Radiocarbon analysis has changed our understanding of the last 50,000 years. Professor Willard Libby first demonstrated it in 1949, for which he later received the Nobel prize.
The Essence of radiocarbon Dating is to compare three different isotopes of carbon. Isotopes of a particular element have the same number of protons but different number of neutrons. This means that when a large chemical affinity, they have different masses.
The Total mass of the isotope is indicated by a numeric index. While the lighter isotopes 12C and 13With the stable, the heaviest isotope 14C (radiocarbon) is radioactive. The core is so large that it is unstable.
Over time 14C – the basis of radiocarbon analysis – breaks down into nitrogen 14N. Most of the carbon-14 is created in the upper atmosphere where neutrons, which are formed under the action of cosmic rays react with atoms of 14N.
Then it is oxidized in the 14CO2, penetrates the atmosphere and is mixed with 12CO2 and 13CO2. Carbon dioxide is used by plants in photosynthesis, and from there passes through the food chain. Therefore, every plant and animal in the chain (including people) will have an equal amount of 14C compared With 12In the atmosphere (the ratio of 14:12).
When living beings die, the tissue is no longer replaced and radioactive decay of 14C becomes apparent. In 55 thousand years 14C decays so that it remains impossible to measure.
What is radiocarbon Dating? Radioactive decay can be used as a “hours”, as it does not depend on physical (e.g. temperature) and chemical (e.g., water content) conditions. In 5730 years, decays to half of 14C present in the sample.
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So, if you know the ratio of 14C:12C at the time of death and the current ratio, you can calculate how much time has passed. Unfortunately, to define not so simply.
The Number of 14In the atmosphere, consequently, in plants and animals, has not always been constant. For example, it varies depending on how many cosmic rays reach the Ground. It depends on solar activity and magnetic field of our planet.
Fortunately, it is possible to measure these fluctuations in samples dated by other methods. You can count the annual rings of trees and the change in their radiocarbon content. From these data we can build a “calibration”.
Currently, work is underway for its extension and improvement. In 2008 it was possible to only calibrate radiocarbon dates to 26,000 years. Today the curve is extended up to 50,000 years.
Not all materials can be dated by this method. Most, if not all, organic compounds allow radiocarbon analysis. Some inorganic substances such as aragonite component of the shells can also be dated, since the formation of the mineral was used carbon-14.
The Materials that have been dated since the inception of the method include charcoal, wood, twigs, seeds, bones, shells, leather, peat, silt, soil, hair, ceramics, pollen, wall paintings, corals, blood residues, fabrics, paper, parchment, resin and water.
Radiocarbon Dating of the metal is impossible if it does not contain carbon-14. With the exception of iron products in the manufacture of which coal is used.
Because Of this complication, radiocarbon dates are presented in two ways. Uncalibrated measurements served a number of years before 1950 (BP). Calibrated dates are presented as BCE and after, as well as using units calBP (calibrated before present before 1950). This is the “best estimate” the actual age of the sample, but you need to be able to go back to old data and to calibrate them because new research is constantly updating the calibration curve.
The Second difficulty is the extremely low prevalence of 14C. Only 0,0000000001% of carbon in the modern atmosphere is a 14C, which causes incredible difficulties for measurement and makes it extremely sensitive to contamination.
In the first years of radiocarbon analysis of decay products required huge samples (e.g. half of a human femur). Many laboratories are now using the mass spectrometer with the accelerator (AMS), which can detect and measure the presence of different isotopes, to count the number of individual atoms of carbon-14.
This method requires less than 1G of bone, but few countries can afford more than one or two AMS, the cost of which exceeds 500 thousand $. For example, Australia has only 2 such a device that are able to produce radiocarbon analysis, and theyunattainable for most of the developing world.
In addition, the samples must be thoroughly cleaned from impurities of carbon from the glue and soil. This is especially important for very old materials. If 1% of the element in the sample by the age of 50 thousand years will come from a modern contaminant, it will be dated as sarcatically.
For this reason, researchers are constantly developing new methods of effective cleaning materials. They can have a significant impact on the result, which yields radiocarbon analysis. The accuracy of the method significantly increased with the development of a new method of purifying activated charcoal ABOx-SC. This allowed, for example, to postpone the date of arrival of the first people in Australia more than 10 thousand years.
The Method of proving that since the beginning of Earth was much more than 10 thousand years mentioned in the Bible, has been repeatedly criticized creationists. For example, they claim that for 50 thousand years in the samples must be free of carbon-14 in coal, oil and natural gas, whose age, presumably, is millions of years old, contained measurable quantities of this isotope, which confirms the radiocarbon analysis. The measurement error is more background radiation from which it is impossible to get rid of in the laboratory. Ie sample, which contains not one atom of radioactive carbon, show date in 50 thousand years. However, this fact does not question the Dating of the objects, and certainly not evidence that oil, coal and natural gas under that age.
Creationists Also say some oddities radiocarbon Dating. For example, the Dating of freshwater molluscs identified their age as greater than 2000 years that, in their opinion, discreditied this method. In fact, it is established that the clams get most of their carbon from limestone and humus, the content of 14C which is very low, as these minerals are very old and do not have access to carbon air. Radiocarbon analysis, the accuracy of which in this case can be questioned, otherwise true. Wood, for example, this problem has since plants get carbon directly from the air, which contains a full dose of 14C.
Another argument against the method is the fact that the trees are able to form in one year more than one ring. This is true, but more often it happens so that they do not form annual rings. Bristlecone pine, which conducted most of the measurements is 5 % rings less than her actual age.
Radiocarbon analysis – this is not only a method but also a spectacular opening to our past and present. The method has allowed archaeologists to place finds in a chronological order without the need for written records or coins.
In the 19th and early 20th century is incredibly patient and careful archaeologists associated ceramics and stone tools of different geographical areas by finding similarities in shape and patterns. Then, using the idea that the object styles evolved and became more complex over time, they could place them in order.
Thus, large-domed tomb (known as the Tolosa) in Greece was considered to be the precursors of similar structures on the Scottish island of Maeshowe. This supported the idea that classical civilization of Greece and Rome was the center of all innovation.
However, the radiocarbon tests revealed that the Scottish tombs were thousands of years older than Greek. The Northern barbarians were able to design complex structures, similar to the classic.
Other well-known projects was the assignment of the shroud of Turin to the medieval period, the Dating of the Dead sea scrolls by the time of Christ, and somewhat controversial periodization of the drawings in the Chauvet cave aged 38 000 calBP (about 32 000 BP), thousands of years earlier than expected.
The Radiocarbon Dating was also used in determining the time of extinction of mammoths and contributed to debate about, did modern humans and Neanderthals or not.
Isotope 14Is not only used to determine the age. The method of radiocarbon Dating allows you to explore ocean circulation and to trace the movement of drugs throughout the body, but that's the topic of another article.
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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."
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