It therefore seems probable that those concerned with the debate about the age of the Earth would have known of Perry's argument. So why was the argument not accepted in the decade before radioactive heat became established or, indeed, thereafter?

Part of the explanation may be that the debate often descended to the use of rhetoric in place of scientific argument. Kelvin (1899) cites many examples of rhetoric from his opponents and, while Kelvin himself was generally quite measured in his replies, P.G. Tait (in his self-appointed role as Kelvin's bulldog) did not hesitate to respond in kind (Lindley, 2004, p. 175–178) (see also letters from Tait, quoted in Perry, 1895a). Faced with all this hot air, Mark Twain (1903) concluded, “As Lord Kelvin is the highest authority in science now living, I think we must yield to him and accept his view.” Perhaps a parallel sentiment led to Kelvin's view being supplanted by Rutherford's, after 1904.

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We are left with the question as to why the myth persists that the discovery of radioactivity simultaneously proved Kelvin wrong and provided the explanation for his error. Part of the answer, perhaps, is that it makes a good story. Rutherford's biographer (Eve, 1939) reports that he repeated his tale of thinking on his feet in front of the “old bird” Kelvin on many occasions; it is entirely possible that the pleasing form of the anecdote, and the eminence of its author, led to the uncritical acceptance of the myth. As Stephen Gould (who himself propagated this myth) wrote: “The most erroneous stories are those we think we know best—and therefore never scrutinize or question” (1996). It is hard to dissuade aging scientists, as they slip into their anecdotage, from repeating stories that they find amusing, but their younger colleagues must not mistake such stories for the history of science.