When is carbon-14 dating impractical?

Carbon 14 dating is only useful up to about 60,000 years because of the half-life of C-14. For example it’s useful for archeological sites. It’s not useful for dating dinosaurs.

@Rarebear This is one of those times where you should cite a source.

Check this out. It covers various radiometric dating techniques.

Generally, c-14 dating is impractical for time periods beyond 60,000 years, as @Rarebear states. More specifically, the half-life of c-14 so it’s useful for dating items that are relatively young. As the half life is about 5000 years though, it’s also impractical for dating items/organisms with more specificity than that (e.g., whether it’s 6000 or 9000 years old, or anything inbetween).

@world_hello Okay, I didn’t feel I needed to, as it’s like citing a source that the Earth revolves around the sun, but if you want.
http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm
http://en.wikipedia.org/wiki/Radiocarbon_dating
http://www.allaboutarchaeology.org/carbon-dating.htm
http://101science.com/Carbon14.htm
http://www.chem.uwec.edu/Chem115_F00/nelsolar/chem.htm

Is that enough, or do you want more?

What’s with all the smartasses on the Internet lately?

Carbon-14 decays exponentially, so a minimum threshold is needed to determine the 60,000 year limit. Since this threshold is arbitrary, different studies may show different results. True though, it’s the generally accepted value.

@Vortico: The half-life of C-14 if 5730 years or so—this is what is known with accuracy. So the 60,000 year figure represents some 10 or 11 half-lives, after which less than one-tenth of 1% of the original amount remains—setting an age limit on specimens to which the method applies. This does not affect the accuracy or validity of carbon dating for specimens younger than this upper limit.

I think part of the question is “Why 60,000 years?” as well. For instance, it seems relatively arbitrary that it should be only 10 or 11 half lives, because many ask, “Well, what if there was more c-14 in the item to begin with?”

From my understanding, I think that the issue rests on a lack of clarity regarding the definition of what “half life” means in relation to “exponentially.”

It’s a question of statistical validity. When you’re looking at the extreme ends of a hyperbolic asymptotic curve, tiny difference can mean huge changes so it’s not statistically valid.