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Carbon-14 dating.

  1. Feb 7, 2006 #1


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    A friend of mine and I got into this conversation, and he said his college teachers had this talk about how it is highly inaccurate.

    I thought this to be silly because if it were highly inaccurate, then why would they even rely on it.

    I understand that it may be inaccurate under certain circumstances, but I doubt it's highly inaccurate most of the time. If this was the case, scientist wouldn't use it period.

    For areas that carbon-14 dating is not possible, they normally use the skills of geology and/or the environment surrounding it (like animal bones or plants). If these other methods are considered pretty inaccurate compared to carbon-14 dating, and if they say carbon-14 is inaccurate in itself, that makes the other methods utterly useless to rely on. Some scientists rely on these other methods, especially the paleonanthropologists in South Africa.

    Can someone please explain?
  2. jcsd
  3. Feb 8, 2006 #2

    c14 dating is not usually used on things that are extremely old since c14 has a 1/2 life of ~5700 years. if you try to analyze a sample that is millions of years old, it will be extremely hard to find any c14 atoms around. scientists use other isotopes of things like potassium to date much older materials. C14 can/should only be used for things that are suspected of being <~70,000 years old. potassium on the other hand has a half life of over 1 billion years, which makes it a much better candidate to use to do radiometric dating of old materials.
  4. Feb 8, 2006 #3
    Radio carbon dating is only for samples less than 40000 years old and they must be still in organic state. Google for other dating techniques such as magnetostratigraphy, Luminescence dating or thermoluminescence...for more infor on dating
  5. Feb 8, 2006 #4


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    That is exactly what I mentionned.

    I told him that you can't date for anything to much older than like 20 000 because there are relatively little amounts of C-14.

    So is the method accurate for things like Egyptian mummies?
  6. Feb 8, 2006 #5
    I'm pretty sure C-14 dating would work fine for Egyptian mummies, seeing as (on average) they are only 5000 years old tops.
  7. Feb 8, 2006 #6
    Okay well, my friend just informed me that it is believed Ancient Egyptians used Uranium/Plutonium to rub over the wrappings, which may cause an issue with the particle decay of common C-14...
  8. Feb 10, 2006 #7
    Plutonium? That would be a neat trick, since the Ancient Egyptians would have needed a time machine in order to go into the 20th century AD to get plutonium and then gone back to rub it on those wrappings. It's not like you could just go into a corner pyramid and buy the stuff.

    If they had rubbed uranium on the wrappings, that could be detected and corrected for.

    Your friend is full of baloney, to put it nicely.

    For paleoanthropologists who want to date, say, australopithecene fossils that are several million years old, they use potassium-argon dating. Which is accurate from ~100,000 to several billion years ago.
  9. Feb 17, 2006 #8
    I uploaded a radiocarbon dating tutorial:

    https://www.physicsforums.com/showthread.php?t=111084 [Broken]
    Last edited by a moderator: May 2, 2017
  10. Feb 17, 2006 #9


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    Currently waiting for approval.

    Will it be readable for someone like me?

    The only thing I know about chemistry and the sort is from reading Asimov books on science (non-fiction).

    I know mathematics, but I think that's irrelevant here.
    Last edited by a moderator: May 2, 2017
  11. Feb 17, 2006 #10
    Every PF user will be able to read it once the moderators have approved it :D

    Well you need to have adobe reader to view it, but i think you have it.
  12. Feb 17, 2006 #11


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    The main problem is - how you define 'highly inaccurate'?

    1% error in case of 191 years old wooden plank is too much to say whether it was used during Battle of Waterloo.

    10% error in case of 1500 years old piece of wood is enough to say it wasn't used for Jesus crucifiction.

    C14 carbon dating is precise enough to answer numerous questions about historical objects.

    Sometimes it may fail, but then there is no method or device used in mesurements that gives always correct results. Last year I bought 4 boards to replace rotten ones in the porch. I have measured several times, yet what I brough home was 5mm thinner than needed :(
  13. Feb 19, 2006 #12
    If atoms decay and turn into energy..? Does that mean that the universe will become matterless in a super-duper long time?
  14. Feb 19, 2006 #13


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    Staff: Mentor

    AFAIK many isotopes are considered stable and they are final products of decay chains. So they should stay forever.
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