Caption: A diagram of the triple-alpha process.

An anthropic principle legend:

1. The triple-alpha process in the diagram looks like a straightforward chain of binary nuclear reactions, but beryllium-8 is a highly unstable radioactive isotope (i.e., it is subject to spontaneous radioactive decay) with super-short half-life 6.7(17)*10**(-17) seconds, and so it was thought circa 1950 that the second nuclear reaction would almost NEVER occur and that carbon in the universe could NOT be produced this way.

2. In 1953, Fred Hoyle (1915--2001) hypothesized the existence of a resonance reaction that enhanced the second nuclear reaction

         ⁸Be + ⁴He → ¹²C + γ

   which is exothermic with a release of 7.367 MeV of energy which is probably mostly in the emitted gamma ray (γ) (see Wikipedia: Triple-alpha process).

   This resonance reaction was discovered soon thereafter by experiment (see Wikipedia: Triple-alpha process: Discovery).

3. The legend has developed that Fred Hoyle's hypothesis was an early explicit use of the anthropic principle (without using that term) in an extended sense: since carbon exists (and therefore we could exist), the relevant resonance reaction must exist.

   But Fred Hoyle did NOT use anthropic principle reasoning in presenting his hypothesis nor does it seem to have been in his thoughts in 1953 (see Helge Kragh, 2010, "When is a prediction anthropic? Fred Hoyle and the 7.65 MeV carbon resonance").

   A hypothetical person could have used anthropic principle to predict the triple-alpha process, but none did.

   So the prediction of the triple-alpha process CANNOT be used for arguing for for anthropic principle as a useful scientific principle for discovery.