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Zhi -> RE: "Young Earth" doctrine????? (8/7/2008 3:50:01 PM)
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I would stand more with your husband on the accuracy of radiometric dating, especially isochron dating which you do not mention.
Well, I didn't want to list every single theory out there. It would get too long. But, since you asked, let's discuss isochron dating.
The problem with this is that isochron dating is somewhat subjective, and is extremely sensitive to contamination. Contamination is obviously going to be pretty problematic out in the "dirty world" where you don't really get closed systems. Another problem is that the lines are never perfect, and outliers tend to get tossed because they don't "fit". So, the person attempting to make the graph has to determine what they believe are the "real" isochron points, and which ones are spurious. Generally, they do this based on how old they "think" it is and whether or not their results are landing where they "should", which is based on their initial assumptions anyway. Furthermore, the method assumes that the samples used all formed simultaneously from a more or less homogeneous material set, which is just as unreliable as trying to guess how much parent you started with.
The thing is, though, that for a true "young earther" insisting on a 6,000 year period since the earth was formed, the entire thing is basically moot... because by necessity the processes involved simply did not have time to happen. So, God would have had to create the rocks in an "old" (or if you would prefer, "finished") state in order to have everything in the proper formation for the following creation... a molten, still-cooling earth in the morning could not have supported plants in the afternoon without supernatural intervention, right?
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The micro-macro difference you outline is based on a misunderstanding of the predictions of evolution. It would actually disprove evolution if the descendants of moths were not moths, the descendants of birds were not birds, etc. Evolution requires that where no gene flow is possible between groups there will be no evolutionary consequence which will take descendants out of the groups their ancestors are part of.
The issue is that at some point, something has to stop being A, in order to be B. A lizard eventually has to stop being a lizard, and start being a bird. A fish has to make its way onto land eventually, along with the necessary structures to do so. There should be massive evidence of the various stages in the fossil record, but the reality is that we have very little, and instead we have anomolies such as the Cambrian Explosion, where evolution would have had to speed up exponentially.
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I would also disagree with the theology that says God's image cannot be imparted to a species which evolved or that evolution poses a problem to the fact of the fall. But that is still another discussion.
And an interesting discussion that would be. I would point out, though, that even the impartation of God's image to something pre-existing (which happens in the creation story with "dust of the ground") still means that humans could not have evolved, per se, because divine intervention was required to make humans human. So, whether the divinely gifted step was dirt->man or apelike thingy->man, the step was certainly not an evolutionary step.
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What I would point out is that for radiocarbon dating, the system can be calibrated against tree rings going back to about 10,000 years ago. Tree rings provide a much more direct measurement of age, and this can be used to directly measure the rate of radiocarbon formation in the atmosphere. When this is done (see Fig. 1) the curve does not deviate that far from the 'naive' straight-line assumption.
So even if we ignore this calibration, our dates for the past 10,000 years are only off by a few percent. With the calibration, the accuracy is even better.
Using varve sediments, another calibration can be made for radiocarbon, and though it's not as clean as dendrochronology, it shows reasonable linearity for the past 40,000 years (see Fig. 2, etc.). Of course, 40,000 years already falsifies a 6000 year old earth, and this conclusion is supported by dendrochronology, varves, and radiocarbon dating separately.
I think your figure got lost in the copy paste. >.> <.<
Using tree rings makes certain assumptions regarding climate and seasons. As I'm sure you're aware, the cambium usually grows more quickly during spring (when there is plenty of moisture and light) to form lighter wood. Then, as fall comes along, growth slows and the smaller, denser cells of that season appear darker due to a lack of light and moisture. So, anything that affects light, or moisture, could affect ring formation. Furthermore, we don't have any trees that are proveable to be more than 4,500 years old, that being the age of the oldest tree we've found (specifically California's "Methuselah tree"). Comparisons of dead trees and attempting to line up the rings in order to try to figure out what goes farther back where, is rather... subjective.
Varve sediments have the same problems... the assumption that the laminar deposits indicate seasonal deposits is also going to depend on what else is happening in the climate at the time. Flooding, windstorms, even fluctuations in pH balance can create varve sedimentation that is basically indistinguishable from the seasonal formations.
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But more importantly, radiocarbon dating appears to be roughly 'linear' in the sense you mean for the past 40,000 years (just about the entire span of time for which it is used). It may be off by 10% or even 20% for all I know, but clearly not the 700% that would be required to squeeze the time frame down to 6000 years.
It's true that it is not as easy to calibrate the other radiometric dating methods (which provide billion-year ages for rocks) against some other method in the same way. But to squeeze billions of years into thousands would require decay rates to increase by a factor of a million, which would just about turn a rock into a nuclear bomb.
Well, of course it "appears" to be roughly linear... because the assumptions regarding it assume that it is linear. So, if you assume something is linear, chart it as linear, even if it's not really linear, it's going to look linear.
So, again, the decay rates do not need to increase if the original assumed ratios of the parent and daughter elements are incorrect.
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And for your point #4, that we may not know the correct mother/daughter ratios in the original rock, some methods, like zircon dating, provide two separate radiometric methods of dating the sample. If assumption #4 was false, then the data would not fall on the concordia curve, except by an unlikely accident.
The problem with zircon dating is that zircons are resistant to thermal changes and tend to be more difficult to, well, melt, than the other rocks with them. So, detrital zircons can just as easily come from sedimentary recycling as from formation in the current strata. Zircon is not resistant thermally in one sense, though, specifically that heating can cause the lead to diffuse out of the crystal, thereby changing the ratio of lead to uranium. Furthermore, zircon is difficult to analyze as the formations tend to be very, very tiny, and it can be difficult to distinguish overgrowth from core material, resulting in age miscalculation.
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