Using the potassium-argon method, Fitch and Miller were the first to measure the age of the tuff.
Their result of 212–230 million years did not agree with the age of the fossils (elephant, pig, ape and tools) so they rejected the date.
So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.
So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive.
The most recent addition to the battery of techniques is cosmogenic nuclide dating, which has been around for only two decades.
So by 1980 there was a new, remarkably concordant date for the KBS tuff, and this became the one that was widely accepted. The internet, and this site in particular, can be a powerful tool for reaching those who would never go to church.decay or the rate of other cumulative changes in atoms resulting from radioactivity. The various isotopes of the same element differ in terms of atomic mass but have the same atomic number..One half-life is the amount of time required for of the original atoms in a sample to decay.So Curtis and others redated the KBS tuff using selected pumice and feldspar samples, and obtained an age of 1.82 million years.This new date agreed with the appearance of the new skull.Some of these, such as radiocarbon and potassium argon dating, have been around for more than 50 years and are widely accepted.Other methods, such as those based on cumulative effects of radioactive decay, have been around for somewhat less time.A large number of techniques have been developed that can provide a timescale for processes that take place during the Quaternary.Many numerical dating methods had their early roots in the enthusiastic study of radioactive decay as a means of obtaining the age of the Earth.The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.