From: Steven M. Smith <smsmith@helios.cr.usgs.gov>
> >However, one of the axioms (or presuppositions) for radiometric dating is
> >that the rocks are old enough to be dated. Thus one must first assume that
> >the rocks are old before you can date them. Consequently, radiometric dates
> >cannot provide evidence of the old age of the rocks because old age is
> >already assumed in the dating method. You cannot prove what you assume.
>
> Allen,
> I don't have time to reply in detail to this entire post but I was enticed
> out of my lurking mode by this "radiometric age dates" argument. I'll leave
> the much anticipated discussion of Evolutionary Creationist's motives,
> theology, etc. for Terry ;^)
>
> This is at least the second time that I have seen you make this argument for
> circular reasoning in age dating. In a sense, you are correct. I assume
> "that the rocks are old enough to be dated." I also assume that my
> 14-yr-old daughter is old enough to be dated ... in the sense that we can
> assign an age to her. The point is that assuming an object is old enough for its
> age to be determined doesn't invalidate the measured age. All I need is the right method.
There is a major flaw in your analogy. You know the age of your daughter, you don't know the age of a rock.
Let me illustrate, Let's say I drop by your place, having never seen a child before, and I decide to determine her age. So, everyday for a month I measure her height. I discover that she grew from 1.366 meters (4' 5 3/4") to 1.370 meters (4' 5 7/8). By extrapolation into the past (to zero, I said I knew nothing of children. :) I find that she is 28.54 years old. You look at me like I am crazy, because you were there from start to finish and you know she is only 13 year old. But I have absolute empirical evidence that a child grows 0.004 meters per month!
We then go out and pick up a piece of igneous rock and you tell me that it is 900 million years old. I ask if you were there from beginning to end. You say, "No, but I have empirical evidence!" So I walk away knowing that your daughter is really 28 and the rocks are 900 million years old.
Obviously, the child is not 28. And just as obviously, the rocks are not 900 million years old (or whatever). The problem lies in the assumptions not in the measurements. You were there from the beginning of your daughters life. We were not there from the formation of the rocks. There is only one person I know of who can say, "Where were you when I laid the earth's foundation? Tell me, if you understand. Who marked off its dimensions? Surely you know! Who stretched a measuring line across it?" (Job 38:4,5) And if we don't believe Him, we cannot know.
My assumption above was that it was possible to measure height and estimate age. Wrong! The problem with radiometric dating is the assumption that it is possible to measure quantities of isotopes and estimate age.
I also had to assume in my estimation that the child could really be as old as I calculated for me to accept it as valid. You have to assume that the rocks can really be as old as your calculations for those ages to be valid.
You don't accept my estimation because you know the child is not that old and therefor you know my assumptions are incorrect. I don't accept radiometric dating because I know from someone who is in the position to know and who has told us so that the rocks (sedimentary rocks in particular) are not that old and therefore I know that the assumptions behind radiometric dating are in error.
But, you say, God has not told us anything about the age of the rocks. The Bible is mythology especially Genesis. The writers of the Bible did not understand science and so they do not qualify as valid observers.
On what basis is Genesis called mythology, especially among Evolutionary Creationists? From what I have read and from what I have observed on this email list and the ASAnet, a straight forward reading of Genesis conflicts with the established conclusions of geology and so Genesis is reinterpreted as myth or symbolic. The assumptions on which geology is based are held in greater respect than what God has chosen to tell us. So, Genesis is subjected to the assumptions of men.
Somehow, we have become so sure that Truth is best found through science. My scientifically based estimation of your daughters age is far more reliable that your witness evidence. We seem to think that one cannot do science within the assumptions given us by the Bible. We have to invent our own assumptions because they are not "Religious." Just as your witness evidence is not allowed because you have a loving relationship with your daughter, even though you could provide sound scientific evidence that your daughter is 13 based on a life time of scientific observations and studies.
>
> But let's take this a little further. I'm assuming that your argument is
> really that we (geologists) assume some igneous rock is in the neighborhood
> of 1 billion yrs old and then we choose a radiometric method (like K-Ar,
> Rb-Sr, U-Pb, Lu-Hf, Re-Os, or Sm-Nd) which will give us measurements in that
> neighborhood. You are again correct ... in the sense that I would use an
> instrument calibrated to thousandths of a second to time a 50-meter dash and
> yet use another timepiece to determine the winning time of the Iditarod dog
> sled race. Those chosen methods do not invalidate the measured age, they
> just differ in their relative precision.
The problem has nothing to do with precision. It, instead has to do with the assumption that a rock is old and we then set out to measure it and sure enough we find the right measuring method that gets the results expected.
> Let me throw out one piece of empirical evidence that suggests that we are
> in the right ballpark when we try to date the oldest rocks in billions of
> years rather than in the 6,000 to 10,000 yr range. For the 103 to 105 known
> elements, there are in the neighborhood of 1,000 known isotopes, of which
> perhaps 60-70% are unstable and decay radiometrically. The majority of
> these radioactive isotopes have half-lives on the order of a few
> milliseconds to a few days. A small but significant number are measured in
> years. Only a handful have half-lives greater than 1 million years. (These
> numbers are guestimates that I've made from the Table of Isotopes found in
> my 57th edition of the CRC Handbook of Chemistry and Physics (pages B-270 to
> B354, 1976). Since they annually review and revise this 4" thick book, you
> should be able to find a new version in any public library.)
> [snip with excerpt from following post]
> With the exceptions
> noted in my first post (and David Bowman's correction of my sunlight/cosmic
> ray blunder), why are there no naturally-occurring radioactive isotopes
> having half-lives of 70 million or less? This question is valid whether all
> Sm-146 (70 M.Y. half life) has decayed or whether it has simply decayed to
> the point that we can no longer detect it. Note that a 4.55 B.Y. old Earth
> would be 65 half lives for Sm-146 or 1 atom left for every 37*10^18 original
> atoms.
This is another topic, only partially related to the age of the rocks by which the sedimentary rocks are dated which we have been discussing. As I have stated before I am a Creationary Catastrophist, i.e. I believe that the Creation Week occurred somewhere in the 6000 to 10000 year ago range and that there was a global catastrophe responsible for all (or nearly all) sedimentary rocks some 4000 years ago. However, unlike many of my Creationary Catastrophist friends, I am not a YEC. I believe that there is non-symbolic Biblical evidence that the universe (including this planet and solar system) could be very old. (The Biblical basis for this is another topic too long to be discussed at this moment). Therefor, that the foundational rocks might be depleted in certain isotopes is not a problem for me. It is a problem for my YEC friends and they have proposed various theories to try to explain away the problem. However, I do not find those theories convincing nor necessary.
Allen
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