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Smolin's two predictions, circa 2006, True ?

  1. Feb 17, 2010 #1


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    In "The Trouble with Physics" by Lee Smolin, Chapter 10, page 167, in a discussion about "fitness landscapes" as they apply to models of evolution, and, as a natural extension, Smolin suggests a "cosomological natural selection" in which Universe(s) are spawned from the interior of black holes.

    In 1992 he published two predictions, and as of the time of the books release, 2006, he claimed were still true. (as of 2006)

    One is that there should be no neutron stars more massive than 1.6 times the mass of our sun. Second, that the spectrum of fluctuations generated by inflation, observed in the cosmic microwave background, should be consistent with the simplest version of inflation, with one parameter and one inflation field.

    I did a search on the maximum mass of neutron stars and there seems to no lack of papers from the mid 80's to the present and none of them predict the smaller mass that Smolin does. They are usually in the 2 - 3.5 range.

    With advances in finding and cataloging stars of all types in the past five year's, does Smolin's prediction of solar masses of neutron starts still hold true ?

    As to his second prediction, does it hold credibility today. If not, why not ? If so, why so ?

    I threw this over the wall to the real cosmologist's who hang out here.


  2. jcsd
  3. Feb 18, 2010 #2


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    Smolin's claim for neutron masses is largely upheld. I discussed exceptions with him a few years back, but, he felt the estimates were inadequately supported. I only know of one such example that remains robust at around 2 solar masses. I find it interesting the vast majority of neutron star masses have such a discrepancy with the least massive black hole[~ 5 solar masses].
  4. Feb 18, 2010 #3


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    In doing a little more research, this http://worldofweirdthings.com/2009/12/05/searching-for-the-biggest-stars-in-the-cosmos/" [Broken] published Dec 5, 2009 states, and says that neutron stars cannot be formed unless they reach the end of their life having more than 1.5 times the mass of our sun.

    This is different than ending up with a mass of less than or equal to 1.5 the mass of our sun as a neutron star. Is this in fact what Smolin was referring to ? And second, is the source of the data, I assume Nature, reliable and trustworthy to quote ?
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  5. Feb 18, 2010 #4
    There are two limits, the white dwarf <-> NS limit, and the neutron star <-> black hole limit. Smolin is more interested in the latter one.

    Depends on what it's to be quoted for. One problem is that even in good journals like Nature, when they have articles for the non-technical reader they sometimes say things that are oversimplified or misleading. For a college term paper it's fine. For a professional article, you'd probably want to quote papers that do the original calculation if for no other reason than to show that you are familiar with the literature.
  6. Feb 18, 2010 #5
    The papers in the early 1970's were talking about 7-8 solar mass limits. Over time, the masses tend to decrease for a physical reason. Basically the limit depends on how soft nuclear material is, and how soft it is depends on the number of particle processes. The more types of particle reactions, the more ways there are for the energy within the material to get distributed and the softer things are. (One way of thinking of this is imagine hitting a brick versus hitting a beanbag).

    Over time people have found more processes, and this causes the mass limit estimate to go down.
  7. Feb 18, 2010 #6
  8. Feb 18, 2010 #7


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    What you said makes perfect sense, but the ultimate test is to compare the revised theory to new measurements of neutron star masses, I assume that measurement technology has progressed and is more in line with the latest predictions.

    Is there any consensus in the physic's community about Smolin's second prediction, or is it simply too "sparse" to begin with ?

  9. Feb 18, 2010 #8
    Personally, I'm not too impressed by the prediction. If he made the prediction in 1975, that the black hole cut off was 1.6 solar mass, that would turn heads since it was very different from the conventional wisdom at the time. A prediction in 1992 that the cutoff would be 1.6 isn't particularly impressive since the conventional wisdom at the time that the EOS would be soft.

    Also, I have to look at Smolin's logic behind that prediction since it seems to me to have a huge gap. From arXiv:hep-th/0612185 he seems to be assuming things about the supernova mechanism that aren't obviously true to me. One other thing is that if there is an observational limit to neutron stars, it's not clear at this point that it's because that is the limit is due to a black hole limitation. We don't understand very much about supernova explosions, and it's very well possible that neutron stars of 2.0 solar masses are physically possible, but that the explosion always behaves in such a way that only 1.5 solar masses are left.
  10. Feb 21, 2010 #9


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    Thanks for the expert opinion on the subject. Without a understanding of what Smolin really meant when he made the comment, it is hard to know for sure, I scanned the page before and after it, looking for clues and could find none to add meaning to his statement to begin with. With what you said in your previous post,
    explains why he may have made the prediction in the first place. No big deal. Thanks for the info.

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