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Carbon dating, or carbon-14 dating, is a method for comparing the ages of organic materials such as bones or things made from organic (containing carbon) material.

Carbon dating, or carbon-14 dating, is a method for comparing the ages of organic materials such as bones or things made from anything that once lived.

The technique is based on comparing the levels of C-14 and C-12 isotopes in the sample.  When the sample was living, the ratio of C-14 to C-12 in the material is the same as in the atmosphere.  But after death the C-14 isotope decays into N-14, while C-12 does not.  The loss in C-14 is then used to estimate how long ago the sample died, which is typically the same as how long the sample existed.

The technique is based on comparing the levels of C-14 and C-12 isotopes in the sample.  When the sample was living, the ratio of C-14 to C-12 in the material is the same as in the atmosphere.  But after death the C-14 isotope decays into N-14, while C-12 does not.  The loss in C-14 is then used to estimate how long ago the sample died, which is typically the same as how long the sample existed.

The rate of decay of C-14 is such that, ''if this rate of decay does not change over time'', then 50% of the C-14 in the sample will decay in 5730 years: 50% of the C-14 in the sample is left, after  11460 years 25% will be left, after 17190 years 12.5% will be left, after 50,000 years only about 1/500th of the C-14 remains - and since even initially it is only present as a minute proportion of the whole (0.0000000001% of all Carbon atoms)<ref>http://www.enviroliteracy.org/article.php/1006.html</ref>, measuring the exact quantity present accurately enough to be of use for dating purposes is extremely difficult. For this reason, scientists do not generally attempt to carbon date material that is believed to be older than about 50,000-60,000 years old.

The rate of decay of C-14 is such that, ''if this rate of decay does not change over time'', then 50% of the C-14 in the sample will decay in 5730 years: 50% of the C-14 in the sample is left, after  11460 years 25% will be left, after 17190 years 12.5% will be left, after 50,000 years only about 1/500th of the C-14 remains - and since even initially it is only present as a minute proportion of the whole (0.0000000001% of all Carbon atoms)<ref>http://www.enviroliteracy.org/article.php/1006.html</ref>, measuring the exact quantity present accurately enough to be of use for dating purposes is extremely difficult. For this reason, scientists do not generally attempt to carbon date material that is believed to be older than about 50,000-60,000 years old.

== Limits of Carbon Dating ==

== Limits of Carbon Dating ==

Currently the upper limit for carbon dating lies at 60,000 years under optimal conditions, until the development of the [[ABOX]] technique in 2005 <ref>Ancient hearth tests carbon dating <i>ABC Science Online</i> [http://www.abc.net.au/science/news/stories/s990775.htm]</ref>, the upper limit lay around 40,000 years, again under optimal conditions.

First, it is impossible to prove scientifically whether the rate of decay of C-14 has remained constant over hundreds or thousands of years.  Some scientists have suggested, based on experimental observations, that the laws of physics do change over time.<ref>"The idea that nature's laws change over time was proposed in the 1930s by one of the titans in the history of physics, Paul Dirac of England. According to Dirac's large numbers hypothesis, the force of gravity changed over time."  See Keay Davidson, "Recent study forces scientists to rethink basic law of physics," San Francisco Chronicle[http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2005/05/09/MNG5LCLEU41.DTL]</ref>

Fluctuations in the concentration of CO2 in the atmosphere have to be accounted for to calibrate the procedure.

Second, estimating the age of material using carbon dating assumes that the ratio of C-14 to C-12 was the same in the past as today, which is also impossible to prove scientifically.  "[T]he proportions of C-14 in the atmosphere in historic times is unknown. The  C-14:C-12 atmospheric ratio is known to vary over time and it is not at all certain that the curve is 'well behaved.'"<ref>Nondestructive Testing (NDT) Resource Center, "Uncertainty in Carbon Dating"[http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/carbondating.htm]</ref>

Carbon dating has been calibrated by comparing the theory with historical Ancient Egyptian sources and tree rings, these sources reveal the CO2 concentrations in the atmosphere over the last 10,000 years <ref>C-14 dating: the method <i>Thomas Higham</i> [http://www.c14dating.com/int.html]</ref>.

Ice samples from the Antarctic reveal CO2 concentrations over the last 650,000 years <ref>Stable Carbon Cycle–Climate Relationship During the Late Pleistocene <i>Science, 25 November 2005</i> [http://www.sciencemag.org/cgi/content/short/310/5752/1313/]</ref>.

Third, "various plants have differing abilities to exclude significant proportions of the C-14 in their intake. This varies with environmental conditions as well. The varying rates at which C-14 is excluded in plants also means that the apparent age of a living animal may be affected by an animals  diet. An animal that ingested plants with relatively low C-14 proportions would be dated older than their true age."<ref>''Id.''</ref>

Various plants have differing abilities to exclude significant proportions of the C-14 in their intake. This varies with environmental conditions as well. The varying rates at which C-14 is excluded in plants also means that the apparent age of a living animal may be affected by an animals  diet. An animal that ingested plants with relatively low C-14 proportions would be dated older than their true age.

 

Due to these fundamental limitations, the only scientific conclusion that can be drawn from carbon dating is that material X is older than material Y when X has lost more C-14 than Y has.  It is not possible to determine, with any degree of scientific certainty, how much older X is than Y.

== Known Errors in Carbon Dating ==

== Known Errors in Carbon Dating ==

Material that is younger than 150 years or older than 50,000 years is known to often give errors. The errors for material younger than 150 years is ascribed to changes in the ratio of C-14 to C-12 in the atmosphere.<ref>http://www.talkorigins.org/indexcc/CD/CD011.html</ref> The errors for material older than 50,000 years is ascribed to statistical uncertainties inherent in the loss of multiple half-lives.

Even the staunchest advocates of carbon dating admit that it gives errors for material that is younger than 150 years or older than 50,000 years. The errors for material younger than 150 years is ascribed to changes in the ratio of C-14 to C-12 in the atmosphere.<ref>http://www.talkorigins.org/indexcc/CD/CD011.html</ref>

Contamination by, for example present-day bacteria, will also result in ancient material being dated to be younger than the carbon dating upper limit.

 

Since the half-life of C-14 is only 5715 years, after 50,000 years only about 1/500th of the C-14 remains - and since even initially it is only present as a minute proportion of the whole (0.0000000001% of all Carbon atoms), measuring the exact quantity present accurately enough to be of use for dating purposes is extremely difficult. For this reason, scientists do not generally attempt to carbon date material that is believed to be older than about 50,000-60,000 years old.

Additional anomalous results from carbon dating, which reinforce its limitations, include:<ref>http://www.creationwiki.org/Carbon_dating</ref>

Additional anomalous results from carbon dating, which reinforce its limitations, include:<ref>http://www.creationwiki.org/Carbon_dating</ref>

*coal, natural gas, and carbonate rocks have yielded dates based on carbon dating between 30,000 and 60,000 years old {{fact}};

*coal, natural gas, and carbonate rocks have yielded dates based on carbon dating between 30,000 and 60,000 years old;

*some unfossilized dinosaur bones have yielded dates between 10,000 and 50,000 years old {{fact}}; and

*some unfossilized dinosaur bones have yielded dates between 10,000 and 50,000 years old {{fact}}; and

*CO2 from gas wells have yielded dates less than 30,000 years old {{fact}}.

*CO2 from gas wells have yielded dates less than 30,000 years old.

== References ==

== References ==

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