Uranium lead dating meteorites
"In a billion years [from now], it seems, intelligent life might be as different from humans as humans are from insects . To change from a human being to a cloud may seem a big order, but it's the kind of change you'd expect over billions of years." Freeman Dyson, Statement made in 1986, quoted in Asimov's Book of Science and Nature Quotations, p. [American mathematician.]"Slowness has really nothing to do with the question.
An event is not any more intrinsically intelligible or unintelligible because of the pace at which it moves.
If modern lead, for example, from marine sediments or modern basalts has the composition of lead in the Earth and if the lead in the troilite phase of iron meteorites has the composition of primordial lead, then a simple model yields about 4.6 billion years for the age of the Earth.
This age is in good agreement with the age of the meteorites and the age of the Moon as determined independently.
Common lead is any lead from a rock or mineral that contains a large amount of lead and a small amount of the radioactive precursors of lead (i.e., the isotopes uranium-235, uranium-238, and thorium-232).
This figure is in good agreement with the age of meteorites and the age of the Moon as determined independently.
In “A century of U-Pb geochronology: The long quest towards concordance,” Corfu, a geologist at the University of Oslo, described geologists’ frustration at persistent discordance between the two methods. Still, he finds it troubling that there should be discordance if the same physical processes are operating for the same amount of time. Despite the enormous progress achieved in this field, the problems of U-Pb discordance have not yet been completely resolved and will be one of the main hurdles to overcome in the future.The technique has been refined over the last century, but “discordances” (mismatches) remain.