Notices
Results 1 to 26 of 26
Like Tree7Likes
  • 6 Post By kojax
  • 1 Post By Strange

Thread: carbon dating

  1. #1 carbon dating 
    Forum Freshman
    Join Date
    Jun 2007
    Location
    wv
    Posts
    49
    Can someone please explain it?


    Reply With Quote  
     

  2.  
     

  3. #2  
    WYSIWYG Moderator marnixR's Avatar
    Join Date
    Apr 2007
    Location
    Cardiff, Wales
    Posts
    5,760
    you mean on top of what wikipedia can tell you ?


    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
    Reply With Quote  
     

  4. #3  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,046
    Quote Originally Posted by Sarah1234 View Post
    Can someone please explain it?

    There is an isotope of Carbon called Carbon 14. This isotope naturally decays, so over time there should be less of it in the air. However, cosmic rays from space hit the Earth at a consistent rate, and when they hit the air, they cause Nitrogen 14 to mutate into Carbon 14. This happens enough to keep the Carbon 14 level at a set amount in the air.

    So, Carbon 14 is constantly decaying into Nitrogen 14. But in the upper atmosphere, the cosmic rays are constantly turning the Nitrogen 14 back into Carbon 14.

    Are you with me up to this point?

    Plants end up absorbing Carbon 14 while they are alive (because it becomes part of the Carbon Dioxide they use). However, after the plant dies, it stops absorbing Carbon 14 from the air.

    So now, the Carbon 14 in the plant is decaying into Nitrogen 14, but the Nitrogen 14 in the plant is not getting hit by cosmic rays, so it doesn't keep getting turned back into Carbon 14. Over time, the amount of Carbon 14 in the plant will diminish.

    This is an extremely consistent process. Isotope decay always exactly corresponds with its half life in any object that is bigger than just a few atoms. It's a very reliable clock.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  5. #4  
    Suspended
    Join Date
    Nov 2013
    Location
    United Kingdom
    Posts
    537
    How reliable is carbon dating?
    How can they date paper and ink?
    I remember reading about the dead sea scrolls and the dating of some other scripts found in caves.
    Reply With Quote  
     

  6. #5  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,598
    Quote Originally Posted by hannah40 View Post
    How reliable is carbon dating?
    How can they date paper and ink?
    I remember reading about the dead sea scrolls and the dating of some other scripts found in caves.
    Carbon dating is very reliable as long as the nature of the sample is well understood and the process is carried out with care. On the other hand, it is rarely used as the only method of dating. It is cross-checked with other sources of information.

    In addition to things like carbon dating, which can provide an age for the materials, other techniques can be used to date and authenticate documents. For example, the material the writing is on (stone, clay, parchment, papyrus, paper, etc), the types of fibres used to manufacture the paper (and even the way the paper was manufactured), the chemical composition of the ink, and so on. In addition, the style of the writing (e.g. the "alphabet" used and the specific script) and the language can also give information about when and by whom it was written.
    hannah40 likes this.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
    Reply With Quote  
     

  7. #6  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    2,655
    Quote Originally Posted by Sarah1234 View Post
    Can someone please explain it?
    Kojax's explanation is excellent. Just one further point, as I notice you posted this in Earth Science, rather than, say, Archaeology.

    It may be worth keeping in mind that, because the Carbon 14:12 ratio starts to change only once a living organism dies, and because its half life is short compared to typical geologcal periods of time, carbon dating is not very widely applicable in geology. It is however very useful in archaeology.
    Reply With Quote  
     

  8. #7  
    Life-Size Nanoputian Flick Montana's Avatar
    Join Date
    Jul 2012
    Location
    Flatland
    Posts
    5,438
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Sarah1234 View Post
    Can someone please explain it?
    Kojax's explanation is excellent. Just one further point, as I notice you posted this in Earth Science, rather than, say, Archaeology.

    It may be worth keeping in mind that, because the Carbon 14:12 ratio starts to change only once a living organism dies, and because its half life is short compared to typical geologcal periods of time, carbon dating is not very widely applicable in geology. It is however very useful in archaeology.
    We use it to date organics in our core samples to determine the age of flood events. It's kind of a pain to pull the organics out, but 14C is so common in our field that you be hard presses to find a similar study that doesn't include the analysis.
    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
    Reply With Quote  
     

  9. #8  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    2,655
    Quote Originally Posted by Flick Montana View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Sarah1234 View Post
    Can someone please explain it?
    Kojax's explanation is excellent. Just one further point, as I notice you posted this in Earth Science, rather than, say, Archaeology.

    It may be worth keeping in mind that, because the Carbon 14:12 ratio starts to change only once a living organism dies, and because its half life is short compared to typical geologcal periods of time, carbon dating is not very widely applicable in geology. It is however very useful in archaeology.
    We use it to date organics in our core samples to determine the age of flood events. It's kind of a pain to pull the organics out, but 14C is so common in our field that you be hard presses to find a similar study that doesn't include the analysis.
    Well if you use it professionally then clearly you're the person to ask. I had always assumed that, since the half life of C14 is about 6,000yrs, then the oldest things it would be able to date would be of the order of, say, 5 times that age, or so. What is the oldest organic sample you can date with any precision, using this method?
    Reply With Quote  
     

  10. #9  
    Forum Ph.D.
    Join Date
    Aug 2011
    Posts
    985
    Carbon dating only works on once living things that still have their original material present. It cannot be used to date a fossil because a fossil has had all of its tissue replaced by crytalizied rock. So you can carbon date a mummy but not a dinosaur.
    Reply With Quote  
     

  11. #10  
    Anti-Crank AlexG's Avatar
    Join Date
    Mar 2012
    Posts
    2,810
    C14 dating is good back to about 60,000 years.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
    Reply With Quote  
     

  12. #11  
    Forum Freshman
    Join Date
    Jun 2007
    Location
    wv
    Posts
    49
    If u can carbon date a mummy and not a dinosaur the how do we know for sure how old a dinosaur is?
    Reply With Quote  
     

  13. #12  
    Life-Size Nanoputian Flick Montana's Avatar
    Join Date
    Jul 2012
    Location
    Flatland
    Posts
    5,438
    Quote Originally Posted by exchemist View Post
    Well if you use it professionally then clearly you're the person to ask. I had always assumed that, since the half life of C14 is about 6,000yrs, then the oldest things it would be able to date would be of the order of, say, 5 times that age, or so. What is the oldest organic sample you can date with any precision, using this method?
    I know what to look for in terms of what to send out for testing, but I don't perform 14C analysis myself. I would agree with other posters that the agreed upon age for carbon dating can go as far as 50,000 to 60,000 years. I primarily date charcoal from paleoindian sites, but we rarely go over 10,000 years or so as we are analyzing post glacial civilizations in the American Midwest.
    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
    Reply With Quote  
     

  14. #13  
    Life-Size Nanoputian Flick Montana's Avatar
    Join Date
    Jul 2012
    Location
    Flatland
    Posts
    5,438
    Quote Originally Posted by Sarah1234 View Post
    If u can carbon date a mummy and not a dinosaur the how do we know for sure how old a dinosaur is?
    We can determine the age of the soils in which the dinosaur fossil was found.
    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
    Reply With Quote  
     

  15. #14  
    Forum Freshman
    Join Date
    Jun 2007
    Location
    wv
    Posts
    49
    So determining the age of the soil is just as good as if we could determine the age from the bones of the dino?
    Reply With Quote  
     

  16. #15  
    Anti-Crank AlexG's Avatar
    Join Date
    Mar 2012
    Posts
    2,810
    The bones will be the same age as the soil they're found in.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
    Reply With Quote  
     

  17. #16  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    2,655
    Quote Originally Posted by Flick Montana View Post
    Quote Originally Posted by exchemist View Post
    Well if you use it professionally then clearly you're the person to ask. I had always assumed that, since the half life of C14 is about 6,000yrs, then the oldest things it would be able to date would be of the order of, say, 5 times that age, or so. What is the oldest organic sample you can date with any precision, using this method?
    I know what to look for in terms of what to send out for testing, but I don't perform 14C analysis myself. I would agree with other posters that the agreed upon age for carbon dating can go as far as 50,000 to 60,000 years. I primarily date charcoal from paleoindian sites, but we rarely go over 10,000 years or so as we are analyzing post glacial civilizations in the American Midwest.
    Thanks for clarifying. So I was out by a factor of 2 in my thinking. I hadn't bothered to do the maths on how slowly the tail of the -ve exponent dies away, after the half-life point.

    But, as I see others have confirmed, with a 60,000yr limit, C14 is not a lot of use for most geological timescales.

    (I understand other radioisotopes can be used for long term geological processes, relying on radioactivity that starts to decay once the rocks in question have been brought up from great depth.)
    Reply With Quote  
     

  18. #17  
    Forum Ph.D.
    Join Date
    Aug 2011
    Posts
    985
    Dino fossils are primarily dated by the age of the strata they are found in. Generally dino "bones" are found in sedimentary rock which by its nature is layed down in yearly layers. Basicly we count the layers of the rock.
    Reply With Quote  
     

  19. #18  
    Administrator KALSTER's Avatar
    Join Date
    Sep 2007
    Location
    South Africa
    Posts
    8,232
    There are a number of different radiometric dating methods, apart from Carbon dating. Read through this: Radiometric dating - Wikipedia, the free encyclopedia
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
    Reply With Quote  
     

  20. #19  
    AI's Have More Fun Bad Robot's Avatar
    Join Date
    Apr 2013
    Location
    Washington state
    Posts
    6,114
    The link below describes how they date meteorites and shows a table of major isotropic systems used as radioactive clocks.

    Methods of Dating the Age of Meteorites
    Reply With Quote  
     

  21. #20  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,598
    For carbon dating, I think the Charcoal Restaurant in Denver would be the perfect venue.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
    Reply With Quote  
     

  22. #21  
    Forum Ph.D.
    Join Date
    Aug 2011
    Posts
    985
    I personnally have never felt any urge to date carbon. Girls yes Carbon no.
    Reply With Quote  
     

  23. #22  
    WYSIWYG Moderator marnixR's Avatar
    Join Date
    Apr 2007
    Location
    Cardiff, Wales
    Posts
    5,760
    Quote Originally Posted by Sealeaf View Post
    I personnally have never felt any urge to date carbon. Girls yes Carbon no.
    all the girls i know are carbon-based - are they silicon-based where you live ?
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
    Reply With Quote  
     

  24. #23  
    Suspended
    Join Date
    Nov 2013
    Location
    United Kingdom
    Posts
    537
    Quote Originally Posted by marnixR View Post
    Quote Originally Posted by Sealeaf View Post
    I personnally have never felt any urge to date carbon. Girls yes Carbon no.
    all the girls i know are carbon-based - are they silicon-based where you live ?
    Ha ha Sealeaf and Marnix.
    Gave me a laugh. Very witty.
    Reply With Quote  
     

  25. #24  
    AI's Have More Fun Bad Robot's Avatar
    Join Date
    Apr 2013
    Location
    Washington state
    Posts
    6,114
    Quote Originally Posted by hannah40 View Post
    Quote Originally Posted by marnixR View Post
    Quote Originally Posted by Sealeaf View Post
    I personnally have never felt any urge to date carbon. Girls yes Carbon no.
    all the girls i know are carbon-based - are they silicon-based where you live ?
    Ha ha Sealeaf and Marnix.
    Gave me a laugh. Very witty.
    You had to get me started.

    Reply With Quote  
     

  26. #25  
    Forum Ph.D.
    Join Date
    Aug 2011
    Posts
    985
    Excellant!
    Reply With Quote  
     

  27. #26  
    Forum Freshman
    Join Date
    Mar 2011
    Location
    Melbourne, Australia
    Posts
    5
    Quote Originally Posted by Sarah1234 View Post
    If u can carbon date a mummy and not a dinosaur the how do we know for sure how old a dinosaur is?
    There are a whole host of isotopes that are used for radiometric dating. Carbon-14 is one of the shorter ones (5,730 years is an eyeblink of course to geochronologists).

    The most common for anything over about 10 million years is Potassium-Argon dating. Where the Potassium-40 isotope decays to Argon-40.* Its half-life is approximately 1.3 billion years. There is also Rubidium-Strontium, plus 3 separate systems that decay to Lead isotopes - Uranium-238 (to Lead-206), Uranium-235 (to Lead-207), and Thorium-232 (to Lead-208). Occasionally samples are found that can be dated with different methods and arrive at the same date independently.

    There's a very good book called "Nature's Clocks" by Doug MacDougall which covers the topic in great detail. It's an excellent introduction for the non-specialist.

    * It actually decays in different proportions to Argon-40 and Calcium-40, but for simplicity's sake we'll call it "Potassium-Argon".
    Reply With Quote  
     

Similar Threads

  1. Carbon 14 Dating
    By qscience in forum Anthropology, Archaeology and Palaeontology
    Replies: 2
    Last Post: October 6th, 2012, 02:03 PM
  2. Carbon Dating
    By gottspieler in forum Biology
    Replies: 40
    Last Post: March 5th, 2009, 02:29 PM
  3. carbon dating accurate?
    By xenobiology in forum Biology
    Replies: 7
    Last Post: December 3rd, 2007, 11:56 AM
  4. time and carbon dating
    By streamSystems in forum Physics
    Replies: 8
    Last Post: October 29th, 2007, 11:39 AM
  5. carbon dating
    By VossistArts in forum Earth Sciences
    Replies: 9
    Last Post: October 1st, 2005, 07:54 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •