I’ve been scoring science questions (you know, the standarized tests kids suffer through. We score several states where I work) for 8th graders this week, and one of the short response questions asked kids to identify " one thing on Earth which(or that) can have its age determined by using carbon dating." At this grade level anything that can be radioactive dated is also an exceptable answer. Most of the kids said rocks, dirt, bones etc. A few of them, however, said people or animals. They got half-credit for those answers because one assumes they are talking about living beings.
Still I wonder, can a living thing be carbon dated? Wouldn’t that be dangerous? I don’t think I’d let anyone try it on me, they’d have to be content with checking my licence.
You can’t be carbon dated, or at least, it wouldn’t tell you how old you are.
Carbon dating works because radioactive carbon 14 is being continuously manufactured in our upper atmosphere and being continuously lost by radioactive decay. This keeps the proportion of carbon 14 roughly constant in the air, which keeps it roughly constant in living plants, which keeps it roughly constant in living animals including yourself.
It’s only when you’ve died and stop exchanging carbon with the environment that the proportions begin to change. Carbon dating can only tell you how long something has been dead.
If you’re asking whether its physically possible to carbon date a living being however, the answer is yes. Carbon dating can be performed on very small samples, so you could do it on sloughed off skin, or on a blood sample, or possibly on hair (not sure) without doing any harm. But it wouldn’t tell you much (well it might tell if you’re an alien, but that’s another story…)
I think some of the correct answers you had were actually wrong. If I recall correctly, in order for an object to be carbon dated it has to have been formerly alive and currently dead. The testing detects a form of carbon which is constantly renewed in living organisms but disappears at a fixed rate in dead ones. So by determining what proportion remains you can tell how long ago an organism died.
To carbon date something, you just need a little sample. Someone could carbon date you with a hair sample. The problem is that as long as you’re alive the carbon in your body is being turned over and replaced, so the ratio of carbon-12 to carbon-14 in your body should stay pretty much the same until you die and start replacing it. So if someone carbon dated you it should give an age of about 0.
Little Nemo, the bones of course have carbon because they were parts of animals or people. The dirt has carbon since it’s made up of dead plants, animals etc at least in part. As for the rocks, the developer of the question contends that they too are partially formed of formerly living material. That sounds far-fetched to me, but I don’t have a PHD in science, so I’ll take her word for it.
Thanks for clearing that up, though, folks. I was under the assumption that you’d have to use a bone sample to gather a thing’s (living or dead) age since soft tissues are shed so often.
One must keep in mind that Carbon dating has a pretty wide margin of error, on the order of three to five thousand years, if I recall correctly.
So a test on, say, a bone sample from a living human, could not give an answer with anything approaching accuracy.
Now, I understand there are other forms of radiocarbon dating- one was used on the Shroud of Turin and placed it in the 13th Century, as I recall- but the original “carbon dating” type system was far better suited to things like fossils and Egyptian mummies.
That’s not strictly true. It can only tell when the SAMPLE died. So if I surgically removed a sample of my bone, it could be carbon dated because that sample is no longer exchanging carbon through my bodily system. But the results would still be useless because it could only give my age to about plus or minus maybe 250 years at best.
Oh, and BTW, hair is dead.
Rocks can’t be carbon dated. The developer of the question is a moron. The margin of error for carbon dating is way less than 3000 years. Such a margin would be useless for dating Egyptian mummies, as it would place a mummy from 1000 BC anywhere from the present to 4000 BC, and thus be of virtually no help.
The margin of error for carbon dating is about 40 years for something around 1000 years old. It can’t be used for anything older than about 40-50,000 years because there’s not enough carbon-14 left after that long.
Once the system was developed, it had to be tested against an object of great – but known – age. That test was conducted on an Egyptian funereal boat, currently on display at Chicago’s Field Museum.
So it seems that carbon dating is useful for determining the age of rocks; but only in those cases where the rock was alive within the last fifty thousand years.
Yes you could date yourself if you really wanted to, but as has been said before you haven’t been dead long enough for it to come out right. You can not date rocks, dirt or any inorganic material, I HATE when text books/tests tell you crap like this. I had a calc book that tried to pull something like that once dating a rock or some such crap.
C-14 dating was calibrated by tree ring dating, don’t ask for the tech term as I can’t spell it, soon after they developed C-14. They found the C-14 to be very accurate, at least for dating stuff 4-5,000 years old.
Such questions are the reason I’m against standard tests. I gave one once to some third graders and they asked something like “How much does a leash for a dog cost?” answers “$1, $100, or $1000”. Couldn’t they make it a little bit better than that? at least 10, 50 and 100.