Radioactive age dating
Because of the expensive equipment necessary and the combination of geologic, chemical, and laboratory skills required, geochronology is usually carried out by teams of experts.
Most geologists must rely on geochronologists for their results.
Likewise, the conditions that must be met to make the calculated age precise and meaningful are in themselves simple:isochron methods that make use of the rubidium-strontium or samarium-neodymium decay schemes, a series of rocks or minerals are chosen that can be assumed to have the same age and identical abundances of their initial isotopic ratios.
The results are then tested for the internal consistency that can validate the assumptions.
Although it is impossible to predict when a particular atom will change, given a sufficient number of atoms, the rate of their decay is found to be constant.
The situation is analogous to the death rate among human populations insured by an insurance company.
By way of explanation it can be noted that since the cause of the process lies deep within the atomic nucleus, external forces such as extreme heat and pressure have no effect.
The age calculated is only as good as the existing knowledge of the decay rate and is valid only if this rate is constant over the time that elapsed.
Fortunately for geochronology, the study of radioactivity has been the subject of extensive theoretical and laboratory investigation by physicists for almost a century.
The particles given off during the decay process are part of a profound fundamental change in the nucleus.
To compensate for the loss of mass (and energy), the radioactive atom undergoes internal transformation and in most cases simply becomes an atom of a different chemical element.