The age of the Earth and of the Sun and the Universe are central questions for mankind.CJ Allègre, G Manhes, C Göpel. 1995. The age of the Earth, Geochim. Cosmochim. Acta 59:1445--1456
Until the 19th century the ages were unknown; however, at that time with the advent of modern time, a significant debate arose concerning the age of the Earth. Geologists with their prestigious leaders Lyell and Darwin defended an old age, estimated to be several tenths of billions of years, while physicists tended to defer to Lord Kelvin who claimed that the Earth was not older than a few tens of millions of years.
Whereas physicists have physical laws and calculations, geologists only have simple observations of geological phenomena: the erosion rates of mountains, sedimentation rates, and the amount of volcanic eruptions today compared to the total amount of volcanic rocks, and maybe just intuition, but geologists were right (Thomson (Lord Kelvin), 1899; Darwin, 1859; Lyell, 1930; Rutherford and Soddy, 1902). The Earth is not 20 to 100 million years old as Kelvin thought, but rather billions of years as Lyell (1930) claimed. the debate was resolved when the physicist Rutherford (1929) used the newly discovered radioactivity for measuring ages of rocks and soon obtained an age of billions of years using the U-He method.
In the middle of this century, Hubble's observations initiated a second debate. This time the target was the age of the Universe (Hubble, 1929). Astronomers and geologists fought about that, and again the geologists were right.