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The age of the Earth has been determined by radiometric dating of meteorites, by seeing how much uranium has decayed into lead.

How do we know the meteor samples weren't formed with lead already in them, and thus confuse the radiometric dating?

Links to references for further research would be much appreciated. I'd just like to know in depth how the process worked and how there's so much certainty in it.

Oddthinking
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LookingForEarthlyAnswers
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    I don't think this is a question for Skeptics... It would suit http://earthscience.stackexchange.com/ or http://physics.stackexchange.com/ – sashkello May 05 '14 at 01:05
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    @sashkello I think there is a skeptical question here. There is an argument often used by young-earth creationists that dating methods are unreliable because we don't know the starting composition of the materials being dated. A good explanation of the technique would challenge that argument and that would be an appropriate answer here. – matt_black May 05 '14 at 10:59

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Radio-isotope dating is not just performed on meteorites, but also on terrestrial rocks. The dates obtained are consistent, with meteorites slightly older than the earth. Are you suggesting the earth was also formed with lead already present?

Isochron dating avoids contamination problems. Meteorites are often dated by iscohron lead-lead methods, and hence are not affected by contamination.

hdhondt
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  • Please provide references for the testing of terrestrial rocks and the resulting ages obtained. Presumably the question with lead-lead methods becomes "How do we now the initial meteor didn't form with Pb-204?" – Oddthinking May 05 '14 at 02:32
  • It would be good to see a simple explanation of how reliable ages are derived in the answer. This would address the key question of how reliable ages are derived when we are uncertain about the starting composition of the material. – matt_black May 05 '14 at 11:00
  • @Oddthinking The Wikipedia link I gave shows the meteorite from the Arizona Meteor crater as well as terrestrial rocks. – hdhondt May 05 '14 at 11:43
  • @matt_black My first link explains why isochron datings do not rely on the initial amount of daughter isotope or addition/removal of daughter isotope afterwards. – hdhondt May 05 '14 at 11:43