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When is a prediction anthropic? Fred Hoyle and the 7.65 MeV carbon resonance

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The case of Fred Hoyle’s prediction of a resonance state in carbon-12, unknown in 1953 when it was predicted, is often mentioned as an example of anthropic prediction. An investigation of the historical circumstances of the prediction and its subsequent experimental confirmation shows that Hoyle and his contemporaries did not associate the level in the carbon nucleus with life at all. Only in the 1980s, after the emergence of the anthropic principle, did it become common to see Hoyle’s prediction as anthropically significant. At about the same time mythical accounts of the prediction and its history began to abound. Not only has the anthropic myth no basis in historical fact, it is also doubtful if the excited levels in carbon-12 and other atomic nuclei can be used as an argument for the predictive power of the anthropic principle, such as has been done by several physicists and philosophers.

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... Furthermore, this state would most likely have a 0 + spin-parity. While such a state at ∼ 7.6 MeV had been measured previously (and subsequently not-detected in later experiments) [5], this renewed insight into the triple-alpha process allowed for measurement of a state at 7.65 MeV, only 30 keV from where Fred Hoyle had predicted it to exist [6]. It is for this reason that this 0 + 2 state in 12 C carries his name. ...
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The structure of the Hoyle state, a near-threshold 0⁺ state of extreme astrophysical significance in ¹²C has long been investigated. An experiment was performed to measure the branching ratio for the decay of this state directly into 3 α-particles. Such a branching ratio is expected to be a good observable for whether the resonance can be described as a dilute gas of α- particles known as an α-condensate. This experiment gave the best upper limits to date for this direct decay via the improvement of the traditionally used DDΦ model to isotropic decay to the available phase space. The new DDP² model includes three-body penetrabilities and gives a limit of < 0.026% (95% C.L.), a factor of 5 improvement over the previous experimentally obtained limit.
... Strong Anthropic Principle (SAP) says: The Universe must have those properties which allow life to develop within it at some stage in its history (Carter 1974). Some authors (see Kragh 2010) argue that the excited levels in 12 C and other atomic nuclei can be used as an argument for the predictive power of the anthropic principle. ...
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... Since carbon is crucial to the existence of life as we know it, and indeed probably for existence of any physical living beings (because there seems to be no alternative to polypeptide chains for creating molecules of the required complexity), one can legitimately regard existence of Hoyle's energy level as an anthropic requirement. Hoyle himself did not make that link at the time of his discovery, but seems to have done so later [34]; one can claim that anthropic requirements predict existence of this state. This is an instance of use of SAP to make a prediction, as originally proposed by Carter in his 1974 paper. ...
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