Dating organic material

How do scientists figure out how old things are?

This page has been archived and is no longer updated. Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4. 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. These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing. As these changes have occurred, organisms have evolved, and remnants of some have been preserved as fossils. 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. The age of the fossil must be determined so it can be compared to other fossil species from the same time period.

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Dating archaeological sites is often challenging due to a poor preservation of datable organic materials bone, plant material, … , especially in the dry and acidic environment of the coversand area in northern Belgium. When organic remains are preserved, their association with the human activities is not always clear: charcoal, for instance, may result from wildfires. In addition, different types of organic materials can be subject to dating problems such as an old wood effect calcined bone, charcoal or reservoir effect human and animal bone, food residue. Pottery is one of the most common finds on archaeological sites and it is the direct outcome of human activities. In many cases, charred remains of these plant additives are preserved inside the pottery and can be used for AMS 14C dating.

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Radiocarbon dating also referred to as carbon dating or carbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon , a radioactive isotope of carbon. The method was developed in the late s at the University of Chicago by Willard Libby. It is based on the fact that radiocarbon 14 C is constantly being created in the Earth's atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14 C combines with atmospheric oxygen to form radioactive carbon dioxide , which is incorporated into plants by photosynthesis ; animals then acquire 14 C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of 14 C it contains begins to decrease as the 14 C undergoes radioactive decay. Measuring the proportion of 14 C in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died.

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Carbon-14 dating, explained

Dating is everything in archaeology. Exciting discoveries of ancient burial sites or jewellery might make headlines, but for scientists, this kind of discovery is only meaningful if we can tell how old the artefacts are. So when chemist Willard Libby developed radiocarbon dating in , it was a breakthrough for archaeology and he was awarded a Nobel prize for his achievement. Nowadays people take radiocarbon technology for granted and many people think you can use radiocarbon on any human remains.

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