Saturday, November 24, 2012

I had decided to limit the time I waste on Mrs. Chatman's foolishness. She seems to have no readers other than a few pro-science readers like myself. Her nonsense turns up in my news feed since I have it look for anything with "creationism" and a half-dozen other buzz words. So, I wanted to pick just one of the last 5 of her "evidences" to debunk. It was too hard to chose.

Item #5 of her "evidences" was about radiocarbon dating. There are five gross errors, and three minor errors. There was only one lonely true statement she made, radiocarbon is made in the upper atmosphere from nitrogen, and decays back to nitrogen. There is a qualification to even that: minor amounts of C14 are generated from neutron capture. I didn't even count this as an error.

Here is her claim:

5. Does carbon dating prove the earth is millions of years old? NO! The sun's radiation hits the earth during the day. That energy is able to convert 21 pounds of nitrogen into radioactive carbon 14. The radio active carbon 14 eventually decays and turns back into nitrogen. Laboratory tests have shown that about half the C-14 molecules have a life of 5,730 years, and the remaining half will decay after another 5,730 years. Tests reveal that there is more C-14 now than there was 40 years ago. This proves that the earth is not even 30,000 years old and its atmosphere has not reached its equilibrium yet.


Her first gross error is particularly amusing because it was accidentally a true statement: "Does carbon dating prove the earth is millions of years old? NO!"

Radiocarbon dating is theoretically limited to about 100,000 years. Technical limitations in our field conditions, and laboratory instruments reduce this to commonly reported dates between 50 and 60 thousands of years. So, even if we had perfect field conditions, and perfect laboratory measurement, we could only "prove" that the Earth was more than 100,000 years old- just 1/10 of a million. Even when Mrs. Chatman is right, she is wrong. Nobody ever has used radiocarbon dating to "prove the earth is millions of years old." That would be stupid.

Back in 1948 when the radiocarbon dating method was first proposed, the assumption was made by Willard Frank Libby that the production of C14 in the upper atmosphere would reach a break-even point with the decay of C14 back to nitrogen. This would have made radiocarbon dating a very tidy, and easy method to apply. However, nature is rarely tidy. Our sun is a variable star, so that the amount of solar radiation producing C14 in the upper atmosphere is also variable. This does lead to the first minor error, that 21 pounds of C14 are produced annually. The production of C14 is variable over the millennia. Then, there are physical, geochemical events that can store carbon, and release carbon. These can effect the available mix of C12, and C14 particularly in marine animals. This can under some conditions substantively change the radiocarbon age of an object. This was discovered in the 1960s, and the first calibrations were being published in the early 1970s. This means that for over 50 years we have known that the "equilibrium" of atmospheric C14 was meaningless. I wish creationists like Mrs. Chatman could catch-up with the rest of us.

The first calibrations were made by counting tree-rings, and taking measure of the amount of C14 in the wood of known age. Over the many years of work, we have a very solid calibration from dendrochronology for the last 12,000 years. The most recent calibration published just this month was "A Complete Terrestrial Radiocarbon Record for 11.2 to 52.8 kyr B.P." (Science 19 October 2012: 370-374. [DOI:10.1126/science.1226660} This research used the annually deposited algal, and sediment layers (varves) in a Japanese lake. Other calibrations have used trapped carbon in ice caps, and marine sediments, and cross-correlation with Uranium/Thorium decay. The measurement errors have been reduced to less than 5% of the age of the material.

Here is the single most stupid thing Mrs. Chatman wrote since I first encountered her many stupid claims, "The sun's radiation hits the earth during the day." The sun's radiation hits the earth somewhere all the time except for the tiny fraction of time our sun is eclipsed by the moon. Upper atmosphere circulation effectively mixes gasses including carbon dioxide loaded with C14. There isn't anything I can say that can make it any better.

Mrs. Chatman wrote that the half-life of C14 was known as, "... C-14 molecules have a life of 5,730 years, and the remaining half will decay after another 5,730 years." We have one minor error, and one gross error in these few words. Above average even for a creationist. The minor error (and I am being charitable) is that there are "C-14 molecules." C-14 is an isotope, and atom of carbon with an excess of neutrons making it radioactive. It is not a "molecule." The gross error is about what a half-life is. If we start with some amount of a radioactive isotope, X, the amount left after one half-life will be X/2. After a second half-life there will be X/4, or one half of that from before. Then after the next interval, there will be X/8 or one half of X/4.

And finally, we have the true but misunderstood statement that, "Tests reveal that there is more C-14 now than there was 40 years ago." There is a considerable excess of C14 over the amount generated by solar radiation currently circulating in biosphere. It was produced by the insanity of open atmospheric atomic weapons exploded between 1945 and 1963 when they were limited by international treaty (France continued until 1974 China continued until 1980). Increasing amounts of ancient C14 depleted carbon released into the atmosphere by burning fossil fuels, and by volcanic eruptions has not significantly diluted the atomic test C14 signal. The last gross error associated with Mrs. Chatman's lack of science reading skills is that this excess could possibly be confused as something that "proves that the earth is not even 30,000 years old."


3 comments:

Aquanerd09 said...

Gary

Even disregarding her nonsensical attempt at disproving anything science related... This post, by itself, serves you well as an outstanding teacher and communicator. Keep it up dude.

Gary S. Hurd said...

Thank you. I am glad you liked it.

jscottbuchanan said...

Great reference you give on C-dating. Following up, I found full pdf version on-line here:
http://cio.eldoc.ub.rug.nl/FILES/root/2012/ScienceBronkRamsey/2012ScienceBronkRamsey.pdf

Has plots showing good matches between completely independent dating methods (lake varves and stalagtites). Nice work. Cheers, Scott