In article , "Richard D.
Saam" writes:

Lord Kelvin(1824 - 1907) did not have the radioactivity concept
available to him
(he did not believe Marie Curie's 1867- 1934 radioactivity)
and thermodynamically predicted the earth's age at 20-200 million years
(off by factor of thousands).

Even 20 million to 4 billion is a factor of only 200. Yes, he was very
wrong, but not by a factor of thousands.

In his famous estimate of the age of the Earth, he did include the
caveat "unless another source of energy is found", as, indeed, it was.