Carbon dating

{{Geology}}
'''Carbon dating''', also known as '''radiocarbon dating''', is a scientific procedure used to date organic matter.  It depends upon the [[radioactive decay]] of '''carbon-14''' (C<sup>14</sup> or <sup>14</sup>C), an unstable isotope of carbon which is continually synthesized in the upper atmosphere by cosmic rays. 

Plants take up atmospheric C<sup>14</sup> for as long as they live, through the process of [[photosynthesis]]. Animals take up atmospheric C<sup>14</sup> indirectly, by eating plants (or by eating other animals that eat plants). Measuring the proportion of C<sup>14</sup> as opposed to C<sup>12</sup> remaining in a sample then tells us how long ago the sample stopped taking up C<sup>14</sup> &mdash; in other words, how long ago the organism died.

Carbon dating has a certain margin of error, usually depending on the age and material of the sample used. Carbon-14 has a half-life of about 5730 years, so researchers use the process to date biological samples up to about 60,000 years in the past. Beyond that timespan, the amount of the original C<sup>14</sup> remaining is so small that it cannot be reliably distinguished from C<sup>12</sup> formed by irradiation of nitrogen by neutrons from the spontaneous fission of uranium, present in trace quantities almost everywhere. For older samples, other dating methods must be used.  So if you ever hear of something claimed to be "carbon-dated" much further back than that, you know they either don't know what they're talking about or are trying to pull the wool over your eyes.

The level of atmospheric C<sup>14</sup> is not constant. Atmospheric C<sup>14</sup> varies over decades due to the sunspot cycle, and over millennia due to changes in the earth's magnetic field. On a shorter timescale, humans also affect the amount of atmospheric C<sup>14</sup> through combustion of fossil fuels and above-ground testing of the [[brinkmanship|largely diplomatic weapon]] of the [[atomic bomb|thermonuclear bomb]]. Therefore dates must be calibrated based on C<sup>14</sup> levels in samples of known ages.<ref>http://www.c14dating.com/corr.html</ref> Heather Graven, an atmospheric scientist, has estimated that by 2050 "the age of fresh organic matter will appear indistinguishable from material created in A.D. 1050" due to fossil-fuel emissions.<ref>[https://www.sciencenews.org/article/carbon-dating-may-soon-lead-mismatches?mode=magazine&context=190633&tgt=nr Carbon dating may soon lead to mismatches: Flood of fossil fuel emissions threatens to make age-calculation method unreliable] by Thomas Sumner (3:06pm, July 20, 2015) ''Science News''.</ref>

==Young-Earth creationists on carbon dating==
[[Radiometric dating]] in general, of course, poses a huge problem for people who believe that the universe is 6000-odd years old. A favorite tactic of [[Young-Earthers]] involves citing studies which show trace amounts of C<sup>14</sup> in coal or [[diamond]] samples, which &mdash; being millions of years old &mdash; should have no original atmospheric C<sup>14</sup> left. Recent studies, however, show that C<sup>14</sup> can form underground. The decay of uranium and thorium, among other isotopes, produces radiation which can create C<sup>14</sup> from C<sup>12</sup>.<ref>[http://www.youtube.com/watch?v=T-o7ArSeSOY This guy with a mustache] provides an excellent, if somewhat long-winded, refutation for this particular bit of creationist nonsense.</ref> Indeed, this results from a unique decay mode known as "cluster decay" where a given isotope emits a particle heavier than an alpha particle (radium<sup>226</sup> is an example).

This fact is extremely inconvenient to YECs, and creationist literature, accordingly, usually does not mention it.

Carbon-dating 
skeptics
 deniers also claim that the inconsistency of C<sup>14</sup> levels in the atmosphere over the past 60,000 years 
[[creationism|creates]]
 causes a validity issue. However, calibration of [[carbon]] levels using tree rings and other sources keep such effects to an extremely small level.

Furthermore, if a sample has been contaminated, scientists will know about it.

Ironically, given how supposedly useless carbon dating is claimed to be, [[Creation Ministries International]] rests part of their [[101_evidences_for_a_young_age_of_the_earth_and_the_universe|"101 Evidences"]] on [[101_evidences_for_a_young_age_of_the_earth_and_the_universe#Radiometric_dating|carbon dating being a useful method]] for within several thousand years. This of course contradicts claims that the [[Great Flood]] messed up how carbon was deposited, destroying their own argument. Less astute creationists often conflate carbon dating with other forms of radiometric dating, attempting to "disprove" the true age of [[dinosaur]] fossils by "refuting" carbon dating. This is meaningless - paleontologists do not use carbon dating to assess dinosaur fossils; dinosaurs became extinct 66 million years ago, more than a thousand times farther back than carbon dating can be used.
===Carbon dating and the [[Bible]]===
In a classic example of [[irony]], carbon dating was used to verify the ages of the [[Dead Sea Scrolls]] to around 2000 years ago, during the period of the {{wpl|Roman-Jewish Wars}} for control of Judea.<ref>"[https://www.jta.org/1991/04/04/archive/age-of-dead-sea-scrolls-determined-through-new-carbon-dating-method Age of Dead Sea Scrolls determined through new carbon dating method]" - ''[[Jewish]] Telegraph Agency''</ref> Don't expect [[fundamentalists|fundies]] to tell you this.

==Abuses of Carbon dating==

The History channel show [[Oak Island money pit|''The Curse of Oak Island'']] frequently brings up the Carbon-14 dates of pieces of wood brought up from underground. They usually conclude, or at least strongly imply, that the <sup>14</sup>C date of any piece of wood is the date when it was used in construction. In actuality, the <sup>14</sup>C date of a given piece of wood is the date when the cells comprising its heartwood died.  (A tree grows in concentric rings; only the outermost layers are alive at any given time.)  A tree cut down in 1782 might have been growing for 50 years, in which case its heartwood would date as early as 1732.

You may also see the occasional silliness in TV or movies, where for instance in the movie ''Stargate'', someone says she carbon-dated petroglyphs.  Though, the movie also shows another character being able to speak with the locals (who had separated from Ancient Egypt 6000 years ago) because somehow their language had hardly changed since then...so the movie wasn't only scientifically wrong, but also linguistically.

==See also==
*[[Radiometric dating]]

==References==
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[[Category:Archaeology]]
[[Category:Evidence against a recent creation]]
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[[Category:Physics]]
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Categories: Archaeology, Evidence against a recent creation, Geology, Physics, science