### Images of radioactive dating

A fourth article discusses the "uniformitarian" assumption and how it relates to evolution, radiometric dating and the age of the earth: But with the advent of mass spectrometry beginning in the s, even very small samples can now be accurately dated. Reliability of radiometric dating The reliability of radiometric dating is discussed in detail in this article: However, in February researchers at the University of Oxford in the U. That is, at some point in time, an atom of such a nuclide will spontaneously change into a different nuclide by radioactive decay. Isochron graphs As mentioned above, the isochron dating method boils down to plotting multiple data points, after some calculation, on a graph, which, if the measurements and calculations are done properly, should lie on a straight line, or very nearly on a straight line. Elements exist in different isotopes , with each isotope of an element differing in the number of neutrons in the nucleus. For additional discussion, see Conspiracy. At the time, the Cretaceous-Tertiary meteorite impact was thought to have occurred approximately In June , researchers announced that some red handprints and dots in a cave in northwestern Spain are more than 40, years old, based on a uranium-thorium dating of the calcite covering of the specimens. Preconditions The method works best if neither the parent nuclide nor the daughter product enters or leaves the material after its formation. This section may be omitted if readers do not wish to follow the math although the math used here is nothing beyond what is typically taught in a good high-school math analysis class. It should be emphasized, though, that even relatively unsophisticated equipment can perform radiometric measurements of dates fairly well. Some nuclides are naturally unstable. The age is calculated from the slope of the isochron line and the original composition from the intercept of the isochron with the y-axis. Details about linear regression are available in any elementary statistics book, or online -- see [ Linear ]. One interesting and timely application of advanced radiometric dating techniques in paleontology is in attempts to disentangle a controversy as to whether or not all dinosaurs and numerous other species were extinguished by a giant meteorite impact at a spot just north of the present-day Yucatan Peninsula. Measurements should be taken on samples from different parts of the rock body. All the samples show loss of lead isotopes, but the intercept of the errorchron straight line through the sample points and the concordia curve shows the correct age of the rock. Different dating methods may be needed to confirm the age of a sample. Thus these new findings offer dramatic confirmation to the theory that the meteorite impact caused the extinction although climate-related phenomena prior to that time may have exacerbated stress on these species [ Sandersa ]. Uranium-lead Uranium-thorium Each method has its own particular range of applicability, which derives from the half-life of the particular radioactive decay involved. Instead, they use a statistical technique known as linear regression, which computes the least-squares best fit of a straight line through a sequence of points. Uranium-thorium dating, for instance, can be used to date specimens up to about , years old since the half-life of the U-Th decay is 75, years , but Rubidium-Strontium dating can be used to date specimens billions of years old since the half-life of the Rb-Sr decay is It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration. The decay may happen by emission of particles usually electrons beta decay , positrons or alpha particles or by spontaneous nuclear fission , and electron capture.