How is radiometric dating done
"Near the end you imply that low petrologic type chondrites are the most easily dated.Actually, meteorites that formed by melting, e.g., the various types of achondrites, usually give more precise ages.Notable observations included: ran from about 1780-1850.By the end of the 18'th century it was clear that the Earth had a long and varied history. The major debate was between the catastrophists, e.g., Cuvier, who held that the history of Earth was dominated by major catastrophic revolutions and the uniformitarians, e.g.If, in the year AD 1600, you had asked an educated European how old the planet Earth was and to recount its history he would have said that it was about 6000 years old and that its ancient history was given by the biblical account in Genesis.If you asked the same question of an educated European in AD 1900 you would have received a quite different answer.
"The idea that Rb-Sr is the most used chronometer for meteorites is largely based on work done 10-30 years ago.The use of 14C in meteorite dating is solely based on its production by cosmic rays (and for terrestrial samples, with its production in the atmosphere).26Al and some other nuclides not mentioned are also used in this way.After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.
For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. A small portion of a meteorite is vaporized in the device forming ions.
In this period a number of comprehensive cosmogonies were proposed.