fit into our observable sphere? From what Wiki says it is about 10^{184}, which is a large number by ordinary reckoning, but infinitesimal compared to infnity. Now suppose each Planck length can have only some fixed number of states, say 2 for simplicity. Then the number of states of each observable sphere is 2 to that number, gigantic, but finite. Thus there are only finitely many observable spheres possible. Each one occurs, with probability 1, infintely often. But be careful. When talking about infinite state spaces, having probablilty 1 does not mean certain, as it does when the state space is finite. For example, in the space of infinite decimals, the chances that one taken at random is non-repeating is 1, but that is still not a certainty, since there are repeating decimals. Thus it is probable, with probability 1, that there are exact duplicates of our observable sphere somewhere, in fact, infinitely many of them. Same answer for a universe that differs from outs only in that I just scratched my left ear, while in this one it was the right. But since they are all unobservable, what difference does it make? ---
**Author:** ![Meltdown](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Meltdown](https://boards.straightdope.com/u/Meltdown)\ **Post date:** [December 4, 2008, 2:39pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/28 "2008-12-04T14:39:32Z")
> [@Chronos](#): > > Before we go any further, let’s get one key question out of the way: Can something be said to “exist” if there’s no way it could possibly have any effect whatsoever on you, nor you on it? Interesting question. My gut reaction is “yes” – something either exists or it doesn’t, and is not dependent upon the possibility of my interaction with it. I’ve always assumed that there are planets in the universe that I cannot see, that there’s no way I could possibly see, but still exist in the sense that, yes, they’re there. Maybe I’m thinking about it too simplistically. Thanks for all the replies and the links. I haven’t had a chance to check the links out yet, but plan to do so over the weekend. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [December 4, 2008, 2:40pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/29 "2008-12-04T14:40:34Z")
I think things exist whether or not you can “feel” them. Kinda makes it hard to test with science. How do you test for these mirror worlds? Even if you could get to them, or at least observe them how would you find them? You’d be looking for infinitesimally small needle in a hay stack. There’s no way to apply the scientific method. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [December 4, 2008, 2:42pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/30 "2008-12-04T14:42:51Z")
Btw this thread is kinda zen. If a tree falls on a mirror earth a hundred trillion miles away and no one from this earth is there to hear it, does it make a sound? ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [December 4, 2008, 2:52pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/31 "2008-12-04T14:52:59Z")
I think the program the OP saw must have been _The Elegant Universe_ - it was a book by Brian Greene, then was made into a series on PBS. The book is about string theory, and reads almost like a marketing campaign for it. However, I came away after reading it thinking much less favorably to string theory than I had before I started. The book did a pretty good job of convincing me that it will never pan out, even though I think it intended to do the opposite. Anyway, Brian Greene was featured on the Radio Lab episode that tofergregg linked to above: [http://blogs.wnyc.org/radiolab/2008/08/12/the-multi-universes/](http://blogs.wnyc.org/radiolab/2008/08/12/the-multi-universes/) You should listen to it. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [December 4, 2008, 7:44pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/32 "2008-12-04T19:44:33Z")
> [@Hari\_Seldon](#): > > Interesting thread, full of misconceptions. > > The argument is independent of quatum mechanics and has nothing to do with Zeno. > … > Thus it is probable, with probability 1, that there are exact duplicates of our observable sphere somewhere, in fact, infinitely many of them. Same answer for a universe that differs from outs only in that I just scratched my left ear, while in this one it was the right. While we’re making the assumptions clear, we might as well note that this argument also relies on a principle at least something like “Every finite volume has a non-zero probability of existing in any particular configuration, even after conditionalizing on the configuration of any other finite volume”. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 4, 2008, 7:58pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/33 "2008-12-04T19:58:47Z")
> [@CurtC](#): > > I think the program the OP saw must have been _The Elegant Universe_ - it was a book by Brian Greene, then was made into a series on PBS. No. It’s a History Channel original weekly series called [“The Universe.”](http://shop.history.com/?v=history_show_the-universe&SESSID=e12468f47e6828107fb4a3282ab5a584) ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [December 4, 2008, 8:18pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/34 "2008-12-04T20:18:32Z")
> [@AllWalker](#): > > Slight sidetrack, but here is a fun thought experiment > > 1. Assume infinite number of universes, as with the many worlds interpretation > 2. Assume travel between universes is possible - not even likely, just not outright impossible > 3. So therefore, any scenario you can imagine occurs in some of the universes - like in the OP, we have Rhode Sea universes, or universes with life but no planets. In infinite Creation, it is all inevitable. > 4. So therefore, in a different universe, a giant lizard opens a portal to our universe, comes through and declares underpants illegal. I imagined it, so it is possible, nay, inevitable. I started watching the same program as the OP, then found myself screaming at the TV, and had to turn it off. Statement #3 is NOT necessitated by statement #1. Assuming that there are an infinite number of universes does NOT mean everything is inevitable. There may just be lots of duplication. There’s no reason why there can’t be things that NEVER occur; all you need is for the things that DO occur to repeat. Heck, for all we know, we can have an infinite number of IDENTICAL universes. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [December 4, 2008, 8:31pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/35 "2008-12-04T20:31:38Z")
> [@panache45](#): > > There’s no reason why there can’t be things that NEVER occur; all you need is for the things that DO occur to repeat. But that would require some kind of spooky-action-at-a-distance communication between these distant universes, which we don’t think would be possible. For example, think of the Schroedinger’s Cat experiement being conducted in two otherwise identical universes. The scientist in Universe A opens the box to find a dead cat. In a situation with many duplicate universes, whether the particle decayed or not would have to be somehow entangled to Universe B, so that the scientist in it would also be sure to find a dead cat. This incredibly-entangled idea is not what’s being proposed by the infinite universes with many near-identical versions of me in it. It’s simply that if there are truly an _infinite_ number of independent universes, you are bound to cover every possible quantum state, so there will be infinite small variations. ---
**Author:** ![AllWalker](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@AllWalker](https://boards.straightdope.com/u/AllWalker)\ **Post date:** [December 5, 2008, 12:04am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/36 "2008-12-05T00:04:32Z")
> [@panache45](#): > > I started watching the same program as the OP, then found myself screaming at the TV, and had to turn it off. Statement #3 is NOT necessitated by statement #1. Assuming that there are an infinite number of universes does NOT mean everything is inevitable. There may just be lots of duplication. There’s no reason why there can’t be things that NEVER occur; all you need is for the things that DO occur to repeat. > > Heck, for all we know, we can have an infinite number of IDENTICAL universes. Reread point 1) - it is not just infinite number of parallel universes, but it is infinite number of parallel universes **in accordance with many worlds hypothesis**. In this hypothesis, every possible outcome, no matter its probability, occurs. So 1) actually does lead to 3), as long as there is a non-zero probability of what you are imagining occuring. > [@chronos](#): > > As a great computer once said, I’m sorry Dave, I can’t do that. Sure you can. It’s a thought experiment. Like I said, indulge me. (What you are saying is true, by the way, but pretend for the moment that it’s not. Please?) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 5, 2008, 1:13am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/37 "2008-12-05T01:13:47Z")
OK, if I pretend for the moment that we have the Many Worlds model and that the Worlds can communicate, then 0 = 1. Better? ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [December 5, 2008, 6:33am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/38 "2008-12-05T06:33:21Z")
> [@CurtC](#): > > But that would require some kind of spooky-action-at-a-distance communication between these distant universes, which we don’t think would be possible. > > For example, think of the Schroedinger’s Cat experiement being conducted in two otherwise identical universes. The scientist in Universe A opens the box to find a dead cat. In a situation with many duplicate universes, whether the particle decayed or not would have to be somehow entangled to Universe B, so that the scientist in it would also be sure to find a dead cat. > > This incredibly-entangled idea is not what’s being proposed by the infinite universes with many near-identical versions of me in it. It’s simply that if there are truly an _infinite_ number of independent universes, you are bound to cover every possible quantum state, so there will be infinite small variations. No, because not every occurrence is equally likely to occur. Likely occurrences may be identical in a large number of universes; unlikely ones may in fact never occur. If you flip a coin 1000 times, in an infinite number of universes, it’s possible that 1000 heads will never occur. There’s no reason why it must. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [December 6, 2008, 3:12pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/39 "2008-12-06T15:12:54Z")
I think the most on-point research on this question is by Max Tegmark, who points out that there must be an infinite variety of worlds out there, at unimaginable distances that must be written like 10^(10^(100+)) meters. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 6, 2008, 9:05pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/40 "2008-12-06T21:05:08Z")
> [@](#): > > If you flip a coin 1000 times, in an infinite number of universes, it’s possible that 1000 heads will never occur. There’s no reason why it must. On the other hand, if I flip a _fair_ coin 1000 times in a row, and repeat the experiment in an infinite number of universes, then I must get 1000 heads in a row in some of them (in an infinite number, in fact). Why? Because if I didn’t, then the coin would not be fair, by definition. It should be noted, by the way, that we don’t know that the Universe is infinite, and if it is, we can never prove it. The best we can say is that the simplest models which are consistent with out observations correspond to an infinite universe, but one can also come up with equally-consistent models which are only slightly more complicated, but which are finite. If the Universe is in fact finite, then it all depends on its size, and it’s almost certainly not large enough to allow for the OP’s shenanigans. [Previous page](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577.md?page=1) [Next page](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577.md?page=3)