- A Close Look at Dr. Hovind's List of Young-Earth Arguments and Other Claims
- Carbon Dating Gets a Reset - Scientific American
- Answers to Creationist Attacks on Carbon-14 Dating
- Carbon Dating Gets a Reset
The carbon clock is getting reset.
A Close Look at Dr. Hovind's List of Young-Earth Arguments and Other Claims
Climate records from a Japanese lake are set to improve the accuracy of the dating technique, which could help to shed light on archaeological mysteries such as why Neanderthals became extinct. Carbon dating is used to work out the age of organic material — in effect, any living thing. The technique hinges on carbon, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.
Organisms capture a certain amount of carbon from the atmosphere when they are alive. By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon decay can be worked out, thereby giving an age for the specimen in question. But that assumes that the amount of carbon in the atmosphere was constant — any variation would speed up or slow down the clock. The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the Nobel Prize in Chemistry.
Various geologic, atmospheric and solar processes can influence atmospheric carbon levels. Since the s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.
Carbon Dating Gets a Reset - Scientific American
As a rule, carbon dates are younger than calendar dates: The problem, says Bronk Ramsey, is that tree rings provide a direct record that only goes as far back as about 14, years. If they are right, this means all C ages greater than two or three thousand years need to be lowered drastically and that the earth can be no older than ten thousand years.
Yes, Cook is right that C is forming today faster than it's decaying. However, the amount of C has not been rising steadily as Cook maintains; instead, it has fluctuated up and down over the past ten thousand years. How do we know this? From radiocarbon dates taken from bristlecone pines. There are two ways of dating wood from bristlecone pines: Since the tree ring counts have reliably dated some specimens of wood all the way back to BC, one can check out the C dates against the tree-ring-count dates.
Admittedly, this old wood comes from trees that have been dead for hundreds of years, but you don't have to have an 8,year-old bristlecone pine tree alive today to validly determine that sort of date. It is easy to correlate the inner rings of a younger living tree with the outer rings of an older dead tree.
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The correlation is possible because, in the Southwest region of the United States, the widths of tree rings vary from year to year with the rainfall, and trees all over the Southwest have the same pattern of variations. When experts compare the tree-ring dates with the C dates, they find that radiocarbon ages before BC are really too young—not too old as Cook maintains. For example, pieces of wood that date at about BC by tree-ring counts date at only BC by regular C dating and BC by Cook's creationist revision of C dating as we see in the article, "Dating, Relative and Absolute," in the Encyclopaedia Britannica.
Answers to Creationist Attacks on Carbon-14 Dating
So, despite creationist claims, C before three thousand years ago was decaying faster than it was being formed and C dating errs on the side of making objects from before BC look too young , not too old. But don't trees sometimes produce more than one growth ring per year? Wouldn't that spoil the tree-ring count? If anything, the tree-ring sequence suffers far more from missing rings than from double rings. This means that the tree-ring dates would be slightly too young, not too old. Of course, some species of tree tend to produce two or more growth rings per year.
But other species produce scarcely any extra rings. Most of the tree-ring sequence is based on the bristlecone pine. This tree rarely produces even a trace of an extra ring; on the contrary, a typical bristlecone pine has up to 5 percent of its rings missing. Concerning the sequence of rings derived from the bristlecone pine, Ferguson says:. In certain species of conifers, especially those at lower elevations or in southern latitudes, one season's growth increment may be composed of two or more flushes of growth, each of which may strongly resemble an annual ring.
In the growth-ring analyses of approximately one thousand trees in the White Mountains, we have, in fact, found no more than three or four occurrences of even incipient multiple growth layers. In years of severe drought, a bristlecone pine may fail to grow a complete ring all the way around its perimeter; we may find the ring if we bore into the tree from one angle, but not from another. Hence at least some of the missing rings can be found. Even so, the missing rings are a far more serious problem than any double rings.
Other species of trees corroborate the work that Ferguson did with bristlecone pines. Before his work, the tree-ring sequence of the sequoias had been worked out back to BC. The archaeological ring sequence had been worked out back to 59 BC. The limber pine sequence had been worked out back to 25 BC. The radiocarbon dates and tree-ring dates of these other trees agree with those Ferguson got from the bristlecone pine. But even if he had had no other trees with which to work except the bristlecone pines, that evidence alone would have allowed him to determine the tree-ring chronology back to BC.
See Renfrew for more details. So, creationists who complain about double rings in their attempts to disprove C dating are actually grasping at straws. If the Flood of Noah occurred around BC, as some creationists claim, then all the bristlecone pines would have to be less than five thousand years old. This would mean that eighty-two hundred years worth of tree rings had to form in five thousand years, which would mean that one-third of all the bristlecone pine rings would have to be extra rings.
Creationists are forced into accepting such outlandish conclusions as these in order to jam the facts of nature into the time frame upon which their "scientific" creation model is based. Barnes has claimed that the earth's magnetic field is decaying exponentially with a half-life of fourteen hundred years.
Not only does he consider this proof that the earth can be no older than ten thousand years but he also points out that a greater magnetic strength in the past would reduce C dates. Now if the magnetic field several thousand years ago was indeed many times stronger than it is today, there would have been less cosmic radiation entering the atmosphere back then and less C would have been produced. Therefore, any C dates taken from objects of that time period would be too high.
How do you answer him? Like Cook, Barnes looks at only part of the evidence. What he ignores is the great body of archaeological and geological data showing that the strength of the magnetic field has been fluctuating up and down for thousands of years and that it has reversed polarity many times in the geological past.
So, when Barnes extrapolates ten thousand years into the past, he concludes that the magnetic field was nineteen times stronger in BC than it is today, when, actually, it was only half as intense then as now. This means that radiocarbon ages of objects from that time period will be too young, just as we saw from the bristlecone pine evidence. But how does one know that the magnetic field has fluctuated and reversed polarity?
Aren't these just excuses scientists give in order to neutralize Barnes's claims? The evidence for fluctuations and reversals of the magnetic field is quite solid. Bucha, a Czech geophysicist, has used archaeological artifacts made of baked clay to determine the strength of the earth's magnetic field when they were manufactured. He found that the earth's magnetic field was 1. See Bailey, Renfrew, and Encyclopedia Britannica for details. In other words, it rose in intensity from 0.
Even before the bristlecone pine calibration of C dating was worked out by Ferguson, Bucha predicted that this change in the magnetic field would make radiocarbon dates too young. This idea [that the fluctuating magnetic field affects influx of cosmic rays, which in turn affects C formation rates] has been taken up by the Czech geophysicist, V. Bucha, who has been able to determine, using samples of baked clay from archeological sites, what the intensity of the earth's magnetic field was at the time in question. Even before the tree-ring calibration data were available to them, he and the archeologist, Evzen Neustupny, were able to suggest how much this would affect the radiocarbon dates.
There is a good correlation between the strength of the earth's magnetic field as determined by Bucha and the deviation of the atmospheric radiocarbon concentration from its normal value as indicated by the tree-ring radiocarbon work. As for the question of polarity reversals, plate tectonics can teach us much.
It is a fact that new oceanic crust continually forms at the mid-oceanic ridges and spreads away from those ridges in opposite directions. When lava at the ridges hardens, it keeps a trace of the magnetism of the earth's magnetic field. Therefore, every time the magnetic field reverses itself, bands of paleomagnetism of reversed polarity show up on the ocean floor alternated with bands of normal polarity. These bands are thousands of kilometers long, they vary in width, they lie parallel, and the bands on either side of any given ridge form mirror images of each other.
Thus it can be demonstrated that the magnetic field of the earth has reversed itself dozens of times throughout earth history. Barnes, writing in , ought to have known better than to quote the gropings and guesses of authors of the early sixties in an effort to debunk magnetic reversals. Before plate tectonics and continental drift became established in the mid-sixties, the known evidence for magnetic reversals was rather scanty, and geophysicists often tried to invent ingenious mechanisms with which to account for this evidence rather than believe in magnetic reversals.
However, by , sea floor spreading and magnetic reversals had been documented to the satisfaction of almost the entire scientific community. Yet, instead of seriously attempting to rebut them with up-to-date evidence, Barnes merely quoted the old guesses of authors who wrote before the facts were known.
Carbon Dating Gets a Reset
But, in spite of Barnes, paleomagnetism on the sea floor conclusively proves that the magnetic field of the earth oscillates in waves and even reverses itself on occasion. It has not been decaying exponentially as Barnes maintains. When we know the age of a sample through archaeology or historical sources, the C method as corrected by bristlecone pines agrees with the age within the known margin of error.