What is Radiometric dating?
[[Image:Ales stenar bred.jpg|300px|thumb|right|Ale's Stones at Kåseberga, around ten kilometres south east of [[Ystad]], [[Sweden]] were dated at 600 <small>AD</small> using the [[Carbon–14]] method on organic material found at the site.<ref>{{cite web |url=http://www.raa.se/cms/extern/en/places_to_visit/our_historical_sites/ales_stenar.html |title=Ales stenar |publisher=The Swedish National Heritage Board |date=11 October 2006 |accessdate=9 March 2009 |archive-date=31 March 2009 |archive-url=https://web.archive.org/web/20090331132307/http://www.raa.se/cms/extern/en/places_to_visit/our_historical_sites/ales_stenar.html |url-status=dead }}</ref>]] '''Radiometric dating''' (often called '''radioactive dating''') is a way to find out how old something is. The method compares the amount of a naturally occurring [[radioactive]] [[isotope]] and its decay products, in [[Sample (statistics)|samples]]. The method uses known decay rates.<ref>International Union of Pure and Applied Chemistry. ''Radioactive dating''. Compendium of chemical terminology, internet edition. [http://goldbook.iupac.org/R05082.html]</ref> It is the most used method of [[geochronology]], the main way to learn the age of rocks and other geological features, including the [[age of the Earth]] itself. It is used to date many kinds of natural and man-made materials. [[Fossil]]s may be dated by taking samples of rocks from above and below the fossil's original position. [[Radiocarbon dating]] is much used to date [[archaeology|archaeological]] materials, including ancient [[Artifact (archaeology)|artifact]]s. Radiometric dating methods are used to establish the [[Historical geology|geological time scale]].<ref>McRae A. 1998. ''Radiometric dating and the geological time scale: circular reasoning or reliable tools?'' [http://www.talkorigins.org/faqs/dating.html Radiometric dating and the geological time scale. TalkOrigins Archive]</ref> Among the best-known techniques are [[radiocarbon dating]], [[potassium-argon dating]] and [[uranium-lead dating]].