What is radiocarbon dating

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 that it is older than Christianity, but by two years, two hundred years or 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 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 ​​radiocarbon dating as “ exact science” is wrong, and in truth, only a 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 areas 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 the C14 atoms that are formed with constant speed, 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, various plants C14 is absorbed differently, 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 were already dated because the ancient Egyptians were careful about their chronology. Unfortunately, radiocarbon dating gave too low an age, in some cases 800 years less 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 things associated with radiocarbon dating. serious problems, which even today can lead to great misunderstandings. 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 almost the same radiocarbon age of the wood of the pharaoh's boat: 3621-3700 BP years based on application 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.”

Many photographs from the early period of radiocarbon dating show 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 species contaminants and how to combat them are discussed in an 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. Required further research. 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 over different periods of 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 the normal experimental research(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 transformations of radioactive elements in the 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). The secular scientific literature provides 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 top part Earth's mantle, located directly below 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 analysis isotopes using rubidium-strontium isochron dating showed that a relatively recent lava flow at 270 million years 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 upper layers atmosphere under the influence of cosmic rays, then mixes 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 constant value, measured by a half-life of 5568 years (it is assumed that during this time half of the 14C isotopes turn into 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: analysis of recently deceased organisms sometimes gives a very ancient age, or, conversely, a sample contains such a huge amount of an isotope that 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 supported Libby's suggestion that the Old Kingdom chronology was incorrect because it had been "scientifically proven." Libby was actually wrong.

Radiocarbon dating is useful as a complement to other data, and this is its strength. 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.

The researchers measured the carbon-14 content of trees growing in southern Jordan, determined their age and compared the resulting dates with the standard method scale. As a result, they found discrepancies of an average of 19 years. A relatively minor inaccuracy can nevertheless have a significant impact on early biblical archaeological research and paleoecological reconstructions. The results are presented in the journal Proceedings of the National Academy of Sciences.

Radiocarbon dating is one of the main methods for dating plants and archaeological objects containing organic material. Scientists have been using it for a long time, so standard scales have now been developed for the Northern and Southern Hemispheres, which are called calibration curves. They represent the dependence of calendar and radiocarbon ages. These curves are fairly close to a straight line, but reflect variations in isotope ratios at different times.

“We have begun to test the assumptions on which the entire field of radiocarbon dating rests,” says lead author Stuart Manning from Cornell University in the US. - From atmospheric measurements of the last 50 years, we know that the content of carbon isotopes varies throughout the year, and we also understand that in different parts of the Northern Hemisphere, plants often grow actively in different time. "We wanted to find out how much the [accuracy of radiocarbon dating] varies depending on the [geographic] area being studied, and whether this might affect archaeological dating."

The material for the study was trees growing in the south of Jordan, the age of which is known to scientists. The authors measured the age of their tree rings using radiocarbon dating and found a shift of 19 years relative to the standard Northern Hemisphere calibration curve. As a result, scientists say, many works on the history of this region, which also includes modern territory Israel may be based on incorrect assumptions. For example, it makes sense to double-check the dating of early biblical events, since the calibration curves used in many studies are simply not suitable for this area.

The authors applied the results to several previously published chronological tables and found that even a small shift in dating can lead to a change in calendar dates, which must be taken into account when resolving controversial issues of history, archeology and climate of the past. “Our work should be the beginning of a reexamination and rethinking of the timeline of archeology and early history of the southern Levant during the early biblical period,” Manning concludes.

Did you like the material? in “My sources” of Yandex.News and read us more often.

Physical foundations

Carbon, which is one of the main components of 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 isotopes of carbon 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 environment, and isotopes, due to their chemical indistinguishability, participate in biochemical processes in almost the same way. In a living organism specific activity 14 C is equal to 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 14 C contents and/or very small sample masses (several mg), accelerator mass spectrometry is used to directly determine the 14 C content. Age limit sample, which can be determined by the radiocarbon method - 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 about millions of years, due to the fact that the grass was picked on a lawn near a road with constant heavy traffic, and was heavily contaminated with substances exhaust gases. Over the decades since the development of the method, extensive experience has been accumulated in identifying contaminants and in 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 cases of using the radiocarbon method is the study of fragments (a Christian shrine that supposedly contains 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 current state 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 correct application The method was carefully calibrated, taking into account changes in the ratio of isotopes for different eras and geographical 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 .

Radiocarbon dating has changed our understanding of the last 50,000 years. Professor Willard Libby first demonstrated it in 1949, for which he was later awarded the Nobel Prize.

Dating method

The essence of radiocarbon dating is to compare three different isotopes of carbon. Isotopes of a particular element have same number protons in the nucleus, but different number neutrons. This means that although they are very chemically similar, they have different masses.

The total mass of the isotope is indicated by a numerical index. While the lighter isotopes 12 C and 13 C are stable, the heaviest isotope 14 C (radiocarbon) is radioactive. Its core is so large that it is unstable.

Over time, 14 C - the basis of radiocarbon dating - breaks down into nitrogen 14 N. Most of Carbon-14 is created in the upper atmosphere, where neutrons produced by cosmic rays react with 14N atoms.

It is then oxidized into 14 CO 2, enters the atmosphere and mixes with 12 CO 2 and 13 CO 2. Carbon dioxide is used by plants during photosynthesis and from there passes through the food chain. Therefore, every plant and animal in this chain (including humans) will have an equal amount of 14 C compared to the 12 C in the atmosphere (14 C: 12 C ratio).

Limitations of the method

When living things die, tissue is no longer replaced and radioactive decay of 14 C becomes apparent. After 55 thousand years, 14 C decays so much that its residues can no longer be measured.

What is radiocarbon dating? can be used as a "clock" since it is independent of physical (eg temperature) and chemical (eg water content) conditions. In 5730 years, half of the 14 C contained in the sample decays.

Therefore, if the ratio of 14 C: 12 C at the time of death and the ratio today are known, then it is possible to calculate how much time has passed. Unfortunately, identifying them is not so easy.

Radiocarbon dating: uncertainty

The amount of 14 C in the atmosphere, and therefore in plants and animals, was not always constant. For example, it varies depending on how many cosmic rays reach the Earth. This depends on solar activity and the magnetic field of our planet.

Fortunately, it is possible to measure these variations in samples dated by other methods. It is possible to calculate tree rings and changes in their radiocarbon content. From this data a "calibration curve" can be constructed.

Currently, work is underway to expand and improve it. In 2008, only radiocarbon dates up to 26,000 years could be calibrated. Today the curve has been extended to 50,000 years.

What can be measured?

Not all materials can be dated using this method. Most, if not all, organic compounds allow radiocarbon dating. Some inorganic substances, such as the aragonite component of the shells, can also be dated because carbon-14 was used in the formation of the mineral.

Materials that have been dated since the method's inception include wood, twigs, seeds, bones, shells, leather, peat, silt, soil, hair, pottery, pollen, wall paintings, coral, blood remains, textiles, paper, parchment, resins and water.

Radiocarbon dating is impossible unless it contains carbon-14. The exception is iron products, in the manufacture of which coal is used.

Double count

Because of this complication, radiocarbon dates are presented in two ways. Uncalibrated measurements are reported in number of years prior to 1950 (BP). Calibrated dates are also presented as BC. BC, and after, and also using the calBP unit (calibrated up to the present, until 1950). This is the "best estimate" of the actual age of the sample, but it is necessary to be able to go back to old data and calibrate it as new research continually updates the calibration curve.

Quantity and quality

The second difficulty is the extremely low abundance of 14 C. Only 0.0000000001% of the carbon in the modern atmosphere is 14 C, which causes incredible difficulties for measurements and makes it extremely sensitive to pollution.

In the early years, radiocarbon dating of decay products required huge samples (for example, half a human femur). Many laboratories now use an accelerator mass spectrometer (AMS), which can detect and measure the presence of various isotopes, as well as count the number of individual carbon-14 atoms.

This method requires less than 1 g of bone tissue, but few countries can afford more than one or two AMS, which cost more than $500 thousand. For example, Australia has only 2 such instruments that are capable of radiocarbon dating, and they are unattainable for much of the developing world.

Cleanliness is the key to precision

In addition, the samples must be thoroughly cleaned of carbon contaminants from the adhesive and soil. This is especially important for very old materials. If 1% of an element in a 50,000-year-old sample comes from a modern contaminant, it will be dated as 40,000 years old.

For this reason, researchers are constantly developing new methods effective cleaning materials. They can have a significant impact on the result given by radiocarbon dating. The accuracy of the method has increased significantly with the development of a new cleaning method activated carbon ABOx-SC. This made it possible, for example, to delay the date of the arrival of the first people in Australia by more than 10 thousand years.

Radiocarbon dating: criticism

The method proving that much more than the 10 thousand years mentioned in the Bible has passed since the origin of the Earth has been repeatedly criticized by creationists. For example, they argue that after 50,000 years there should be no carbon-14 left in the samples, but coal, oil and natural gas, believed to be millions of years old, contain measurable amounts of this isotope, which is confirmed by carbon dating. at the same time there is more background radiation, which cannot be eliminated in the laboratory. That is, a sample that does not contain a single atom of radioactive carbon will show a date of 50 thousand years. However, this fact does not cast doubt on the dating of the objects, and certainly does not indicate that oil, coal and natural gas are younger than this age.

Creationists also note some oddities in radiocarbon dating. For example, dating of freshwater mollusks determined their age to be greater than 2000 years, which, in their opinion, discredits this method. In fact, it has been established that mollusks obtain most of their carbon from limestone and humus, which have very low 14 C content, since these minerals are very old and do not have access to carbon from the air. The radiocarbon dating, the accuracy of which in this case can be questioned, is otherwise consistent with reality. Wood, for example, does not have such a problem, since plants receive carbon directly from the air, which contains a full dose of 14 C.

Another argument against the method is the fact that trees are capable of forming more than one ring in one year. This is true, but more often it happens that they do not form growth rings at all. The bristlecone pine, which is the basis for most measurements, has 5% fewer rings than its actual age.

Setting the date

Radiocarbon dating is not only a method, but also exciting discoveries about our past and present. The method allowed archaeologists to arrange finds in chronological order without the need for written records or coins.

In the 19th and early 20th centuries, incredibly patient and careful archaeologists linked pottery and stone tools from different geographic areas by looking for similarities in shape and pattern. Then, using the idea that object styles evolved and became more complex over time, they could place them in order.

Thus, large domed tombs (known as tholos) in Greece were considered to be the predecessors of similar structures on the Scottish island of Maeshowe. This supported the idea that the classical civilizations of Greece and Rome were at the center of all innovation.

However, radiocarbon dating revealed that the Scottish tombs were thousands of years older than the Greek ones. Northern barbarians were able to design complex structures, similar to the classic ones.

Other notable projects were the dating of the Shroud of Turin to the medieval period, the dating of the Dead Sea Scrolls to the time of Christ, and the somewhat controversial periodization of the paintings at 38,000 calBP (about 32,000 BP), thousands of years earlier than expected.

Radiocarbon dating has also been used to determine the timing of the extinction of mammoths and has contributed to the debate over whether modern people and Neanderthals or not.

The 14 C isotope is used not only to determine age. Radiocarbon dating allows us to study ocean circulation and trace the movement of drugs throughout the body, but this is a topic for another article.

Encyclopedic YouTube

1 / 5

Radiocarbon dating, part 1

Radiocarbon dating, part 2

Radioisotope dating: are the fundamentals of the technique reliable?

Shroud of Turin - radiocarbon dating

Antikythera Mechanism: Fact and Fiction

Subtitles

In this video I would like to focus, firstly, on how carbon-14 appears and how it penetrates into all living things. And then, either in this video or in future videos, we'll talk about how it's used for dating, that is, how it can be used to discover that this bone is 12,000 years old, or that this person died 18,000 years ago - anything. Let's draw the Earth. This is the surface of the Earth. More precisely, only a small part of it. Then comes the Earth's atmosphere. I'll paint it yellow. This is where we have the atmosphere. Let's sign it. And 78% - the most common element in our atmosphere is nitrogen. It's 78% nitrogen. I'll write it down: "nitrogen". Its symbol is N. It has 7 protons and 7 neutrons. So the atomic mass is approximately 14. And the most common isotope of nitrogen... We discuss the concept of isotope in a chemistry video. In an isotope, protons determine what element it is. But this number can change depending on the available number of neutrons. Variants of a given element that differ in this way are called isotopes. I think of these as versions of a single element. In any case, we have an atmosphere, as well as so-called cosmic radiation emanating from our sun, but this is not actually radiation. These are cosmic particles. You can think of them as single protons, which is the same as hydrogen nuclei. They can also be alpha particles, which is the same thing as helium nuclei. Sometimes there are also electrons. They arrive, then collide with the components of our atmosphere and, in fact, form neutrons. So, neutrons are produced. Let's denote a neutron with a small letter n, then 1 is its mass number. We don't write anything because there are no protons here. Unlike nitrogen, where there were 7 protons. So it is, strictly speaking, not an element. A subatomic particle. So, neutrons are formed. And every now and then... Let's face it, this doesn't seem like a typical reaction. But every now and then one of these neutrons collides in a certain way with a nitrogen-14 atom. It knocks out one of the nitrogen protons and, in fact, itself takes its place. I'll explain now. It knocks out one of the protons. Now, instead of seven protons, we get 6. But this number 14 will not change to 13, because a replacement has occurred. So there will be 14 left here. But now, since there are only 6 protons, this, by definition, is no longer nitrogen. Now it's carbon. And the proton that was knocked out will be emitted. I'll paint this in a different color. This is a plus. A proton emitted into space... You can call it hydrogen 1. Somehow it can attract an electron. If it doesn't gain an electron, it will simply be a hydrogen ion, positive ion, in any case, or the hydrogen nucleus. This process is not a typical phenomenon, but it happens from time to time - this is how carbon-14 is formed. So here's carbon-14. Essentially, you can think of it as nitrogen-14, where one of the protons is replaced by a neutron. The interesting thing is that it is constantly formed in our atmosphere, not in huge quantities, but in noticeable quantities. I'll write this down. Constant formation. Fine. Now... I want you to be clear. Let's look at the periodic table. By definition, carbon has 6 protons, but the typical, most common isotope of carbon is carbon-12. Carbon-12 is the most common. Most of the carbon in our body is carbon-12. But what's interesting is that it produces a small amount of carbon-14, and then that carbon-14 can combine with oxygen to form carbon dioxide. The carbon dioxide is then absorbed into the atmosphere and ocean. It can be taken over by plants. When people talk about carbon sequestration, they are actually talking about energy use. sunlight to capture carbon gas and convert it into organic tissue. So carbon-14 is constantly being created. It's in the oceans, it's in the air. Mixes with the whole atmosphere. Let's write: oceans, air. And then it gets into the plants. Plants are, in fact, composed of this fixed carbon, which has been captured in gaseous form and transferred, so to speak, into solid form, into living tissue. For example, this is what wood is made of. Carbon is built into plants and then ends up in those who eat the plants. It could be us. Why is this interesting? I have already explained the mechanism, even if carbon-12 is the most common isotope, part of our body accumulates carbon-14 during our lifetime. What's interesting is that you can only get this carbon-14 while you're alive and while you're eating food. Because once you die and you're buried underground, carbon-14 can no longer become part of your tissues because you no longer eat anything that contains carbon-14. And once you die, you no longer receive carbon-14 replenishment. And the carbon-14 that you had at the time of death will decay through β-decay - we have already studied this - back into nitrogen-14. That is, the process is going backwards. So it decays to nitrogen-14, and β decay releases an electron and an anti-neutrino. I won't go into details now. Essentially, that's what's going on here. One of the neutrons turns into a proton, and during the reaction it emits this. Why is this interesting? As I said, as long as you live, carbon-14 is coming in. Carbon-14 is constantly decaying. But once you're gone and you're no longer consuming plants, or breathing in the atmosphere, if you're a plant yourself, taking up carbon from the air - which is what plants are all about... When a plant dies, it's no longer consuming carbon dioxide from the atmosphere or incorporating it in the fabric. The carbon-14 in this fabric is “frozen.” Then it disintegrates at a certain speed. It can then be used to determine how long ago the creature died. The rate at which this happens, the rate at which carbon-14 decays until half of it disappears or disintegrates by half is about 5,730 years. This is called the half-life. We talk about this in other videos. This is called the half-life. I want you to understand this. It is unknown which half has disappeared. This is a probabilistic concept. You can only assume that all the carbon-14 on the left will decay, and all the carbon-14 on the right will not decay within those 5,730 years. Essentially, this means that any given carbon-14 atom has a 50 percent chance of decaying to nitrogen-14 within 5,730 years. That is, in 5,730 years, approximately half of them will decay. Why is it important? If you know that all living things have a certain amount of carbon-14 in their tissues as part of their constituent substances, and then you find some bone... Let's say you find a bone during an archaeological dig. You will say that this bone has half the carbon-14 of the living things around you. It would be perfectly reasonable to assume that this bone must be 5,730 years old. It's even better if you dig even deeper and find another bone. Maybe a couple of feet deeper. And you will find that it contains 1/4 of the carbon-14 that would be found in a living thing. Then how old is he? If it is only 1/4 carbon-14, it has gone through 2 half-lives. After one half-life it would have 1/2 carbon left. Then, after the second half-life, half of that will also turn into nitrogen-14. So 2 half-lives have occurred here, giving 2 times 5,730 years. What would be the conclusion about the age of the item? Plus or minus 11,460 years. Subtitles by the Amara.org community

Physical foundations

In 2015, scientists from Imperial College London calculated that the continued use of hydrocarbons would negate radiocarbon dating.