Start Reliability of radioactive dating

Reliability of radioactive dating

other isotope pairs cover intermediate time periods between the spans for carbon 14 and uranium.

There are about two dozen decay pairs used for dating.

Uranium 235 decay to lead has a half-life of 713 million years, so it is well suited to dating the universe.

In fact, they track because radiometric data is accurate.

An expert scientist summarizes: "The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old.

Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates.

A key point is that it is no longer necessary simply to accept one chemical determination of a rock's age.

Age estimates can be cross-tested by using different isotope pairs.

Results from different techniques, often measured in rival labs, continually confirm each other.

Thus the physical principle of the method is well established. The dates obtained by radiometric dating are verified by independent methods, including dendrochronology (tree rings), varve chronology (sediment layers), ice cores, coral banding, speleotherms (cave formations), fission track dating, and electron spin resonance dating.

The multiple checks verify that the rate of isotope decay does not change over time, and it verifies the accuracies of the methods.

Every few years, new geologic time scales are published, providing the latest dates for major time lines.