How do we know that radiometric dating is reliable?

Scientists are extremely confident in the reliability of the absolute ages of rocks and fossils established through radiometric dating. There are many reasons that they can be so confident.

First, the principles of radiometric dating are based on the well-understood mechanisms through which radioactive materials undergo change, and the steady rates at which these changes occur have been measured and verified many times. This means that, if you have the necessary laboratory equipment and make the measurements with sufficient care, the idea of finding a rock’s age with radiometric dating is not much different than the idea of calculating how fast a rock would be falling due to gravity after a particular amount of time.

Moreover, scientists have numerous ways of verifying the ages found through radiometric dating. One important validation comes from relatively young objects for which we already know absolute ages, such as archaeological artifacts that have dates printed on them or wood artifacts that can be dated with tree rings. In these cases, radiometric dating gives the same absolute ages that we already know, verifying the general accuracy of the method.

For older rocks and fossils, scientists can often verify radiometric ages by finding the ages in more than one way. The most important of these verifications comes from the many cases in which a rock contains more than one radioactive material. In those cases, scientists find that they can get the same age no matter which material they use for the radiometric dating.

Additional verification (though less precise) can come from cases in which scientists have other ways to estimate ages. For example, even though rock layers usually tell us only relative ages, in some cases scientists have ways to estimate their absolute ages — and in those cases, the ages found with radiometric dating agree with the estimates. One remarkable confirmation comes from astronomy: Scientists know enough about stars to be able to estimate the Sun’s age from its basic properties, and these estimates tell us that the Sun is between about 4 and 5 billion years old, which agrees with the 4.5-billion-year age of our solar system found with radiometric dating.

Additional confidence comes from the fact that absolute ages found with radiometric dating fall into the same order as the relative ages we find for rocks and fossils. This provides a further general confirmation of the validity of the technique.

Overall, radiometric dating has been checked in so many ways and relies on such basic scientific principles that there is no serious scientific debate about its validity.