Peg, its clear that you don't know anything about C14 dating from your own research and that you are reading about it only on creationist websites. They are lying to you.
On this site you have several people who are very familiar with the method. I've done nearly 600 samples in my career as an archaeologist, and I've both written and lectured on the subject. Now, to your creationist websites' objections:
contamination of the samples tested for instance. Its always possible that a bit of wood, for example, from the heart of an old tree might contain live sap. Or if it was extracted with an organic solvent (often made from petroleum), a trace of the solvent might be left in the portion analyzed. Charcoal could have been penetrated by rootlets from living plants. Any of these senarios could affect the levels of C14
That's why you never rely on just one sample! My last major excavation included 31 radiocarbon dates on a variety of materials, and those results were compared to two other dating methods and the results from other local sites.
There is also a method for estimating the trustworthiness of your sample--establishing the C13/C12 ratio. C13 is a stable isotope, and because it is heavier it is taken up slightly differently into different parts of the food chain. If you find a piece of marine shellfish with a -26.0 ratio, or a piece of wood charcoal with a 1.0 ratio you know those samples are questionable!
Sap is not a problem. And if there was sap, it would make the sample artificially younger. A more serious problem is dating part of a 1,000 year old tree that was collected and burned on an archaeological site. That would make your date artificially old.
Extraction is not a problem. Give the laboratories some credit for not being total dolts, eh? And rootlets! Don't you think the professionals have thought of that one too? The pretreatment methods include a procedure for dissolving those rootlets!
Live shellfish have been found with carbonate from minerals long buried or from seawater upwelling from the deep ocean where it had been for thousands of years. Such things can make a specimen appear either older or younger than it really is.
No, only older. Dating freshwater shellfish in an area heavily influenced by old carbonates is just not done. That's where you get your living shellfish that are thousands of years old. But marine shellfish are different--they make a fine dating material. They are short-lived, so you don't have the problem of a 300 year old abalone. They are usually dense, so you don't have much rootlet or ground water penetration. And they represent a single event--a person collecting a shellfish from the ocean and bringing it back to the site.
But its still too old, you say? The laboratories correct for that. They have established a worldwide correction for marine shellfish. To that you add your local correction, called the Delta-R. In my area the Delta-R is 225 years. This was established by dating 1) marine shells collected at a known time prior to the beginning of nuclear testing, and 2) comparison of charcoal/shellfish pairs from identical proveniences. The last such test I ran produced a difference, following calibrations, of 15 years between the shellfish and the charcoal. That's well within the limit of error.
there is also the assumption that the level of carbon 14 in the atmosphere has always been the same as it is now. But we know that the carbon level has increased a lot since the explosion of neuclar bombs into the atmosphere and since the use of burning fossil fuels. So how do we really know what the levels were thousands of years ago?
This is probably the biggest creationist mistake. We don't just assume the levels of C14 in the atmosphere have been the same! De Vries published on this back in 1958, and by comparison to tree rings and other annualar materials a calibration curve has been worked out which corrects for atmospheric variation. There are examples of these charts upthread, if you had bothered to read those long posts.
The nuclear testing only effects organisms that are taking up carbon after that testing began. It does not effect older samples.
volcanic eruptions also add to the stable carbon-dioxide reservoir, thus diluting the radiocarbon....so how do they account for all these possible variences in c14 in the atmosphere??? How can they honestly know how much to make allowance for???
By tree rings! If you date a tree ring that is 11,000 years old (and you know its age by direct counting) then you can tell how far off the measured or conventional radiocarbon age is and correct for it, resulting in an accurately calibrated date.
Peg, your objections are all standard creationist fodder, and have been answered thousands of times.
Admit it--you just want radiocarbon dating to be worthless so it fits with your
a priori beliefs, and no amount of evidence that we present will make any difference to those beliefs. That's the usual pattern that we see.
If you are willing to read some basic information try this article (which I already linked to you above) I suggest you begin with:
Radiometric Dating: A Christian Perspective by Dr. Roger C. Wiens
If your response shows that you have not seriously considered any of this, and that you are still relying only on creationist websites, you can expect a somewhat less polite response.
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
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