Most absolute age determinations in geology rely on radiometric methods. The earth is billions of years old. The main condition for the method is that the production rate of isotopes stays the same through ages, i. The production of isotopes from chemical elements is known as decay rate and it is considered a constant. Because it is driven by sun activity it was always questioned. Recent article S.
See also Counterexamples to an Old Earth. Radiometric dating is a method of determining the age of an artifact by assuming that on average decay rates have been constant see below for the flaws in that assumption and measuring the amount of radioactive decay that has occurred. Because radiometric dating fails to satisfy standards of testability and falsifiability , claims based on radiometric dating may fail to qualify under the Daubert standard for court-admissible scientific evidence. It is more accurate for shorter time periods e. Radiometric dating proceeds from the fact that certain substances radioactive isotopes decay, with near-clockwork accuracy, into other elements, and that the old elements and the new elements can be chemically distinguished and can be quantitatively measured. Even the individual isotopes of an element can be accurately measured, though they can't be chemically separated. The radioactive decay of a given isotope proceeds by a well-known exponential decay function involving a "half-life" for that isotope:.
Earth's Creation and the Concept of Deep Time. The Principle of Superposition tells us that deeper layers of rock are older than shallower layers. Principle of Cross-Cutting tells us that the radiological colored granite must be older than the darker basalt dike intruding the granite. Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks.
Another approach to describing reaction rates is based on the time required for the concentration of a reactant to decrease to one-half its initial value. If two reactions have the same order, the faster reaction will have a shorter half-life, and the slower reaction will have a longer half-life. The half-life of a first-order reaction under a given set of reaction conditions is a constant. This is not true for zeroth- and second-order reactions.