Scientist Realizes Important Flaw in Radioactive Dating
An Essay on Radiometric Dating. By Jonathon Woolf http: Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth. All these methods point to Earth being very, very old -- several billions of years old. Young-Earth creationists -- that is, creationists who believe that Earth is no more than 10, years old -- are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error.
When I first became interested in the creation-evolution debate, in lateI 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 non-geologist to understand them.
Thus this essay, which is my attempt at producing such a source. Theory of Radiometric Dating. Common Methods of Radiometric Dating. Possible Sources of Error. Creationist Objections to Radiometric Dating. Independent Checks on Radiometric Dating. Theory of radiometric dating. What is radiometric dating? Simply stated, radiometric dating is a way of determining the age of a sample of material using the decay rates of radio-active nuclides to provide a 'clock.
The rules are the same in all cases; the assumptions are different for each method. To explain those rules, I'll need to talk about some basic atomic physics. There are 90 naturally occurring chemical elements. Elements are identified by their is radiometric dating flaws numberthe number of protons in the atom's nucleus. All atoms except the simplest, hydrogen- 1, have nuclei made up of is radiometric dating flaws and neutrons.
Hydrogen-1's nucleus consists of only a single proton. Protons and neutrons together are called nucleonsmeaning particles that can appear is radiometric dating flaws the atomic nucleus. A nuclide of an element, also called an isotope of an element, is an atom of that element that has a specific number of nucleons. Since all atoms of the same element have the same number of protons, different nuclides of an element differ in the number of neutrons they contain.
For example, hydrogen-1 is radiometric dating flaws hydrogen-2 are both nuclides of the element hydrogen, but hydrogen-1's nucleus contains only a proton, while hydrogen-2's is radiometric dating flaws contains a proton and a neutron. Uranium contains 92 protons and neutrons, while uranium contains 92 protons and neutrons. Many nuclides are stable -- they will always remain as they are unless some external force changes them. Some, however, are unstable -- given time, they will spontaneously undergo one of the several kinds of radioactive decay, changing in the process into another element.
There are two common kinds of radioactive decay, alpha decay and beta decay. In alpha decay, the radioactive atom emits an alpha particle. An alpha particle contains two protons and two neutrons. After emission, it quickly picks up two electrons to balance the two protons, and becomes an electrically neutral helium-4 He4 atom. When a nuclide emits an alpha particle, its atomic number drops by 2, and its mass number number of nucleons drops by 4.
Thus, an atom of U uranium, atomic is radiometric dating flaws 92 emits an alpha particle and becomes an atom of Th thorium, atomic number A beta particle is radiometric dating flaws an electron. When an atom emits a beta particle, a neutron inside the nucleus is transformed to is radiometric dating flaws proton. The mass number doesn't change, but the atomic number goes up by 1.
Thus, an atom of carbon C14atomic number 6, emits a beta particle and becomes an atom of nitrogen N14atomic number 7. A third, very rare type of radioactive decay is called electron absorption. In electron absorption, a proton absorbs an electron to become a neutron. In other words, electron absorption is the exact reverse of beta decay.
So an atom of potassium K40atomic number 19 can absorb an electron to become an atom of argon Ar40atomic number The half-life of a radioactive nuclide is defined as the time it takes half of a sample of the element to decay. A is radiometric dating flaws formula can be used to calculate the half-life from the number of breakdowns per second in a sample of the nuclide.
Some nuclides 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. The decay rate and therefore the half-life are fixed characteristics of a nuclide. Different nuclides of the same element can have substantially different half-lives. The half-life is a purely statistical measurement.
A sample of U ten thousand years old will have precisely the same half-life as one ten billion years old. Obviously, the major question here is "how much of the nuclide was originally present in our sample? Such cases are useless for radiometric dating. We must know the original quantity of the parent nuclide in order to date our sample radiometrically.
Fortunately, there are cases where we can do that. This is the second axiom of radiometric dating. 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. It may not form the same kinds of compounds. 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. How do these axioms translate into useful science? This section describes several common methods of radiometric dating. To start, let's look at the one which almost everyone has heard of: The element carbon occurs naturally in three nuclides: C12, C13, and C The vast majority of carbon atoms, about About one atom in billion is C The remainder are C Of the three, C12 and C13 are stable.
C14 is radioactive, with a half-life of years. C14 is also formed continuously from N14 nitrogen in the upper reaches of the atmosphere.