On this date, Arthur Holmes
, one of the foremost geologists of the twentieth century, was born in England. He developed a method of determining the age of the Earth based on the radioactive decay of uranium in igneous rocks (which invalidated Lord Kelvin’s hypothesis that the Earth’s age can be established on the basis of the planet’s cooling from a initial molten state). Holmes’ method proved to be remarkably accurate and laid the foundation of isotope geology
. This was the first quantitative time scale for geology based on measuring the radioactive constituents of rocks.
Cherry Lewis, The Dating Game: One Man’s Search for the Age of the Earth (Cambridge, UK: Cambridge University Press, 2000).