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  1. #1 radiometric dating 
    Forum Isotope
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    I'm not an expert (nor even an amateur) in this field, and would like a layman's explanation for how it works, if anyone has that knowledge at their disposal and is willing to educate a simpleton without the information to explain radioactive decay and it's intricacies.


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  3. #2  
    Forum Ph.D.
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    There is more than one way that it works. I'll give two examples.

    1. Carbon 14: Because of exposure to natural radiation, C14 ratio to C12 (ordinary carbon) is at a given level. This is the ratio in living things. When an animal is buried, the C14 is no longer created, while the C14 present decays. The C14 to C12 ratio then is a measure of the time since burial.

    2. Uranium 238: In rock formations, the ratio of U238 to its decay products is a measure of when the rock was formed.


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  4. #3  
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    that was a little over simplified, I'm aware of those processess, but I thought it had more to do (in carbon dating) with the ratio of "radioactive" to
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  5. #4  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by Arcane_Mathamatition
    that was a little over simplified, I'm aware of those processess, but I thought it had more to do (in carbon dating) with the ratio of "radioactive" to

    is the radioactive isotope that decays to , with a half-life of 5730 yrs.

    Due to cosmic rays striking our atmosphere, is converted to , Which begins to decay back to . A balance is struck, with cosmic rays producing more carbon 14 to replace that which decays and the ratio of to remains steady. Plants, taking in CO2, therefore have the same ratio of Carbon isotopes as the atmosphere, as do the animals that eat the planets and the animals that eat those animals. When the plants and animals die, they are no longer cycling the carbon through their bodies. The remaining continues to decay and the ratio of Carbon isotopes changes. After about 5730 yrs, half the is gone, and after another 5730 yrs, half of that is gone, etc.

    Comparing the ratios gives a good measurement of the time that has past since the the plant or animal died.

    Radioactive decay is statistical. You can't tell when any given atom will decay, but if you have a large enough sample, you can tell when half of them will have decayed. So in order for the radiocarbon dating to work accurately you need enough Carbon 14 left to be statistically significant. As a result, radiocarbon dating is only good for dating back to a few tens of thousands of years.
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  6. #5  
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    and that was very helpful, thanks Janus
    am I lucky enough to get any other processes for radiometric dating other than the carbon14 out of you?
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