These figures for temperature and density are only a guide. More massive stars burn their nuclear fuel more quickly, since they have to offset greater gravitational forces to stay in approximate hydrostatic equilibrium. That generally means higher temperatures, although lower densities, than for less massive stars. The principal reactions are: . This sequence of reactions can be understood by thinking of the two interacting carbon nuclei as coming together to form an excited state of the 24 Mg nucleus, which then decays in one of the five ways listed above. The third reaction is strongly endothermic, as indicated by the large negative energy indicating that energy is absorbed rather than emitted.
Dating techniques are procedures used by scientists to determine the age of rocks, fossils, or artifacts. Relative dating methods tell only if one sample is older or younger than another; absolute dating methods provide an approximate date in years. The latter have generally been available only since Many absolute dating techniques take advantage of radioactive decay , whereby a radioactive form of an element decays into a non-radioactive product at a regular rate. Others, such as amino acid racimization and cation-ratio dating, are based on chemical changes in the organic or inorganic composition of a sample. In recent years, a few of these methods have come under close scrutiny as scientists strive to develop the most accurate dating techniques possible. Relative dating methods determine whether one sample is older or younger than another.
Whenever the worldview of evolution is questioned, the topic of carbon dating always comes up. Here is how carbon dating works and the assumptions it is based upon. Radiation from the sun strikes the atmosphere of the earth all day long. This energy converts about 21 pounds of nitrogen into radioactive carbon This radioactive carbon 14 slowly decays back into normal, stable nitrogen.
Radiocarbon dating also referred to as carbon dating or carbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon , a radioactive isotope of carbon. The method was developed in the late s at the University of Chicago by Willard Libby , who received the Nobel Prize in Chemistry for his work in It is based on the fact that radiocarbon 14 C is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14 C combines with atmospheric oxygen to form radioactive carbon dioxide , which is incorporated into plants by photosynthesis ; animals then acquire 14 C by eating the plants.