What is Radiocarbon dating?
[[Image:Carbon-14 with activity labels.png|thumb|right|350px|The amount of C<sup>14</sup> in the atomsphere varies over time]] [[Image:Radiocarbon bomb spike.svg|thumb|250px|right|Atmospheric <sup>14</sup>C, [[New Zealand]] <ref>{{cite web |url=http://cdiac.esd.ornl.gov/trends/co2/welling.html |title=Atmospheric δ<sup>14</sup>C record from Wellington |work=Carbon Dioxide Information Analysis Center |accessdate=1 May 2008 |archive-date=1 February 2014 |archive-url=https://web.archive.org/web/20140201222225/http://cdiac.esd.ornl.gov/trends/co2/welling.html |url-status=dead }}</ref> and [[Austria]].<ref>{{cite web |url=http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html |title=δ<sup>14</sup>Atmospheric δ<sup>14</sup>C record from Vermunt |work=Carbon Dioxide Information Analysis Center |accessdate=1 May 2008 |archive-date=23 September 2008 |archive-url=https://web.archive.org/web/20080923105819/http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html |url-status=dead }}</ref> The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of <sup>14</sup>C in the Northern Hemisphere.<ref>{{cite web |url=http://www1.phys.uu.nl/ams/Radiocarbon.htm |title= Radiocarbon dating |publisher=Utrecht University |accessdate=1 May 2008}}</ref>]] '''Radiocarbon dating''', also known as the '''C14 dating method''', is a way of telling how old an object is. It is a type of [[radiometric dating]]. The method uses the [[radioactivity|radioactive]] [[isotope]] [[carbon]]-14. Most organic matter contains [[carbon]]. Carbon has different [[isotope]]s, which are usually not radioactive. <sup>14</sup>C is the radioactive one, its [[Half-life (element)|half-life]] (time it takes to reduce its radioactivity by half) is about 5,730 years. This makes it possible to tell the age of substances that contain carbon. The method works to about 60,000 years old. Dates obtained are usually written as ''before prese