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.Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.Mountains have been built and eroded, continents and oceans have moved great distances, and the Earth has fluctuated from being extremely cold and almost completely covered with ice to being very warm and ice-free.A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved.However, by itself a fossil has little meaning unless it is placed within some context.Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. As we age, our hair turns gray, our skin wrinkles and our gait slows.
All isotopes of a given element have the same number of protons in each atom.As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.In a separate article (Radiometric dating), we sketched in some technical detail how these dates are calculated using radiometric dating techniques.The age of the fossil must be determined so it can be compared to other fossil species from the same time period.Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.So, we rely on radiometric dating to calculate their ages. From left to right, the isotopes are protium ( Isotopes are variants of a particular chemical element which differ in neutron number. The fact that each isotope has one proton makes them all variants of hydrogen: the identity of the isotope is given by the number of neutrons.