C-14 will no longer work

Cecil's Columns/Staff Reports
1

Here’s another minor (possibly) point about Carbon-14 dating that I just recently read somewhere but I can’t remember where… (at least I didn’t get it from a friend of a friend):

C-14 dating will not work for anything that has died after 1945. Seems that we messed up the isotopal (?) mix of the elements in the environment at about that time…

You can still use C-14 dating with reasonable accuracy for anything that kicked the bucket before then, but our bodies haven’t been absorbing the same “baseline” level of radioactive isotopes since 1945.

2

What I should have said was:

http://www.straightdope.com/mailbag/mcarbon14.html

I’ll never do it again! Honest!

3

I don’t think any isotope ratios have changed that dramatically - even if they had, we could correct for it. More likely, the reason is that even under the best of circumstances, the margin of error for carbon dating is at least a century or so, so dating something that recent would be meaningless.

4

No, the margin for error is NOT a century or so… the margin of error depends on many factors, as outlined in the Mailbag Answer.

Note that the margin of error in dating the Shourd of T is plus or minus 65 years, and we’re dating back almost 700 years ago. That’s not bad for a margin of error under 10%.

[Edited by CKDextHavn on 10-03-2000 at 07:27 AM]

5

The isotopal change that occurred with the advent of A-bomb testing is Strontium-90. This is a naturally occuring isotope that is found in bones among other things). Sr-90 can be used to date bones (not fossils) but the increase in Sr-90 levels have to be accounted for.

Cavaet Emptor: This is from memory.

6

You can’t date jack with C14 if it’s younger than 500 years. The ratio is too small to be counted.

If your saying that all C14 dates are correct for 1950, not 2000, that’s true, but again, the difference is too small to count. Don’t worry about it.

Caveat emptor for me, too…

7

As you can see, my Emptor has already been Caveated. Thanks for the fix, Dex.

8

I think that a old creationist canard should have been explicitly mentioned:

You do not expect accurate C-14 dates from carbon samples that come from under the ocean. (Like the “living 20,000 year old” molluscs that creationists keep bringing up.

Even seals and otters that eat a lot of shellfish will have very old C-14 dates.