Editing Age of Earth (section)

===Convective mantle and radioactivity===
The discovery of radioactivity introduced another factor in the calculation. After [[Henri Becquerel]]'s initial discovery in 1896,<ref>{{cite journal|author=Henri Becquerel|title=Sur les radiations émises par phosphorescence|journal=Comptes Rendus|volume=122|pages=420–421|year=1896|url=http://gallica.bnf.fr/ark:/12148/bpt6k30780/f422.chemindefer}}</ref><ref>''Comptes Rendus'' '''122''': 420 (1896), [http://web.lemoyne.edu/~giunta/becquerel.html translated by Carmen Giunta]. Accessed 12 April 2021.</ref><ref>{{cite journal|author=Henri Becquerel|title=Sur les radiations invisibles émises par les corps phosphorescents|journal=Comptes Rendus|volume=122|pages=501–503|year=1896|url=https://gallica.bnf.fr/ark:/12148/bpt6k30780/f503.item}}</ref><ref>''Comptes Rendus'' '''122''': 501–503 (1896), [http://web.lemoyne.edu/~giunta/becquerel.html translated by Carmen Giunta]. Accessed 12 April 2021.</ref> [[Marie Curie|Marie]] and [[Pierre Curie]] discovered the radioactive elements [[polonium]] and [[radium]] in 1898;<ref>{{cite journal |year=1898 |title=Sur une nouvelle substance fortement radio-active, contenue dans la pechblende (On a new, strongly radioactive substance contained in pitchblende) |journal=Comptes Rendus |volume=127 |pages=1215–1217 |url=http://www.aip.org/history/curie/discover.htm |access-date=12 April 2021 |author=Curie, Pierre |author2=Curie, Marie |author3=Bémont, Gustave |name-list-style=amp |archive-url=https://web.archive.org/web/20090806083923/http://www.aip.org/history/curie/discover.htm |archive-date=6 August 2009 |url-status=live }}</ref> and in 1903, Pierre Curie and [[Albert Laborde]] announced that radium produces enough heat to melt its own weight in ice in less than an hour.<ref>{{cite journal |author1=Curie, Pierre |author2=Laborde, Albert |title=Sur la chaleur dégagée spontanément par les sels de radium |journal=Comptes Rendus |volume=136 |pages=673–675 |year=1903 |url=https://gallica.bnf.fr/ark:/12148/bpt6k3091c/f673.item}}</ref> Geologists quickly realized that this upset the assumptions underlying most calculations of the age of Earth. These had assumed that the original heat of Earth and the Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished. George Darwin and John Joly were the first to point this out, in 1903.<ref>{{cite book
 | first=John | last=Joly | date=1909
 | title=Radioactivity and Geology: An Account of the Influence of Radioactive Energy on Terrestrial History | url=https://archive.org/details/radioactivitygeo00jolyrich | edition=1st | page=[https://archive.org/details/radioactivitygeo00jolyrich/page/36 36]
 | publisher=Archibald Constable & Co., ltd
 | location=London, UK }} Reprinted by BookSurge Publishing (2004) {{ISBN|1-4021-3577-7}}.</ref>