Sure do! Flash frozen mammoths dont appear in the original text.
@Dale (or anyone else who understands this stuff well),
I looked over that short Wolgemuth article in the link, and have a question: How does Carbon-14 fit into this model, w/ it’s half-life of 5700-ish years?
Just wanting to understand better what Wolgemuth is establishing here.
C-14 is continuously cosmogenically ‘locally’ produced, so its presence on earth is to be expected. Per Wikipedia,
Per the article,
The [other, not man-made or cosmogenically produced] short‐lived nuclides are no longer around, and the reason is obvious: the solar system is much older than 100 million years, because the short‐lived nuclides have simply decayed themselves out of existence.
(The table on the right simply has the locally produced man-made and cosmogenic radionuclides removed from the list for clarity.)
Maybe an analogy with evaporation might work – a system with a slowly evaporating fluid and a more quickly evaporating one, with known rates of evaporation for each. To begin with, you have both, but if your system no longer has the quickly evaporating one and with no means of replenishing it, then your system has to be at least as old as it takes for the quickly evaporating one to have completely disappeared. (Carbon-14 is ‘quickly evaporating’, but it has a means of replenishment.)
(Does that help?)
As Dale has stated, carbon-14 is continuously replenished by cosmogenic radiation. Flux can vary with solar activity, and one outcome of this is that some especially powerful solar flare signatures have been captured in the worldwide tree ring record, dating up to nine thousand years ago. Carbon dating reveals not only age, but a global history of past events.
Another implication of the half life of carbon-14 that is important, is that it is a shorter yard-stick among the unstable isotope dating techniques. Pushing it beyond 50,000 years is very challenging as sources of measurement error and contamination progressively swamp out the signal. Claims of carbon-14 in ancient dead sources such as diamonds or natural gas betray a deep ignorance of the practicalities of sampling and carbon-14 dating.
Properly applied, however, carbon-14 dating yields brilliant results. Viking settlements have recently been dated to within an exact year. Tree rings have been dated by individual annual rings from the pith outward and displayed the progression in age. Historical artifacts such as Hezekiah’s tunnel and the dead sea scrolls have been accurately dated. It is incontrovertible that carbon dating yields a record of settlement and life on earth which is continuous for at least the past 25,000 years, precluding any possibility of a punctuating global flood over that time frame.
Thank you both for your replies. I already understood most of what you guys just shared; I guess the better way I should have asked my question is: “So the effects of cosmogenic radiation on the heavier metal isotopes are essentially nil?” That is, “the energy input from cosmic radiation doesn’t turn the heavier metal elements in rocks into their less stable isotopes?”
I can presumably guess the answer. But thank you both again, and thanks for that table, @Dale . I had definitely never seen that before.
FWIW, in medicine & pharmacology, the conventional rule is that after five half-lives of a drug since it’s last dose (ie, 3.125% residual plasma concentration), the drug effect is considered negligible. That’s why patients are asked to stop anticoagulant drugs like coumadin & Eliquis for three days prior to surgery.
Correct. Nitrogen is of course 80% of the atmosphere and exposed to cosmic radiation continuously. Other minerals, not so much. I’m almost a half a century out from being familiar with my nuclide chart, but it takes more than gamma irradiation to convert many isotopes into something else.
Thanks for clarifying further.
There are dating methods which exploit the action of cosmogenic radiation on surface rock.
While not as precise as other methods, these are yet another set of measurements which fill in details of overall Earth history.
Thanks, especially for that second one!
Depending on how easy to contaminate and how common the isotopes are, there can be quite a range of maximum numbers of half-lives for detectability. 14-C is one of the worst, because it is incredibly easy to contaminate. In poor settings ~4 half-lives is good, in near-ideal ones 12 is possible. For something like 238-U to 208-Pb or 40-K to 40-Ar, the theoretical limit is much higher, but we have no real way to test their limits, as those isotopes haven’t existed for more than ~2 and ~10 half-lives, respectively.
To add to the points already made:
Besides 14C, most of the other short-lived isotopes found naturally on Earth are part of the decay chain of longer-lived isotopes (e.g., radon).
Cosmogenic radionucleotides besides 14C are generally quite rare on Earth. A cosmic ray whacking into a meteoroid in space may hit a nucleus and create a distinctive radioisotope, but making it through the atmosphere and past the magnetic field is rather less common. There are some reports suggesting occasional higher levels of rare isotopes in the geological record, perhaps pointing to a relatively nearby supernova.
We do have evidence of prehistoric decay of various shorter-lived isotopes (e.g., http://www.psrd.hawaii.edu/Nov09/Al-26-distribution.html ), and can also watch their decay patterns in distant supernovas.
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