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→Zircon Dating
::::: As for a section on criticisms, that depends on whether there are any criticisms that don't have answers (i.e. something that doesn't fit under the ''Responses to criticisms'' section).
::::: As for a section on criticisms, that depends on whether there are any criticisms that don't have answers (i.e. something that doesn't fit under the ''Responses to criticisms'' section).
::::: [[User:Philip J. Rayment|Philip J. Rayment]] 11:38, 6 May 2008 (EDT)
::::: [[User:Philip J. Rayment|Philip J. Rayment]] 11:38, 6 May 2008 (EDT)
::::Well, let's look at the <sup>207</sup>Pb/<sup>206</sup>Pb dating done on those crystals. Those two isotopes of lead are chemically very similar. Any process by which one isotope of the lead can enter or leave the crystals likely acts on the other isotope, so it's not surprising that the <sup>207</sup>Pb/<sup>206</sup>Pb dating on one sample produced results with 97% concordance. I still don't see why the discordinant results of the U-Th dating affects other methods of dating the crystals. From what I understand in the ''Nature'' article [http://www.geology.wisc.edu/~valley/zircons/Wilde2001Nature.pdf], the point of the U-Th dating was not to find the total age of the crystals, but to determine the conditions under which the crystals formed and existed. The age of the crystals is actually determined by the <sup>207</sup>Pb/<sup>206</sup>Pb dating. You've encouraged me to study this article further, and now I understand it a lot better than I did before we started this. The point of this zircon project wasn't even to determine the age of the Earth (though it does serve that purpose well), but to examine the conditions that existed billions of years ago. What we are debating is actually a relatively simple part of a much more complex project. Actually, according to an article on the usgs.gov website I just found, dating of a meteorite from Arizona may show that the earth is even older, at 4.54 billion years, but I'll have to look into this before I understand it enough to start arguing about it.
::::I never said that this is all an argument against creationism or intelligent design. I just said that these are valid arguments against the Earth being less than 8,000 years old.
::::It is not wrong to suggest that the speed of light is different than the currently accepted value (but this would actually change the definition of the meter, while the value for the speed of light would stay the same), I'm just saying that it's a bit silly for someone to conclude that the speed of light is changing based on the fact that the measurements of the speed of light have changed over the centuries. It shows a lack of understanding of the methods used to conduct those measurements. Measuring the speed of light requires either modern knowledge of electromagnetism or mirrors rotating very fast that are very far apart and extremely precise knowledge of how fast those mirrors are spinning and how far apart they are. It also requires measuring the displacement of a beam of light which can be unimaginably difficult using anything but a laser and large-radius spherical mirrors (neither of which existed hundreds of years ago). --[[User:MichaelK|MichaelK]] 14:06, 10 May 2008 (EDT)