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Tales from the multiverse. AFP publishes a story about the theoretical possibilities of so-called parallel universes:

"The idea of multiple universes is more than a fantastic invention — it appears naturally within several scientific theories, and deserves to be taken seriously," said Aurelien Barrau, a French particle physicist at the European Organization for Nuclear Research (CERN), hardly a hotbed of flaky science.

"The multiverse is no longer a model, it is a consequence of our models," explained Barrau, who recently published an essay for CERN defending the concept.

There are several competing and overlapping theories about parallel universes, but the most basic is based on the simple, if mind-boggling, idea that if the universe is infinite then logically everything that could possible occur has happened or will happen.

Try this on for size: a copy of you living on a planet and in a solar system like ours is reading these words just as you are. Your lives have been carbon copies up to now, but maybe he or she will keep reading even if you don't, says Max Tegmark, a cosmologist at MIT in Boston, Massachusetts.

The existence of such a doppleganger "does not even assume speculative modern physics, merely that space is infinite and rather uniformly filled with matter as indicated by recent astronomical observations," Tegmark concluded in a study of parallel universes published by Cambridge University.

"Your alter ego is simply a prediction of the so-called concordance model of cosmology," he said.

They tie it in to The Golden Compass, but the concept has been around for years in science fiction and fantasy writing. Robert Heinlein wrote a lot of his later stuff about that exact concept. So have a lot of others. (I can't remember off the top of my head who wrote the science fiction short story about a man going for a walk in the fog and losing his place in the multiverse. The idea that a light shining through fog represented the multitude of possible universes has stuck with me even if the name of the author escapes me at the moment. Was it Larry Niven?) These articles pop up now and again in the media, by the way. Search "parallel universe" on Google. Here's one example from 2003.

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13 Responses to Dopplegangers-R-Us

  1. Mwalimu Daudi says:

    The problem with these parallel “universes” is that they cannot be proven to exist. By definition, that are completely separate our own universe, and therefore inaccessible to us. If we could “reach” them (by using some sort of Star Trek alien machine like the one that was used in one of the worst episodes of the original series), then they are not really “parallel” at all. For this same reason we cannot even prove – however indirectly – that they exist.

    One of the more popular theories that I have encountered is by Andre Linde, who speculated that our universe is one of many infinitely possible ones formed out of a kind of “superuniverse”. It, too, is a consequence of the cosmological theory being advanced. But it, too, is completely unprovable.

    On the other hand… what Tegmark seems to be suggesting is not really a parallel universe at all, but a variation of the “infinite number of monkeys” theory. If there are an infinite number of monkeys each with a typewriter, one of them will eventually produce the complete works of Shakespeare. Tegmark seems to be saying they might be two or more such monkeys in our universe.

    The problem that I have with Tegmark’s theory is that it, too, is unprovable. Short of completely exploring an infinite universe how could you disprove it? One could always argue that the mythical doppelganger is just in the next solar system. If not that one, then for sure the next one. Or the next. Or the next. Or…do you see my objection? I think that at some point Occam’s Razor should make itself felt.

  2. McGehee says:

    I believe the “walk in the fog” story is from Larry Niven’s collection “All the Myriad Ways,” one of two on the multiverse theme in that book. I forget what the “lost in the fog” story was called, but the other story was called … um, “All the Myriad Ways.”

  3. feeblemind says:

    It seems like I remember reading about a team form Oxford(?) that recently published a paper mathematically proving that parallel universes could exist. This gets into the realm where things get too complex for my feeble mind. But here is where it doesn’t add up for me. Let’s pick on Gaius. Suppose in another universe he adds another post to his blog while in this one he does not. Where does all the mass and energy and what not to create an entire universe from one random act come from? I just don’t see how it can happen, but maybe someone can explain it?

  4. Mwalimu Daudi says:

    When I was an engineering graduate student, a mathematics prof set up differential equations that indicated that the very tip of a bullwhip (or even a dangling necklace) was a singularity that traveled at an infinite speed. But that violates Einstein’s relativity theory, right? What the prof was trying to show us was the danger of using mathematical equations without taking into account the limits in the assumptions behind the equations.

    Feeblemind has an excellent point about energy. I clicked in Gaius’ link, and was only able to access the beginning of the article. The author (also Tegmark, by the way) said that his estimate about the existence of doppelgangers “is derived from elementary probability and does not even assume speculative modern physics.” But what happens when physics – and its limitations – rears it ugly head?

    One other note – I was startled to read in the AFP article that space is both infinite and uniform. I thought that the existence of background radiation (which was used to bolster the case for the Big Bang theory) put a limit on the size of the universe, since we are supposedly still surrounded by this gigantic shell of super-hot matter racing away from us as the universe expands. Is this theory now out of favor?

  5. Mwalimu Daudi says:

    As if I have not posted enough on this thread (but I do so love physics and mathematics)….

    Peter Ward and Donald Brownlee (a pathologist and astronomer, respectively) are the authors of Rare Earth, a book that hypothesizes that complex forms of life such as plants and animals may be extremely rare in the universe.

    If their theory is true, then that would be a powerful blow to Tegmark’s doppelganger hypothesis.

  6. Mwalimu Daudi says:

    Sorry – in my last post Ward is a paleontologist, not a pathologist. Don’t know what I was thinking…

  7. NortonPete says:

    Mwalimu ,
    You are referring to cosmic microwave background or CMB. Although a recent study found that there was some matter missing, I don’t think the overall theory has changed since this 2004 article. The universe is said to be 13.7 billion years old.

    from scienceastronomy/mystery_monday_040524.html

    Hall of mirrors

    The scientists studied the cosmic microwave background (CMB), radiation unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Temperature differences in the CMB left an imprint on the sky that was used last year to reveal the age of the universe and confirm other important cosmological measurements.

    The CMB is like a baby picture of the cosmos, before any stars were born.

    The focus of the new work, which was published last week in the journal Physical Review Letters, was a search of CMB data for paired circles that would have indicated the universe is like a hall of mirrors, in which multiple images of the same object could show up in different locations in space-time. A hall of mirrors could mean the universe is finite but tricks us into thinking it is infinite.

    Think of it as a video game in which an object disappearing on the right side of the screen reappears on the left.

    “Several years ago we showed that any finite universe in which light had time to ‘wrap around’ since the Big Bang would have the same pattern of cosmic microwave background temperature fluctuations around pairs of circles,” Cornish explained. They looked for the most likely patterns that would be evident in a CMB map generated by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP).

    They didn’t find those patterns.

  8. martian says:

    My, oh, my! I do love a good scientific discussion in the middle of all the election hype. It’s like taking a literary vacation! Thanks, Gaius.

  9. Gaius says:

    I try to mix things up – otherwise, it can be dull to read – and duller to write!

  10. Mwalimu Daudi says:

    Thanks, NortonPete!

  11. Bleepless says:

    The Niven story is “Of a Foggy Night.” Fog occurs when the normal atmospheric water comes together from several alternates.
    Try Ward Moore’s “Bring the Jubilee,” which takes place in a rather nasty world wherein the Confederacy won. For an even nastier one, Philip K. Dick’s “The Man in the High Castle” is mostly in San Francisco, in a country called the Pacific States of America, about 15 years after the United States surrendered unconditionally in WWII. Try to figure out who or what is really what he, she or it appears to be. Harry Turtledove (yes, that is his real name — at least, on this timeline) has written dozens of alternate history novels; I still think that his best is “The Last Article,” a short story about Gandhi and Nehru versus Field Marshall Walter Model, Nazi military governor of occupied India.
    For mini-descriptions of every alternate history piece the proprietor coud find, see the website Uchronia.

  12. sam says:

    I used to read Discover Magazine and every once in a while one of the parallel/multiple/infinite universe articles would crop up. It made for interesting reading but in every case it was based on some mathematical manipulation and was an untestable or unprovable hypothesis. Which makes the idea some combination of idle speculation and religious belief.

  13. I personally prefer Erci Flint’s 1632 universe. Small town in West Virginia gets hit by a chunk of Alien Experiment gone wrong and get’s sent back to the middle of the Thirty Year War. (Shameless plug) You should really think about buying “The Ring of Fire” an anthology set in the 1632 Universe; quite a few authors in that anthology are known to blog…………….

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