From: Stephen E. Jones <sejones@iinet.net.au>
[...]
>Here is an example of how a type of `design inference' made a major
>contribution to science:
>
>---------------------------------------------------------------------------
>In 1952, Ed Salpeter, an American astrophysicist, suggested (more or
>less in desperation) that carbon-12 might be produced in a very rapid
>two-step process, with two alpha particles colliding to form a nucleus
>of beryllium-8, which was then in turn hit by a third alpha particle in
>the 10^-17 seconds before it had time to disintegrate. Since this did at
>least give 10^-17 seconds for the third particle to arrive, instead of
>requiring three to meet simultaneously, it was an improvement on the
>triple-collision idea. But since the arrival of a third particle might very
>effectively smash the unstable beryllium-8 nucleus to bits, it wasn't
>much of an improvement. Then, Fred Hoyle, who had, back in 1946
>written a classic paper expounding the idea that the chemical elements
>were made in stars, entered the story.
>
>Hoyle's Anthropic Insight
>
>Hoyle (now Sir Fred) was based in Cambridge, England, but in the 1950s
>spent time in California, working with his friend, nuclear physicist Willy
>Fowler. Hoyle puzzled over the problem of how hearty nuclei might be
>built up in stars (stellar nucleosynthesis), and became intrigued by the
>possibility that the energy levels of beryllium, helium, and carbon might
be
>- just right to encourage the two-step reaction Salpeter had proposed. It
all
>hinged on a property known as resonance.
>
>Resonance works like this. When two nuclei collide and stick together, the
>new nucleus that is formed carries the combined mass-energy of the two
>nuclei, plus the combined energy of their motion, their kinetic energy (and
>minus a small amount of energy from the strong force, the binding energy
>that holds the new nucleus together). The new nucleus "wants" to occupy
>one of the steps on its own energy ladder, and if this combined energy from
>the incoming particles is not just right then the excess has to be
eliminated,
>in the form of leftover kinetic energy, or as a particle ejected Prom the
>nucleus. This reduces the likelihood that the two colliding nuclei will
stick
>together; in many eases, they simply bounce off each other and continue to
>lead their separate lives. If everything meshes perfectly, however, the new
>nucleus will be created with exactly the energy that corresponds to one of
>its natural levels (it can then, of course, emit packets of energy and hop
>down the steps to the lowest; level). In that ease, the interaction will
>proceed verry effectively, and the conversion of lighter nuclei into a
heavier
>form will be complete. This matching of energies to one of the levels
>appropriate for the new nuclei is the effect known as resonance, and it
>depends crucially on the structure of the nuclei involved in the
collisions.
>
>In 1954, Hoyle realised that the only way to make enough carbon inside
>stars is if there is a resonance involving helium-4, beryllium-8, and
carbon-
>12. The mass-energy of each nucleus is fixed and cannot change; the
>kinetic energy that each nucleus has depends on the temperature inside a
>star, which Hoyle could calculate. Using that temperature calculation,
>Hoyle predicted that there must be a previously undetected energy level in
>the carbon-12 nucleus, at an energy that would resonate with the combined
>energies, including kinetic energy, of its constituent parts, under the
>conditions prevailing inside stars. He made a precise calculation of what
>that energy level must be, and he cajoled Willy Fowler's somewhat
>sceptical nuclear physics colleagues until they carried out experiments to
>test his prediction. To the astonishment of everyone except Hoyle, the
>measurements showed that carbon-12 has an energy level just 4 percent
>above the calculated energy. This is so close that the kinetic energies of
the
>colliding nuclei can readily supply the excess. This resonance greatly
>increases the chances of a helium-4 and a beryllium-8 nucleus sticking
>together, and ensures that enough alpha particles can be fused into carbon
>nuclei inside stars to account for our existence.
>
>The remarkable nature of Hoyle's successful prediction cannot be
>overemphasised. Suppose, for example, that the energy level in carbon had
>turned out to be just 4 percent lower than the combined energy of helium-4
>and beryllium-8. There is no way that kinetic energy could subtract rather
>than add the difference, so the trick simply would not have worked. This is
>made clear when we look at the next putative step in stellar
>nucleosynthesis, the production of oxygen-16 from a combination of
>carbon-12 and helium-4. When a carbon-12 nucleus and a helium-4 nucleus
>meet, they would fuse into oxygen if there were an appropriate resonance.
>But the nearest oxygen-16 resonance has one percent less energy than
>helium-4 plus carbon-12. But that 1 percent is all it takes to ensure that
this
>time resonance does not occur. Sure, oxygen-16 is manufactured in stars,
>but only in small quantities (at least, at this early stage of a star's
life)
>compared with carbon. If that oxygen energy level were 1 percent lower,
>then virtually all the carbon made inside stars would be processed into
>oxygen, and then (much of it) into heavier elements still. Carbon-based
life
>forms like ourselves would not exist.
>
>Most anthropic arguments are made with the benefit of hindsight. We look
>at the Universe, notice that it is close to flat, and say, "Oh yes, of
course, it
>must be that way, or we wouldn't be here to notice it." But Hoyle's
>prediction is different, in a class of its own. It 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 in that way.
>
>Hoyle's remarkable insight led directly to a detailed understanding of the
>way in which all of the other elements are built up from hydrogen and
>helium inside stars. He worked closely with Willy Fowler on this, and with
>the husband-and-wife team Geoffrey and Margaret Burbidge. Fowler
>(without Hoyle) later received a Nobel Prize for his part in the study of
>stellar nucleosynthesis.
>
>This combination of coincidences, just right for resonance in carbon-12,
>just wrong in oxygen-16, is indeed remarkable. There is no better evidence
>to support the argument that the Universe has been designed for our
>benefit-tailor-made for man.
>
>(Gribbin J. & Rees M., "Cosmic Coincidences: Dark Matter, Mankind, and
>Anthropic Cosmology", Bantam Books: New York, 1989, pp.244-247)
>---------------------------------------------------------------------------
[...]
I fail to see how this is an example of a "genuine anthropic principle
prediction." Hoyle noticed some property of nature--that carbon-12 is
produced in stars--and gave an explanation of this property, from which he
made a prediction. He didn't need the anthropic principle in order to make
this prediction.
Richard Wein (Tich)
--------------------------------
"Do the calculation. Take the numbers seriously. See if the underlying
probabilities really are small enough to yield design."
-- W. A. Dembski, who has never presented any calculation to back up his
claim to have detected Intelligent Design in life.
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