First, we are here dealing with my hobby horse : C14. Not the halflife of Americium as used in Smoke detectors, not the halflife of Ka-40 (Potassium 40) decaying into the argon which is so easily upset in the dating process by excess argon, at least we creationists think so, but carbon 14.
According to theory, it should be dated to one half life old, right?
Well, suppose one half life ago the carbon14/carbon12 in atmosphere's CO2 was about 100 % of the present carbon, and supposing one half life is what it takes to decay to 50%, obviously we would have remaining now 50 %, that is 50 pmc, 50 "percent modern carbon".
As you may imagine, if instead the real c14 content relative to c12 was just 50 pmc back then, we would have only 25 pmc remaining now, and it would look like two half lives old.
A half life ago was a little before the deluge, using the Cambridge halflife.
So, one half life back is 1486 Anno Mundi. Deluge was later, Anno Mundi 2242. Using the LXX. Using the calculus of Roman Martyrology - the Byzantine one having instead more time back to Deluge:
Which means that we get:
One half life ago would still be before Deluge, which in Byzantine counting also is 2242 Anno Mundi.
For my part, I'll stick to Roman chronology. One hlaf life ago is Anno Mundi 1486.
Since this was before the Flood and since probable Flood remains are dated (when Creationists manage to arrange it) to dates which suggests that C14 level was c. 3.9 pmc at Flood, we can tentatively - this is theoretical and might be wrong - assume C-14 was rising to 3.9 pmc between Creation and Deluge.
Whatever the reason why the rise was so slow initially (it can hardly have been decaying amount starting to equal produced amount yet, it could be a drastically lower production or production being diluted in a drastically higher overall carbon, or both), the curve is so flat one can treat it as an even slope (in the diagrams I am always thinking of but never making).
This placees the C14 level - checking my notebook from tonight - for 1486 Anno Mundi at 2.6625 pmc.
This means there should remain 1.33125 pmc.
And what would halflives starting at a spurious 100 pmc get in order to get to 1.33125 pmc?
|pmc remain||after years|
|25||11 460 BP|
|12.5||17 190 BP|
|6.25||22 920 BP|
|3.125||28 650 BP|
|1.5625||34 380 BP|
|0.78125||40 110 BP|
Since 1.33125 pmc is between 1.5625 and 0.78125, the dating should, for a real sample of just one halflife back, be between 34 380 BP and 40 110 BP. Let's check the carbon calculator*: 1.33125 % remaining carbon = 35 700 years. One half life, disguised as 6 to 7 half lives, due to rising carbon levels since back then.
Hans Georg Lundahl
Thursday after Ash
* Short url : http://ppt.li/3m8
Long url : https://www.math.upenn.edu/~deturck/m170/c14/carbdate.html