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Justifying Radiocarbon Dating vs YEC

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3/3/2014 3:14:13 PM
Posted: 4 years ago
I thought I would take some time to address this.

In radiocarbon dating a number of assumptions are made:
1. Rate of Radioactive Decay remains constant
2. Organism's intake of carbon is predominantly derived from the atmosphere e.g. Deer's carbon comes form grazing, and the organic material grazed builds mostly from atmospheric c-14.
3. No, or insignificant additional c-12 or c-14 enters the sample after the organism dies
4. A constant atmospheric c-14 ratio.

#1 is the easiest to justify, as radioactive decay depends entirely on quantum tunnelling. And the rate at which quantum tunnelling is calculable form first principles (from the fundamental constants of nature) which has shown it to be completely independent of temperature, chemical composition and time. Furthermore even if the rate of decay was higher in the past, it would have had substantial immediate concequences. For the rate to increase the strong nuclear binding force would need ot be weaker, which would affect fusion in the Sun (Sun would give out much, much less energy) and also the rate of ratioactive decay of all elements in the Earth would skyrocket, leading to a molten/vaporized Earth, or at the very least a very dead one.

#2 is also relatively easy to justify. Most organic material we consume ourselves for example have been in the lower levels of the biosphere for less than a century. Almost all the carbon we and the animals we consume is converted to CO2 within 10 years and hence re-enters the atmospheric circulation. Only a handful of examples are invalidated by this, for example mollusks, who are known to derive most of their carbon from calcium carbonate rocks (which are much, much older than the atmospheric carbon, and hence very, very c-14 poor).

#3 is a little harder to justify. Contamination in very old samples can be a problem (see attached graph). Since almost every contamination are of old samples being contaminated with recent carbon, the contamination is to enrich the sample with c-14. Thereby yielding erroneously young dates. This is especially true when the original C-14 abundance is exceptionally low, and even instrumental precision plays a role. In the +2% natural c-14 abundance line, the dates that were >50,000 years old are erroneously dates to be a maximum of 35,000 years assuming a 2% contamination. Note however that a 2% contamination has negligible effect on the younger dates (which are still substantially older than YEC's claim). Also there are very low-level background sources of c-14, such as that derived from alpha or neutron decay capture. Uranium and thorium have incredibly long half lives (4.5 & 15 billion years respectively), therefore the level at which this occurs is exceptionally low. It does completely rule our using c-14 for ages >55,000 years however as this low level production is comparable to the 'true' c-14 concentration expected to be present.
There are very few known mechanisms known where c-12 can contaminate a sample, off the top of my head a Cliff face could dissolve in acid rain and flush over a sample. Such cases are unlikely however, and unlike c-14, a tremendous amount of c-12 would need to contaminate the sample in order to yield an erroneous date.

#4 Is the critical assumption. The graph below shows what will happen if the original abundance was 10% lower than expected, which yields large accuracy errors. For example, a sample dated at 33,000 years would actually be ~18,000 years old. Still substantially older than a YEC earth. This original ratio is what needs to be addressed. (Explained below)

C-14 dates + assumptions chart:

From the graph, the main thing one needs to observe is the most dramatic errors are expected to come in the oldest samples. At 10% original abundance, a 2% error in this assumption will yield inherent accuracy error of ~ +/- 1,000 years. At 95% Abundance the error increases to +/- 4,000 years, and at 97% this error becomes +/- ~ 8,000 years.

Contrast that with the result at 25% natural abundance (which contradicts a YEC claim), the same error at 25% gives an accuracy error of just +/- 450 years. In practice these errors are much, much smaller, I have exaggerated them for the purposes of illustration.

To confirm the assumption that the c-14 ratio has been approximately the same in the past as it is today, the technique is calibrated against dendrochronology (take the wood with the tree-ring of interest and c-14 date it), and also ESR dating ( From these and a number of other techniques, we can see that the atmospheric abundance has deviated by much, much less than 10% in the past, and also allows for fine-tuning of the assumptions made.

If anybody has any questions/points about the assumptions made/assumptions I have missed out, please leave a post.

P.S. Is there any way to include a picture in my post? I couldn't figure it out so I had to leave a link
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