Carbon Dating and Fossils

Hi all👋🏼!

My wife and I were talking about the creation account, fossils that date back 30000 years, etc. And one thing that came up was carbon dating, and how it works. I’m no scientist so forgive my ignorance. So pertaining to carbon dating, which seems to be the method by which the dates of a lot of archeological findings are based on. How did scientists land on the half life of C14 being 5700yrs old? How are scientists able to make that determination? Is 5700 years definitive or an estimate? If carbon dating is accurate, how do Christians reconcile the creation story, humans being descendants of Adam, with archaeological discoveries that date back 50000yrs, and show that humans might have evolved from apes or another species of humanoid?

Thank you in advance for taking the time to help me understand all of this!

I am a scientist, but this is still outside my wheelhouse as a biologist. However, the scientist in me was curious about a few things. Namely, what are the parameters for measuring the half life of 14C. I am also practicing Python scripting wherever I can, so this is what I wrote up. You can copy and paste the code below into an online Python interpreter: . (everything after the # is ignored by the interpreter)

I also double-checked my math over here, and it agreed with their results when I put in the values for 238U.

# equation for calculations
# remaining atoms = 1/2^n * starting atoms
# where n is number of halflives

halflife = 5730 # halflife in years
mw = 14 # molecular weight of isotope
mass = 0.001 # mass of starting sample in grams (0.001 = 1 mg)

avogadros = 6.022E23 # number of atoms per mole

oneday = 1/(halflife*365) # number of halflives in one day
num_atoms = (mass/mw)*avogadros
num_remaining = 1/(2**oneday) * (num_atoms)
num_decays = num_atoms - num_remaining
dps = num_decays/(24*60*60)

print(f'number of atoms in {mass} grams of isotope = {num_atoms:E}')
print(f'number of disintegrations in one day = {num_decays:E}')
print(f'number of disintegrations in one second = {dps:E}')

The results:

I’ve only tangentially dealt with radioactivity in the biology lab, much of which was phased out 15 years ago (anyone remember using 32P?). However, I do know one thing. You can detect the decay of a single atom. They are quite energetic. Isotopes decay in a first order reaction which are easy to model and easy to calculate.

Even with just one milligram of 14C you will get ~165 million decays per second which is exceedingly easy to measure in the lab. The other parameters you would need to measure is the ratio of isotopes in your sample and the weight of the sample. The efficiency of detection is also a thing. However, all of these parameters can be controlled for and are known, at least to within an a level of accuracy needed to rule out YEC.

In fact, I would strongly suspect that the half-life of 14C is the most reliable factor in carbon dating. Factors such as historic atmospheric concentrations, sample preservation, and the ecological history of the sample are going to be larger wildcards than the decay rate of 14C.

Unsurprisingly, the initial estimate of the half-life of carbon-14 has been improved on. Because 14C dating is used so extensively, instead of constantly tweaking the calculation, for consistency a “radiocarbon year” is often reported, using the old formulas, which then needs to be translated into the best current equivalent in versus actual calendar years if one wants that information…

But the physics behind half-lives is very fundamental. Changing decay rates will generally make all atoms unstable. As atoms exist, we can be confident that decay rates have not significantly changed over time.

(I did learn using radioactive labels in DNA sequencing but did not use the technique.)

That makes a lot of sense. Having to determine which calibration someone used and then working out the conversions would be a pain. Reporting a standard measure would be a lot easier. I suppose it may be worth citing Intcal (the scientific working group that oversees 14C dating calibrations):

The dinosaurs remember. :wink: When I first started in the lab I did 32P labelled Southern blots and old school film.

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