Closed system radiometric dating
The isotope potassium-40 (k-40) decays into a fixed ratio of calcium and argon (88.8 percent calcium, 11.2 percent argon).Since argon is a noble gas, it would have escaped the rock-formation process, and therefore any argon in a rock sample should have been formed as a result of k-40 decay.James Hutton, a physician-farmer and one of the founders of the science of geology, wrote in 1788, “The result, therefore, of our present inquiry is, that we find no vestige of a beginning, — no prospect of an end.” Although this may now sound like an overstatement, it nicely expresses the tremendous intellectual leap required when geologic time was finally and forever severed from the artificial limits imposed by the length of the human lifetime.By the mid- to late 1800s, geologists, physicists, and chemists were searching for ways to quantify the age of the Earth.Lord Kelvin and Clarence King calculated the length of time required for the Earth to cool from a white-hot liquid state; they eventually settled on 24 million years.James Joly calculated that the Earth’s age was 89 million years on the basis of the time required for salt to accumulate in the oceans.he question of the ages of the Earth and its rock formations and features has fascinated philosophers, theologians, and scientists for centuries, primarily because the answers put our lives in temporal perspective.
This means that lifeless organic matter is effectively a closed system, since no carbon-14 enters the organism after death, an occurrence that would affect accurate measurements.
Other methods such as Potassium-argon dating and Isochron dating are based on faulty assumptions and so unreliable as to be useless.
Many atoms (or elements) exist as numerous varieties called isotopes, some of which are radioactive, meaning they decay over time by losing particles.
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.
By the late 18th century, some naturalists had begun to look closely at the ancient rocks of the Earth.