When we know how much has decayed, we know how old the sample is.
That's all you really need to know to understand radiometric dating techniques. In the next part of this article, I'll examine several different radiometric dating techniques, and show how the axioms I cited above translate into useful age measurements. Common Methods of Radiometric Dating This section describes several common methods of radiometric dating. C14 is radioactive, with a half-life of 5730 years.
To start, let's look at one that almost everyone has heard of: radiocarbon dating, AKA "carbon-14 dating" or just "carbon dating." Method 1: Carbon-14 Dating The element carbon occurs naturally in three isotopes: C12, C13, and C14. C14 is also formed continuously from N14 (nitrogen-14) in the upper reaches of the atmosphere.
Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth.
When I first became interested in the creation-evolution debate, in late 1994, I looked around for sources that clearly and simply explained what radiometric dating is and why young-Earth creationists are driven to discredit it.
I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a nongeologist to understand them.
Thus this essay, which is my attempt at producing such a source.
Contents: The half-life of a radioactive isotope is defined as the time it takes half of a sample of the element to decay.
A mathematical formula can be used to calculate the half-life from the number of breakdowns per second in a sample of the isotope.
If an element has more than one isotope present, and a mineral forms in a magma melt that includes that element, the element's different isotopes will appear in the mineral in precisely the same ratio that they occurred in the environment where and when the mineral was formed. The third and final axiom is that when an atom undergoes radioactive decay, its internal structure and also its chemical behavior change.
Losing or gaining atomic number puts the atom in a different row of the periodic table, and elements in different rows behave in different ways. Well, an atom's chemical activity pattern is a result of its electron shell structure.
Some isotopes have very long half-lives, measured in billions or even trillions of years.