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→Zircon Dating: Open system, other measurements of the speed of light.
::::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)
::::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)
::::[[User:MichaelK/Measuring_c|Here]] is a copy of the the report I made describing the method I used. Maybe you'll understand why I feel this way after reading it?--[[User:MichaelK|MichaelK]] 14:38, 10 May 2008 (EDT)
::::[[User:MichaelK/Measuring_c|Here]] is a copy of the the report I made describing the method I used. Maybe you'll understand why I feel this way after reading it?--[[User:MichaelK|MichaelK]] 14:38, 10 May 2008 (EDT)
::::: There are various factors that can affect a radiometric date determination, including the parent material leaching in or out and the daughter material leaching in or out. In a "closed system", this cannot occur, but if it does, then it indicates an "open system". Of course, this is not an either/or situation; you might have a nearly-closed system, or a system that is closed to some chemicals but open to others, for example. If I understand it correctly, the fact that the U-Th dating produced a "wildly discordant" date shows that these zircons comprised an ''open system'', where material was able to leach in or out. As such, the U-Pb dates cannot be considered to be reliable.
::::: "''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.''": You actually said, "The composition of these crystals is the strongest evidence against the conjecture of ''Young Earth Creationism''" (my emphasis).
::::: It's an interesting point that the speed of light is effectively defined in such a way that it ''cannot'' change. And the other way of seeing it is not that the ''definition'' of the metre would change, but that actual length of the metre would change! Hmmm, that's an interesting concept!
::::: I don't see how it shows a lack of understanding of the methods used to conduct the measurements. You appear to have a misunderstanding, as you seem to be saying that there's only one way of measuring it, which was not available until relatively recent times. But the speed of light has been measured in various ways for 400 years. Granted, the latest method is probably the most accurate, but that doesn't mean that it is the only method that can be used.
::::: [[User:Philip J. Rayment|Philip J. Rayment]] 00:11, 11 May 2008 (EDT)