Radiocarbon dating provides us with the opportunity to "order time." Determining when something happened based on the age of land formations or artifacts, or figuring out in what order certain events happened, can be crucial to understanding human culture and environmental changes. Radiocarbon dating has significantly changed humans' approach to history during the last 50 years.
How Radiocarbon Dating Works
Three types of carbon occur naturally in living material: C12, C13 and C14. Carbon14 (C14) is unstable and present in a very small percentage relative to the other components. The rate of decay (or half-life) of C14 was proven linear, allowing scientists to determine the approximate date of the expiration of a life form based on the amount of C14 remaining in the fossil. This dating can be used on once-living items and can provide information on related spaces. For example, an age can be estimated for a strata of rock based on the age of the skeletons it holds.
Carbon was first used for dating by Willard F. Libby, a professor at the University of Chicago, in 1949. Libby compared C14 samples from wood in an Egyptian tomb with that from living trees to determine the half-life of C14. He then conducted experiments on other samples and realized that the numbers held consistent. For his work, Libby received the Nobel Prize in Chemistry in 1960. The colleague who nominated him noted: "Seldom has a single discovery in chemistry had such an impact on the thinking of so many fields of human endeavour. Seldom has a single discovery generated such wide public interest."
Uses of Radiocarbon Dating
Carbon dating was initially used by archeologists to date discoveries and add (or confirm) necessary context for a find. One of the second groups to use radiocarbon dating was that of climate scientists, who were interested in the facts about human evolution and how it was shaped by climate change. Carbon dating is also used to search for evidence of cosmic ray activity, which may provide a sense of past astronomical events and potentially reveal a pattern. C14 is widely used as a biomedical tracer to help trace the path/rate of absorption of various chemicals throughout the body.
Despite the information provided through radiocarbon dating, the process does have its limitations. Samples must be large enough to allow for purification, and they need to be carefully removed and packaged to prevent any chance of contamination. Also, because of the relatively small amount of C14 in life forms and the long half-life, dating is not accurate for recent samples or for those beyond nine half-lives, or approximately 50,000 years. As well, the ratio of C14 in the atmosphere fluctuates slightly over time.
Carbon dating began with one lab and is now done in more than 130 labs worldwide. It is seen by many scientists to be crucial for making the connection between the past, the present and the future. Climatologists want to understand the correct timing of past warming, thawing and freezing cycles so that they can understand the likelihood of future cycles. Anthropologists and archeologists want to have factual dates so that they can understand the spread of cultures across the world. The discovery of radiocarbon dating, while over 50 years old, still provides new opportunities to scientists on a regular basis.
- C14 Dating: The Method
- "Radiocarbon Dating: An archaeological perspective"; R.E. Taylor; 1987.
- American Institute of Physics: Uses of Radiocarbon Dating
- BBC: Radiocarbon Dating
- The Regents of the University of California: Chronological Methods 8 -- Radiocarbon Dating
- Photo Credit fossils image by ZoltÃ¡n Pataki from Fotolia.com
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