The controversy of using radioactive dating

25 Sep

The new atom doesn't form the same kinds of chemical bonds that the old one did. It may not even be able to hold the parent atom's place in the compound it finds itself in, which results in an immediate breaking of the chemical bonds that hold the atom to the others in the mineral. (The exact details of this are rather complicated, so I won't go into them here.) When the number of electrons change, the shell structure changes too.

So when an atom decays and changes into an atom of a different element, its shell structure changes and it behaves in a different way chemically. That's the sum total of the chemical and physical basis of radiometric dating.

So, if we know how much of the isotope was originally present, and how much there is now, we can easily calculate how long it would take for the missing amount to decay, and therefore how long it's been since that particular sample was formed.

That's the essence of radiometric dating: measure the amount that's present, calculate how much is missing, and figure out how long it would take for that quantity of the isotope to break down.

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.

The vast majority of carbon atoms, about 98.89%, are C12. And since carbon is an essential element in living organisms, C14 appears in all terrestrial (landbound) living organisms in the same proportions it appears in the atmosphere. Animals and fungi get C14 from the plant or animal tissue they eat for food. The C14 already in the organism doesn't stop decaying, so as time goes on there is less and less C14 left in the organism's remains.

The story of radiocarbon dating shows science at its finest.When I first got involved in the creationism/evolution controversy, back in early 1995, I looked around for an article or book that explained radiometric dating in a way that nonscientists could understand. Young-Earth creationists -- that is, creationists who believe that Earth is no more than 10,000 years old -- are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error. All these methods point to Earth being very, very old -- several billions of years old.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.The second assumption is that the organism in question got its carbon from the atmosphere.A third is that the thing has remained closed to C14 since the organism from which it was created died. 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.Some isotopes have very long half-lives, measured in billions or even trillions of years.Others have extremely short half-lives, measured in tenths or hundredths of a second.