Those who promote the reliability of the method spend a lot of time impressing you with the technical details of radioactive decay, half-lives, mass-spectroscopes, etc.
But they don’t discuss the basic flaw in the method: you cannot determine the age of a rock using radioactive dating because no-one was present to measure the radioactive elements when the rock formed and no-one monitored the way those elements changed over its entire geological history.
You can get any date you like depending on the assumptions you make.
And that is what geologists do—they make up an assumed geological history for rock depending on the numbers that come from the geochronology lab that measures the isotopes in the rocks now.
We note that at the instant the swimmer touches the end of the pool our wristwatch reads and 53 seconds.
How long has the competitor taken to swim the race?
Many people assume that the dates scientists quote of millions of years are as reliable as our knowledge of the structure of the atom or nuclear power.
The fact is that you can only establish the time for the race if it was timed by two or more reliable eyewitnesses who observed the you cannot measure the age of a rock using radioactive dating because no-one was present to measure the radioactive elements when the rock formed and no-one monitored the way those elements changed over its entire geological history This illustrates the problem with the radioactive dating of geological events.Dating secrets explains how this works in practice.Some real-life examples of how geologists change their assumptions after the event include the dating of Skull KNM-ER 1470 (see The pigs took it all) and of the Mungo skeletal remains, Australia (see The dating game).Keep that in mind when you think about working out the age of something. Actually, knowing the starting time is still not enough.During the race you have to watch the swimmer and count how many laps he has swum so you know that he has done 1,500 metres.