1908 and rutherford and radiometric dating
In 1830, the geologist Charles Lyell, developing ideas found in Scottish natural philosopher James Hutton, popularized the concept that the features of Earth were in perpetual change, eroding and reforming continuously, and the rate of this change was roughly constant.
This was a challenge to the traditional view, which saw the history of Earth as static, with changes brought about by intermittent catastrophes.
By the process of radioactive decay of radioactive isotopes occurring in a rock, exotic elements can be introduced over time.
By measuring the concentration of the stable end product of the decay, coupled with knowledge of the half life and initial concentration of the decaying element, the age of the rock can be calculated.
This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples.
Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.
The process of solar nuclear fusion was not yet known to science.
Other scientists backed up Thomson's figures as well. Darwin of the University of Cambridge, proposed that Earth and Moon had broken apart in their early days when they were both molten.
Lomonosov's ideas were mostly speculative, but in 1779, the French naturalist the Comte du Buffon tried to obtain a value for the age of Earth using an experiment: He created a small globe that resembled Earth in composition and then measured its rate of cooling.
Thus the age of the oldest terrestrial rock gives a minimum for the age of Earth assuming that a rock cannot have been in existence for longer than Earth itself.
In 1892, Thomson had been made Lord Kelvin in appreciation of his many scientific accomplishments.
His calculations did not account for heat produced via radioactive decay (a process then unknown to science) or convection inside the Earth, which allows more heat to escape from the interior to warm rocks near the surface.
Geologists had trouble accepting such a short age for Earth.