RAZD,
I agree, with coyote, good post, thanks for the info. I think the idea of “calibrating” C14 with tree rings is great. Yet, I see a couple of problems here. First of all, tree rings are not always annual. So, we have to assume these are annual rings, I am assuming for the most part they are, but over a long period (say thousands of years), a few extra rings here and there could give an older date for the tree. Just a thought, I am not willing to die on this mountain. Correct me if I am mistaken, but the oldest trees I have been able to find, based on their rings alone, have been in the 4500 range. It is interesting that as you look at the graph, and just for kicks, drop the 5K and beyond, the graph appears to start a significant divergent from the linear path it appears to be taking.
With parent daughter systems you can estimate the amount that has decayed by the amount of daughter mass to the remaining parent mass.
Again, an assumption has to be made that all the “daughter” mass actually is daughter mass (came from the parent isotope), and was not already present in the sample. This is a very large assumption, especially since the consequence of being off could mean the difference in millions of years versus tens of thousands. How this estimation can be done with any accuracy is beyond me.
With radiocarbon we can estimate the amount from the amount in the atmosphere today as a first approximation. We can also find correlations that tell us the actual age of objects and then use that to calculate the actual amount of carbon-14 in the atmosphere at different times, and once that correlation is known we can then calculate more accurate ages from samples.
What correlations are you referring to that tell us the actual age of objects that goes beyond say, 5K years? If we have correlations that tell us actual object ages, why are we even belaboring the issue of radioactive dating? We must know what these calibrations are, and see how many assumptions there are in these. If we are not accurate with our calibration tools, calibrating against an inaccurate instrument is useless. This sounds like we are getting somewhere.
By the way, I sure appreciate the tips on posting. We will see if I have learned any posting etiquette.