Editing Age of Earth (section)

== Development of modern geologic concepts ==
{{Life timeline}}
{{Main|History of geology}}
{{Further|Relative dating}}

Studies of [[stratum|strata]]—the layering of rocks and soil—gave [[natural history|naturalists]] an appreciation that Earth may have been through many changes during its existence. These layers often contained [[fossil|fossilized remains]] of unknown creatures, leading some to interpret a progression of organisms from layer to layer.<ref>{{cite book
 | first=Charles, Sir | last=Lyell
 | author-link=Charles Lyell | date=1866
 | title=Elements of Geology; or, The Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments
 | edition=Sixth | location=New York
 | url=https://books.google.com/books?id=pbkQAAAAIAAJ | access-date=2008-12-19
 | publisher=D. Appleton and company
}}</ref><ref name="stiebing">{{cite book | first=William H. | last=Stiebing | date=1994 | title=Uncovering the Past | publisher=Oxford University Press US | isbn=978-0-19-508921-9 | url-access=registration | url=https://archive.org/details/uncoveringpasthi00stie }}</ref>

[[Nicolas Steno]] in the 17th century was one of the first naturalists to appreciate the connection between fossil remains and strata.<ref name="stiebing" /> His observations led him to formulate important [[stratigraphy|stratigraphic]] concepts (i.e., the "[[law of superposition]]" and the "[[principle of original horizontality]]").<ref name=Brookfield>{{cite book
 | first=Michael E. | last=Brookfield | date=2004
 | title=Principles of Stratigraphy | page=116
 | publisher=Blackwell Publishing
 | isbn=978-1-4051-1164-5 }}</ref> In the 1790s, [[William Smith (geologist)|William Smith]] hypothesized that if two layers of rock at widely differing locations contained similar fossils, then it was very plausible that the layers were the same age.<ref>{{cite web
 |last=Fuller
 |first=J. G. C. M.
 |date=2007-07-17
 |publisher=The Geological Society
 |work=Geoscientist
 |access-date=2008-12-19
 |url=http://www.geolsoc.org.uk/gsl/geoscientist/features/page1017.html
 |title=Smith's other debt, John Strachey, William Smith and the strata of England 1719–1801
 |archive-url=https://web.archive.org/web/20081124213722/http://www.geolsoc.org.uk/gsl/geoscientist/features/page1017.html
 |archive-date=24 November 2008
 |url-status=dead
}}</ref> Smith's nephew and student, [[John Phillips (geologist)|John Phillips]], later calculated by such means that Earth was about 96 million years old.<ref>{{cite journal
 | last=Burchfield | first=Joe D.
 | title=The age of the Earth and the invention of geological time | journal=Geological Society, London, Special Publications | date=1998
 | volume=143
 | issue=1 | pages=137–143
 | doi=10.1144/GSL.SP.1998.143.01.12 |bibcode = 1998GSLSP.143..137B | citeseerx=10.1.1.557.2702
 | s2cid=129443412
 }}</ref>

In the mid-18th century, the naturalist [[Mikhail Lomonosov]] suggested that Earth had been created separately from, and several hundred thousand years before, the rest of the universe.{{Citation needed|date=February 2023}} Lomonosov's ideas were mostly speculative.{{Citation needed|date=February 2023}} In 1779 the [[Georges-Louis Leclerc, Comte de Buffon|Comte du Buffon]] tried to obtain a value for the age of Earth using an experiment: he created a small globe that resembled Earth in composition and then measured its rate of cooling. This led him to estimate that Earth was about 75,000 years old.<ref>{{Cite book |last=BUFFON |first=GEORGES LOUIS LECLERC |url=https://www.worldcat.org/oclc/1354275595 |title=HISTOIRE NATURELLE, GA (C)NA (C)RALE ET PARTICULIARE, : introduction a l'histoire... des mina (c)raux (classic reprint). |date=2022 |publisher=FORGOTTEN BOOKS |isbn=978-0-265-92735-9 |location=[S.l.] |oclc=1354275595}}</ref><ref>{{Cite book |last=Merrill |first=Ronald T. |url=https://books.google.com/books?id=auZaEAAAQBAJ&pg=PA86 |title=Our Magnetic Earth: The Science of Geomagnetism |date=2010 |publisher=University of Chicago Press |isbn=978-0-226-52053-7 |location=Chicago |pages=86}}</ref> Even earlier, in 1687, in his ''[[Philosophiæ Naturalis Principia Mathematica|Principia]]'', the mathematician and physicist [[Isaac Newton]] was the first to calculate the age of the Earth by experiment, coming to a conclusion of 50,000 years.<ref>{{Cite journal |last=Simms |first=D. L. |date=2004 |title=Newton's Contribution to the Science of Heat |url=https://www.tandfonline.com/doi/full/10.1080/00033790210123810 |journal=Annals of Science |language=en |volume=61 |issue=1 |pages=33–77 |doi=10.1080/00033790210123810 |issn=0003-3790}}</ref> 

Other naturalists used these hypotheses to construct a [[history of Earth]], though their timelines were inexact as they did not know how long it took to lay down stratigraphic layers.<ref name=Brookfield/> In 1830, geologist [[Charles Lyell]], developing ideas found in [[James Hutton]]'s works, popularized the concept that the features of Earth were in perpetual change, eroding and reforming continuously, and the rate of this change was roughly constant. This was a challenge to the traditional view, which saw the history of Earth as dominated by intermittent [[Catastrophism|catastrophes]]. Many naturalists were influenced by Lyell to become "[[Uniformitarianism|uniformitarians]]" who believed that changes were constant and uniform.{{citation needed|date=March 2015}}