Uranium 238 dating process
Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable.Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence.With 238U the Pb/U ratio grows much more slowly with age, but the idea is the same.If you took rocks of all ages and plotted their two Pb/U ratios from their two isotope pairs against each other on a graph, the points would form a beautiful line called a concordia (see the example in the right column).Natural uranium consists of three isotopes: uranium-238, uranium-235, and uranium-234. The nuclei of radioactive elements are unstable, meaning they are transformed into other elements, typically by emitting particles (and sometimes by absorbing particles).This process, known as radioactive decay, generally results in the emission of alpha or beta particles from the nucleus.
In a rock twice as old there will be one 235U atom left for every three 207Pb atoms (Pb/U = 3), and so forth.
Lead atoms created by uranium decay are trapped in the crystal and build up in concentration with time.
If nothing disturbs the grain to release any of this radiogenic lead, dating it is straightforward in concept.
In 1938, German physicists Otto Hahn and Fritz Strassmann showed that uranium could be split into parts to yield energy.
Uranium is the principal fuel for nuclear reactors and the main raw material for nuclear weapons.