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Carbon dating, or radiocarbon dating, like any other laboratory testing technique, can be extremely reliable, so long as all of the variables involved are controlled and understood. Several factors affect radiocarbon test results, not all of which are easy to control objectively. For this reason, it’s preferable to date objects using multiple methods, rather than relying on one single test.
Carbon dating is reliable within certain parameters but certainly not infallible. When testing an object using radiocarbon dating, several factors have to be considered: First, carbon dating only works on matter that was once alive, and it only determines the approximate date of death for that sample.
For example, a steel spearhead cannot be carbon dated, so archaeologists might perform testing on the wooden shaft it was attached to. This provides good information, but it only indicates how long ago that piece of wood was cut from a living tree.
Radiocarbon dating can’t tell the difference between wood that was cut and immediately used for the spear, and wood that was cut years before being re-used for that purpose. Nor can it tell if a much older spearhead was attached to a brand-new shaft. Most archaeological items can’t be directly carbon dated, so their dating is based on testing done on nearby objects or materials.
This makes the results subject to the researchers’ assumptions about those objects. If the spear head is dated using animal bones nearby, the accuracy of the results is entirely dependent on the assumed link between the spear head and the animal.
This is perhaps the greatest point of potential error, as assumptions about dating can lead to circular reasoning, or choosing confirming results, rather than accepting a “wrong” date.
Second, radiocarbon dating becomes more difficult, and less accurate, as the sample gets older. The bodies of living things generally have concentrations of the isotope carbon-14, also known as radiocarbon, identical to concentrations in the atmosphere. When an organism dies, it stops taking in new carbon-14, and whatever is inside gradually decays into other elements. Carbon-14 normally makes up about 1 trillionth (1/1,000,000,000,000) of the earth’s atmosphere.
So even brand-new samples contain incredibly tiny quantities of radiocarbon. Eventually, the amount of carbon-14 remaining is so small that it’s all but undetectable. Tiny variations within a particular sample become significant enough to skew results to the point of absurdity.
Carbon dating therefore relies on enrichment and enhancement techniques to make smaller quantities easier to detect, but such enhancement can also skew the test results. Normal errors in the test become magnified. As a result, carbon dating is only plausible for objects less than about 40,000 years old. The other major factor affecting the results of carbon dating is gauging the original proportion of carbon-14 itself.
Carbon dating is based on the loss of carbon-14, so, even if the present amount in a specimen can be detected accurately, we must still know how much carbon-14 the organism started with. Scientists must assume how much carbon-14 was in the organism when it died. Complicating matters is the fact that Earth’s carbon-14 concentrations change drastically based on various factors.
As samples get older, errors are magnified, and assumptions can render carbon dating all but useless. For example, variations in greenhouse effects and solar radiation change how much carbon-14 a living organism is exposed to, which drastically changes the “starting point” from which a radiocarbon dating test is based.
Likewise, different living things absorb or reject carbon-14 at different rates. Two plants that died at the same moment, but which naturally contained different levels of radiocarbon, could be dated to drastically different times. Modern effects such as fossil fuel burning and nuclear testing have also changed atmospheric carbon-14 levels and in turn change the “starting point” for a radiocarbon test.
All in all, setting the parameters of the carbon-14 test is more of an art than a science. Contamination and repeatability are also factors that have to be considered with carbon dating. A tiny amount of carbon contamination will greatly skew test results, so sample preparation is critical. Even then, a large proportion of radiocarbon dating tests return inconsistent, or even incoherent, results, even for tests done on the same sample.
The explanation given for these outliers is usually “contamination.” Inconsistent results are another reason why multiple samples, multiples tests, and various parallel methods are used to date objects. Due to all these factors, it’s common for carbon dating results of a particular sample, or even a group of samples, to be rejected for the sole reason that they don’t align with the “expected” results. That’s not unusual in science, so far as it goes, but the relationship between assumptions and interpretations must be kept in mind.
At best, it needs to be acknowledged. At worst, it can make carbon dating circular and self-confirming, though there are other means of dating that can reduce this risk.
In short, carbon dating is as useful as any other technique, so long as it’s done properly and the results are objectively interpreted. It is not, however, an inherently error-free or black-and-white method for dating objects. In order to explain the Carbon 14 dating process itself, were going to have to get a little science-cee.
Atoms are the basic building blocks of matter. Atoms are made up of much smaller particles called protons, neutrons, and electrons. Protons and neutrons make up the center (nucleus) of the atom, and electrons form shells around the nucleus. The number of protons in the nucleus of an atom determines the element.
For example, all carbon atoms have 6 protons, all atoms of nitrogen have 7 protons, and all oxygen atoms have 8 protons. The number of neutrons in the nucleus can vary in any given type of atom. So, a carbon atom might have six neutrons, or seven, or possibly eight—but it would always have six protons. An “isotope” is any of several different forms of an element, each having different numbers of neutrons. The illustration below shows the three isotopes of carbon. Carbon-14, is expressed as (14C) also referred to, as I stated earlier, as radiocarbon.
Biblical claims of a young earth (about 6,000 years) has been in question, since 14C dates of tens of thousands of years have become common. When a scientist’s interpretation of data does not match the clear meaning of the text in the Bible, we should never reinterpret the Bible.
God knows just what He meant to say, our science as far as God is concerned is laughable and menial and His understanding of our science is infallible, whereas ours is fallible.
So we should never think it necessary to modify His Word. Genesis 1 defines the days of creation to be literal days (a number with the word “day” always means a normal day in the Old Testament, and the phrase “evening and morning” further defines the days as literal days). Since the Bible is the inspired Word of God, we should examine the validity of the standard interpretation of 14 C dating by asking several questions: Some isotopes of certain elements are unstable; they can spontaneously change into another kind of atom in a process called “radioactive decay.” Since this process presently happens at a known measured rate, scientists attempt to use it like a “clock” to tell how long ago a rock or fossil formed.
There are two main applications for radiometric dating. One is for potentially dating fossils (once-living things) using carbon-14 dating, and the other is for dating rocks and the age of the earth using uranium, potassium and other radioactive atoms. Radiocarbon (14C) is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14C combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire 14C by eating the plants.
When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died.
The older a sample is, the less 14C there is to be detected, and because the half-life of 14C (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples.
In nature, carbon exists as two stable, nonradioactive isotopes: carbon-12 (12C), and carbon-13 (13C), and a radioactive isotope, carbon-14 (14C), also known as "radiocarbon". The half-life of 14C (the time it takes for half of a given amount of 14C to decay) is about 5,730 years, so its concentration in the atmosphere might be expected to reduce over thousands of years, but 14C is constantly being produced in the lower stratosphere and upper troposphere, primarily by galactic cosmic rays, and to a lesser degree by solar cosmic rays.
There are three naturally occurring isotopes of carbon in the environment: carbon-12, carbon-13, and carbon-14. They all have six protons since they are carbon, and therefore they are identical chemically.
Biological and chemical processes cannot tell them apart, so they maintain approximately the same relative abundance in living tissue as they do in the atmosphere. The chemical processes that bring carbon into the body and those which remove it from the body treat all carbon the same.
Therefore, the percentages of the three isotopes will be the same in a living organism as it is in the organism’s environment. Carbon-14 is not stable against beta-minus decay with a half-life of 5,730±40 years, but is constantly replenished in the atmosphere by cosmic ray interaction with nitrogen-14.
The relative abundance of carbon-14 varies slightly with solar flares, magnetic field fluctuations, etc. At any given time, there will be a small fraction of all the carbon which is carbon-14.
The naturally occurring ratio of C-14/C-12 is about 10^-12 (0.000000000001). After a living organism dies, the carbon-14 in the organism will decay away, but it is no longer replenished by intake by breathing or eating.
Therefore the ratio of C-14/C-12 decreases. If any chemical or mechanical processes remove carbon from the dead organism, all carbon will be equally affected so the ratio is unaffected. Only the radioactive decay of the carbon-14 can affect the C-14/C-12 ratio. By measuring how much the ratio has changed, the date of dead organisms can be calculated.
After about ten half-lives there is so little C-14 left that dating is impossible. Therefore carbon dating can only be used on organisms that were alive less than ≈57,000 year ago. Note that we don’t measure carbon-14 and compare it to how much carbon we assume was in the sample.
We don’t need to know how much carbon was in the sample. We don’t care if some carbon was removed. We measure the current ratio of C-14/C-12 and compare it to naturally occurring ratio. It does not depend on the amount of carbon in the environment or even the amount in the sample. It only depends on the ratio. So how do we know what the naturally occurring ratio of C-14 to C-12 was in the past?
The most straightforward method is with tree rings. By counting tree rings and by correlating them with older tree rings (by matching up sequences of drought, etc.) we can go back about 8000 years.
We can do similar analysis with ice cores and varves. We can measure the C-14/C-12 ratio in the tree rings. We can count the rings to see how old the ring is to a very high precision. Since we know the half-life of carbon-14 we can calculate what the C-14/C-12 ratio was at the time the ring was formed.
Through this method we can produce a curve or table that shows exactly what the C-14/C-12 ratio was for thousands of years into the past. So when we find a sample of organic material and we want to know how old it is, we measure the ratio of C-14/C-12 in the sample.
This is generally not done by measuring the radioactivity of the carbon-14 atoms. Instead scientist use an accelerator mass spectrometer to measure the ratio of the carbon-14 atoms to the carbon-12 atoms. A mass spec can do this easily with proper preparation. When a sample is dated, the ratio of C-14/C-12 is measured and compared to the curve or table I discussed in the previous paragraph.
That gives how long ago the biological sample stopped exchanging carbon with the environment. That is when it died. First question: How does Carbon dating work? First some background. Regular Carbon, C-12 is the most common isotope of Carbon.
An isotope is an element with the same “atomic number” (number of protons) , but a different “atomic weight” ( protons + neutrons + electrons.) Some isotopes are stable, which means they don't change over time ( well… relatively long times, as in millions or billions of years) Most common Isotopes of Carbon Carbon- C-12 6- Neutrons 6- Protons Natural abundance- 98.93% Half life- Stable Mass- 12u Carbon- C-13 7- Neutrons 6- Protons Natural abundance- 1.109% Half life- Stable Mass- 13.003355 u Radiocarbon, C-14 8- Neutrons 6- Protons Natural abundance- 1 part per trillion Half life- 5,730 ± 40 years Mass- 14.00324u ____________________ OK.
So maybe that is more information than you wanted, but it's important to be aware of. So, what is Carbon dating? The idea is fairly simple.
We take Carbon from a sample of biological material, and measure the ratio of stable Carbon to unstable Radiocarbon, essentially C-12 to C-14. Since C-14 has a half life of about 5,700 years, and we know the normal ratio in fresh biological material, we have a “clock” to measure the age of the sample.
The older the material, the less C-14 it will contain, as the C-14 will have decayed over time at a fairly regular rate. So we can date the material. Is it reliable? This is where it gets a bit fuzzy… Yes, it's reliable, within certain constraints.
C-12 to C-14 ratios are somewhat variable in normal samples. Plants take up Carbon as both isotopes, and incorporate that Carbon into their cells. Animals eat plants, and incorporate the Carbon into their cells.
Animals eat other animals, etc. So the ratio should be similar throughout the food chain. But, since C-14 is primarily created in the atmosphere by the interaction of cosmic rays with Nitrogen, the actual fluctuation of cosmic ray intensity can alter the natural abundance.
Additionally, fossil Carbon can be introduced into the atmosphere through burning fossil fuels, or from volcanic activity. Atomic testing in the atmosphere will also alter ratios. The result of this variable “baseline” of “natural” ratios, is to limit the accuracy of the test.
So, to improve accuracy, it is important to have other samples from the same area which have been dated by an alternate method.
The technique is only as reliable as the baseline. The strata where the sample is found should not be disturbed. Example: I have found a bit of bone in a strata with pottery shards from a known culture, and a bit of charcoal from the same strata.
I can get approximate dates from the Carbon in the bone and charcoal, and since I already know from other sources about when that particular pottery style was being made, I can date the bone with more confidence.
You might have noticed that Carbon dates are almost always stated with a (+- years), or simply stated as “between” date-to-date. That is the “reliability” of the process, and the source of many disagreements between Archeologists.
The actual measurement of the ratio is quite accurate. It's the interpretation that gets fuzzy. If someone told you that they have Carbon dated a sample to October 13, 1492, your BS detector should immediately start flashing.
Carbon dating is an excellent tool, along with many others, to determine age and chronology. It is limited by constraints mentioned, and by itself gives only a fuzzy approximation.
Also note, you cannot Carbon date glass, metal, or pottery. They do not contain biological Carbon. You could perhaps find a bit of leftover plant material from the crock, wine residue from the bottle, or blood on the knife. If you are fairly sure the material has not been contaminated with Carbon compounds that are older or newer, then you can get an approximate date for the artifact. Or, at least have an idea when it was last used.
If you find a bit of bone that dates to 30,000 yrs. BP, in strata known by other methods to be only 10,000 yrs. BP, then you can be fairly sure it does not belong there, and was deposited by flood, or digging by rodents, or some other way.
Hope this simplified explanation helps you understand Carbon Dating, how it works, and how accurate it is. _______________ Notes: ( 6C) has 15 known , from 8C to 22C, of which and are . The longest-lived radioisotope is , with a of 5,700 years. This is also the only carbon radioisotope found in nature—trace quantities are formed by the reaction 14N + 1 neutron → 14C + 1H. The most stable artificial radioisotope is 11C, which has a half-life of 20.334 minutes.
All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is 8C, with a half-life of 2.0 x 10−21 s.
best carbon dating how does it work yahoo answers - How Does Carbon Dating Work? � Science ABC
Carbon is indispensable to biological life. . If it weren’t for the amiability of carbon, simple organic matter couldn’t have evolved to achieve the extraordinary, inscrutable complexity it now boasts: the complexity to develop a system to sense, to breathe, to digest, to excrete and in a lean, hairless primate, even a system to think. All life on earth is based on carbon. (Photo Credit: Subham Dey) However, a tiny percentage of this carbon is radioactive!
Measuring the quantity of this radioactive carbon in organic matter allows us to determine its age; the method of doing so is called radioactive carbon dating or, simply, carbon dating. Here’s how it works. Carbon-14 Carbon has a twin brother that only a few know about. Our planet is constantly pelted with high-energy cosmic rays hurled by the sun.
These rays, which teem with neutrons, react with the nitrogen in our atmosphere to produce carbon-14 or C-14 atoms, an isotope of the carbon-12 or C-12 atom.
An element and its isotope exhibit the same electric properties, but different physical properties. This is because both elements comprise the same number of protons and electrons, but a different number of neutrons.
The twins are then identified by different denotations, highlighting the number of neutrons, which is appended to the element’s symbol. C-12 has 12 neutrons, while C-14 has 14 neutrons; both, however, have 6 protons and electrons.
The key things about C-14 are that it is radioactive, that it is unstable, which forces it to emit particles and therefore decay over time. (Photo Credit : Sciencing) The Principle of Carbon-Dating The radioactive carbon will react with oxygen in the atmosphere to produce radioactive carbon dioxide. This radioactive carbon dioxide is breathed in and stored by plants, which are consumed by herbivores, who are preyed on by carnivores or omnivores, such as humans.
The carbon content of every organism under the atmosphere therefore is composed of mostly C-12 atoms and a minuscule number of C-14 atoms. The organisms, while they do consume carbon, also expel it when they exhale. The transaction or the cycle of producing, consuming and expelling C-14 atoms occurs in a way that, even though the amounts of C-12 and C-14 atoms in the environment and in an organism may vary, their ratio will remain the same.
This is the working principle of carbon dating: despite the transactions, a living organism maintains the same ratio of C-14 to C-12 atoms as found in the environment.
However, when an organism dies, it ceases to consume carbon. Now, because C-14 is radioactive, it begins to decay. The ratio of C-14 to C-12 atoms in the organism now decreases. The older the organism, the more C-14 is decayed, so the smaller the ratio.
This ratio is used by archaeologists to date, say, a tree or a fossil. They refer to the following equation to measure a sample’s age: The equation dictates the decay of a radioactive isotope.
Here, N ᵒ represents the number of atoms of the isotope in the sample at t=0 or when the organism, a part of whom now forms the sample, died, while N represents the number of atoms left after time t has passed . Remember that the ratio of C-14 to C-12 atoms in the organism and the environment is the same when it is alive. The knowledge of this ratio, which we already possess, allows us to obtain the value of N ᵒ, the original number of C-14 atoms. The current value N, however, must be measured.
The C-14 atoms in the sample are counted by delicate instruments, such as beta-counters and mass accelerator spectrometers.
λ is an element constant whose value for C-14 is 8,267. The time t that has since passed or the age of the sample can be obtained by rearranging the equation: Is Carbon Dating Reliable? The radioactivity of an element is measured in terms of its half-life: the time it takes to decay half of its constituents.
The half-life of C-14 is 5,370 years, which means that it becomes half of what it originally was in 5,370 years, one-fourth in 10,740 years, one-eighth in 16,110 years and so on. Extend the trend and one discerns that accurately measuring that the entirety of the atoms decays or, at least the percentage below which they become undetectable, after around 50,000 years.
Consequently, dating a sample older than 50,000 years may produce erroneous results. Composite techniques have been devised that combine carbon dating with techniques to calibrate and extend its scope, but even those techniques are inherently fallible. Carbon dating is therefore only unquestionably accurate for a few thousand years; any results beyond that frame is questionable. This is the major limitation of carbon dating. Photo Credit: Wikimedia Commons What’s more, carbon dating seems to be based on a fallacy.
It is fundamentally based on the assumption that the ratio of C-14 to C-12 atoms in the environment has always been the same throughout each and every Age. This is certainly not true. Since the Industrial Revolution, in particular, we have diluted the amount of C-12 atoms in the environment by shamelessly dumping into it an alarming quantity of carbon dioxide, produced by the burning of fossil fuels. An increase in C-12 means that the ratio is now reduced, which means that the age of a sample will measure to be older than it really is!
Conversely, nuclear explosions produce tremendous amounts of C-14, so the plethora of nuclear tests we have conducted has increased its amount in the atmosphere.
This increases the ratio, causing the age of a sample to measure younger than it really is. Since the Industrial Revolution, in particular, we have diluted the amount of C-12 atoms in the environment by shamelessly dumping in it an alarming quantity of carbon dioxide.
Photo Credit: Pixabay Still, with the knowledge of the amount of deviation that an increase or decrease in C-14 atoms will cause, we can account for these discrepancies by simply subtracting or adding the error from or to the apparent age to obtain the real age.
Again, carbon dating might not be unquestionably accurate, but it’s good enough. References • • • About the Author: is an Electronic Engineer from the University of Mumbai, India and a science writer at ScienceABC. Enamored with science ever since discovering a picture book about Saturn at the age of 7, he believes that what fundamentally fuels this passion is his curiosity and appetite for wonder. . Related Articles ScienceABC participates in the Amazon Associates Program, affiliate advertising program designed to provide a means for sites to earn commissions by linking to Amazon.
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They key to carbon dating is that the carbon isn't the carbon that's been on Earth ever since the Earth was formed. The carbon that's in carbon dating is carbon that's been newly made. Where that comes from is when cosmic rays - high energy particles from the sun - hit the Earth's atmosphere they interact with atoms and send neutrons flying around.
when one of these neutrons hit a Nitrogen-14 (14N) atom, it knocks out a proton, and the 14N becomes Carbon-14 (14C). This then circulates in the atmosphere but because this process is happening roughly at the same rate continuously the amount of carbon that's in the atmosphere is roughly continuous. Most of it ends up in the atmosphere as carbon dioxide so you have 14C carbon dioxide.
Plants then pick that up in their process of photosynthesis and they turn it into sugar. You then eat the plant and all the time that you are alive you're gaining radioactive carbon in your body which you incorporate into your body.
The level in your body will be roughly constant because you're taking it in at a roughly constant rate from the environment. The ratio of radioactive to non-radioactive carbon should be the same all the time you or a plant are alive. But when you die you stop adding new carbon-14 to your body and the 14C you've already got starts to break down to 14N because it's radioactive. The half-life is about 5500 years or so.
When you find an ancient specimen all you have to do is to compare how many 14C atoms are in it to the number of 12C atoms. The ratio tells you how long it was since it was last alive and this gives you a ballpark figure for its age.
This does make the assumption that the production of 14C and incorporation into the food chain is the same now as it was thousands and thousands of years ago. This assumption but it's assumed to be a fairly reasonable and accurate way to do it.
The guy we have to credit is Willard Libby who discovered carbon dating in the 1940s, got the Nobel Prize for it actually.
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