Seventy years ago, American chemist Willard Libby devised an ingenious method for dating organic materials. His technique, known as carbon dating, revolutionized the field of archaeology. Now researchers could accurately calculate the age of any object made of organic materials by observing how much of a certain form of carbon remained, and then calculating backwards to determine when the plant or animal that the material came from had died. An isotope is a form of an element with a certain number of neutrons, which are the subatomic particles found in the nucleus of an atom that have no charge. While the number of protons and electrons in an atom determine what element it is, the number of neutrons can vary widely between different atoms of the same element. Nearly 99 percent of all carbon on Earth is Carbon, meaning each atom has 12 neutrons in its nucleus.
Though archaeologists can come up with good guesses about the date of artifacts through different processes, most methods of dating are trumped by a relatively new technique called radiocarbon dating. Developed in , it is considered the most useful way of determining the dates of artifacts for archaeologists. Since 14 C is radioactive, it decays at a relatively quick exponential rate Figure 1 , while non-radioactive carbon 12 C does not. While Libby noted that radiocarbon dating remains effective because the amount of 14 C produced in the atmosphere does not vary with time, this may not always be the case. Fossil fuel emissions have undoubtedly raised the amount of 12 C in the atmosphere, with there being an upward trend in in the metric tons of Carbon in the atmosphere since the industrial revolution Figure 2. When fossil fuels are released into the atmosphere, they release 12 C, and not 14 C.
Thanks to Fossil Fuels, Carbon Dating Is in Jeopardy. One Scientist May Have an Easy Fix
A child mummy is found high in the Andes and the archaeologist says the child lived more than 2, years ago. How do scientists know how old an object or human remains are? What methods do they use and how do these methods work?
Radiocarbon dating is a key tool archaeologists use to determine the age of plants and objects made with organic material. But new research shows that commonly accepted radiocarbon dating standards can miss the mark -- calling into question historical timelines. Archaeologist Sturt Manning and colleagues have revealed variations in the radiocarbon cycle at certain periods of time, affecting frequently cited standards used in archaeological and historical research relevant to the southern Levant region, which includes Israel, southern Jordan and Egypt. These variations, or offsets, of up to 20 years in the calibration of precise radiocarbon dating could be related to climatic conditions. Pre-modern radiocarbon chronologies rely on standardized Northern and Southern Hemisphere calibration curves to obtain calendar dates from organic material.