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Bibliographie </a> </li> </ul> <button class="btn btn-sm btn-universalis" data-bs-toggle="collapse" data-bs-target="#free-toc" aria-expanded="false" title="Afficher / masquer le sommaire"> <i aria-hidden="true" class="fa fa-fw fa-eye"></i> Sommaire </button> </div> <h1 class="mb-1"> <strong>ÂGE DE LA TERRE</strong> </h1> <ul class="pagination justify-content-center public-links "><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 1" class="page-link" title="Abonnez-vous" data-loaded="true">1</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 2" class="page-link" title="Abonnez-vous" data-loaded="true">2</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 3" class="page-link" title="Abonnez-vous" data-loaded="true">3</a></li><li class="page-item active"><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 4" class="page-link" title="Abonnez-vous" data-loaded="true">4</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 5" class="page-link" title="Abonnez-vous" data-loaded="true">5</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 6" class="page-link" title="Abonnez-vous" data-loaded="true">6</a></li></ul><p class="text-sm text-muted mb-1">Article modifié le <time datetime="2025-01-29"> 29/01/2025 </time></p><div class="content paged type-article" ><div class="block_1" data-ucode="yC170047_4"><i class="anchor" id="yC170047_4"></i><h2>La rigueur de la physique</h2><div class="clearfix"></div><div class="media-container float-md-start me-2 col-md-3 text-center"><figure class="figure text-center w-100 mb-0 p-1" style="position: relative"><a data-ucode="PH170563" data-showMediaPlayer="1" class="protected media-reference-copy " title="Média : La mort thermique de l’ Univers" href="/media/la-mort-thermique-de-l-univers-ph170563/"><img id="PH170563" loading="lazy" src="/typo3temp/assets/_processed_/3/2/csm_ph170563_f0c46da3fd.webp" class="figure-img rounded mx-auto media_resized" alt="La mort thermique de l’ Univers - crédits : D.R." data-description="Au XIXème siècle, a mort thermique de la Terre sera causée par une dissipation complète de sa chaleur dans l'espace : «surprise par le froid, la dernière famille humaine a été touchée du doigt de la Mort et bientôt ses ossements seront ensevelis sous le suaire des glaces éternelles» (C. Flammarion, …" data-copyright="D.R." width="692" height="1024" /></a><figcaption class="figure-caption"><p class="m-0 mt-1 fw-bold text-gray-700 text-truncate"> La mort thermique de l’ Univers </p><p class="m-0 copyright text-sm text-gray-700 text-truncate"> D.R. </p></figcaption></figure></div><p> La lointaine origine de ce débat remontait à des réflexions de Georges Louis Leclerc, comte de Buffon (1707-1788), qui s’était lui-même inspiré de <a data-bs-toggle="popover" data-bs-content="Biographie de RENÉ DESCARTES (1596-1650). René Descartes est à la fois le plus célèbre et le plus grand des philosophes français. En France, cependant, sa célébrité ne tient pas toujours à son génie, mais à une simplification désastreuse de sa doctrine, où l'on ne voit qu'un rationalisme étroit et à courte vue : chacun, alors, croit pouvoir invoquer à tout propos l'autorité d..." title="Article : RENÉ DESCARTES (1596-1650)" href="/encyclopedie/rene-descartes/">René Descartes</a> (1596-1650) et de <a data-bs-toggle="popover" data-bs-content="Biographie de GOTTFRIED WILHELM LEIBNIZ (1646-1716). Sartre et Nizan s'amusaient à dessiner une monade au bain. Mais une monade peut-elle prendre un bain ? On dirait aujourd'hui : oui ! Car il n'est pas de monades sans organes. Les concepts de G. W. Leibniz, parfois étranges, demandent une grande attention aux textes et à leurs contextes. C'est sans doute pourquoi son œuvre connut une ..." title="Article : GOTTFRIED WILHELM LEIBNIZ (1646-1716)" href="/encyclopedie/gottfried-wilhelm-leibniz/">Gottfried Wilhelm Leibniz</a> (1646-1716) pour postuler que la Terre avait initialement été une masse en fusion arrachée du <a data-bs-toggle="popover" data-bs-content="Le fait que le Soleil ne soit qu'une étoile parmi les quelque 200 milliards – de toutes tailles, masses et couleurs – qu’abrite notre Galaxie, lui conférant ainsi le statut d'étoile « banale », ne doit pas faire oublier que c'est l’étoile de notre système solaire . Il lui fournit lumière et énergie. Passé, présent et futur lointain de la Terre dépendent essentiell..." title="Article : SOLEIL" href="/encyclopedie/soleil/">Soleil</a> lors de l’impact d’une comète. L’idée de Buffon fut alors de mesurer les vitesses de refroidissement de boulets de différentes matières chauffées à blanc, qu’il extrapola audacieusement à des objets de la taille des <a data-bs-toggle="popover" data-bs-content="Les planètes du Système solaire sont connues depuis l’Antiquité. Leur nombre a évolué en fonction des découvertes successives et n’est peut-être pas définitif. Les huit planètes connues sont, en s’éloignant du Soleil : Mercure, Vénus, la Terre, Mars, Jupiter, Saturne, Uranus et Neptune. Elles se trouvent toutes à proximité du plan de l’orbite terrestre (l’écliptique). L..." title="Article : PLANÈTES" href="/encyclopedie/planetes/">planètes</a>. Pour la Terre, il détermina de la sorte que 75 000 ans s’étaient écoulés avant qu’elle ne devienne habitable et qu’elle le resterait ensuite 80 000 ans. En ayant par ailleurs observé les vitesses très faibles auxquelles des sédiments se déposaient dans la mer, Buffon consigna en vérité dans ses carnets un âge de dix millions d’années. S’il préféra ne pas le publier, ce ne fut pas en raison de la censure ecclésiastique, mais parce qu’il jugea que l’immensité d’une telle durée ne pourrait pas être appréhendée par ses contemporains.</p><div class="clearfix"></div><div class="media-container float-md-start me-2 col-md-3 text-center"><figure class="figure text-center w-100 mb-0 p-1" style="position: relative"><a data-ucode="DE170564" data-showMediaPlayer="1" class="protected media-reference-copy " title="Média : Profils de température à l’intérieur de la Terre" href="/media/profils-de-temperature-a-linterieur-de-la-terre-de170564/"><img id="DE170564" loading="lazy" src="/typo3temp/assets/_processed_/7/1/csm_de170564_e0ce1d5c41.webp" class="figure-img rounded mx-auto media_resized" alt="Profils de température à l’intérieur de la Terre - crédits : Encyclopædia Universalis France" data-description="Les profils de température à l'intérieur d'une Terre entièrement solide sont calculés avec la méthode de Kelvin. Sont ici considérés trois différents temps écoulés depuis le début d'un refroidissement à partir d'une température initiale de 3 870 0C, la flèche représentant le gradient géothermique…" data-copyright="Encyclopædia Universalis France" width="1505" height="2000" /></a><figcaption class="figure-caption"><p class="m-0 mt-1 fw-bold text-gray-700 text-truncate"> Profils de température à l’intérieur de la Terre </p><p class="m-0 copyright text-sm text-gray-700 text-truncate"> Encyclopædia Universalis France </p></figcaption></figure></div><p> Un des effets les plus notables du problème cosmologique soulevé par Buffon fut d’inciter <a data-bs-toggle="popover" data-bs-content="Biographie de JOSEPH FOURIER (1768-1830). C'est surtout grâce à la série et à l'intégrale qui portent son nom que le mathématicien français Joseph Fourier est connu du mathématicien et du physicien modernes ; mais il a aussi amélioré les techniques d'approximation des racines des équations polynomiales. En fait, ses intérêts furent des plus variés, allant de la physique expérimen..." title="Article : JOSEPH FOURIER (1768-1830)" href="/encyclopedie/joseph-fourier/">Joseph Fourier</a> (1768-1830) à élaborer sa célèbre théorie de la propagation de la <a data-bs-toggle="popover" data-bs-content="La première tentative d'interprétation physique assimilait la chaleur à un fluide dit subtil et indestructible dénommé le calorique , répandu partout au sein de la matière. Son passage d'un corps à un autre était notamment responsable du refroidissement du premier et de l'échauffement du second. L'adoption vers le milieu du xix e siècle du principe de l'équivalence de la chaleur..." title="Article : CHALEUR" href="/encyclopedie/chaleur/">chaleur</a>, dans laquelle il introduisit une distinction fondamentale entre les capacités qu’avait une <a data-bs-toggle="popover" data-bs-content="Une idée reçue particulièrement tenace occupe le devant de la scène philosophique depuis l'époque du positivisme d' Auguste Comte , c'est-à-dire depuis plus d'un siècle : l'idée selon laquelle la métaphysique serait morte avec Kant, à la fin du xviii e siècle, pour ne laisser la place qu'à des recherches éparses, empiriques et positives, se constituant comme sciences particuli..." title="Article : SUBSTANCE" href="/encyclopedie/substance/">substance</a> de conduire et d’accumuler cette chaleur. Jugeant que ces deux variables n’étaient pas connues, Fourier s’abstint toutefois finalement de toute application au refroidissement de la Terre. Grand admirateur de Fourier, Kelvin fut plus audacieux en s’appuyant également sur les deux principes de la thermodynamique entre-temps énoncés (conservation de l’énergie et augmentation d’entropie d’un système isolé). En supposant assez arbitrairement que la température initiale de la Terre avait été de 3 870 <sup>0</sup>C, il calcula avec les paramètres thermiques jugés appropriés qu’il avait fallu de 20 à 400 millions d’années pour que le profil de température observé à la surface de la Terre (le gradient géothermique) atteigne sa valeur mesurée d’environ 30 <sup>0</sup>C par kilomètre. Le résultat était spécialement probant, car il s’accordait à l’âge déterminé pour le Soleil par une tout autre méthode : si l’énergie fournie par un combustible comme le charbon ou par la chute de <a data-bs-toggle="popover" data-bs-content="En 1950, l’astronome américain Fred Whipple fut l’un des premiers à comprendre qui étaient ces voyageuses capables d’illuminer le ciel nocturne de leur vaste chevelure. En des termes inversement proportionnels à leur beauté, il les décrivit comme des « boules de neige sale ». D’après ce modèle, la matière glacée qui compose les comètes passe directement de l’état soli..." title="Article : COMÈTES" href="/encyclopedie/cometes/">comètes</a> sur le Soleil était très insuffisante pour assurer le flux connu de chaleur solaire, celle que libérait une contraction gravitationnelle du Soleil sur lui-même autorisait en revanche des durées de 40 à 100 millions d’années.</p><p>Pour leur part, les géologues avaient eu tendance à évoquer des temps beaucoup plus longs. Le débat ainsi lancé fut d’autant plus vif que Kelvin ne cessa de reprendre ses calculs pour annoncer des durées de plus en plus courtes, qu’il limita à 24 millions seulement en 1893 à partir de paramètres thermiques qu’il pensait plus précis. Sa position fut cependant vite rendue intenable à la suite de la découverte de la <a data-bs-toggle="popover" data-bs-content="La radioactivité désigne un vaste ensemble de phénomènes physiques, dont le dénominateur commun consiste en une modification du noyau atomique des éléments.. Il existe dans la nature une centaine de type d'atomes. Ils ont été regroupés par Mendeleïev en 1869 sur un tableau montrant les analogies chimiques. Un atome (dimension environ 10 —10 m) est lui-même constitué d'un n..." title="Article : RADIOACTIVITÉ" href="/encyclopedie/radioactivite/">radioactivité</a> en 1896 par Henri Becquerel (1852-1908), puis des travaux de Pierre (1859-1906) et <a data-bs-toggle="popover" data-bs-content="Marie, la mère de Jésus de Nazareth, n'est mentionnée que de façon très discrète et épisodique dans l'ensemble de la littérature néo-testamentaire. En revanche, en tant que personne faisant l'objet de culte et de vénération, elle occupe progressivement une place singulière et éminente dans la foi et la spiritualité chrétiennes, tant orientale qu'occidentale. On a pu dire que «..." title="Article : MARIE" href="/encyclopedie/marie/">Marie</a><a data-bs-toggle="popover" data-bs-content="Biographie de LES CURIE. Dans l'histoire de la radioactivité , depuis sa découverte et pendant les soixante années qui suivirent, le nom des Curie s'inscrit au premier plan. Les plus éminents représentants de cette famille de savants français ont été Pierre Curie (1859-1906), sa femme Marie Curie née Sklodowska (1867-1934), leur fille Irène (1897-1956) devenue en 1926 la femme de ..." title="Article : LES CURIE" href="/encyclopedie/les-curie/"> Curie</a> (1867-1934) sur l’uranium, le <a data-bs-toggle="popover" data-bs-content="En 1828, Jöns Jacob Berzelius découvrit un nouveau métal qu'il baptisa thorium en l'honneur de Thor, dieu de la mythologie scandinave.. Bien qu'il soit radioactif et relativement rare, cet élément a été utilisé depuis longtemps dans l'industrie, principalement pour la fabrication des manchons de becs de gaz. Il entre maintenant dans la composition des filaments de tungstène des lamp..." title="Article : THORIUM" href="/encyclopedie/thorium/">thorium</a> et le <a data-bs-toggle="popover" data-bs-content="En 1898, quelques mois après avoir découvert le polonium , Pierre et Marie Curie et leur collaborateur Gustave Bémont, poursuivant l'étude du fractionnement de la pechblende de Joachimsthal (aujourd'hui Jáchymov, en République tchèque), purent révéler l'existence d'un élément d'un comportement chimique voisin de celui du baryum et pour lequel ils proposèrent le nom de radium, en ..." title="Article : RADIUM" href="/encyclopedie/radium/">radium</a>, le premier nouvel élément chimique qu’ils découvrirent. Les calculs de Kelvin présupposaient l’absence de sources de chaleur interne à la Terre. Or Pierre Curie observa en 1903 avec son collaborateur Albert Laborde que les effets thermiques de la radioactivité étaient énormes et il démontra en outre que l’intensité des rayonnements émis décroissait avec le temps d’une manière rigoureusement exponentielle. Comme il le souligna, le temps pouvait désormais être mesuré de manière absolue, indépendamment du mouvement des astres.</p><div class="clearfix"></div><div class="media-container float-md-start me-2 col-md-3 text-center"><figure class="figure text-center w-100 mb-0 p-1" style="position: relative"><a data-ucode="DE170565" data-showMediaPlayer="1" class="protected media-reference-copy " title="Média : Âge de la Terre calculé selon les compositions en isotopes du plomb" href="/media/age-de-la-terre-calcule-selon-les-compositions-en-isotopes-du-plomb-de170565/"><img id="DE170565" loading="lazy" src="/typo3temp/assets/_processed_/d/5/csm_de170565_6d656b220d.webp" class="figure-img rounded mx-auto media_resized" alt="Âge de la Terre calculé selon les compositions en isotopes du plomb - crédits : Encyclopædia Universalis France" data-description="Les variations avec le temps des compositions isotopiques de plomb de minéraux de teneurs initiales différentes en uranium et en plomb (µ = U/Pb) à partir d'une composition primordiale commune permettent de calculer l'âge de la Terre par les pentes des isochrones, les droites en tireté (en millions…" data-copyright="Encyclopædia Universalis France" width="2000" height="1448" /></a><figcaption class="figure-caption"><p class="m-0 mt-1 fw-bold text-gray-700 text-truncate"> Âge de la Terre calculé selon les compositions en isotopes du plomb </p><p class="m-0 copyright text-sm text-gray-700 text-truncate"> Encyclopædia Universalis France </p></figcaption></figure></div><p> La première datation géologique suivit rapidement. En 1905, elle fut l’œuvre du physicien anglais <a data-bs-toggle="popover" data-bs-content="Biographie d'ERNEST RUTHERFORD lord (1871-1937). Physicien anglais, lauréat du prix Nobel de chimie en 1908, dont les recherches sur les rayonnements et la structure atomique ont ouvert la voie aux développements ultérieurs de la physique nucléaire du xx e siècle.. Né à Nelson (Nouvelle-Zélande), il y effectue ses études secondaires ; boursier de l'université de Nouvelle-Zélande à..." title="Article : ERNEST RUTHERFORD lord (1871-1937)" href="/encyclopedie/ernest-rutherford/">Ernest Rutherford<a href="javascript:" title="Lire la suite" class="read-more ms-1">[...]</a></a></p></div><div class="clearfix"></div></div><ul class="pagination justify-content-center public-links "><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 1" class="page-link" title="Abonnez-vous" data-loaded="true">1</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 2" class="page-link" title="Abonnez-vous" data-loaded="true">2</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 3" class="page-link" title="Abonnez-vous" data-loaded="true">3</a></li><li class="page-item active"><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 4" class="page-link" title="Abonnez-vous" data-loaded="true">4</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 5" class="page-link" title="Abonnez-vous" data-loaded="true">5</a></li><li class="page-item "><a href="/abonnement" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="page 6" class="page-link" title="Abonnez-vous" data-loaded="true">6</a></li></ul><div class="folio-block"><p class="folio-block-title text-center text-uc"><strong>La suite de cet article est accessible aux abonnés</strong></p><ul class="list-unstyled"><li><i class="fa fa-fw fa-check-circle"></i> Des contenus variés, complets et fiables</li><li><i class="fa fa-fw fa-check-circle"></i> Accessible sur tous les écrans</li><li><i class="fa fa-fw fa-check-circle"></i> Pas de publicité</li></ul><p class="text-center"><a href="/abonnement/" class="btn btn-cta text-uc" id="folio-button" data-matomo-category="Article" data-matomo-name="Folio" data-matomo-value="Block bottom">Découvrez nos offres </a></p><p class="text-center text-sm"> Déjà abonné ? 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Flammarion, …" data-copyright="D.R." width="692" height="1024" /> </a> <figcaption class="figure-caption"> <p class="m-0 mt-1 fw-bold text-gray-700 text-truncate"> La mort thermique de l’ Univers </p> <p class="m-0 copyright text-sm text-gray-700 text-truncate"> D.R. </p> </figcaption> </figure> </div> <div class="col-12 col-md-4 text-center p-1"> <figure class="figure text-center w-100 mb-0 p-1" style="position: relative"> <a data-ucode="DE170564" data-showMediaPlayer="1" class="protected media-reference-copy " title="Média : Profils de température à l’intérieur de la Terre" href="/media/profils-de-temperature-a-linterieur-de-la-terre-de170564/"> <img id="DE170564" loading="lazy" src="/typo3temp/assets/_processed_/7/1/csm_de170564_e0ce1d5c41.webp" class="figure-img rounded mx-auto media_resized" alt="Profils de température à l’intérieur de la Terre - crédits : Encyclopædia Universalis France" data-description="Les profils de température à l'intérieur d'une Terre entièrement solide sont calculés avec la méthode de Kelvin. Sont ici considérés trois différents temps écoulés depuis le début d'un refroidissement à partir d'une température initiale de 3 870 0C, la flèche représentant le gradient géothermique…" data-copyright="Encyclopædia Universalis France" width="1505" height="2000" /> </a> <figcaption class="figure-caption"> <p class="m-0 mt-1 fw-bold text-gray-700 text-truncate"> Profils de température à l’intérieur de la Terre </p> <p class="m-0 copyright text-sm text-gray-700 text-truncate"> Encyclopædia Universalis France </p> </figcaption> </figure> </div> </div> <div class="text-center"> <a class="btn btn-sm btn-primary" rel="related" href="/medias/age-de-la-terre/"> Afficher les 5 médias de l'article <span class="rg">ÂGE DE LA TERRE</span> <i aria-hidden="true" class="fa fa-fw fa-chevron-right"></i> </a> </div> </section> <section class="mb-5 d-print-none article-indexes learn-more"> <i class="anchor" id="yC170047_INDEXES"></i> <p class="title-minor">Voir aussi</p> <ul class="list-inline 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href="/index/histoire-des-sciences-antiquite-et-moyen-age/"> <span class="rg">SCIENCES </span><span class="pc">HISTOIRE DES, </span><em class="it">Antiquité et Moyen Âge</em> </a> </li> <li class="list-inline-item m-1"> <a title="Index : SÉDIMENTATION MARINE" href="/index/sedimentation-marine/"> <span class="rg">SÉDIMENTATION MARINE</span> </a> </li> <li class="list-inline-item m-1"> <a title="Index : GRECQUE PHILOSOPHIE" href="/index/philosophie-grecque/"> <span class="rg">GRECQUE </span><span class="pc">PHILOSOPHIE</span> </a> </li> <li class="list-inline-item m-1"> <a title="Index : CHRONOMÉTRIE" href="/index/chronometrie/"> <span class="rg">CHRONOMÉTRIE</span> </a> </li> <li class="list-inline-item m-1"> <a title="Index : COUCHES ou STRATES, géologie" href="/index/couches-strates/"> <span class="rg">COUCHES </span><span class="rm">ou </span><span class="rg">STRATES, </span><em class="it">géologie</em> </a> </li> <li class="list-inline-item m-1"> <a title="Index : ASTRONOMIE 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