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{{Short description|Time scales on the billions of years}}
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'''Deep time''' is the concept of [[Geologic time scale|geological time]] that spans billions of years, far beyond the scale of human experience. It provides the temporal framework for understanding the [[Formation of Earth|formation]] and [[Geological history of Earth|evolution of Earth]], the [[Abiogenesis|development of life]], and the slow-moving processes that shape planetary change. First developed as a scientific idea in the 18th century and popularized in the 20th century by writers such as [[John McPhee]],{{sfn|McPhee|1998|p=77}} the concept of deep time has influenced fields ranging from [[geology]] and [[evolutionary biology]] to [[climate science]], philosophy, education, and [[environmental ethics]]. Today, deep time is increasingly used in [[science communication]] and public engagement, offering a powerful lens for understanding human impact during the [[Anthropocene]].

== Origins and definition ==
The philosophical concept of geological time was developed in the 18th century by [[Scottish people|Scottish]] geologist [[James Hutton]];{{sfn|Palmer|Zen}}{{sfn|Kubicek|2008}} his "system of the habitable Earth" was a [[deism|deistic]] mechanism keeping the world eternally suitable for humans.<ref name="Rudwick68">{{cite book|author=M. J. S. Rudwick|title=Earth's Deep History: How It Was Discovered and Why It Matters|url=https://books.google.com/books?id=lYyRBAAAQBAJ&pg=PA68|date=15 October 2014|publisher=University of Chicago Press|isbn=978-0-226-20393-5|pages=68–70}}</ref> The modern concept entails huge changes over the [[age of the Earth]] which has been determined to be, after a long and complex history of developments, around 4.55 billion years.<ref>{{Cite news|url=http://www.scientificamerican.com/article/how-science-figured-out-the-age-of-the-earth/|title=How Science Figured Out the Age of Earth|last=Braterman|first=Paul S.|work=Scientific American|access-date=2016-04-17|archive-date=2016-04-12|archive-url=https://web.archive.org/web/20160412054317/http://www.scientificamerican.com/article/how-science-figured-out-the-age-of-the-earth/|url-status=live}}</ref>{{Life timeline}}
James Hutton based his view of deep time on a form of geochemistry that had developed in Scotland and Scandinavia from the 1750s onward.<ref>{{cite book |last = Eddy |first = Matthew Daniel |title = The Language of Mineralogy: John Walker, Chemistry and the Edinburgh Medical School 1750–1800 |date = 2008 |publisher = [[Ashgate Publishing]] |location = London |page = Ch. 5 |url = https://www.academia.edu/1112014 |archive-date = 2015-09-03 |access-date = 2014-04-17 |archive-url = https://web.archive.org/web/20150903230852/http://www.academia.edu/1112014/The_Language_of_Mineralogy_John_Walker_Chemistry_and_the_Edinburgh_Medical_School_1750-1800_2008_ |url-status = live }}</ref> As mathematician [[John Playfair]], one of Hutton's friends and colleagues in the [[Scottish Enlightenment]], remarked upon seeing the [[stratum|strata]] of the [[Unconformity|angular unconformity]] at [[Siccar Point]] with Hutton and [[Sir James Hall, 4th Baronet|James Hall]] in June 1788, "the mind seemed to grow giddy by looking so far into the abyss of time".{{sfn|Playfair|1805}}<ref>{{cite book |last= McPhee |first= John |date= 1981 |title= Book 1: Basin and Range, in Annals of the Former World |location= New York |publisher= [[Farrar, Straus and Giroux]] |page= [https://archive.org/details/annalsofformerwo00mcph/page/79 79] |isbn= 0-374-10520-0 |author-link= John McPhee }}</ref>

== Early theories ==
Early [[geologists]] such as [[Nicolas Steno]] and [[Horace Bénédict de Saussure]] had developed ideas of geological strata forming from water through chemical processes, which [[Abraham Gottlob Werner]] developed into a theory known as [[Neptunism]], envisaging the slow crystallisation of minerals in the ancient oceans of the Earth to form [[rock (geology)|rock]]. Hutton's innovative 1785 theory, based on [[Plutonism]], visualised an endless cyclical process of rocks forming under the sea, being uplifted and tilted, then eroded to form new strata under the sea. In 1788 the sight of [[Hutton's Unconformity]] at Siccar Point convinced Playfair and Hall of this extremely slow cycle, and in that same year Hutton memorably wrote "we find no vestige of a beginning, no prospect of an end".{{sfn|Montgomery|2003}}{{sfn|Rance|1999}}

== Developments in the 19th century ==
The 19th century saw major expansion in how scientists conceptualized Earth's history, transforming deep time from a radical idea into a foundational principle of geology and evolutionary theory. Building on the foundations laid by James Hutton, several competing theories emerged that attempted to explain the formation of Earth's features over immense timescales.

[[Georges Cuvier]], a pioneer of paleontology, proposed that Earth's history was marked by a series of catastrophic events, each followed by the sudden appearance of new life forms. This theory of [[catastrophism]] suggested a segmented past, rather than a continuous one. [[Adam Sedgwick]], who helped popularize catastrophism in Britain, introduced his student Charles Darwin to his way of thinking—prompting Darwin to later joke that Sedgwick was adept at "drawing large cheques upon the Bank of Time."{{sfn|Darwin|1831}}

In a competing theory, [[Charles Lyell]] advanced a theory known as [[uniformitarianism]], articulated in his ''Principles of Geology'' (1830–1833). Lyell proposed that slow, gradual processes such as erosion, sedimentation, and volcanic activity had shaped the Earth's surface over vast periods—implying an Earth far older than previously imagined. His view echoed and extended Hutton's original ideas, and positioned deep time as essential to understanding Earth's dynamic systems.

Darwin, deeply influenced by Lyell's thinking, read ''Principles of Geology'' during his voyage on [[Second voyage of HMS Beagle|''HMS Beagle'']] in the 1830s. Lyell's framing of deep time provided Darwin with the necessary timescale to support his own emerging theory of [[evolution]] by natural selection. Without a vast temporal backdrop, evolutionary change would have seemed implausible. Thus, the acceptance of deep time in geology directly enabled new theories of life's development and diversification.

== Intellectual responses ==
Throughout history, scholars and thinkers have attempted to make the vastness of deep time more intelligible. In ''[[The Science of Life]]'' (1929), [[H. G. Wells]] and [[Julian Huxley]] dismissed the difficulty of grasping geological time, arguing that "The use of different scales is simply a matter of practice."<ref>H. G. Wells, Julian S. Huxley, and G. P. Wells, ''The Science of Life'' (New York: The Literary Guild, 1934; orig. publ. 1929), p. 326.</ref> Like maps or microscopes, deep time requires training the imagination.

[[File:Nature_timespiral_vertical_layout.png|thumb|300px|In this illustration of the [[Big History]] the unit [[Billion years|Ga ("giga-annum")]] has been chosen to bring the different periods and events into graspable numbers.]]Modern authors have echoed this need for reframing. Physicist [[Gregory Benford]]'s ''Deep Time: How Humanity Communicates Across Millennia'' (1999) and paleontologist [[Henry Gee]]'s ''In Search of Deep Time: Beyond the Fossil Record to a New History of Life'' (2001){{sfn|Korthof|2000}}{{sfn|Campbell|2001}} both explore how science and storytelling intersect to help people comprehend timescales far beyond human experience. [[Stephen Jay Gould]]'s ''[[Time's Arrow, Time's Cycle]]'' (1987) traces how scientific metaphors shape our temporal assumptions.

11th century thinkers, like [[Avicenna]]{{sfn|Toulmin|Goodfield|1965|p=64}} in Persia and [[Shen Kuo]]{{sfn|Sivin|1995|pp=iii,23-24}} in China, proposed timelines that stretched far beyond biblical frameworks.{{clarification needed|reason=Is it really meaningful to claim that a Muslim and a Daoist-Confucian had any relation to "biblical frameworks"?|date=April 2025}} Meanwhile, [[Thomas Berry]] and [[Joanna Macy]] argue that experiencing deep time is essential to planetary stewardship, influencing movements like [[deep ecology]] and [[ecosophy]].<ref>{{Cite web |title=THOMAS BERRY |url=https://ecozoicstudies.org/musings/2014/thomas-berry/ |access-date=2025-02-18 |website=Center for Ecozoic Studies |language=en-US}}</ref>

Together, these voices highlight a central challenge of deep time: not only measuring it, but making it meaningful.

== Today's applications ==

=== The Anthropocene ===
The concept of deep time has taken on renewed urgency in discussions surrounding the Anthropocene—the proposed geological epoch defined by human impact on Earth's systems. In a landmark ''Science'' article, a multidisciplinary group of researchers argued that the Anthropocene is stratigraphically and functionally distinct from the Holocene marking a break in Earth's natural history that is visible in the geologic record.<ref>{{Cite journal |last1=Waters |first1=Colin N. |last2=Zalasiewicz |first2=Jan |last3=Summerhayes |first3=Colin |last4=Barnosky |first4=Anthony D. |last5=Poirier |first5=Clément |last6=Gałuszka |first6=Agnieszka |last7=Cearreta |first7=Alejandro |last8=Edgeworth |first8=Matt |last9=Ellis |first9=Erle C. |last10=Ellis |first10=Michael |last11=Jeandel |first11=Catherine |last12=Leinfelder |first12=Reinhold |last13=McNeill |first13=J. R. |last14=Richter |first14=Daniel deB. |last15=Steffen |first15=Will |date=2016-01-08 |title=The Anthropocene is functionally and stratigraphically distinct from the Holocene |url=https://www.science.org/doi/10.1126/science.aad2622 |journal=Science |volume=351 |issue=6269 |article-number=aad2622 |doi=10.1126/science.aad2622 |pmid=26744408 |bibcode=2016Sci...351.2622W |url-access=subscription |archive-date=2023-01-15 |access-date=2025-04-14 |archive-url=https://web.archive.org/web/20230115153014/https://www.science.org/doi/10.1126/science.aad2622 |url-status=live }}</ref>

=== Rethinking human time ===
Anthropologists and philosophers have further explored the cultural and conceptual ramifications of this shift. The ''University of Vienna's Anthropocene Project'' promotes "deep time literacy" as a tool for understanding our species' geological footprint,<ref>{{Cite web |title=Deep Time |url=https://anthropocene.univie.ac.at/resources/deep-time/ |access-date=2025-04-14 |website=anthropocene.univie.ac.at |language=en |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184535/https://anthropocene.univie.ac.at/resources/deep-time/ |url-status=live }}</ref> while scholars such as Matt Edgeworth argue that archaeological traces from the modern world blur traditional boundaries between human time and geological time.<ref>{{Cite journal |last=Edgeworth |first=Matt |date=2021-10-21 |title=Transgressing Time: Archaeological Evidence in/of the Anthropocene |url=https://www.annualreviews.org/content/journals/10.1146/annurev-anthro-101819-110118 |journal=Annual Review of Anthropology |language=en |volume=50 |pages=93–108 |doi=10.1146/annurev-anthro-101819-110118 |issn=0084-6570|url-access=subscription }}</ref>

Scholar Jakko Kemper argues that deep time offers a necessary counterbalance to the "microtime" of tech-driven economies, which prioritize short-term profits and optimization over long-term planetary care. By grounding human activity within geological time, he suggests, deep time thinking challenges anthropocentric timelines and encourages more reflective approaches to environmental and technological governance.<ref>{{Cite journal |last=Kemper |first=Jakko |date=2024-11-01 |title=Deep Time and Microtime: Anthropocene Temporalities and Silicon Valley's Longtermist Scope |journal=Theory, Culture & Society |language=EN |volume=41 |issue=6 |pages=21–36 |doi=10.1177/02632764241240662 |issn=0263-2764|doi-access=free }}</ref>

=== Science communication ===
The concept of deep time has become a tool for science communication, especially in the context of climate change and environmental responsibility. The Smithsonian National Museum of Natural History opened the David H. Koch Hall of Fossils, a deep time exhibit contextualizing Earth's evolutionary past alongside present ecological challenges. This presentation encourages visitors to think beyond human lifespans and understand the long arc of planetary transformation.<ref>{{Cite web |title=David H. Koch Hall of Fossils - Deep Time {{!}} Smithsonian National Museum of Natural History |url=https://naturalhistory.si.edu/exhibits/david-h-koch-hall-fossils-deep-time |access-date=2025-04-14 |website=naturalhistory.si.edu |language=en |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184534/https://naturalhistory.si.edu/exhibits/david-h-koch-hall-fossils-deep-time |url-status=live }}</ref>

Media outlets have similarly leveraged the idea of deep time to encourage a shift in public perception. The BBC describes how contemplating deep time can foster patience, humility, and long-term thinking—qualities increasingly recognized as essential in the Anthropocene era.<ref>{{Cite web |date=2023-03-30 |title=The benefits of 'deep time thinking' |url=https://www.bbc.com/future/article/20230329-the-benefits-of-deep-time-thinking |access-date=2025-04-14 |website=www.bbc.com |language=en-GB |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184534/https://www.bbc.com/future/article/20230329-the-benefits-of-deep-time-thinking |url-status=live }}</ref> Podcasts are chiming in, as an episode of the ''Land and Climate Review'' podcast explored how nuclear waste repositories—designed to remain secure for tens of thousands of years—offer a real-world case study in communicating and planning across deep time scales.<ref>{{Cite web |date=2024-04-19 |title=Can nuclear waste teach us about long-term thinking? - Land and Climate Review |url=https://www.landclimate.org/can-nuclear-waste-teach-us-about-long-term-thinking/ |access-date=2025-04-14 |language=en-US |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184536/https://www.landclimate.org/can-nuclear-waste-teach-us-about-long-term-thinking/ |url-status=live }}</ref>

=== Legacy and the future ===
Public-facing scholarship and exhibitions echo this view. The Smithsonian Human Origins Program describes deep time as a framework that helps us "understand how we arrived at our present moment and how our choices will shape the future"—placing current human behaviors in the context of long evolutionary arcs and environmental change.<ref>{{Cite web |title=The Age of Humans: Evolutionary Perspectives on the Anthropocene |url=https://humanorigins.si.edu/research/age-humans-evolutionary-perspectives-anthropocene |access-date=2025-04-14 |website=Smithsonian National Museum of Natural History |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184534/https://humanorigins.si.edu/research/age-humans-evolutionary-perspectives-anthropocene |url-status=live }}</ref> Popular science outlets like ''Discover Magazine'' also continue to amplify this discourse, helping readers grapple with the scale and implications of deep time in an age of accelerating change.<ref>{{Cite web |title=The Notion of Deep Time |url=https://www.discovermagazine.com/planet-earth/the-notion-of-deep-time |access-date=2025-04-14 |website=Discover Magazine |language=en |archive-date=2025-04-14 |archive-url=https://web.archive.org/web/20250414184534/https://www.discovermagazine.com/planet-earth/the-notion-of-deep-time |url-status=live }}</ref>

== See also ==

* {{annotated link|Timeline of human evolution}}
* {{annotated link|History of life}}
* {{annotated link|History of Earth}}
* {{annotated link|Big History}}
* {{annotated link|Chronology of the Universe}}
* {{annotated link|Clock of the Long Now}}
* {{annotated link|Deep history}}
* {{annotated link|Formation of the Solar System}}
* {{annotated link|Long-term nuclear waste warning messages}}
* {{annotated link|The World Without Us|''The World Without Us''}}

== Notes and references ==
{{reflist|30em}}

== Sources ==
=== Web ===
* {{cite web |url= http://www.acampbell.ukfsn.org/bookreviews/r/gee.html |title= Book review: ''In Search of Deep Time'' |author-link= Anthony Campbell (physician) |first= Anthony |last= Campbell |year= 2001 |access-date= 2006-11-17 |archive-date= 2007-01-02 |archive-url= https://web.archive.org/web/20070102025927/http://www.acampbell.ukfsn.org/bookreviews/r/gee.html }}
* Colebrook, Michael (2014). "Thomas Berry". Archived from the original on 2014-12-08. Retrieved 2025-02-17.
* {{cite web|last=Darwin|first=C. R.|url=http://www.darwinproject.ac.uk/darwinletters/calendar/entry-101.html|title=Darwin Correspondence Project – Letter 101 — Darwin, C. R. to Fox, W. D., (9 July 1831)|date=1831-07-09|access-date=26 March 2010|archive-url=https://web.archive.org/web/20090116035539/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-101.html|archive-date=16 January 2009}}
* {{cite web |url= http://wasdarwinwrong.com/kortho49.htm |title= A Revolution in Palaeontology: Review of Henry Gee's ''In Search of Deep Time'' |author-link= Gert Korthof |first= Gert |last= Korthof |year= 2000 |access-date= 2013-07-30 |archive-date= 2014-05-29 |archive-url= https://web.archive.org/web/20140529225428/http://wasdarwinwrong.com/kortho49.htm |url-status= live }}
* {{cite web |url=http://nagt.org/files/nagt/jge/abstracts/Montgomery_v51n5.pdf |title=Siccar Point and Teaching the History of Geology |access-date=2008-03-26 |first=Keith |last=Montgomery |year=2003 |publisher=[[University of Wisconsin]] |archive-date=2016-04-15 |archive-url=https://web.archive.org/web/20160415125556/http://nagt.org/files/nagt/jge/abstracts/Montgomery_v51n5.pdf |url-status=live }}
* {{cite journal |url=http://bcn.boulder.co.us/basin/local/sustain2.htm |title=The Context of Humanity: Understanding Deep Time |first1=A. R. |last1=Palmer |first2=E-an |last2=Zen |editor=Critical Issues Committee |journal=[[Geological Society of America]] |archive-date=2006-03-26 |access-date=2005-10-16 |archive-url=https://web.archive.org/web/20060326000556/http://bcn.boulder.co.us/basin/local/sustain2.htm |url-status=live }}
* {{cite web |url= http://geowords.com/histbookpdf/a22.pdf |title= Hutton's unconformities |first= Hugh |last= Rance |year= 1999 |work= Historical Geology: The Present is the Key to the Past |publisher= QCC Press |access-date= 2008-10-20 |archive-url= https://web.archive.org/web/20081203173042/http://www.geowords.com/histbookpdf/a22.pdf |archive-date= 2008-12-03 }}

=== Books ===
* {{cite book|last=Ialenti|first=Vincent|title=Deep Time Reckoning: How Future Thinking Can Help Earth Now|url=https://mitpress.mit.edu/books/deep-time-reckoning|location=Cambridge, Massachusetts|publisher=The MIT Press|year=2020|archive-date=2021-06-16|access-date=2020-07-31|archive-url=https://web.archive.org/web/20210616121008/https://mitpress.mit.edu/books/deep-time-reckoning|url-status=live}}
* {{cite book |last=McPhee |first=John |date=1998 |title=Annals of the Former World |location=New York |publisher=Farrar, Straus and Giroux}} 
* {{cite book |first=Jack |last=Repcheck |title=The Man Who Found Time: James Hutton and the Discovery of the Earth's Antiquity |chapter=Chapters 2 and 5 |location=[[Cambridge, Massachusetts|Cambridge]] |publisher=[[Perseus Books]] |year=2003 |isbn=0-7382-0692-X}}
* Rossi, Paolo (1984). ''The Dark Abyss of Time: The History of the Earth and the History of Nations from Hooke to Vico'', tr. by Lydia Cochrane, Chicago: University of Chicago Press, pp. 338, {{ISBN|0226728358}}.
* {{cite book | last = Sivin | first = Nathan | author-link = Nathan Sivin | title = Science in Ancient China: Researches and Reflections | publisher = Ashgate Publishing [[Variorum]] series | year = 1995 | location = [[Brookfield, Vermont]] | pages = III, 23–24 }}
* {{cite book|author-link=Stephen Toulmin |author-link2=June Goodfield|first1=Stephen |last1=Toulmin|first2=June |last2= Goodfield |year=1965|title= The Ancestry of Science: The Discovery of Time| page=64 |publisher=[[University of Chicago Press]]}}
* {{cite book|last=White|first=Andrew Dickson|author-link=Andrew Dickson White|title=A History of the Warfare of Science with Theology in Christendom|url=http://www.infidels.org/library/historical/andrew_white/Chapter5.html|location=New York|publisher=D. Appleton & Company|year=1896|archive-date=2007-10-05|access-date=2007-12-21|archive-url=https://web.archive.org/web/20071005071350/http://www.infidels.org/library/historical/andrew_white/Chapter5.html|url-status=live}}
* {{cite book|last=Winchester|first=Simon |author-link= Simon Winchester|title= The Map That Changed the World: William Smith and the Birth of Modern Geology|chapter = Chapter 2 |location=New York |publisher=HarperCollins|year=2001|isbn=0-06-019361-1|title-link=The Map That Changed the World: William Smith and the Birth of Modern Geology }}

=== Journals ===
* {{cite journal|last1=Ialenti|first1=Vincent|title=Adjudicating Deep Time: Revisiting The United States' High-Level Nuclear Waste Repository Project At Yucca Mountain|journal=Science & Technology Studies|year=2014|volume=27|issue=2|doi=10.23987/sts.55323 |ssrn=2457896|doi-access=free}}
* {{cite journal |title=Ages in Chaos: James Hutton and the Discovery of Deep Time |last=Kubicek |first=Robert |journal=[[The Historian (journal)|The Historian]] |volume=70 |issue=1 |isbn=978-0-7653-1238-9 |date=2008-03-01 |pages=[https://archive.org/details/agesinchaosjames0000unse/page/142 142–143] |url=https://archive.org/details/agesinchaosjames0000unse/page/142 }}
* {{cite journal |title= Hutton's Unconformity |first=John|last=Playfair|journal= Transactions of the Royal Society of Edinburgh|volume= V |issue=III|year=1805}}

== External links ==
* [https://www.bbc.com/future/article/20201209-the-benefits-of-embracing-deep-time-in-a-year-like-2020 "The benefits of embracing 'deep time' in a year like 2020" (Vincent Ialenti)] {{Webarchive|url=https://web.archive.org/web/20220807100146/https://www.bbc.com/future/article/20201209-the-benefits-of-embracing-deep-time-in-a-year-like-2020 |date=2022-08-07 }}—[[BBC Future]].
* [http://www.chronozoom.com/ ChronoZoom] {{Webarchive|url=https://web.archive.org/web/20170508234636/http://www.chronozoom.com/ |date=2017-05-08 }} is a timeline for Big History being developed for the [[International Big History Association]] by [[Microsoft Research]] and [[University of California, Berkeley]]
* [https://www.pbs.org/wgbh/evolution/change/deeptime/low_bandwidth.html Deep Time] {{Webarchive|url=https://web.archive.org/web/20170909140754/http://www.pbs.org/wgbh/evolution/change/deeptime/low_bandwidth.html |date=2017-09-09 }} in [[Evolution (TV series)|''Evolution'' (TV series)]]. Note: This [[Public Broadcasting Service|PBS]]/[[WGBH-TV|WGBH]] website advises [[Flash Player]] and [[Shockwave Player]] installation.
* [http://deeptime.info/ Deep Time – A History of the Earth: Interactive Infographic] {{Webarchive|url=https://web.archive.org/web/20110529010824/http://deeptime.info/ |date=2011-05-29 }}
* [http://www.deeptimewalk.org/kit/app Deep Time Walk App – A new story of the living Earth: Interactive Walking Experience]
* [https://www.npr.org/sections/13.7/2014/09/28/351692717/embracing-deep-time-thinking "Embracing 'Deep Time' Thinking" (Vincent Ialenti)] {{Webarchive|url=https://web.archive.org/web/20190706115100/https://www.npr.org/sections/13.7/2014/09/28/351692717/embracing-deep-time-thinking |date=2019-07-06 }} NPR Cosmos & Culture.
* [https://www.npr.org/sections/13.7/2014/09/21/350344129/pondering-deep-time-could-inspire-new-ways-to-view-climate-change "Pondering 'Deep Time' Could Inspire New Ways to View Climate Change" (Vincent Ialenti)] {{Webarchive|url=https://web.archive.org/web/20190706115101/https://www.npr.org/sections/13.7/2014/09/21/350344129/pondering-deep-time-could-inspire-new-ways-to-view-climate-change |date=2019-07-06 }} NPR Cosmos & Culture.

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Deep time - Revision history

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