How Accurate Is Radiocarbon Dating?

Radiocarbon dating can be quite accurate, and the techniques improve yearly. However, before accepting a radiocarbon date, one should understand how the technique works, its limitations, and its assumptions. One limitation is that the radiocarbon technique only dates material that was once part of an animal or plant. To understand the other capabilities and limitations of radiocarbon dating, we must first understand how it works and consider the flood.

Most carbon atoms weigh 12 atomic mass units. However, about one in a trillion carbon atoms weighs 14 atomic units. This carbon is called carbon-14. It is also called radio carbon since it is radio active. Half of it will decay in about 5730 years to form nitrogen. Half of the remainder will decay in another 5730 years, and so on.

Cosmic radiation striking the upper atmosphere converts about 21 pounds of nitrogen each year into radiocarbon (carbon-14). Most carbon-14 quickly combines with oxygen to form radioactive carbon dioxide, which then spreads throughout the atmosphere. Plants take in carbon dioxide, and thus incorporate both carbon-14 and normal carbon-12 into their tissues in the same proportion as occurs in the atmosphere. Carbon-14 then moves up the various food chains to enter animal tissue--again, in about the same ratio carbon-14 has with carbon-12 in the atmosphere.

When a living thing dies, it no longer takes in radiocarbon. Therefore, its radiocarbon clock begins "ticking" since the radiocarbon in its dead body steadily decreases with a half-life today of 5730 years. If one knew what fraction of the organism's carbon atoms were carbon-14 when it died, then one could attempt to date the time of death. The key questions, then, are "Has the atmospheric ratio of carbon-14 to carbon-12 changed in the past, and if so, why and how much?"

The assumption usually made (but rarely acknowledged) is that the ratio of carbon-14 to carbon-12 in the atmosphere has always been about what it is today--about one in a trillion. But that may not have been true in the ancient past. For example, a worldwide flood would uproot and bury preflood forests. Afterwards, less carbon would be available to cycle between living things and the atmosphere. With less carbon-12 to dilute the carbon-14 that is continually forming in the upper atmosphere, the ratio of carbon-14 to carbon-12 in the atmosphere would slowly begin to increase. If the ratio of carbon-14 to carbon-12 doubled and we did not know it, radiocarbon ages of things living then would appear to us to be one half-life (or 5730 years) older than their true ages. If that ratio quadrupled, organic remains would appear 11,460 (2 x 5730) years older, etc. Consequently, a "radiocarbon year" would not correspond to an actual year. 1

Another consequence of the flood would have greatly diluted the carbon-14 to carbon-12 ratio. The precipitation of limestone during the flood involved the release of vast quantities of dissolved carbon dioxide from the subterranean water chamber. (See pages 84 - 115 and the technical note on page 235.) Since that carbon was isolated from the atmosphere before the flood, it would have been free of carbon-14. Much of that released carbon dioxide undoubtedly mixed with some of the carbon dioxide in the preflood seas before all the limestone precipitated. This would have diluted the biosphere's ratio of carbon-14 to carbon-12, resulting in artificially old carbon-14 dates.

If all of this is true, the ratio of carbon-14 to carbon-12 should have been building up in the atmosphere since the flood. In fact, it should still be increasing. This is precisely what recent measurements show. 2

Radiocarbon dating of organic-rich, sedimentary layers worldwide has consistently shown a surprising result. Radiocarbon ages do not increase steadily as we go down into layers of old (but postflood) organic matter, as one might expect. Instead, they increase at an accelerating rate. 3 In other words, the concentration of carbon-14 decreases rapidly with depth. The concentration of carbon-14 starts unexpectedly low just after the flood, as represented in the lower organic layers, and increases more rapidly than expected as the centuries passed. For the reasons mentioned above, the rapidity and direction of this change is what we would expect in the centuries after a worldwide flood.

One way to infer how the atmospheric concentration of carbon-14 changed in the past is by tree-ring dating. Some types of trees, that grow at high elevations and have a steady supply of moisture, reliably add only one ring each year. In other environments, multiple rings can be added in a year. 4 The thickness of a tree ring depends on the tree's growing conditions, which will naturally vary from year to year. Some rings may even show frost or fire damage. By comparing sequences of ring thicknesses in two different trees, a correspondence can sometimes be shown. Ring patterns will correlate strongly for two trees of the same species that grew near each other at the same time. Weaker correlations (or less confident matches) exist between trees of different species growing simultaneously in different environments. Claims are frequently made that wood growing today can be matched up with some scattered pieces of dead wood so that tree-ring counts can be extended back more than 8,600 years. This may not be true.

These claimed "long chronologies" begin with either living trees or dead wood that can be accurately dated by historical methods. This carries the chronology back perhaps 3,500 years. Then the more questionable links are established based on the judgment of a tree-ring specialist. Standard statistical techniques could establish just how good the dozen or more supposedly overlapping tree-ring sequences are. However, tree-ring specialists refuse to subject their judgments to these statistical tests, and they have not released their data so others can carry out these statistical tests. 5

Several laboratories in the world are now equipped to perform a much improved radiocarbon dating procedure. Using atomic accelerators, the carbon-14 atoms in a specimen can now be actually counted. This gives more precise radiocarbon dates with even smaller specimens. The standard, but less accurate, radiocarbon dating technique only attempts to count the rare disintegrations of carbon-14 atoms, which are sometimes confused with other types of disintegrations. This new atomic accelerator technique has consistently detected at least small amounts of carbon-14 in every organic specimen--even materials that evolutionists claim are millions of years old, such as coal. The minimum amount of carbon-14 found is so consistent among various specimens that contamination can probably be ruled out. If the specimens were millions of years old, virtually no carbon-14 would remain in them.

Eleven human skeletons, the earliest known human remains in the western hemisphere, have been dated by this new "accelerator mass spectrometer" technique. All eleven were dated at about 5000 radiocarbon years or less! 6 If more of the claimed evolutionary ancestors of man are tested and are also found to contain carbon-14, a major scientific revolution will occur, and thousands of textbooks will become obsolete. PREDICTION 15: Hominid and dinosaur bones that have retained enough carbon to be dated by this precise technique will be shown to be relatively young in blind tests.

Radiocarbon dating is becoming increasingly important in interpreting the past. However, one must understand how it works and especially how a flood as proposed in this book would have affected radiocarbon dating.

References and Notes

1. A radiocarbon year would also not equal a calendar year if, for example, the half-life of carbon-14 has changed, if carbon-12 or carbon-14 was added to, or leached from, the specimen being dated, or if the global rates of formation or decay of carbon-14 differed.

2. In 1952, when Willard Libby first published his work on radiocarbon dating, he called attention to the critical assumption that the ratio of carbon-14 to carbon-12 has been constant. He tested that assumption by making various measurements and calculating how rapidly carbon-14 was forming and decaying. Surprisingly, carbon-14 seemed to be forming faster than it was decaying. That would mean that there was less carbon-14 in the atmosphere in the past. If we did not know that, we would falsely conclude that the lack of carbon-14 in dead animals and plants was because much time had passed.

Libby believed his measurements were in error, since he thought the earth was so old that a balance between formation and decay must exist. He tried to justify this as follows: "If the cosmic radiation has remained at its present intensity for 20,000 or 30,000 years, and if the carbon reservoir has not changed appreciably in this time, then there exists at the present time a complete balance between the rate of disintegration of radiocarbon atoms and the rate of assimilation of new radiocarbon atoms for all material in the life-cycle." [See Willard F. Libby, Radiocarbon Dating (Chicago: University of Chicago Press, 1952), pp. 4-9.]

Recently, others have duplicated Libby's measurements with much greater accuracy. They concluded that the out-of-balance condition is real and even worse than Libby believed. Radiocarbon is forming 28-37% faster than it is decaying. [See Melvin A. Cook, "Nonequilibrium RadioCarbon Dating Substantiated," Proceedings of the First International Conference on Creationism, Vol. 2 (Pittsburgh, Pennsylvania: Creation Science Fellowship, 1986), pp. 59-68.] Notice that this is what we would expect from the flood.

"It now appears that the C14 decay rate in living organisms is about 30 per cent less than its production rate in the upper atmosphere." Stansfield, p. 83.

3. Robert H. Brown, "Implications of C-14 Age vs. Depth Profile Characteristics," Origins, Vol. 15, No. 1, 1988, pp. 19-29.

4. W. S. Glock and S. Agerter, "Anomalous Patterns in Tree Rings," Endeavor, Vol. 22, January 1963, pp. 9-13.

5. The oldest living thing known is a bristlecone pine in the White Mountains of California. The American Forestry Association estimates that it is 4600 years old. Amazingly, it is not part of any "long chronology." Its age, however, is remarkably close to the probable time of the flood, about 4300-5000 years ago. It should not be surprising that some trees, which started growing right after the flood, might still be alive today.

6. R. E. Taylor et al., "Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry," American Antiquity, Vol. 50, No. 1, 1985, pp. 136-140.

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