Radiometric dating methods reliability international dating agensy
Radiometric dating is very reliable in theory - the decay of radioactive materials is very-very predictable.
But like any other bit of experimental physics "the difference between practice and theory is small in theory but large in practice." It's especially tricky for Carbon14 dating (which most recent stuff relies on).
Recognizing this problem, scientists try to focus on rocks that do not contain the decay product originally.
For example, in uranium-lead dating, they use rocks containing zircon (Zr Si O Zircon and baddeleyite incorporate uranium atoms into their crystalline structure as substitutes for zirconium, but strongly reject lead.
Zircon has a very high closure temperature, is very chemically inert, and is resistant to mechanical weathering.
For these reasons, if a rock strata contains zircon, running a uranium-lead test on a zircon sample will produce a radiometric dating result that is less dependent on the initial quantity problem.
One key assumption is that the initial quantity of the parent element can be determined.
That is, the analysis of the isotopic and chemical composition of the sample has far greater uncertainty than any uncertainty in the decay rate itself.Careful astronomical observations show that the constants have not changed significantly in billions of years—spectral lines from distant galaxies would have shifted perceptibly if these constants had changed.In some cases radioactive decay itself can be observed and measured in distant galaxies when a supernova explodes and ejects unstable nuclei.Electron capture requires that there be an electron in the vicinity of the nucleus, so its activity depends strongly on the configuration of the electron cloud, which depends on the chemical state.In fact, it is possible to shut down electron capture completely—simply ionize the substance so that there are no electrons nearby.