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View Diary: Stellar Evolution Measured on Earth: Clues from Ti-44 "Nuclear Fossils" (53 comments)

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  •  Moi aussi (3+ / 0-)
    Recommended by:
    NNadir, jessical, kurt
    before attending the lecture, I kind of thought that the majority of elements on earth originated in supernovae - because I haven't really seriously studied stellar evolution and mechanisms of element distributions from various types of stars
    The seminal paper is the famous B2FH of 1957, which is what I remember from my year in an astrophysics PhD program (long enough ago that the buttons on our Frieden calculators were labeled in Roman numerals). Upon reflection it makes much more sense to cook up the lighter "metals" (NB to an astrophysicist any element heavier than helium is a "metal") somewhere there's lots of helium for building blocks, & that would be the He-burning shell of an AGB star.

    I ran across the Barrow-Tipler book years & years ago, & you may be right about the latter going off the deep end, but Barrow seems to have survived more or less intact. NB there are different flavors of the Anthropic Principle, & almost no one will argue with the weak form, which boils down to observer bias: We see certain structural features in the universe because if they didn't exist we wouldn't be around to see anything. That's a helluva lot different from the strong form, which holds that the universe is specifically arranged so as to permit the evolution of intelligence.

    It's interesting to note that the fellow who coined the term "Big Bang" as a tag of derision--Fred (later Sir Fred) Hoyle --is also credited with making the first scientific prediction based purely on the anthropic principle. In 1954 he predicted a hitherto-unobserved resonance involving the helium-4, beryllium-8, and carbon-12 nuclei at about 7.6 MeV--because unless such a resonance existed, the triple-alpha process wouldn't work & there wouldn't be enough carbon in the universe for for carbon-based life like us to exist. When the physicists looked, there it was.

    Hoyle's prediction is ... a genuine scientific prediction, tested and confirmed by SUBSEQUENT experiments. Hoyle said, in effect, 'since we exist, then carbon must have an energy level at 7.6 MeV.' THEN the experiments were carried out and the energy level was measured. As far as we know, this is the only genuine anthropic principle prediction; all the rest are 'predictions' that MIGHT have been made in advance of the observations, if anyone had had the genius to make them, but that were never in fact made that way.
    Here's a nice little webpage with that quote & the rest of the story.

    snarcolepsy, n: a condition in which the sufferer responds to any comment with a smartass comeback.

    by Uncle Cosmo on Tue Jun 07, 2011 at 11:17:04 PM PDT

    [ Parent ]

    •  Thanks for that informative and stimulating... (1+ / 0-)
      Recommended by:
      Uncle Cosmo

      ...comment.

      I wasn't aware that it was Hoyle played that role in triple alpha fusion.

      I always learn from stuff people post in my diaries.

      I should really go to sleep - I've taken my "business trip" Ambien - now but may stay up a little longer to see what else I can learn about.

      •  Went to a lecture by Hoyle during that PhD year (1+ / 0-)
        Recommended by:
        NNadir

        Don't remember what he spoke about, but I do remember what happened when he was muttering & no one in the audience had the nerve to ask him to speak louder...funny story.

        Another funny story:

        The great physicist Wolfgang Pauli died & went to Heaven, where he was escorted into a classroom with YHWH Hisownself standing behind a huuuuuge black book. "Well, Dr Pauli," He said, "I'm sure you have many questions as to how I designed the Universe, and I'm here to answer them."

        Pauli immediately asked, "Why 137?"

        God smiled. "I knew you'd ask," and He opened the big book to the center. "It's all right there, starting in the middle of the page. Have a look."

        Pauli fairly leaped to the desk & began reading, a huge smile on his face--which gradually faded as he read the second page, and turned to the third--

        Suddenly he straightened up, jabbed his finger at a formula & with a look of disgust turned to the Creator and said:

        Das ist falsch!*

        ( * German for This is wrong!)

        snarcolepsy, n: a condition in which the sufferer responds to any comment with a smartass comeback.

        by Uncle Cosmo on Tue Jun 07, 2011 at 11:49:23 PM PDT

        [ Parent ]

        •  Das ist der beste Witz, den ich in dem langer (1+ / 0-)
          Recommended by:
          Uncle Cosmo

          Zeit gehört habe.

          I will definitely steal that joke.

          •  Also mussten Sie im langer Zeit (1+ / 0-)
            Recommended by:
            NNadir

            nur schlimme Witz gehören!

            Wear it in good health, don't spend it all in one place, etc. (Somehow I knew you'd be enthralled when the magic number appeared...)

            Pauli, who was infamous for demolishing bad physics (& bad physicists), once said of someone's idea that it was so bad it "wasn't even wrong". (By which he meant, IIRC, that it was too vague or imprecise to be vulnerable to falsification.)

            snarcolepsy, n: a condition in which the sufferer responds to any comment with a smartass comeback.

            by Uncle Cosmo on Wed Jun 08, 2011 at 06:55:51 PM PDT

            [ Parent ]

            •  And now we live in a time where ideas not (0+ / 0-)

              subject to falsification are all emperors wearing new clothes.

              Someday I intend to crawl out of my black hole.

              Thanks for the bits of history.   I enjoy them very much.

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