Carbon-14, definition and study. A-Z index of Cognitio.

Carbon-14, 14C (or radiocarbon) is a radioactive isotope of carbon having 6 protons and 8 neutrons. Carbon-14 was discovered on February 27, 1940 at the University of California radiology laboratory at Berkeley, but its existence had already been hypothesized 1934. Carbon-14 is present in nature with a relative abundance of 1 part out of a trillion of all the carbon present on Earth, due to a half-life of only 5730 years.

Earth origins, definition and study. A-Z index of Cognitio.

Earth origins

The main source of carbon-14 on Earth is the reaction between cosmic rays and gaseous nitrogen present in the atmosphere (in the troposphere and in the stratosphere): the absorption of thermal neutrons by nitrogen forms a carbon atom- 14: The largest production of carbon-14 occurs at a height between 9 and 15 km and at high geomagnetic latitudes.

Atmosphere, definition and study. A-Z index of Cognitio.

Atmosphere

The carbon-14 thus produced reacts with oxygen to give 14CO2 carbon dioxide, which is reused by plants during chlorophyll photosynthesis. In this way carbon-14 is transferred into organic compounds and, through the food web, is present everywhere according to a precise ratio (isotopic abundance). It also penetrates into the oceans, melting into the water. Carbon-14 can also be produced by lightning but in negligible quantities compared to cosmic rays. Thanks to its long half-life compared to the life of living organisms, carbon-14 remains integrated into every living organic system. After death, the body stops taking carbon-14. The quantity of the isotope present in the organism at the moment of his death will gradually fade over the years due to radioactive decay.  This principle is exploited in the radiometric dating of organic samples, a technique used to measure the residual quantity of carbon-14 present in an organic archaeological find (such as a fossil or a wooden structure): knowing the decay curve and the initial quantity of carbon-14 present in the find when its organic structure was still vital (ie an instant before dying), we can easily determine how many years have passed since the death of the organism.

In general, it is only possible to retrieve findings dating back to 40,000-60,000 years ago. Surface nuclear tests that were performed in many countries between 1945 and 1980 dramatically increased the amount of carbon-14 in the atmosphere and therefore also in the biosphere. Since the tests have been suspended, the concentration of the isotope has begun to decrease. Over the years, archaeology has obtained information on the cultures of the past that otherwise would have remained unknown had it not been for the intervention of technologies such as radiocarbon dating, dendrochronology, archeomagnetic dating, fluoride dating, therm luminescence dating and dating with obsidian hydration. Radiocarbon dating was born more than 50 years ago and has revolutionized archaeology. Carbon-14 dating remains a powerful, reliable and widely applicable technique, very valuable for archaeologists and other scientists.

Carbon-14, definition and study. A-Z index of Cognitio.

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Carbon-14, definition and study. A-Z index of Cognitio.

Carbon-14