Radioisotope Dating and Circular Logic

Radioisotope Dating and Circular Logic

Author: Curt Sewell
Subject: Creation Overviews
Date: 11/2/1999

DEFINITION — Circular logic is a logical error, caused by first making some assumption that can’t be proven true, then, on the basis of that assumption, deriving some result that is then used to “prove” that the first assumption is true.

We’ll see that radiogenic dating, used to try to prove that the earth is extremely old, is a prime example of circular logic. It’s often quoted as being an accurate measurement, but we’ll show that many errors are quietly discarded, and blamed on some unknown contamination in the rock sample that was measured.

The process (as used by secular scientists) goes something like this:

1) Assume that the early parts of the Bible are not literally true.

2) Therefore, God didn’t really create the world and its inhabitants in only six days.

3) Thus, we can try to find a way to explain the world without relying on a supernatural cause.

4) Now assume that the world developed slowly, by natural processes similar to those we see working today. This is called the theory of uniformitarianism.

5) It’s obvious that this would take a long time, but how do we prove how long that would take?

Notice that points #1 and #4 contain assumptions that we can’t prove. But let’s

go on and see what happens if we “temporarily” assume that they’re both true.

6) We know that certain radioactive metals have extremely long half-life (that is, they decay very slowly). Maybe they could be used to show that the earth is very old.

7) When these metals decay (at a rate determined by their long half-life) they are transformed into other kinds of metals. For example, Uranium-238 changes into Lead-206. This reaction has a 4.55-billion-year half-life.

8) Therefore, if a certain mineral contains both Uranium-238 and Lead-206, and if we assume that most of the Lead-206 was derived radiologically, the ratio of these two isotopes should allow an estimate of the fraction of Uranium-238 that had decayed, and since we know the half-life of Uranium-238, we can therefore find how long it took for this process to take place.

Notice another assumption in point #8 –no one can prove that one either..

9) If all of these steps are correct, then we can show an ancient age for many rocks. After many such rocks are dated, if they seem to agree with each other, we can say the earth must be older than they are, and come up with an estimate of the earth’s age. The current guess is some 4-1/2 billion years.

10) This line of reasoning is used by the majority of scientists to “prove” that God didn’t create the earth in a very short time (the Bible says six days), since this “proves” that the earth is very ancient.

Now, what’s wrong with this picture? It sounds reasonable, if all of the assumptions in all of the above steps are true and correct. But suppose that steps 1) and 2) are bad assumptions, and that God really did create the world in a very short time, as the Bible says (in many places other than just early Genesis). Suppose that, in step 8), the Lead-206 got there some other way than by radioactive decay. Is there anything in the above process that could adequately contradict these suppositions? Not at all! Here’s a good example of circular logic.

Let’s look at some actual scientific evidences and see how they apply to the above discussion. Radiogenic dating is not the primary way that paleontologists determine the date of most fossils. It can’t always be used, because the material surrounding the fossil often doesn’t contain the right isotopes, and the measurement for radiogenic dates is destructive and thus the fossil itself can’t be dated. Usually there are other fossils located nearby, and often these have been determined to be index fossils — that is, fossils of creatures that only lived during certain times of earth history before they became extinct. But this process also involves a number of assumptions, including the assumption of an evolutionary development of those creatures!

If there is a conflict between a radiogenic date and a stratigraphic date (that is, one determined from index fossils), the radiogenic date is discarded in favor of the stratigraphic date. It’s easy for a dating lab to blame some contamination in the mineral’s history for this conflict.

John Woodmorappe did an extensive literature search, looking at 445 technical articles from 54 reputable geochronology and geology journals. . John Woodmorappe, “Radiometric Geochronology Reappraised,” in Creation Research Society Quarterly, Vol.16, September, 1979, pp. 102-129, 147. These reports listed over 350 dates, measured by radiometric methods, that conflicted badly with the ages assigned to fossils found in these same strata. They covered “expected” ages ranging from 1 to >600 million years. In almost every case of a discrepancy, the fossil dates were accepted as correct, while the radiometric dates were discarded. Woodmorappe quoted one researcher as saying:

“In general, dates in the ‘correct ball part’ are assumed to be correct and are published, but those in disagreement with other data are seldom published nor are discrepancies fully explained.”

Henry Faul, in his classic geochronology textbook, gives a good illustration of how the assumptions mentioned above are used. He wrote:. Henry Faul, Ages of Rocks, Planets, and Stars, (New York: McGraw-Hill Inc., 1966), pg. 65.

“If one assumes that the solar system condensed from a primordial cloud, it follows that the materials of planets, asteroids, and meteorites have a common origin. Iron meteorites contain some lead but only infinitesimal traces of uranium and thorium, and therefore the lead is uncontaminated by radiogenic lead and can be regarded as a good sample of primordial lead. … and all that remains to be found to permit a calculation of the age of the earth is a lead sample from a closed subsystem of well-known age.”

I described these reports more fully, as well as many other evidences, in another article.. Curt Sewell, “The Faith of Radiometric Dating,” in Bible-Science News, Vol.32:8, November 1994, pp.1-6. This article also describes, in much more detail, four different radiogenic dating schemes, based on different isotopes.

How does this affect the Christian? Might it actually be just as reasonable for a Christian to assume that the Bible really is correct, and that God did actually create our world as He said He did? Might He have created the Lead-206 already in the rocks? Absolutely! I think that’s the way He expects us to believe. Why else would the Bible be loaded with statements such as “By His word He created the heavens and earth?”

We see that the big difference between believing the Bible and believing what secular science says is primarily a choice of philosophical beliefs — a form of mental idolatry. There are no physical scientific reasons that a reasonable person is forced, by the actual facts, to believe in a long, slow, materialistic origin of the earth and the universe. How much better it is for a Christian to accept God at His word. Otherwise, we’re trying to put Him into a corner of our life — believing part of what He says, but holding back on full acceptance. Jesus, the Son of God, came to earth in the body of a man, died on the cross for our sins, so that we could become members of the family of God, and rose from the dead as a proof of His divinity, so that we can live with Him forever. Shouldn’t we give Him our full faith, belief, worship, and praise?

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