by Helen Fryman
Question: What about radiocarbon dating? Is it accurate?
Response: I asked several people who know about this field. Their responses are numbered below.
(1.) C14 dating is very accurate for wood used up to about 4,000 years ago. This is only because it is well calibrated with objects of known age. Example: wood found in a grave of known age by historically reliable documents is the standard for that time for the C14 content. This standard content of C14 can then be used for wood not associated with a historically documented date. Dates up to this point in history are well documented for C14 calibration.
For object over 4,000 years old the method becomes very unreliable for the following reason: Objects older then 4,000 years run into a problem in that there are few if any known artifacts to be used as the standard. Libby, the discoverer of the C14 dating method, was very disappointed with this problem. He understood that archaeological artifacts were readily available. After all, this what the archeologist guessed in their published books.
Some believe trees are known to be as old as 9,000 years. They use tree rings as the calibration standard. A lot of people doubt this claim for various good reasons I wont go into here. We believe all the dates over 5,000 years are really compressible into the next 2,000 years back to creation. So when you hear of a date of 30,000 years for a carbon date we believe it to be early after creation and only about 7,000 years old. If something carbon dates at 7,000 years we believe 5,000 is probably closer to reality (just before the flood).
Robert Whitelaw has done a very good job illustrating this theory using about 30,000 dates published in Radio Carbon over the last 40 years. One of the impressive points Whitewall makes is the conspicuous absence of dates between 4,500 and 5,000 years ago illustrating a great catastrophe killing off plant and animal life world wide (the flood of Noah)!
I hope this helps your understanding of carbon dating. If you have any more questions about it don't hesitate to write.
(2.) I just listened to a series of lectures on archaeology put out by John Hopkins Univ. The lecturer talked at length about how inaccurate C14 Dating is (as 'corrected' by dendrochronology). The methodology is quite accurate, but dendrochronology supposedly shows that the C14 dates go off because of changes in the equilibrium over time, and that the older the dates the larger the error.
Despite this she continually uses the c14 dates to create 'absolute' chronologies. She says this is ok so long as you take into account the correction factors from dendrochronology. (They conveniently forget to mention that the tree ring chronology was arranged by C14 dating. The scientists who were trying to build the chronology found the tree rings so ambiguous that they could not decide which rings matched which (using the bristlecone pine). So they tested some of the ring sequences by C14 to put the sequences in the 'right' order. Once they did that they developed the overall sequence. And this big sequence is then used to 'correct' C14 dates. Talk of circular reasoning!!!!
(3.) Even if the rate of decay is constant, without a knowledge of the exact ratio of C12 to C14 in the initial sample, the dating technique is still subject to question.
(4.) Traditional 14C testing assumes equilibrium in the rate of formation and the rate of decay. In fact, 14C is forming FASTER than the observed decay rate. This skews the 'real' answer to a much younger age.
You can find some further good information here:
http://www.cs.unc.edu/~plaisted/ce/dating.html#Carbon -- read the full page if you get the chance.