Radiocarbon method. What is radiocarbon dating

Physical foundations

Carbon, which is one of the main components biological organisms, is present in the earth's atmosphere in the form of stable 12 C and 13 C and radioactive 14 C. The 14 C isotope is constantly formed under the influence (mainly, but also radiation from terrestrial sources too). The ratio of radioactive and stable carbon isotopes in the atmosphere and in the biosphere at the same time in the same place is the same, since all living organisms constantly participate in carbon metabolism and receive carbon from the environment, and isotopes, due to their chemical indistinguishability, participate in biochemical processes in almost the same way. In a living organism, the specific activity of 14 C is approximately 0.3 decays per second per gram of carbon, which corresponds to an isotopic content of 14 C of about 10–10%.

With the death of the body, carbon metabolism stops. After this, stable isotopes are preserved, and radioactive (14 C) is experienced from 5568 ± 30 years, as a result, its content in the remains gradually decreases. Knowing the initial ratio of isotope content in the body and measuring their current ratio in biological material, it is possible to determine how much carbon-14 has decayed and, thus, establish the time that has passed since the death of the organism.

Application

To determine the age, carbon is isolated from a fragment of the sample under study (by burning the fragment), radioactivity is measured for the released carbon, based on this, the isotope ratio is determined, which shows the age of the sample. A carbon sample for activity measurement is usually introduced into a gas that fills a proportional counter, or into a liquid. IN Lately for very low contents of 14 C and/or very small masses of samples (several mg), accelerator mass spectrometry is used, which makes it possible to directly determine the content of 14 C. The maximum age of a sample that can be determined by the radiocarbon method is about 60,000 years, i.e. about 10 half-lives of 14 C. During this time, the content of 14 C decreases by about 1000 times (about 1 decay per hour per gram of carbon).

Measuring the age of an object using the radiocarbon method is possible only when the ratio of isotopes in the sample has not been disturbed during its existence, that is, the sample has not been contaminated with carbon-containing materials of later origin, radioactive substances and has not been exposed to strong sources of radiation. Determining the age of such contaminated samples can lead to huge errors. For example, a case is described when a test determination of grass picked on the day of analysis gave an age of the order of millions of years, due to the fact that the grass was picked on a lawn near a road with constant strong movement, and turned out to be heavily contaminated with exhaust gases. Over the decades since the development of the method, accumulated great experience in identifying contaminants and cleaning samples from them. The error of the method is currently believed to range from seventy to three hundred years.

One of the most famous applications radiocarbon method- study of fragments ( Christian shrine, allegedly containing traces of the body of a crucified person), carried out in a year, simultaneously in several laboratories. Radiocarbon dating made it possible to date the shroud to a period of centuries.

Calibration

Libby's initial assumptions on which the idea of ​​the method was based were that the ratio of carbon isotopes in the atmosphere does not change in time and space, and the content of isotopes in living organisms exactly corresponds to the current state of the atmosphere. It is now firmly established that all these assumptions can only be approximately accepted. The content of the 14 C isotope depends on the radiation environment, which varies in time due to fluctuations in the level of cosmic rays and activity, and in space, due to the unequal distribution of radioactive substances on the Earth's surface and events associated with radioactive materials (for example, at present The formation of the 14 C isotope still contributes to radioactive materials that were formed and dispersed during atmospheric testing in the middle of the century). In recent decades, due to the combustion of fossil fuels, in which 14 C is practically absent, the atmospheric content of this isotope has been decreasing. Thus, accepting a certain isotope ratio as constant can generate significant errors (on the order of millennia). In addition, research has shown that some processes in living organisms lead to excessive accumulation of the radioactive isotope of carbon, which disrupts the natural ratio of isotopes. Understanding of the processes associated with carbon metabolism in nature and the influence of these processes on the isotope ratio in biological objects was not achieved immediately.

As a result, radiocarbon dates made 30-40 years ago often turned out to be very inaccurate. In particular, a test of the method carried out at that time on living trees several thousand years old showed significant deviations for wood samples over 1000 years old.

Currently, for the correct application of the method, careful calibration has been carried out, taking into account changes in the ratio of isotopes for different eras and geographic regions, as well as taking into account the specifics of the accumulation of radioactive isotopes in living beings and plants. To calibrate the method, the determination of isotope ratios is used for objects whose absolute dating is known. One source of calibration data is . A comparison was also made of determining the age of samples using the radiocarbon method with the results of other isotope dating methods. The standard curve used to convert the measured radiocarbon age of a sample to an absolute age is given here: .

It can be stated that in its modern form over the historical interval (from tens of years to 60-70 thousand years in the past), the radiocarbon method can be considered a fairly reliable and qualitatively calibrated independent method for dating objects of biological origin.

Criticism of the method

Despite the fact that radiocarbon dating has long been included in scientific practice and is quite widely used, there is also criticism of this method, calling into question both individual cases of its application and the theoretical foundations of the method as a whole. As a rule, the radiocarbon method is criticized by proponents and others. The main objections to radiocarbon dating are given in the article .

Changes in the atmospheric concentration of the 14 C isotope caused by nuclear testing. Blue line indicates natural concentration

Radiocarbon method absolute geochronology is used to date recent sediments (up to 60-80 thousand years) with high content organic material, biological remains, objects and materials of biological origin by measuring the ratio of the content of the radioactive carbon isotope 14 C in the material. Proposed by Willard Libby in 1946, who was later awarded for this method Nobel Prize in chemistry in 1960.

Radioactive 14 C undergoes beta decay with a half-life of 5730±40 years. By knowing the initial ratio of isotopes in the body and measuring their current ratio in the sample, it is possible to determine how much carbon-14 has decayed and thus determine the time that has passed since the death of the organism.

Radiocarbon concentration (Δ 14 C - deviation from the international standard radiocarbon level) in samples of long-lived trees of known age, measured with high accuracy in wood blocks for 10 years over 4500 years.

It was initially assumed that the ratio of carbon isotopes in the atmosphere does not change in time and space, and the content of isotopes in living organisms exactly corresponds to the current state of the atmosphere. In fact, the content of the 14 C isotope depends on the radiation environment, which varies in time due to fluctuations in the level of solar radiation, and in space due to the unequal distribution of radioactive substances on the Earth's surface and events associated with radioactive waste and nuclear weapons testing (for example , at present, radioactive materials that were formed and dispersed during atmospheric nuclear weapons tests in the mid-20th century still contribute to the formation of the 14 C isotope). The 14 C/12 C ratio also depends on the total concentration of CO 2 in the atmosphere, which is also not constant. All these natural fluctuations, however, are not very large in amplitude and can be taken into account with a certain degree of accuracy. Thus, the resulting pre-procedure radiocarbon age calibration is not absolute. Detailed studies have resulted in a calibration curve that allows one to convert radiocarbon years V absolute.

Today, over the historical interval (from tens of years to 60-70 thousand years), the radiocarbon method can be considered a fairly reliable and qualitatively calibrated independent method for dating objects of organic origin. Its only problem is contamination of samples with foreign carbon.

Dating technology

The radiocarbon method is used to date soils, peats, coals, mollusk shells, bones and other objects of organic origin.

The amount of 14 C isotope can be obtained directly from a sample using mass spectroscopy, which detects all atoms with a mass of 14, and extremely small samples (up to 1 mg) can be used. A special filter allows you to distinguish between 14 C and 14 N. This method is also called AMC dating. It requires complex, highly sensitive instruments, which few laboratories and institutes possess.

The traditional radiocarbon dating method requires lengthy sample preparation. First of all, the sample must be cleaned of younger (for example, tree roots) or older (carbonate rock fragments, etc.) carbon sources. The sample is also washed with an acid or alkaline solution to remove outside sources carbon trapped in the sample. From the bones, by decomposition in HCl, a collagen fraction is isolated, the dating of which is considered the most accurate, because bone carbonates may be replaced by younger ones during burial.

The most accurate dating is the liquid scintillation method of measuring the activity of 14 C. For this method, benzene (C 6 H 6) is obtained from the sample. A special substance is added to benzene - a scintillator - which is charged with the energy of electrons released during the decay of 14 C. The scintillator almost immediately emits the accumulated energy in the form of photons of light. Light can be captured using a photomultiplier tube. A scintillation counter contains two such tubes. A false signal can be identified and excluded as being sent by only one handset. To isolate the counters from background radiation, they are placed in a lead casing several centimeters thick.

The radiocarbon (RC) dating method was invented by the American chemist Willard Libby in 1946; in 1960, Libby became a Nobel laureate in chemistry for the rationale for this method and its application. The RU method consists of measuring the percentage of the radioactive carbon isotope C14 in organic matter and calculating the age of the organic matter on this basis. Initially, Libby's idea was based on the following

hypotheses:

1. C14 is formed in the upper layers of the atmosphere under the influence of cosmic rays, then mixes in the atmosphere, becoming part of carbon dioxide. It was assumed that the percentage of C14 in the atmosphere is constant and does not depend on time and place, despite the heterogeneity of the atmosphere itself and the decay of isotopes.
2. The rate of radioactive decay is a constant value, measured by a half-life of 5568 years (it is assumed that during this time half of the C14 isotopes turn into C12).
3. Animal and plant organisms build their bodies from carbon dioxide extracted from the atmosphere, and at the same time living cells contain the same percentage of the C14 isotope that is in the atmosphere.
4. Upon the death of an organism, its cells leave the carbon metabolism cycle, therefore the C14 carbon isotopes, according to the exponential law of radioactive decay, turn into the stable C12 isotope. This allows us to calculate the time that has passed since the death of the body. This time is called "radiocarbon age".

This theory, as material accumulated, began to have counterexamples: recently deceased organisms suddenly turned out to be very ancient, or, on the contrary, they could contain such a huge amount of the isotope that they received a negative RU age. Some obviously ancient objects had a young RU age (such artifacts were declared to be late fakes). As a result, it turned out that RU-age does not always coincide with the true age, in the case when the true age can be verified. But the RU method is used mainly for dating organic objects of unknown age, thus these dates may not have independent verification. The resulting paradoxes can be explained by the following shortcomings of Libby’s theory (these and other factors are analyzed in the book by M.M. Postnikov “A critical study of the chronology of the ancient world, in 3 volumes,” M.: Kraft+Lean, 2000, in volume 1, pp. 311-318, written in 1978):

1) Inconsistency, unevenness of the percentage of C14 in the atmosphere, its heterogeneous distribution. The content of C14 depends on the cosmic factor (the intensity of solar radiation) and the terrestrial factor (the entry of “old” carbon into the atmosphere due to the combustion or decay of ancient organic matter, the emergence of new sources of radioactivity, fluctuations magnetic field Earth). A change in this parameter by 20% entails an error in the RU-age of almost 2 thousand years.
2) The rate of radioactive decay of isotopes is not constant - indeed, since the time of Libby, the half-life of C14 according to official reference books has “changed” by a hundred years, that is, by a couple of percent (this corresponds to a change in the RU-age of one and a half hundred years). Apparently, the value of this period depends significantly (within a few percent) on the experiments in which it is determined. And perhaps it depends on some external conditions, fields and forces.
3) Carbon isotopes are not completely chemically equivalent, and therefore cell membranes can use them selectively: some absorb C14, some, on the contrary, avoid it. Since the percentage of C14 is negligible (one C14 atom to 10 billion C12 atoms), even a slight isotopic selectivity of a cell will lead to a large change in the RU age (a 10% fluctuation leads to an error of about 600 years).
4) After the death of an organism, its tissues do not leave carbon metabolism, participating in the processes of decay and diffusion.

Since Libby's time, radiocarbon physicists have been able to very accurately determine the isotope content of a sample, even claiming to be able to count individual atoms of an isotope. Of course, such a calculation is only possible for a small sample of organic tissue, but in this case the question arises - how accurately does this small sample represent the entire object? How uniform is the isotope content in it? After all, errors of a few percent lead to hundred-year changes in the RU-age.

Calibration scale C14.

Recognizing the significant variability in the content of C14 in the atmosphere, radiocarbon physicists, starting around the 70s, began to build the so-called. “calibration scales” of the C14 isotope: from the distribution of the isotope in the rings of long-lived trees (thousand-year-old American redwoods), the content of the isotope in the atmosphere over the past few thousand years was extrapolated. Such a scale has a certain meaning for the region where it was compiled, but transferring it to other regions, to other continents is unfounded and, most likely, erroneous.
Attempts to construct similar scales for short-lived trees in Europe give rise to a different problem: the RU scale turns out to be tied to the dendroscale of the region, compiled, as indicated above, even less reliably. As a result, it turns out that the RU-scale is tied to an arbitrary and erroneous dendroscale, and the latter is justified by reference to agreement with the RU-scale: and the blind lead the blind. Russian archaeologists from the Kolchin school like to repeat these kinds of arguments.
The C14 calibration scale experiences significant variation in its values. This has led to the fact that now, in order to determine the RC age, radiocarbon daters need to know the search interval for the required date, since the required isotope content values ​​can now be located in all historical millennia. This interval is taken from the a priori instructions of traditional historians: historians indicate a suspicious century - radiocarbon dating gives historians an “exact” date, in other centuries the dates would be different. The process of obtaining other datings on the same material was illustrated by A.M. Tyurin<2>.

All these innovations of the RU method try to remove the influence of factor 1) from the previous ones, and the others cannot be taken into account. The bottom line is that radiocarbon dating is no more reliable or scientific than eye-dating, but it is used to create the impression that traditional chronology created by medieval astrologers and theologians is scientific. Sometimes you even hear statements from historians that ancient coins were dated using the RU method! But even if these coins were cast iron and contained a sufficient amount of carbon, then RU dating would have to show not the time of manufacture of the coin, but the age of the ore (many hundreds of thousands of years). One should think that many references to RU dating are the same deception of the scientific world.

Literature
1. Postnikov M.M. “A critical study of the chronology of the ancient world, in 3 volumes, 1978,” M.: Kraft + Lean, 2000, volume 1, pp. 311-318.
2. Articles by A.M. Tyurin in Almanac NH No. 3:

Everything that has come down to us from paganism is shrouded in thick fog; it belongs to that interval of burden which we cannot measure. We know what it is older than Christianity, but for two years, for two hundred years or for a whole millennium - here we can only guess. Rasmus Nierup, 1806.

Many of us are intimidated by science. Radiocarbon dating, as one of the results of the development of nuclear physics, is an example of such a phenomenon. This method has important implications for different and independent scientific disciplines such as hydrology, geology, atmospheric science and archaeology. However, we leave the understanding of the principles of radiocarbon dating to the scientific experts and blindly accept their conclusions out of respect for the accuracy of their equipment and admiration for their intelligence.

In fact, the principles of radiocarbon dating are amazingly simple and easily accessible. Moreover, the idea of ​​carbon dating as an “exact science” is misleading, and in truth, few scientists hold this opinion. The problem is that representatives of many disciplines who use radiocarbon dating for chronological purposes do not understand its nature and purpose. Let's look into this.

Principles of Radiocarbon Dating
William Frank Libby and members of his team developed the principles of radiocarbon dating in the 1950s. By 1960, their work was complete, and in December of that year, Libby was nominated for the Nobel Prize in Chemistry. One of the scientists involved in his nomination noted:

“Rarely has it happened that one discovery in the field of chemistry has had such an impact on different fields human knowledge. Very rarely has a single discovery attracted such widespread interest.”

Libby discovered that the unstable radioactive isotope of carbon (C14) decays at a predictable rate into stable isotopes of carbon (C12 and C13). All three isotopes occur naturally in the atmosphere in the following proportions; C12 - 98.89%, C13 - 1.11% and C14 - 0.00000000010%.

Stable carbon isotopes C12 and C13 were formed along with all the other atoms that make up our planet, that is, a very, very long time ago. The C14 isotope is formed in microscopic quantities as a result of the daily bombardment of the solar atmosphere by cosmic rays. When cosmic rays collide with certain atoms, they destroy them, as a result of which the neutrons of these atoms become free in the earth's atmosphere.

The C14 isotope is formed when one of these free neutrons fuses with the nucleus of a nitrogen atom. Thus, radiocarbon is a "Frankenstein isotope", an alloy of different chemical elements. Then C14 atoms, which are formed at a constant rate, undergo oxidation and penetrate into the biosphere through the process of photosynthesis and the natural food chain.

In the organisms of all living beings, the ratio of C12 and C14 isotopes is equal to the atmospheric ratio of these isotopes in their geographical region and is maintained by the rate of their metabolism. However, after death, organisms stop accumulating carbon, and the behavior of the C14 isotope from this point on becomes interesting. Libby found that the half-life of C14 was 5568 years; After another 5568 years, half of the remaining atoms of the isotope decay.

Thus, since the initial ratio of C12 to C14 isotopes is a geological constant, the age of a sample can be determined by measuring the amount of residual C14 isotope. For example, if some initial amount of C14 is present in the sample, then the date of death of the organism is determined by two half-lives (5568 + 5568), which corresponds to an age of 10,146 years.

This is the basic principle of radiocarbon dating as an archaeological tool. Radiocarbon is absorbed into the biosphere; it stops accumulating with the death of the organism and decays at a certain rate that can be measured.

In other words, the C 14 / C 12 ratio gradually decreases. Thus, we get a “clock” that begins to tick from the moment of death of a living being. Apparently this clock only works on dead bodies that were once living beings. For example, they cannot be used to determine the age of volcanic rocks.

The decay rate of C 14 is such that half of this substance turns back into N 14 within 5730 ± 40 years. This is the so-called “half-life”. After two half-lives, that is, 11,460 years, only a quarter of the original amount will remain. Thus, if the C14/C12 ratio in a sample is one-quarter that of modern living organisms, the sample is theoretically 11,460 years old. It is theoretically impossible to determine the age of objects older than 50,000 years using the radiocarbon method. Therefore, radiocarbon dating cannot show ages of millions of years. If the sample contains C14, this already indicates that its age less million years.

However, everything is not so simple. Firstly, plants absorb carbon dioxide containing C14 worse. Consequently, they accumulate less of it than expected and therefore appear older than they actually are when tested. Moreover, different plants assimilate C14 in different ways, and allowances should be made for this too. 2

Secondly, the C 14 / C 12 ratio in the atmosphere was not always constant - for example, it decreased with the onset of the industrial era, when, due to the combustion of huge quantities of organic fuel, a mass of carbon dioxide depleted in C 14 was released. Accordingly, organisms that died during this period appear older under radiocarbon dating. Then there was an increase in C14O2 associated with ground-based nuclear testing in the 1950s, 3 as a result, organisms that died during this period began to appear younger than they actually were.

Measurements of C14 content in objects whose age has been accurately established by historians (for example, grain in tombs indicating the date of burial) make it possible to estimate the level of C14 in the atmosphere at that time and, thus, partially “correct the progress” of the radiocarbon “clock”. Accordingly, radiocarbon dating, carried out taking into account historical data, can give very fruitful results. However, even with this “historical setting,” archaeologists do not consider radiocarbon dates to be absolute, due to frequent anomalies. They rely more on dating methods associated with historical records.

Outside of historical data, “setting” the “clock” from 14 is not possible

In the laboratory
Given all these irrefutable facts, it is extremely strange to see the following statement in the journal Radiocarbon (which publishes the results of radiocarbon studies around the world):

“Six reputable laboratories carried out 18 age analyzes on wood from Shelford in Cheshire. Estimates range from 26,200 to 60,000 years (before the present), with a range of 34,600 years."

Here's another fact: Although the theory of radiocarbon dating sounds convincing, when its principles are applied to laboratory samples, human factors come into play. This leads to errors, sometimes very significant ones. In addition, laboratory samples are contaminated by background radiation, altering the residual level of C14 that is measured.

As Renfrew pointed out in 1973 and Taylor in 1986, radiocarbon dating relies on a number of unsubstantiated assumptions made by Libby during the development of his theory. For example, in last years There has been much discussion about C14's supposed half-life of 5,568 years. Today, most scientists agree that Libby was wrong and that the half-life of C14 is actually about 5,730 years. The discrepancy of 162 years becomes great importance when dating samples from thousands of years ago.

But along with the Nobel Prize in Chemistry, Libby came to full confidence in his new system. His radiocarbon dating of archaeological samples from ancient Egypt had already been dated because the ancient Egyptians were careful about their chronology. Unfortunately, radiocarbon analysis gave too low an age, in some cases 800 years younger than according to the historical chronicle. But Libby came to a startling conclusion:

“The distribution of the data shows that ancient Egyptian historical dates before the beginning of the second millennium BC are too high and may be 500 years older than the true dates at the beginning of the third millennium BC.”

This is a classic case of scientific conceit and a blind, almost religious belief in the superiority of scientific methods over archaeological ones. Libby was wrong; radiocarbon dating had failed him. This problem has now been resolved, but the self-proclaimed reputation of carbon dating still exceeds its reliability.

My research shows that there are two serious problems with radiocarbon dating that can still lead to great misunderstandings today. These are (1) contamination of the samples and (2) changes in atmospheric C14 levels over geological epochs.

Radiocarbon dating standards.

The value of the standard adopted when calculating the radiocarbon age of a sample directly affects the resulting value. Based on the results of a detailed analysis of the published literature, it was established that several standards were used in radiocarbon dating. The most famous of them are the Anderson standard (12.5 dpm/g), the Libby standard (15.3 dpm/g) and the modern standard (13.56 dpm/g).

Dating the pharaoh's boat.

The wood of the pharaoh Sesostris III's boat was radiocarbon dated based on three standards. When dating wood in 1949, based on the standard (12.5 dpm/g), a radiocarbon age of 3700 +/- 50 BP years was obtained. Libby later dated the wood based on the standard (15.3 dpm/g). The radiocarbon age has not changed. In 1955, Libby re-dated the boat's wood based on the standard (15.3 dpm/g) and obtained a radiocarbon age of 3621 +/-180 BP years. When dating the wood of the boat in 1970, the standard (13.56 dpm/g) was used. The radiocarbon age remained almost unchanged and amounted to 3640 BP years. The factual data we provide on the dating of the pharaoh's boat can be checked using the corresponding links to scientific publications.

Price issue.

Obtaining practically the same radiocarbon age of the wood of the pharaoh's boat: 3621-3700 BP years based on the use of three standards, the values ​​of which differ significantly, is physically impossible. The use of the standard (15.3 dpm/g) automatically increases the age of the dated sample by 998 years, compared to the standard (13.56 dpm/g), and by 1668 years, compared to the standard (12.5 dpm/g). There are only two ways out of this situation. Recognition that:

When dating the wood of the boat of Pharaoh Sesostris III, manipulations were carried out with standards (the wood, contrary to declarations, was dated based on the same standard);

Magic boat of Pharaoh Sesostris III.

Conclusion.

The essence of the phenomena considered, called manipulations, is expressed in one word - falsification.

After death, the C 12 content remains constant, and the C 14 content decreases

Sample contamination
Mary Levine explains:

“Contamination is the presence in a sample of organic material of foreign origin that was not formed with the sample material.”

In many photographs early period radiocarbon dating depicts scientists smoking cigarettes while collecting or processing samples. Not too smart of them! As Renfrew points out, “drop a pinch of ash on your samples as they prepare for analysis and you will get the radiocarbon age of the tobacco from which your cigarette was made.”

Although such methodological incompetence is considered unacceptable today, archaeological samples still suffer from contamination. Known types of pollution and methods of controlling them are discussed in the article by Taylor (1987). He divides contaminants into four main categories: 1) physically removable, 2) acid-soluble, 3) alkali-soluble, 4) solvent-soluble. All these contaminants, if not eliminated, greatly affect the laboratory determination of the age of the sample.

H. E. Gove, one of the inventors of the accelerator mass spectrometry (AMS) method, radiocarbon dated the Shroud of Turin. He concluded that the fabric fibers used to make the shroud dated back to 1325.

Although Gove and his colleagues are quite confident in the authenticity of their determination, many, for obvious reasons, consider the age of the Shroud of Turin to be much more respectable. Gove and his associates gave a fitting response to all the critics, and if I had to make a choice, I would venture to say that the scientific dating of the Shroud of Turin is most likely accurate. But either way, the storm of criticism that has descended on this particular project shows how costly a carbon dating error can be, and how suspicious some scientists are of the method.

It was argued that the samples may have been contaminated by younger organic carbon; cleaning methods may have missed traces of modern contaminants. Robert Hedges of Oxford University notes that

“a small systematic error cannot be completely ruled out.”

I wonder if he would call the discrepancy in dates obtained by different laboratories on the Shelford wood sample a “small systematic error”? Doesn't it seem like we are once again being fooled by scientific rhetoric into believing that existing methods are perfect?

Leoncio Garza-Valdez certainly holds this opinion in relation to the dating of the Shroud of Turin. All ancient tissues are covered with a bioplastic film as a result of bacterial activity, which, according to Garza-Valdez, confuses the radiocarbon analyzer. In fact, the Shroud of Turin may well be 2000 years old, since its radiocarbon dating cannot be considered definitive. Further research is needed. It is interesting to note that Gove (although he disagrees with Garza-Valdez) agrees that such criticism warrants new research.

Radiocarbon cycle (14C) in the atmosphere, hydrosphere and biosphere of the Earth

Level C14 in the earth's atmosphere
According to Libby's "principle of simultaneity", the level of C14 in any given geographic region is constant throughout geological history. This premise was vital to the reliability of radiocarbon dating in its early development. Indeed, to reliably measure residual C14 levels, you need to know how much of this isotope was present in the body at the time of death. But this premise, according to Renfrew, is false:

“However, it is now known that the proportional ratio of radiocarbon to ordinary C12 did not remain constant through time and that before 1000 BC the deviations are so great that radiocarbon dates can differ markedly from reality.”

Dendrological studies (the study of tree rings) convincingly show that the level of C14 in the Earth's atmosphere has been subject to significant fluctuations over the past 8,000 years. This means that Libby chose a false constant and his research was based on erroneous assumptions.

Colorado pine, growing in the southwestern regions of the United States, can be several thousand years old. Some trees still alive today were born 4,000 years ago. In addition, using logs collected from the places where these trees grew, it is possible to extend the tree-ring record back another 4,000 years. Other long-lived trees useful for dendrological research include oak and California redwood.

As you know, every year a new growth ring grows on a cut of a living tree trunk. By counting the growth rings, you can find out the age of the tree. It is logical to assume that the level of C14 in a 6000-year-old tree ring would be similar to the level of C14 in the modern atmosphere. But that's not true.

For example, analysis of tree rings showed that the level of C14 in the earth's atmosphere 6,000 years ago was significantly higher than now. Accordingly, radiocarbon samples dating to this age were found to be noticeably younger than they actually were, based on dendrological analysis. Thanks to the work of Hans Suisse, C14 level correction charts were compiled to compensate for its fluctuations in the atmosphere in different periods time. However, this significantly reduced the reliability of radiocarbon dating of samples older than 8,000 years. We simply do not have data on the radiocarbon content of the atmosphere before this date.

Accelerator mass spectrometer of the University of Arizona (Tucson, Arizona, USA) manufactured by National Electrostatics Corporation: a - diagram, b - control panel and C¯ ion source, c - accelerator tank, d - carbon isotope detector. Photo by J.S. Burra

"Bad" results?

When the established “age” differs from what was expected, researchers quickly find a reason to declare the dating result invalid. The widespread prevalence of this posterior evidence shows that radiometric dating has serious problems. Woodmorappe gives hundreds of examples of the tricks researchers resort to when trying to explain “inappropriate” age values.

So, scientists have revised the age of fossil remains Australopithecus ramidus. 9 Most of the basalt samples closest to the layers in which these fossils were found have been shown to be about 23 million years old by the argon-argon method. The authors decided that this figure was "too high" based on their understanding of the fossils' place in the global evolutionary scheme. They looked at basalt that was located away from the fossils and, by selecting 17 of 26 samples, came up with an acceptable maximum age of 4.4 million years. The remaining nine samples again showed a much older age, but the experimenters decided that the matter was due to contamination of the rock and rejected these data. Thus, radiometric dating methods are significantly influenced by the dominant “long eras” worldview in scientific circles.

A similar story is associated with establishing the age of the primate skull (this skull is known as specimen KNM-ER 1470). 10, 11 At first, a result of 212-230 million years was obtained, which, based on fossils, was found to be incorrect (“there were no people at that time”), after which attempts were made to establish the age of volcanic rocks in this region. A few years later, after the publication of several different research results, they “agreed” on the figure of 2.9 million years (although these studies also included separating the “good” results from the “bad” - as in the case of Australopithecus ramidus).

Based on preconceived ideas about human evolution, researchers could not come to terms with the idea that the skull 1470 "so old." After studying pig fossils in Africa, anthropologists readily believed that the skull 1470 actually much younger. After the scientific community established itself in this opinion, further studies of rocks further reduced the radiometric age of this skull - to 1.9 million years - and again data was found that “confirmed” another number. This is the “radiometric dating game”...

We do not claim that evolutionists conspired to fit all the data to the most convenient result for themselves. Of course, this is not normally the case. The problem is different: all observational data must correspond to the dominant paradigm in science. This paradigm - or rather the belief in millions of years of evolution from molecule to man - is so firmly entrenched in consciousness that no one allows himself to question it; on the contrary, they talk about the “fact” of evolution. It is under this paradigm that must fit absolutely all observations. As a result, researchers who appear to the public to be “objective and unbiased scientists” unconsciously cherry-pick observations that are consistent with belief in evolution.

We must not forget that the past is inaccessible to normal experimental research (a series of experiments conducted in the present). Scientists cannot experiment with events that once happened. It is not the age of the rocks that is measured - the concentrations of isotopes are measured, and they can be measured with high accuracy. But “age” is determined taking into account assumptions about the past, which cannot be proven.

We must always remember God's words to Job: “Where were you when I laid the foundations of the earth?”(Job 38:4).

Those who deal with unwritten history collect information in the present and thus try to reconstruct the past. At the same time, the level of requirements for evidence is much lower than in empirical sciences, such as physics, chemistry, molecular biology, physiology, etc.

William ( Williams), a specialist in the transformation of radioactive elements into environment, identified 17 flaws in isotope dating methods (based on the results of this dating, three very respectable works were published, which made it possible to determine the age of the Earth at approximately 4.6 billion years). 12 John Woodmorappe is a sharp critic of these dating methods 8 and exposes hundreds of related myths. He argues convincingly that the few "good" results remaining after the "bad" data have been filtered out can easily be explained by a lucky coincidence.

“What age do you prefer?”

Questionnaires offered by radioisotope laboratories typically ask, “What do you think the age of this sample should be?” But what is this question? There would be no need for it if dating techniques were absolutely reliable and objective. This is probably because laboratories are aware of the prevalence of anomalous results and are therefore trying to figure out how “good” the data they are getting is.

Testing radiometric dating methods

If radiometric dating methods could truly objectively determine the age of rocks, they would also work in situations where we know the exact age; Besides, various methods would give consistent results.

Dating methods must show reliable results for objects of known age

There are a number of examples where radiometric dating methods incorrectly established the age of rocks (this age was precisely known in advance). One such example is potassium-argon "dating" of five andesitic lava flows from Mount Ngauruhoe in New Zealand. Although the lava was known to flow once in 1949, three times in 1954, and once again in 1975, the "established ages" ranged from 0.27 to 3.5 million years.

The same retrospective method gave rise to the following explanation: when the rock hardened, there was “extra” argon left in it due to magma (molten rock). In secular scientific literature There are many examples of how excess argon leads to “extra millions of years” when dating rocks of known historical age. 14 The source of excess argon appears to be the upper part of the Earth's mantle, located directly below the Earth's crust. This is quite consistent with the “young Earth” theory - the argon had too little time, it simply did not have time to be released. But if an excess of argon led to such glaring errors in dating rocks famous age, why should we trust the same method when dating rocks whose age unknown?!

Other methods - particularly the use of isochrones - involve various hypotheses about initial conditions; But scientists are increasingly convinced that even such “reliable” methods also lead to “bad” results. Here again, the choice of data is based on the researcher's assumption about the age of a particular breed.

Dr. Steve Austin (Steve Austin), a geologist, took samples of basalt from the lower layers of the Grand Canyon and from lava flows at the canyon rim. 17 According to evolutionary logic, the basalt at the edge of the canyon should be a billion years younger than the basalt from the depths. Standard laboratory isotope analysis using rubidium-strontium isochron dating showed that the lava flow was relatively recent at 270 million years ago. older basalt from the depths of the Grand Canyon - which, of course, is absolutely impossible!

Methodological problems

Initially, Libby's idea was based on the following hypotheses:

1. 14C is formed in the upper layers of the atmosphere under the influence of cosmic rays, then mixed in the atmosphere, becoming part of carbon dioxide. Moreover, the percentage of 14C in the atmosphere is constant and does not depend on time or place, despite the heterogeneity of the atmosphere itself and the decay of isotopes.
2. The rate of radioactive decay is a constant, measured by a half-life of 5568 years (it is assumed that during this time half of the 14C isotopes are converted to 14N).
3. Animal and plant organisms build their bodies from carbon dioxide extracted from the atmosphere, and living cells contain the same percentage of the 14C isotope that is found in the atmosphere.
4. Upon the death of an organism, its cells leave the carbon metabolism cycle, but atoms of the 14C isotope continue to transform into atoms of the stable 12C isotope according to the exponential law of radioactive decay, which allows us to calculate the time that has passed since the death of the organism. This time is called “radiocarbon age” (or “RU age” for short).

This theory, as material accumulated, began to have counterexamples: the analysis of recently deceased organisms sometimes gives very ancient age, or, conversely, the sample contains such a huge amount of the isotope that the calculations give a negative RU age. Some obviously ancient objects had a young RU age (such artifacts were declared to be late fakes). As a result, it turned out that RU-age does not always coincide with the true age in cases where the true age can be verified. Such facts lead to reasonable doubts in cases where the X-ray method is used to date organic objects of unknown age, and the X-ray dating cannot be verified. Cases of erroneous determination of age are explained by the following well-known shortcomings of Libby's theory (these and other factors are analyzed in the book by M. M. Postnikov "A Critical Study of the Chronology of the Ancient World, in 3 Volumes",— M.: Kraft+Lean, 2000, in volume 1, pp. 311-318, written in 1978):

1. Variability in the percentage of 14C in the atmosphere. The 14C content depends on the cosmic factor (the intensity of solar radiation) and the terrestrial factor (the entry of “old” carbon into the atmosphere due to the combustion and decay of ancient organic matter, the emergence of new sources of radioactivity, and fluctuations in the Earth’s magnetic field). A change in this parameter by 20% entails an error in the RU-age of almost 2 thousand years.
2. Uniform distribution of 14C in the atmosphere has not been proven. The rate of atmospheric mixing does not exclude the possibility of significant differences in 14C content in different geographic regions.
3. The rate of radioactive decay of isotopes may not be determined accurately. So, since Libby’s time, the half-life of 14C according to official reference books has “changed” by a hundred years, that is, by a couple of percent (this corresponds to a change in the RU-age of one and a half hundred years). It is suggested that the half-life value depends significantly (within a few percent) on the experiments in which it is determined.
4. Carbon isotopes are not completely equivalent , cell membranes can use them selectively: some absorb 14C, some, on the contrary, avoid it. Since the percentage of 14C is negligible (one atom of 14C to 10 billion atoms of 12C), even a slight isotopic selectivity of a cell entails a large change in the RU age (a 10% fluctuation leads to an error of approximately 600 years).
5. After the death of an organism, its tissues do not necessarily leave carbon metabolism , participating in the processes of decay and diffusion.
6. The 14C content of an item may not be uniform. Since Libby's time, radiocarbon physicists have become very precise at determining the isotope content of a sample; They even claim that they are able to count individual atoms of the isotope. Of course, such a calculation is only possible for a small sample, but in this case the question arises - how accurately does this small sample represent the entire object? How uniform is the isotope content in it? After all, errors of a few percent lead to century-long changes in the RU-age.

Summary
Radiocarbon dating is an evolving scientific method. However, at every stage of its development, scientists unconditionally supported its overall reliability and fell silent only after revealing serious errors in the estimates or in the method of analysis itself. The errors shouldn't be surprising given the number of variables a scientist must take into account: atmospheric fluctuations, background radiation, bacterial growth, pollution and human error.

As part of a representative archaeological survey, radiocarbon dating remains of utmost importance; it just needs to be placed into cultural and historical perspective. Does a scientist have the right to discount contradictory archaeological evidence just because his carbon dating indicates a different age? Is it dangerous. In fact, many Egyptologists have supported Libby's suggestion that the chronology Old Kingdom written incorrectly because it has been “scientifically proven.” Libby was actually wrong.

Radiocarbon dating is useful as a complement to other data, and this is where it comes from. strong point. But until the day comes when all variables are under control and all errors are eliminated, radiocarbon dating will not have the final word on archaeological sites.
sources
Chapter from the book by K. Ham, D. Sarfati, K. Wieland, ed. D. Batten “BOOK OF ANSWERS: EXTENDED AND UPDATED”
Graham Hancock: Footsteps of the Gods. M., 2006. Pp. 692-707.

There has been a lot of debate on the City lately, covering topics such as alternative history, chronology, creationism and the theory of evolution. In the course of disputes, the topic of “is the scientific/generally accepted evidence of the age of a particular artifact, phenomenon, event, etc., reliable?”

Therefore, I bring to your attention a description of the radiocarbon dating method, as one of the most common for determining the age of artifacts.

Raw age data, i.e. data that has not been calibrated is usually called radiocarbon years"until now". As a zero reference, i.e. "present time", is considered to be 1950 AD.

Radiocarbon dating was invented by Willard Libby, a professor at the University of Chicago, and his colleagues in 1949. In 1960 he received the Nobel Prize in Chemistry for his invention.

The essence of the method is that a stable isotope of nitrogen (14 N) in the atmosphere is exposed to cosmic rays, converting it into the carbon isotope 14 C, which has a half-life of 5730 ± 40 years. Living organisms, in the process of life activity, assimilate atmospheric carbon, accumulating a certain amount of 14 C in their tissues, which then gradually disintegrates (it is assumed that after the death of the organism there are no new intakes of 14 C into the tissues). It is enough for a researcher to know how much 14 C a given type of organism accumulates on average during its life, and to determine how much of it remains in the tissues - based on these data, the age in radiocarbon years is calculated.

One of the first demonstrations of the efficiency and accuracy of the method was the measurement of the age of wood from the burial of an ancient Egyptian pharaoh, whose age was known in advance from historical documents.

Physics of the process

Carbon has 2 stable isotopes - 12 C (98.89%) and 13 C (1.11%). In addition, there are trace amounts of the unstable isotope 14 C on Earth (0.0000000001%). This isotope has a half-life of about 5,730 years, and thus should have disappeared from the face of the Earth long ago. However, constant streams of cosmic rays bombarding the Earth's atmosphere renew this supply. Neutrons produced by bombardment of the atmosphere by cosmic rays enter into a nuclear reaction with the nuclei of nitrogen atoms:

n+ 14 7 N → 14 6 C+p

The largest amount of 14 C is observed in the atmosphere at altitudes of 9 - 15 km and at high latitudes, from where it spreads throughout the atmosphere and dissolves in the oceans. For rough analysis it is believed that the “production” of 14 C occurs at approximately a constant rate, and the content of 14 C in the atmosphere is approximately constant (600 billion atoms of 14 C per mole).

The resulting carbon is quickly oxidized to 14 CO 2 and is subsequently absorbed by plants and microorganisms, subsequently entering the food chain of other organisms. Thus, every living organism constantly receives a certain amount of 14 C throughout its life. As soon as it dies, this exchange stops, and the accumulated 14 C gradually disintegrates in the beta decay reaction:

14 6 C → 14 7 N + e - +v e

By emitting an electron and an antineutrino, 14 C turns into stable nitrogen.

In 1958, Hessel de Vries proved that the concentration of 14 C in the atmosphere can vary greatly, both in different time, and in different places. For more accurate measurements, these changes are taken into account in the form of calibration curves. The figure below shows the dynamics of changes in the concentration of 14 CO2 in the atmosphere over Australia and New Zealand - a significant surge is due to numerous uses of nuclear weapons in the atmosphere.

In addition, it is known that marine organisms can obtain carbon from carbonates dissolved in water, the age of which can be very significant - due to this, they may have a “deficiency” of the 14 C isotope, which makes the radiocarbon method much less reliable for this type of material.

The decay of 14 C obeys the exponential law. In other words, the number of atoms that decay in a given period depends on the initial number of atoms at the beginning of that period. Number of remaining atoms WITH after time has passed t , will be expressed by the formula:

C = C 0 e -t/T

Where From 0 - initial number of atoms, T - average decay time = t 1/2 (half-life) *ln2 , e is the base of the natural logarithm.

Thus, the radiocarbon age t RV (without correction for fluctuations in the amount of 14 C) will be expressed by the formula:

t RV= -t 1/2 * log 2 (C/C 0 )

Measurements and scales

Traditional methods calculations of the 14 C material remaining in samples are based on counting the number of still decaying atoms (gas and liquid methodsscintillation based on direct counting of “flares” generated by the decays of individual 14 C atoms in special scintillation chambers equipped with sensors), but they are insensitive and can lead to large errors when studying small samples (less than 1 gram of carbon). So, for example, in a 10,000 year old sample, the average number of decays would be 4 atoms/second per mole of carbon (about 30-40 grams for wood), which is either too low to obtain reliable statistics or takes too long (which may also lead to the accumulation of errors due to extraneous scintillations).

Isotope mass spectrometry
in recent years has become the main tool for radiocarbon dating. This method is based on the fact that atoms of different isotopes (and substances containing them) have different masses. Samples of the substance are oxidized to form carbon dioxide (the remaining oxides are removed), then the resulting gas is ionized and passes at high speed through a magnetic chamber, where charged molecules deviate from the original trajectory. The greater the deviation, the lighter the molecule, and the less 14 C it contains. By calculating the ratio of weakly deviated and strongly deviated molecules, it is possible to determine the concentration of 14 C in the sample with high accuracy. This method allows samples with a mass of only a few milligrams to be dated to a range of up to 60,000 years (2005 data).

Calibration

As has been said many times, this method depends significantly on the assumption that the content of 14 C in the atmosphere is approximately constant. However, in practice this is not the case. The level of 14 C depends on many factors. First of all, on the intensity of cosmic radiation, which changes depending on changes in the Earth's magnetic field, which, in turn, is affected by flares on the Sun. In addition, the 14 C balance may be disrupted due to large emissions of carbon into the atmosphere from the ocean (gas condensate), volcanic and other activities. Climate change and human activity may also upset this balance.

The main methods of calibrating the method, that is, calculating the balance of 14 C in the required period, are comparisons of the results of the radiocarbon method with other independent methods - dendrochronology, studies of ancient ice cores, bottom sediments, samples of ancient corals, cave deposits and sediments.

The calibration graph shows the dependence of the radiocarbon age of the samples on their age, calculated using a combination of other methods. The modern (according to 2004 data) calibration accuracy is ±16 years for ages up to 6,000 years and no more than ±160 years for ages up to 26,000 years.

However, now (again, with a certain caveat) this method can be considered reliable, especially since there are about 130 independent laboratories in the world performing this research, and work is constantly underway to improve calibration.

Literature

1. Arnold, J. R. and Libby, W. F. (1949)Age Determinations by Radiocarbon Content: Checks with Samples of Known Age , Science 110, 678-680.
2. Libby, W.F. Radiocarbon dating, 2nd Edition, Chicago, University of Chicago Press, 1955.
3. C. Crowe, Carbon-14 activity during the past 5000 years, Nature, 182, (1958): 470 + refutations in the same issue: a) K. O. Münnich, H. G. Östlund, and H. de Vries, Nature, 182, (1958): 1432 and b) H. Barker, Nature, 182, (1958): 1433 - both provide evidence of widespread changes in 14 C levels and, accordingly, provide calculations giving much younger ages for the samples presented by C. Crowe.
4. de Vries, H. L. (1958). Variation in Concentration of Radiocarbon with Time and Location on Earth, Proceedings Koninlijke Nederlandse Akademie Wetenschappen B, 61: 94-102; and in Researches in Geochemistry, P. H. Abelson (Ed.) (1959) Wiley, New York, p. 180
5. Aitken, M.J. Physics and Archaeology, New York, Interscience Publishers, 1961.
6. Libby, W.F. Radiocarbon; an Atomic Clock, Annual Science and Humanity journal, 1962.
7. Kovar, A. J. (1966)