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? In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon dating. Carbon dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50, years old.
18.5D: Carbon Dating and Estimating Fossil Age
Carbon Dating Background
Carbon dating , also known as radiocarbon dating, is a scientific procedure used to date organic matter. It depends upon the radioactive decay of carbon C 14 , an unstable isotope of carbon which is continually synthesized in the upper atmosphere by cosmic rays. Plants take up atmospheric C 14 for as long as they live, through the process of photosynthesis. Animals take up atmospheric C 14 indirectly, by eating plants or by eating other animals that eat plants. Measuring the proportion of C 14 as opposed to C 12 remaining in a sample then tells us how long ago the sample stopped taking up C 14 — in other words, how long ago the thing died.
How do scientists figure out how old things are?
The history of the Earth and of life on Earth is written in sedimentary rock layers. To understand the history, you must understand the rocks. Sedimentary rock layers of million years old, from the Cambrian Period, provide a record of incredible mystery—what caused the fairly abrupt, in geologic terms, appearance on Earth of a great diversity of early animal forms and their preservation as fossils? This question is tied to several other questions about the environments the animals lived in: how much oxygen was there in the atmosphere and oceans, how was carbon cycled between organisms and the oceans, and how were the continents arranged in terms of the plate tectonic assembly and break up of supercontinents? James Hagadorn from the Denver Museum of Nature and Science is coordinating a team of paleontologist to study the fossils.
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature. C is by far the most common isotope, while only about one in a trillion carbon atoms is C C is produced in the upper atmosphere when nitrogen N is altered through the effects of cosmic radiation bombardment a proton is displaced by a neutron effectively changing the nitrogen atom into a carbon isotope. The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous. It is naturally unstable and so it will spontaneously decay back into N after a period of time.