Relative dating and absolute dating of fossils
One argument in favor of the absolute dating methods presented in the preceding articles is that they should work in principle.
If they don't, then it's not just a question of geologists being wrong about geology, but of physicists being wrong about physics and chemists being wrong about chemistry; if the geologists are wrong, entire laws of nature will have to be rewritten.
But by the same token, the other 999 times they don't, and so although any particular date produced by these methods might be called into question, it must be the case that the vast majority of dates that pass through these filters must be good; for we can hardly suppose that the confounding factors are actively conspiring to deceive us, and so these long-shot events must be as rare as statistical considerations would lead us to expect.
You might perhaps suggest that if some unknown factor, contrary to our present understanding of physics existed that sped up or slowed down radioactive decay in the past, then we would expect the radiometric dates to be concordant whether they were right or wrong.
Similar remarks may be made about the agreement between radiometric dating of rocks, sclerochronology, and dating by rhythmites.
Are we to believe that one single mechanism interfered with the decay of radioactive isotopes, the secretion of calcium carbonate by molluscs, and the action of the tide? But are we instead to believe that three separate mechanisms interfered with these processes in such a way as to leave all the dates concordant? The straightforward explanation for the concordance of the dates is that they are in fact correct.
But it is equally far-fetched to imagine that three different mechanisms interfered with the three processes in such a way as to leave the dates concordant; that would require either a preposterous coincidence, or for natural processes to be actually conspiring to deceive us: an idea which is, if anything, even more preposterous. But in this case there is a perfectly reasonable and straightforward explanation for why the dates are concordant, namely that they are correct.
There is no particular reason to suspect that this will turn out to be the case when it comes to the laws underlying absolute dating; nonetheless, an argument from principle alone can never be entirely convincing. You will recall from our discussion of sea floor spreading that the sea floor spreads out from mid-ocean rifts, and so ought to be younger nearer the rifts and progressively older further away from them.
What is more, we can measure the rate of spreading directly by GPS, SLR, and VLBI.
The polarity of the Earth's magnetic field is a global phenomenon: at any given time it will either be normal everywhere or reversed everywhere.
So if our methods of radiometric dating are correct, then we would predict that rocks dated to the same age would have the same polarity, which they do.