Reliability of radiometric dating
Over the last few decades the advancement in the instrumentation (mass spectrometers) has improved precision of measurement, hence reducing the uncertainty of measurement of rock age.Dates determined by one radiometric scheme can often be verified by independantly determining the age by an alternative radiometric scheme.Creationists often criticize radiocarbon dating in the context of discussions of the age of the Earth.But, as is clear even from the very brief discussion in the previous paragraph, radiocarbon dating can say nothing one way or the other about whether the Earth is many millions of years old, since such dates are far beyond this method's range of resolution.I have read several blog sites in which there is discussion on the age of the earth and inevitably the topic of the dating of rocks and the reliability of this method and it's data is questioned.Radiometric dating relies on the natural decay of radioactive isotopes.In any event, it must be emphasized once again that radiocarbon dating has no relevance one way or the other for the overall question of whether the Earth is many millions of years old, since the scheme can only be used to reliably date specimens less than approximately 50,000 years old.Additional background is available in a well-written Wikipedia article on the topic [Radiocarbon2011], and in Richard Wiens' article [Wiens2002].
A quantity is said to be subject to exponentional decay if it decreases at a rate proportional to its value.
In 2009, several leading researchers in the field established a detailed calibration of radiocarbon dating, based on a careful analysis of pristine corals, ranging back to approximately 50,000 years before the present epoch [Reimer2009].
Here is a graph showing radiocarbon dates on the vertical axis and the calibrated age on the horizontal axis (shown here with permission from Johannes van der Plicht, one of the authors of the 2009 study).
In other words, those hoping that uncertainties in radiocarbon dating, say in the assumption of constancy of atmospheric carbon-14 levels, will mean that specimens are really much younger than the measured dates, are in for a big disappointment -- it is now clear that specimens are actually somewhat older than the raw, uncalibrated reckonings.
As mentioned above, young-earth creationist writers have cited various anomalies and potential difficulties with radiocarbon dating, and have used these examples to justify their conclusion that the entire scheme is flawed and unreliable.