Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do they date ancient times?

  1. Sep 23, 2005 #1
    I mean billions of years ago, when carbon dating is too inaccurate.
     
  2. jcsd
  3. Sep 23, 2005 #2

    matthyaouw

    User Avatar
    Gold Member

    They use radioactive/radiometric dating using isotopes with long half lives
     
  4. Sep 23, 2005 #3

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    There are other dating methods aside from just carbon dating. I'm going to recommend this topic get moved to the "Earth" forum since your question addresses more than just organisms.
     
  5. Sep 23, 2005 #4
    Sorry for the wrong location, it was the first place I could think of. X.X


    What is the accuracy of this dating?
     
  6. Sep 23, 2005 #5

    russ_watters

    User Avatar

    Staff: Mentor

    HERE is more on long-term radioactive dating, but essentially the accuracy is a fraction of the half-life of the isotope you are using, not a specific number of years. So if one dating technique gives a 10% error over 3 billion years, that's a possible error of 300 million years. Obviously, such a technique wouldn't work too well if you want to measure the age of something that is only 30 million years old.
     
  7. Sep 23, 2005 #6
    Error margins of radiometric dating are order of magnitude of 1%, which is rather disturbing when trying to find out what is cause and what is effect.

    Another important tool for dating of very old stratifocations is paleo-magnetism. As the Earth magnetic field has reversed many times, this is recorded in the rocks and an excellent record of these reversals is available. So many scientists earn their living with investigating sediments for magnetic polarisation, trying to identify those reversals.

    Yet another dating method is identificing fossils. Many extinct species like planktonic type of micro-organisms that fossilize easily, did have a short livespan. The Sepkoski Compendium (Bulletin American Paleontology no. 363, Ithaca 2002) contains 36,380 of those "marine genera" (single: genus, a group of closely related species) dated back to 540 million years ago.

    For the short term there are loads of additional methods, dendrochronology, varve counting (yearly lake sediment layers), Ice core layers and contents, volcanic glass layers (tephra) of known eruptions, thermo - opto illuminicense, wiggle matching and what have you.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Similar Discussions: How do they date ancient times?
  1. Ancient floods (Replies: 9)

  2. Ancient artifacts (Replies: 3)

Loading...