Radiometric dating mm lab married dating in monticello illinois
Radiometric dating is based on the decay of long-lived radioactive isotopes that occur naturally in rocks and minerals.
These parent isotopes decay to stable daughter isotopes at rates that can be measured experimentally and are effectively constant over time regardless of physical or chemical conditions.
By the early 1960s, most of the major radiometric dating techniques now in use had been tested and their general limitations were known.
No technique, of course, is ever completely perfected and refinement continues to this day, but for more than two decades radiometric dating methods have been used to measure reliably the ages of rocks, the Earth, meteorites, and, since 1969, the Moon.
Until the 18th century, this question was principally in the hands of theologians, who based their calculations on biblical chronology.Some of the methods have internal checks, so that the data themselves provide good evidence of reliability or lack thereof.Commonly, a radiometric age is checked by other evidence, such as the relative order of rock units as observed in the field, age measurements based on other decay schemes, or ages on several samples from the same rock unit.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.
Bishop James Ussher, a 17th-century Irish cleric, for example, calculated that creation occurred in 4004 B. There were many other such estimates, but they invariably resulted in an Earth only a few thousand years old.