Carbon dating is a technique used to determine the approximate age of once-living materials.
It is based on the decay rate of the radioactive carbon isotope 14 C, a form of carbon taken in by all living organisms while they are alive. Before the twentieth century, determining the age of ancient fossils or artifacts was considered the job of paleontologists or paleontologists, not nuclear physicists.
By comparing the placement of objects with the age of the rock and silt layers in which they were found, scientists could usually make a general estimate of their age.
However, many objects were found in caves, frozen in iceor in other areas whose ages were not known; in these cases, it was clear that a method for dating the actual object was necessary. Inthe American chemist Bertram Boltwood — proposed that rocks containing radioactive uranium could be dated by measuring the amount of lead in the sample.
This was because uranium, as it underwent radioactive decaywould transmute into lead over a long span of time. Thus, the greater the amount of lead, the older the rock. Boltwood used this method, called radioactive datingto obtain a very accurate measurement of the age of Earth.
While the uranium-lead dating method was limited being only applicable to samples containing uraniumit was proved to scientists that radioactive dating was both possible Facts on carbon dating reliable. The first method for dating organic objects such as the remains of plants and animals was developed by another American chemist, Willard Libby — He became intrigued by carbon — 14, a radioactive isotope of carbon.
Carbon has isotopes with atomic weights between 9 and The most abundant isotope in nature is carbon — 12, followed in abundance by carbon — Among the less abundant isotopes is carbon — 14, which is produced in small quantities in the earth 's atmosphere through interactions involving cosmic rays.
In any living organism, the relative concentration of carbon — 14 is the same as it is in the atmosphere because of the interchange of this isotope between the organism and the air. This carbon — 14 cycles through an organism while it is alive, but once it dies, the organism accumulates no additional carbon — Whatever carbon — 14 was present at the time of the organism's death begins to decay to nitrogen — 14 by emitting radiation in a process known as beta decay.
The difference between the concentration of carbon — 14 in the material to be dated and the concentration in the atmosphere provides a basis for estimating the age of a specimen, given that the rate of decay of carbon — 14 is well known. The length of time required for one-half of the unstable carbon — 14 nuclei to decay i. Libby began testing his carbon — 14 dating procedure by dating objects whose ages were already known, such as samples from Egyptian tombs.
He found that his methods, while not as accurate as he had hoped, were fairly reliable.
Libby's method, called radiocarbon or carbon — 14 dating, gave new impetus to the science of radioactive dating. Using the carbon — 14 method, scientists determined the ages of artifacts from many ancient civilizations. Still, even with the help of laboratories worldwide, radiocarbon dating was only accurate up to 70, years old, since objects older than this contained far too little carbon — 14 for the equipment to detect.
Starting where Boltwood and Libby left off, scientists began to search for other long-lived isotopes. They developed the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method, all of which are based on the transformation of one element into another. They also improved the equipment used to detect these elements, and inscientists first used a cyclotron particle accelerator as a mass spectrometer.
Using the cyclotron, carbon — 14 dating could be used for objects as old asyears, while samples containing radioactive beryllium could be dated as far back as 10 — 30 million years.
Challenges of the method
A newer method of radioactive tracing involves the use of a new clock, based on the radioactive decay of uranium to protactinium. Cite this article Pick a style below, and copy the text for your bibliography. April 16, Retrieved April 16, from Encyclopedia. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia. As a result of cosmic radiation a small of atmospheric nitrogen nuclei are continuously being transformed by neutron bombardment into radioactive nuclei of carbon— Some of these radiocarbon atoms find their way into living trees and other plants in the form of carbon dioxideas a result of photosynthesis.
When the tree is cut down photosynthesis stops and the ratio of radiocarbon atoms to stable carbon atoms begins to fall as the radiocarbon decays. The technique was developed by Willard F. Libby —80 and his coworkers in — This radio-isotope decays to form nitrogen, with a half-life of years.
When a living organism dies, it ceases to take carbon dioxide into its body, so that the amount of C 14 it contains is fixed relative to its total weight. Over the centuries, this quantity steadily diminishes.
Refined chemical and physical analysis is used to determine the exact amount remaining, and from this the age of a specimen is deduced. The ratio between them changes as radioactive carbon decays and is not replaced by exchange with the atmosphere. Carbon Dating gale. Learn more about citation styles Citation styles Encyclopedia. More From encyclopedia. The two main types of dating methods are… Radioactive DatingRadioactive dating is a method of determining the approximate age of an old object by measuring the amount of a known radioactive element it contains… Potassium-argon Datingpotassium—argon dating A dating technique for certain rocks that depends on the decay of the radioisotope potassium—40 to argon—40, a process with a… Radiocarbon DatingRadiocarbon dating is a technique for determining the age of very old objects consisting of organic carbon-based materials, such as wood, paper, cl… Carbon Isotopescarbon isotopes Natural carbon is composed of three isotopes: 12C making up about About this article Carbon Dating All Sources .
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