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Radioactive dating calculates the age of rocks and fossils by measuring concentrations of radioactive elements. Different methods are used for organic and inorganic materials. Carbon dating is commonly used for human-made artifacts, while uranium and potassium dating are used for older materials. The accuracy of radioactive dating is based on assumptions about the original state of the material and accepted geological time scales. Controversy arises from the possibility of elements being deposited in the sample over time, invalidating age calculations.
Radioactive dating is a method of calculating the age of rocks and fossils through the concentrations of certain radioactive elements in the vicinity of those objects or as part of their chemical structure. There are various radioactive dating methods used depending on whether what is being analyzed is organic or inorganic, and each process is based on assumptions about the original state of the material being dated and accepted geological time scales. While the nature of radioactive decay is based on established scientific principles for radioactive elements that are well established, the assumptions used to calculate an object’s actual age from these principles are subject to debate and controversy.
Radioactive carbon dating is the most common method used to date human-made fossils or artifacts from ancient human civilizations. The carbon isotope 14 (14C) is used, as it has a short effective decay half-life of 5.725 years in which it decays to nitrogen 14 (14N), and is found in minute concentrations in virtually all organic compounds on Earth. Carbon 14 is present in known concentrations in the atmosphere and in all plants and animals involved in the exchange of CO2 gas through respiration processes. After a plant or animal has died and been sealed off from further exposure to air, the amount of carbon 14 slowly decreases in the remains, as well as the surrounding soil. This variation can be compared to atmospheric concentrations to determine an approximate age for when the creature died or when an inorganic artifact was buried in the ground near organic remains.
Radioactive dating methods for older time periods or fossils thought to be millions of years old involve the use of elements with decay rates much slower than carbon 14. Commonly, uranium 238 (238U) is used, as it decays slowly into a stable form of lead (206Pb) over 4,500,000,000 years. Another isotope with a long decay rate that is used to date geological formations is potassium 40 (40K), which decays to argon 40 (40Ar) in 1,250,000,000 years. As radioactive elements such as isotopes of carbon or uranium decay, they remain unaffected by other processes going on around them, such as changes in heat, pressure and chemical reactions. This makes them predictable in terms of their rate of change, and their decay rates are the fundamental assumption upon which the science of radioactive dating is built.
The main argument for radioactive dating accuracy centers on the geological age science assumes for the Earth, as of 2011. Since it is impossible for humans to know the exact state of a rock or fossil deposit when was originally created thousands or millions of years ago, it is possible that the deposit elements accounted for in the present were not a byproduct of the decay of other elements in the sample. Elements that appear to be byproducts of decay may have been deposited in the sample over time through other methods, or always present in higher-than-expected concentrations with the decaying elements, invalidating calculations about an object’s true age. Age tests of recently formed rock samples from volcanic eruptions, conducted by multiple independent laboratories, have also yielded wildly variable ages of several million years, when the rocks themselves were formed through processes that occurred less than 100 years ago. casting some doubt on the methodology used in conventional dating practices.
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