Radiocarbon dating tools
Biostratigraphy: One of the first and most basic scientific dating methods is also one of the easiest to understand.Layers of rock build one atop another — find a fossil or artifact in one layer, and you can reasonably assume it’s older than anything above it.And if the assumptions are questionable, what about the results?How many individuals who submit samples for dating understand the limitations of the dating results? There is no loss of C14 except by radioactive decay.Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating.These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating.A certain amount of carbon in the living plant or animal tissue is C14, usually obtained in the form of C14O2 from its environment. According to the technical monograph, Origin and destiny of the Earth’s Magnetic Field (Barnes, Thomas G., “Origin and Destiny of the Earth’s Magnetic Field,” Technical Monograph number 4, Second Ed., 1983, p.In a stable environment, the amount of C14 is in equilibrium; that is, the amount of decay equals the amount of new C14 taken in. 17), the magnetic field is decaying as a first order exponential with a half life of 1,400 years, a number much less than the 5,700 year half life of C14.
A submethod within biostratigraphy is faunal association: Sometimes researchers can determine a rough age for a fossil based on established ages of other fauna from the same layer — especially microfauna, which evolve faster, creating shorter spans in the fossil record for each species.
Sometimes only one method is possible, reducing the confidence researchers have in the results. “They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.” Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts.
Methods fall into one of two categories: relative or absolute.
Archaeologists, anthropologists and others involved in researching things of the past have used the tools of radiocarbon (C14) dating as a supposedly accurate measurement of time in past history by which they could correlate activities from remote parts of the world.
As the method has been used and the procedures improved with modern technology, the assumptions on which the method has been based have been brought into question.
Chances are, right now, you have a Gregorian calendar stuck to your wall.