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Answering Questions Concerning Radiocarbon Dating

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Archives / 1973 / April

 

 

Answering Questions Concerning Radiocarbon Dating

R.H. Brown
-President of Union College, Lincoln, Nebraska at the time this article was written

 

ARGUMENTS against the historical authenticity of the book of Genesis appear with increasing frequency. Because radiocarbon dating is used in many of these arguments, those who are endeavoring to proclaim the everlasting gospel depicted in Revelation 14: 6-12 should understand this dating technique.

The radiocarbon "age" of an object is determined by relating its level of radiocarbon to a standard of carbon-14 activity supplied by the U.S. National Bureau of Standards. The greater the ratio, the more recent the specimen; the smaller the ratio, the older the specimen.

As long as a plant or animal lives, it ingests radioactive carbon, which has been created by cosmicray bombardment in the earth's upper atmosphere, oxidized to carbon dioxide, and mixed throughout the atmosphere and in the water. Death of the plant or animal terminates this process. Since radioactive carbon is unstable, it converts to nitrogen but at a rate slow enough to be useful in measuring objects of antiquity.

A radiocarbon date is, in the strictest meaning, A.D. 1950 minus a radiocarbon age. For example, a radiocarbon age of 4000 corresponds to a 2051 B.C. radiocarbon date (A.D. 1950-4000=2051 B.C.). Common usage often makes no distinction between the terms radiocarbon date and radiocarbon age.

A radiocarbon age is the usual way of reporting a measurement of the relative amount of radioactive carbon (carbon with isotope weight 14) in a specimen with a chemical composition that includes carbon. Measurements made at various laboratories throughout the world have determined that within 5,730 years half an initial amount of carbon-14 will have spontaneously transformed to nitrogen. This carbon14 half-life measurement of 5,730 years is precise to within less than one hundred years. Measurements of radioactive carbon con tent in specimens of historical interest are reported in.terms of the time that would be required for radiocarbon activity characteristic of the carbon dioxide in Earth's atmosphere during recent time to diminish to the level exhibited by the specimen. 1 Given the assumptions upon which this procedure is based, any carefully determined radiocarbon age is correct, for it is actually a report of a contemporary situation.

Interpreting Radiocarbon Age

An interpretation of a radiocarbon age in terms of real time (or of a radiocarbon date in terms of an actual calendar date) may be speculative, for the amount of radioactive carbon in a given specimen depends on two factors (1) The amount of time that has elapsed since the specimen ceased to exchange carbon with its surroundings (died), and (2) the concentration of radioactive carbon that the specimen contained when carbon exchange ceased. Knowledge of one of these factors is necessary for conversion of a radiocarbon age measurement into a determination of the other. Remains of a plant or animal that derived its carbon from the atmosphere at a time when the ratio of carbon-14 to carbon- 12 was the same as has been characteristic of recent time would have a radiocarbon age equal to the time since death of the organism that furnished the remains (assuming there has been no subsequent contamination with carbon from a different period of time). No certain real time interpretation of a radiocarbon age can be made without knowledge of the carbon-14 concentration that characterized the specimen at the time it ceased to maintain equilibrium with the carbon in its environment.

The maximum sensitivity of present means for detecting car bon-14 corresponds to a radio carbon age between 40,000 and 50,000. Anthracite coal, gas, and oil from deep wells, as well as shells, bones, and fragments of vegetation from the deeper portions of the sedimentary column, have been found to contain no detectable amount of carbon-14. Such materials are described as of infinite radiocarbon age. The radiocarbon dating literature contains a large number of references to plant and animal remains that have radiocarbon ages in every portion of the range between zero (contemporary) and infinite (greater than about 50,000).

If a person assumes a one-to-one correspondence between real time and radiocarbon ages in excess of 4500, he finds his datato be in contradiction to the inferences concerning time based on the eleventh chapter of Genesis and supported in the testimony of Ellen G. White. According to the Masoretic text for Genesis 5 and 11, one would not expect this planet to contain plant or animal remains older than about 6,000 years of real time. The Septuagint extends this period to about 7,500 years. One must presume either that the eleventh chapter of Genesis has little historical validity other than a selected listing of prominent men who lived over a period of time exceeding 40,000 years, or that radiocarbon ages in excess of 3,500 to 4,000 describe initial radioactive characteristics rather than a lapse of time. According to the latter viewpoint the Flood came at the end of a period during which Earth's biosphere contained less than 1/300th as much carbon- 14 in proportion to carbon-12 as has been characteristic over the past 3,000 years.

The Earlier Periods

Radiocarbon age has been firmly correlated with real time over the past 3,000 years by means of wood fiber that has been dated by dendrochronological techniques (study of growth rings) and by specimens to which a firm historical age can be assigned. For times earlier than 1000 B.C. correlation becomes increasingly uncertain. Radiocarbon dates for ancient Egyptian material are younger than those that are generally accepted by archeologists, the discrepancy ranging from about 250 years for the time of Ramses II (c. 1200 B.C.) to about 600 years for the first dynasty (generally considered c. 3000 B.C.).2 A chronology of Bristlecone Pine growth striations has been developed that extends to 5300 B.C., but the radiocarbon age for the oldest dendrochronological dated Bristlecone Pine fiber is about 1,000 "years" less. 3

The conclusions of archeologists and Bristlecone Pine dendrochronologists require a decreasing carbon-14 concentration in the atmosphere between 6000 B.C. and 1000 B.C. The limitations imposed by Genesis 11 and Ellen G. White comments require that the available radio carbon ages be interpreted to indicate an increasing carbon-14 concentration between the Flood and the latter part of the second millennium B.C.

One can suggest that dendrochronologists are unacquainted with Bristlecone Pine growth characteristics that may have existed during the first millennium following the Flood, and that both dendrochronologists and archeologists have been influenced by the prevailing attitudes concerning evolutionary development over long periods of time. In an article that will soon be published in the Signs of the Times the author presents evidence for an increase in the relative radiocarbon content of the atmosphere during the period between the Flood and the middle of the second millennium B.C.

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Footnotes

1. R. H. Brown, "Radiocarbon Dating," in H. G. Coffin, ed., Creation Accident or Design? (Washington, D.C.: Review and Herald Publishing Association, 1969), pp. 299-316.

2. T. Save-Soderberg and I. U. Olsson, "C-14 Dating and Egyptian Chronology," in I. U. Olsson, ed., Radiocarbon Variations and Absolute Chronology (New York: Wiley interscience Division, 1970), pp. 35-53.

3. D. W. Ferguson, "Dendrochronology of Bristlecone Pine, pinus aristata," in Olsson, ed., Radiocarbon Variations and Absolute Chronology, pp. 237-259.

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