Scientific problems with carbon dating
The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.The approximate time since the organism died can be worked out by measuring the amount of carbon-14 left in its remains compared to the amount in living organisms.Over the years, carbon 14 dating has also found applications in geology, hydrology, geophysics, atmospheric science, oceanography, paleoclimatology and even biomedicine.Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms.The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. It is found in the air in carbon dioxide molecules.The amount of carbon-14 in the air has stayed the same for thousands of years.Scientific American Editor Michael Moyer explains the process of radiocarbon dating.
Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.An age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against an internationally used reference standard.The impact of the radiocarbon dating technique on modern man has made it one of the most significant discoveries of the 20th century.There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.Once an organism dies, it stops taking in carbon-14.There are three principal techniques used to measure carbon 14 content of any given sample— gas proportional counting, liquid scintillation counting, and accelerator mass spectrometry.Gas proportional counting is a conventional radiometric dating technique that counts the beta particles emitted by a given sample. In this method, the carbon sample is first converted to carbon dioxide gas before measurement in gas proportional counters takes place.This scintillator produces a flash of light when it interacts with a beta particle.A vial with a sample is passed between two photomultipliers, and only when both devices register the flash of light that a count is made.It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.