Specifically, he's heard of tests being done on living things and the results (obviously) are way "out of wack" and to him that's enough to negate the entire method altogether. So, I had mentioned to him that carbon dating (specifically) can't work on living things because the carbon in the organism is still being exchanged with the outside world and cannot be accurately measured (nor should it be).
Actually, with sufficiently precise instrumentation (which we are unlikely to ever have) very recently living things could be dated using 14C. THe problem to which your friend refers is this; 14C dating relies on the organism having the same 14C/12C ratio as the atmosphere when the organism died; that is, the organism was in equilibrium with the atmoshperic 14C/12C ratio. Marine organisms such as seals and clams and whatever are not in equilibrium with the atmosphere; they get some (if not all) of their carbon from dissolved limestone which is "old carbon" and makes them appear older than they are when measured by the 14C method. Of course, scientists know about this; the creationist claims of error in 14C dating come from the scientific iterature in which such effects are measured in order to see what can and cannot be measured using 14C dating.
And don't let your friend bring up the common creationist claim that the atmospheric ratio of 14C/12C could have been different in the past; we know it
was different in the past, and we compensate for that by calibrating the 14C method using samples whose age is known by other means (such as tree rings). The maximum error of uncalibrated 14C dating is around 10%.
But winning the Nobel Prize is no guarantee of truth. All scientific results are tentative and are modified as required if new and contradictory evidence appears.
Radiosiotope dating is not plagued with errors. Dating is done using many isotopes, involving three wildly different types of radioactive decay, and with many different methods. 99% of the time all the results agree, and also agree with non-radiometric methods such as stratigraphy. Occasionally different methods do not agree, and that's when the scientists do the real interesting science and the creationists quote-mine the papers to make dating appear unrealiable. E.g. see
Claim CD031: KBS Tuff dating.
There's a good explanation of 14C dating at
How does the radiocarbon dating method work? and a good introduction to all dating methods at
Radiometric Dating: A Christian Perspective. Some brief descriptions of creationist objections to 14C dating, with references to more information, at
CD011.1. Variable C-14/C-12 ratio invalidates C-14 dating,
CD011.2. Vollosovitch and Dima mammoths yielded inconsistent C-14 dates,
CD011.3. Living snails were C-14 dated at 2,300 and 27,000 years old,
CD011.4. A freshly killed seal was C-14 dated at 1,300 years old,
CD011.5. Triassic wood from Australia was dated at 33,000 years old, and
CD011.6. Ancient coal and oil are C-14 dated as only 50,000 years old.
(fixed error in one URL's title)
This message has been edited by JonF, 07-14-2005 09:25 PM
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