Manufacturing universes in a fractal multiverse

I gather that the World Science Festival here in New York a week or so ago was a great success, although I was out of town for most of it. The one part of the program I was dubious about (Infinite Worlds) seems to have come off even more one-sided than planned, since David Gross couldn’t be there.

There’s a report on this at Ars Technica from someone who was sitting near Cameron Diaz while watching the program. Philosopher of science Nick Bostrom did point out the obvious, that for the multiverse to be science it has to predict something. Someone seems to have convinced the author of the piece that there actually is such a prediction:

Early in our Universe’s history (before the mulitiverse’s inflation pulled things apart), it was possible that the Universe bumped into a neighboring one. If that’s the case, there should be remnants of that event buried in the cosmic microwave background. Less than a month from now, the ESA’s Planck mission should arrive at the L2 Lagrange point with instruments sensitive enough to pick up this signal.

So, I guess in a couple years from now, we’ll know if there is a multiverse or not…

For another report, see here.

Sean Carroll reports here on some other parts of the festival, including the panel on Time Since Einstein, where he explained to the audience that “the fact that an a splattered egg cannot turn back into a pristine unbroken egg is the best evidence we have that we live in a multiverse.”

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10 Responses to Manufacturing universes in a fractal multiverse

  1. milkshake says:

    regrettably, Dr. Carroll cannot take back the splattered egg remark because it would collapse our multiverse

  2. ManyMe says:

    I think the nonsense of Sean Carroll is the best proof for the multiverse.

    If there is only one universe, it would be very unlikely that it contains physicists who make such statements.
    It is much more likely that there is a large number of universes with silly physicists trying to explain eggs and such – and we just happen to be the one with Sean Carroll in it …

  3. bjm says:

    It seems to me that whenever nature is able to do something, it does it more than once.

  4. Tim says:

    Is there a reference to a paper to back up Sean Carroll’s claim?

  5. Peter Woit says:


    There’s a paper with a student from 2004, extensive promotion of the idea in Scientific American and elsewhere, and he’s writing a book on the subject. There are some links here:

  6. Tim says:

    Hello Peter,
    thanx for the link, unfortunatly I did not really understand the paper by Collins/Chen, but I think I understand now a little better the motivation of Lubos Motl to write in one and the same sentence about a paper “I don’t understand it, but I am absolutly shure it’s crap” as he does time and again in his blog…

  7. Tomatonator says:

    I am amazed at how catty scientists can get regarding each other and their work.

    I guess you are all human, too.

  8. Peter Woit says:


    I think I understand the paper, but just don’t see how it adds up to a scientific explanation of anything. I see that Sean has a website up for the book

    including a copy of the book prologue

    where he quotes the reaction of one physicist to a talk of his about this, a reaction which I’d guess is pretty common.

    The main problem I see here, with much of the multiverse stuff, including Sean’s, is that extremely speculative ideas that most physicists don’t think deserve to be called science are being heavily promoted to the public, often in a misleading way. There was always a bit of this problem with string theory, but this is far worse.

  9. Arun says:

    …“the fact that an a splattered egg cannot turn back into a pristine unbroken egg is the best evidence we have that we live in a multiverse.”

    Since the microscopic laws of physics are (effectively) time-symmetric, all that I come up with is that there are far fewer initial conditions where splattered eggs unsplatter than where splattered eggs remain splattered. This is a fact independent of cosmology. Whole pristine eggs do not arise from a process of unsplattering, other methods are far more probable.

    I need to broaden the question – “explain a universe in which eggs and observers like myself can arise”, before there is a mystery. It remains a mystery. But it is an even deeper philosophical mystery as to how postulating an infinite number of other universes so that the asymmetry in initial conditions can somehow be erased*** constitutes an explanation.

    *** The fact that there are far fewer initial states that lead to splattered eggs unsplattering than initial states where splattered eggs remain splattered is simply a matter of counting and so remains true in each universe in the multiverse.

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