Parallel Universes

I recently read a Scientific American article on the subject of parallel universes. Interestingly this statement was made:"The simplest and most popular cosmological model today predicts that you have a twin in a galaxy about 10 to the 1028 meters from here. This distance is so large that it is beyond astronomical, but that does not make your doppelganger any less real. The estimate is derived from elementary probability and does not even assume speculative modern physics, merely that space is infinite (or at least sufficiently large) in size and almost uniformly filled with matter, as observations indicate. In infinite space, even the most unlikely events must take place somewhere. There are infinitely many other inhabited planets, including not just one but infinitely many that have people with the same appearance, name and memories as you, who play out every possible permutation of your life choices." Article Link I think it would be interesting to discuss the reasoning behind the existence of parallel universes.------------------(I noticed that there is another forum on this same topic, but it hasn't been posted to in a couple of years and I thought it would be better to start fresh.) Edited by Ender, : Removed theological mumbo-jumbo

Hello, Ender> I was reading along and was considering promoting your topic until I saw where you brought in Jesus. If you limit your discussion to science and Cosmology, we can start your topic in a science forum.If, however, you want to bring Jesus into the discussion, you might be better off attempting to start another topic for the Faith/Belief forums.Science and Faith diverge at the proverbial fork in the road. Science does not involve Faith, and Faith is not scientific.Once you decide where you want this puppy to run in, we can proceed.Other admins--feel free to comment. Ender, please get back to me.

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I Agree. Ender must make clear whether he wants to discuss the theological or scientific implications of the article.

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--	Percy
	EvC Forum Director

I wondered if that was going to be a problem. I'm really much more interested in the scientific aspects. I'll start another topic dealing with the religious aspects if that comes up in the forum.

Thread moved here from the Proposed New Topics forum.

Is it true that because of the inflationary model of the big bang that it is only a matter of distance between us and our copies in a parallel universe?The article was published in 2003, I was wondering if anything had changed with this view.Maybe cavediver or someone can answer.

This all has to be hypothetical, right? I mean...I don't see why there would be another one of meor even another universe....how do people come up with these theories? BBC - Science & Nature - Horizon - Parallel Universes

We keep seeing this gross misinterpretation of what physicists are suggesting in popular news articles, and I've even heard some physicists make statements like this out of shear sloppiness. The existence of an infinite number of universes does not imply that every conceivable universe must exist an infinite number of times, or even once. The real line between zero and one has an infinite number of points, but does not contain two or pi. The infinite number of universes can be all different but still cover a finite range of fundamental parameters.Where these ideas come from is well explained in easy to understand terms in Alan Guth's "The Inflationary Universe" which shows that a usable conceptual model for how the early universe 'inflated' to its current characteristics is given by percolation theory, which, as the name suggests, address sudden localized phase changes such as bubbles forming as a liquid starts to boil or crystals forming as a gas or liquid starts to freeze. The idea is that before the universe formed there was a, let's call it the Ultraverse, made up of a kind of space-time and lots of Higgs fields. At some local point, these fields suddenly (and here, words like 'local' and 'suddenly' have only very week metaphoric meaning since there is no 'space' or 'time' as we understand it) condense (or evaporate - you get to pick your metaphor) into particles and the volume over which this condensation takes place expands exponentially (which is sci-talk for 'grows like a bat out of hell'.)What causes this percolation to occur? Nothing. It just has a statistical probability of happening and does so somewhere. This Ultraverse can be finite (like the surface of a ball), infinite or extremely convoluted. The point is, if 'boiling' began a some point to make our universe, than there's no reason why it couldn't be taking place at (infinitely) many points, creating many or perhaps infinitely many universes. But, this does not necessarily imply that any universe has to be even approximately duplicated. But, keep in mind, at this point in (our) time, this is nothing more than a suggestive model to try to explain a physical underpinning for inflation. The theoreticians working in this field are trying to figure out if there is some telltale aspect of this model that can be observed in our universe that is evidence of the validity of the model and gives some indication of its parameters.Having said all that, I should mention that there are some suggested models that entail an infinite number of universes, but of only a finite different kinds, so that each kind must occur an infinite number of times. In this context, a 'kind' includes all the detailed history and events of any particular universe, like ours. However, this models are really little more than mathematical play things and are not seriously considered. I should also point out that while these modeled underpinnings for inflation are speculative, inflation itself is far from speculative. It is a very predictive theory, and to the extent measurements can be made, its predictions have been verified.If this topic really interests you and you are interested in explainations that are far more authoritative than you are likely to get on any internet forum, read Guth's book. It is easily digested and good fun. It can be considered to be authoritative since Guth invented the inflationary model.

Although Guth is indeed the primary originator of Inflation, your description here of a "percolation" owes more to Andrei Linde's chaotic inflation. It is not by any means accepted, and is much more just an idea behind the more conventional and accepted Guth inflation that we use in the very early universe.In any csae, this is more complicated than the scenario being proposed by Tegmark. He is simply talking about the universe being truly flat or open, and non-compactified. Despite Tegmark's own remarks, this is also completely independent of any type of inflation. Inflation only inflates what it is given, finite or infinite.The issue of infinite numbers of finite possibilities being manifested in an infinite universe has long been debated and argued over coffee, and there is no *easy* dismissal of the issue. Your own analogy fails as we are dealing with repeating exisiting probabilities. A dice with 10^1000000000000000 sides rolled an infinite number of times has equal numbers of each face turning up - an infinite number of times...Personally, I think the situation is a little more complex... will come back to this later

If the universe is infinite, or if the universe is finite but there are an infinite number of universes, then it is inevitable that there are an infinite number of other yous out there. I'm not the right person to try to offer an answer to this one, so I won't. But I will say that we do not at present know whether the universe is finite or infinite. And we don't know whether there is one universe, many universes or an infinity of universes. But the ideas about multiple universes *are* consistent with the available evidence, and there are mathematical models for them.Where's Cavediver and company when you need them?AbE: Ah, just in time!--PercyEdited by Percy, : Note arrival of Cavediver.

Depends on what you mean by "you". What makes you "you" is a combination of physical attributes and personal experiences. Even the slightest difference in an event you(1) have experienced from you(2) makes you two different persons.By the way, that wasn't my idea. Plagaerized that from a science fiction book I've read.

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AKA G.A.S.B.Y.George Absolutely Stupid Bush the Younger

My main objection to the SciAm article is to the phrase which to me gives the impression that there is some broad evidence base consensus concerning a particular infinite universes model. I think this is misleading in both the consensus and the evidence based part. Also, 'simplest' is a very relative term and belies an extremely complicated situation. Linde's contributions are well attributed in Guth's book.My point about non-repeating universes assumes the die has an (non-countably) infinite number of faces. Is there any basis for this to be rejected?My main point is that for anyone trying to get at least a veneer level appreciation of the actual scientific thought and research going into complex topics like this, reading a few paragraphs in an internet forum is unlikely to do it for them. A far better bet is to read a book that is well suited for their background. A great many of the threads at EvC that concern complex issues quickly degenerate into nonsense because someone won't just go to the library and get a well researched book on the topic. For the topic of this thread, I don't know of a better choice that Guth's book.

It's not an infinite number of universes; it is an infinite universe. There is a broad evidence based consensus on a particular universe model, and that is the Friedmann-Lemaitre-Robertson-Walker (FLRW) universe (expanded from the FRW universe upon discovery of the Lambda-like component to the universe). The FLRW, like the FRW universe, presents three possibilities: open, flat and closed. Open and flat are infinite, and closed is finite. So I would argue slightly with the SciAm presentation a little, in that the choice between open and closed is still highly debated. But it is say 50% correct. Inflation of course makes both situations look flat (one of the main reasons for considering inflation in the first place!) True, but it is still the 'simplest' model we have. This was my usual point when we had such discussions. Plenty. At least as much basis as there is for it be accepted. The argument quickly gets bogged down into quantum ontology. As much as coffee times can be greatly extended to cover such arguments, they are always bounded from above by lunch-time. As far as I am aware, there is no deep research into this area in physics... certainly not that you'll find in a book by Guth. Tegmark's ideas belong more in the set that contains Julian Barbour, David Deutsch, etc Unless that forum happens to have a couple of practioners (or ex-practitioners) in the field with a particular interest in this area...That said, I unreservedly back your recommendation to read decent scientific layman literature like that of Guth, Greene, etc.

As I suspected, this SciAm article represents an area of debate that is not very clear cut.Rather than get bogged down in how well the field of Cosmology is represented, I would like to discuss some of the basics first.For example, in a universe that is sufficiently large, is it reasonable to assume that the patterns that matter can take (such as the pattern that represents me) must eventually repeat themselves?

Some have a difficult time defining “universe” as something other than “everything everywhere,” but, the conjecture posits that what we presently see as our “universe” has a finite, though large, distribution of matter over some large but finite distance, and is but one of an infinite number of such structures. The concept of the multi-verse is born.I cannot recall any of the numbers so please excuse my lack of reference. The conjecture, as I recall, is that there is a finite number of matter particles in this “universe.” With a finite number of particles there is then a finite number of ways (exceptional large to be sure, but finite in extent) to combine those particles with each “universe” having its own unique combination of these finite number of particles. In a multi-verse of infinite universes how far away into these other universes must you get before you see a universe with an exact repeat of a matter configuration? Assuming that every possible combination of matter is posited in unique form in unique “universes” before a repeat is seen, and assuming a three-dimentional matrix of universes within the multi-verse, the OP indicates that 10 ^ a really big number of meters away there must be a universe with an exact repeat of our universe's matter configuration. In an infinite number of (finite volume, finite matter, finite configuration) Universes, then there must be an infinite number of universes with an exact repeat of the matter configuration that is you.I read the article many moons ago and have not re-read it since. I remember, however, being impressed by two points. One, if you can accept the assumptions then the logic is impeccable, and B, these guys have nothing better to do than sit around thinking of the most outlandish things.