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Radiometric Dating Assumptions - 7/3/2008 6:03:53 PM
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Method
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All measurements in science are based on assumptions. Every one of them. You can't use a balance without assuming that the company correctly calibrated the instrument, that the constants of electromagnetism haven't changed since the manufacture of the balance, that the laws of quantum physics haven't changed, that the material you are weighing doesn't suddenly change mass between the balance and the lab bench, that the material is not soaking up atmospheric water vapor at high rates, etc. There are a lot of assumptions, but ones that we can either test (e.g. calibration, hydroscopic chemicals) or take for granted (constant laws).
So what assumptions does one need in order to do radiometric dating, and why are these assumptions invalid? Or better yet, are these assumptions testable?
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RE: Radiometric Dating Assumptions - 7/3/2008 6:10:20 PM
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hellohellohi
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One assumption (as I understand it) or prior investigation required for dating is establishing the proportions of isotopes in the relevant open system in order to compare with the dateable open system. Certainly, assumptions are involved here. This is a good and educational discussion I think, Method.
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RE: Radiometric Dating Assumptions - 7/3/2008 6:18:08 PM
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Method
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quote:
ORIGINAL: hellohellohi
One assumption (as I understand it) or prior investigation required for dating is establishing the proportions of isotopes in the relevant open system in order to compare with the dateable open system. Certainly, assumptions are involved here. This is a good and educational discussion I think, Method.
For U/Pb dating of zircons this is not a problem. When a zircon forms it excludes lead and includes uranium. This is due to the charge of each element. It is basic chemistry. The same can be said for U/Th dating which is used to measure the growth rate and age of corals and stalagmites/tites. Uranium is soluble in water while Thorium is not. Therefore, Uranium is included in such structures while Thorium is not. Also, isochron methodologies can actually measure the concentration of daughter products that were present when the crystal first formed.
For this assumption to be invalid you would need to show that the laws of chemistry were different in the past which is a bit preposterous since this would change the chemical properties of everything, from water to the most complex biomolecules making life impossible.
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RE: Radiometric Dating Assumptions - 7/3/2008 6:42:23 PM
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hellohellohi
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quote:
For U/Pb dating of zircons this is not a problem. When a zircon forms it excludes lead and includes uranium.
Didn't know that. This sounds rather reliable. I'll keep thinking on that.
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RE: Radiometric Dating Assumptions - 7/3/2008 6:58:11 PM
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Method
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quote:
ORIGINAL: hellohellohi
quote:
For U/Pb dating of zircons this is not a problem. When a zircon forms it excludes lead and includes uranium.
Didn't know that. This sounds rather reliable. I'll keep thinking on that.
Here is some additional information on isochron dating:
http://www.talkorigins.org/faqs/isochron-dating.html#isochron
All radiometric dating methods require, in order to produce accurate ages, certain initial conditions and lack of contamination over time. The wonderful property of isochron methods is: if one of these requirements is violated, it is nearly certain that the data will indicate the problem by failure to plot on a line. (This topic will be discussed in much more detail below.) Where the simple methods will produce an incorrect age, isochron methods will generally indicate the unsuitability of the object for dating.
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RE: Radiometric Dating Assumptions - 7/7/2008 1:06:51 AM
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swan42
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quote:
You can't use a balance without assuming that the company correctly calibrated the instrument
This is funny wrong. In fact, laboratory procedures commonly include a calibration procedure because no, scientists do not assume the balance manufacturer calibrated the balance correctly.
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