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Meteorites are among the oldest objects we know about - formed about 4.5 billion years ago. This article describes the principles and methods used to make that determination.
There are some things that affect these measurements.He calculated the modern rate of salt delivery to the oceans, and suggested that the present salinity of ocean water would take at least 100 million years to develop.In the 1860's, English physicist Lord Kelvin disagreed with Charles Lyells proposition that the earth behaves in a uniform, unchanging manner.Simply counting the number of rings will give one a fairly good idea of the age of the tree.Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings. When a given quantity of an isotope is created (in a supernovae, for example), after the half-life has expired, 50% of the parent isotope will have decomposed into daughter isotopes.
After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.