In my previous post, “A Brief History of Atomic Theory”, I provided some history of atomic theory and ended with the ideas of nuclear decay and ½-life. In this piece, I want to expand those two points with regards to the dating of archeological objects and, ultimately, the age of the earth.
Decay, for the lack of better terminology, is the chemical and physical breakdown of material over time. Most everything we know of decays, though some things decay at a slower rate than others. And if the conditions are such, decay is sometimes halted. All one has to do is examine the contents of a landfill where trash is covered by earth and compacted. Newsprint, which will decay when exposed to air, is often unchanged after years of coverage with dirt. And one of the reasons that we recycle plastics is that many plastics do not decay. This, in turn, means that much of our 21st century waste, when put into a landfill, is simply going to take up space.
The term ½-life refers to the time it takes for ½ of the original material to decay into something else. If something has a ½-life of 10 minutes and we start with 10 grams of the material, then after 10 minutes we would have 5 grams of material. After another 10 minutes, we would have 2.5 grams of material. The progression would something like this:
After 60 minutes, the 10 grams of material would have decayed in .15 grams of material. Ultimately, of course, it should decay to nothing. It should be noted that if the ½ life of the substance were 10 hours, then this process would take 60 hours. The nature of the substance will determine the ½-life of the substance.
The best possible way to understand the idea of ½-life is to go into the laboratory and do one or two experiments. Obviously, that is not possible with an on-line environment (though there are some who insist that one can do chemistry, physics, and biology completely on-line – that is for another discussion). However, some things are possible and we can take advantage of those methods to illustrate the concept of ½-life.
Patrick Gormley has developed a simulation that illustrates how ½-lives are determined – http://chem.lapeer.org/Chem1Docs/Halflife/Halflife.html. The simulation is set up for a discussion that would have accompanied a discussion of isotopes in the history of atomic theory. There is some mathematics involved but with a common scientific calculator and high school algebra, it is relatively easy to follow. (Patrick provided information about this link in an e-mail sent to the CHEMED discussion list on 29 June 2010).
Stephen Gagon provided the following link – http://education.jlab.org/frost/#halflife – to illustrate the measurement of the ½-life for Barium-137m. (E-mail to CHEMED discussion list on 29 June 2010).
Determining the age of an object
At this point, I was going to describe the process for using Carbon-14 (an isotope of carbon) in determining the age of fossils and other material. This would have lead into a discussion of the potassium/argon process for determining the age of rocks and other inorganic materials. And this would have been followed with a discussion of the use of the uranium decay process for the determination of the age of the earth and the universe. Along the way I wanted to address some of the questions that arise as well as address the critics of these techniques (those who feel that the earth is on the order of 6,000 years old and not 4.5 billion years as the experimental data suggests.
But in preparing and reviewing notes, I discovered “Radiometric Dating – A Christian Perspective” by Dr. Roger C. Wiens. Dr. Wiens has prepared a rather extensive document on this topic and also provided rebuttals for the critics of these techniques. So rather than “re-invent the wheel” and with his permission, I am providing a link to his page.
Quotations to consider
Daniel Boorstin (12th Librarian of Congress) – You must collect things for reasons you don’t yet understand.
Sherlock Holmes – It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.
Thorstein Veblen – The outcome of any serious research can only be to make two questions grow where only one grew before.
Somewhere in the course of time and history, we became conscious of our environment and the world in which we live. That is what defines us as humans. Part of our being is to ask questions and seek answers to those questions. Where did we come from? How long have we been here? These are just a few of the questions that we have asked over the years. Sometimes the answers are easily found; sometimes they are not.
For me, the Bible tells me the story of the struggle to find the answers. We were created in God’s image so we were created to ask questions. If somewhere along the line, we stop asking questions we have to seriously consider what that means about our creation and our role in this universe. When the evidence lies before us, we have to ask ourselves what we are seeing and what it means. To be blind to the evidence is to not ask questions.
Sometimes the answer to the question lies in one’s faith and not the evidence before them. Faith can only grow when one seeks to ask questions about it and seek answers. To seek answers about faith is to seek God. It is what we have been doing for some three thousand years.
I want to address that in my next piece.