Answer to Question #210775 in Mechanics | Relativity for Haileu

Question

For the carbon dating described in this chapter, what important assumption is made about the time variation in the intensity of cosmic rays? 

Answer 1

Solution:-

The radiocarbon dating method is based on certain assumptions on the global concentration of carbon 14 at any given time. One assumption is that the global levels of carbon 14 (also called radiocarbon) in the atmosphere has not changed over time. The other assumption is the corollary of the first; the biosphere has the same overall concentration of radiocarbon as the atmosphere due to equilibrium.

Radioactive dating is a technique that uses naturally occurring radioactivity to determine the age of a material, such as a rock or an ancient artifact. The basic approach is to estimate the original number of nuclei in a material and the present number of nuclei in the material (after decay), and then use the known value of the decay constant  and (Figure) to calculate the total time of the decay, t.

An important method of radioactive dating is carbon-14 dating. Carbon-14 nuclei are produced when high-energy solar radiation strikes  nuclei in the upper atmosphere and subsequently decay with a half-life of 5730 years. Radioactive carbon has the same chemistry as stable carbon, so it combines with the ecosphere and eventually becomes part of every living organism. Carbon-14 has an abundance of 1.3 parts per trillion of normal carbon. Therefore, if you know the number of carbon nuclei in an object, you multiply that number by  to find the number of  nuclei in that object. When an organism dies, carbon exchange with the environment ceases, and  is not replenished as it decays.

By comparing the abundance of  in an artifact, such as mummy wrappings, with the normal abundance in living tissue, it is possible to determine the mummy’s age (or the time since the person’s death). Carbon-14 dating can be used for biological tissues as old as 50,000 years, but is generally most accurate for younger samples, since the abundance of  nuclei in them is greater. Very old biological materials contain no  at all. The validity of carbon dating can be checked by other means, such as by historical knowledge or by tree-ring counting.