Dating how old friends to dating quotes
The discovery of radioactivity in 1896 by Henri Becquerel, the isolation of radium by Marie Curie shortly thereafter, the discovery of the radioactive decay laws in 1902 by Ernest Rutherford and Frederick Soddy, the discovery of isotopes in 1910 by Soddy, and the development of the quantitative mass spectrograph in 1914 by J. Thomson all formed the foundation of modern isotopic dating methods.But it was not until the late 1950s that all the pieces were in place; by then the phenomenon of radioactivity was understood, most of the naturally occurring isotopes had been identified and their abundance determined, instrumentation of the necessary sensitivity had been developed, isotopic tracers were available in the required quantities and purity, and the half-lives of the long-lived radioactive isotopes were reasonably well known.The point is that not all methods are applicable to all rocks of all ages.One of the primary functions of the dating specialist (sometimes called a geochronologist) is to select the applicable method for the particular problem to be solved, and to design the experiment in such a way that there will be checks on the reliability of the results.
Until the 18th century, this question was principally in the hands of theologians, who based their calculations on biblical chronology.
The K-Ar clock works primarily on igneous rocks, i.e., those that form from a rock liquid (such as lava and granite) and have simple post-formation histories.
It does not work well on sedimentary rocks because these rocks are composed of debris from older rocks.
There were other estimates but the calculations were hotly disputed because they all were obviously flawed by uncertainties in both the initial assumptions and the data.
Unbeknownst to the scientists engaged in this controversy, however, geology was about to be profoundly affected by the same discoveries that revolutionized physics at the turn of the 20th century.The main point is that the ages of rock formations are rarely based on a single, isolated age measurement.