{"id":91832,"date":"2026-09-03T17:22:28","date_gmt":"2026-09-03T15:22:28","guid":{"rendered":"https:\/\/www.librairieclavreuil.com\/sagnac-georges-de-loptique-des-rayons-de-rontgen-et-des-rayons-secondaires-qui-en-derivent\/"},"modified":"2026-09-04T09:46:20","modified_gmt":"2026-09-04T07:46:20","slug":"sagnac-georges-de-loptique-des-rayons-de-rontgen-et-des-rayons-secondaires-qui-en-derivent","status":"publish","type":"product","link":"https:\/\/www.librairieclavreuil.com\/en\/sagnac-georges-de-loptique-des-rayons-de-rontgen-et-des-rayons-secondaires-qui-en-derivent\/","title":{"rendered":"SAGNAC Georges De l&#8217;optique des rayons de R\u00f6ntgen..."},"content":{"rendered":"<p style=\"text-align:justify\">Walter. Scott (dir.). <i>La Correspondance entre Henri Poincar\u00e9 et les physiciens, chimistes et ing\u00e9nieurs<\/i>. B\u00e2le, Birkha\u00fcser, 2007. pp. 322-238. Christian&nbsp;Bracco,&nbsp;\u00ab&nbsp;<i>Henri Poincar\u00e9&nbsp;: du \u00ab&nbsp;principe de mouvement relatif&nbsp;\u00bb au \u00ab&nbsp;principe de relativit\u00e9&nbsp;\u00bb en passant par le \u00ab&nbsp;principe de r\u00e9action&nbsp;\u00bb et son rapport \u00e0 la th\u00e9orie de Lorentz<\/i>&nbsp;\u00bb,&nbsp;<i>Philosophia Scienti\u00e6<\/i>, 27-2, 2023, pp. 35-62.&nbsp;<\/p>\n<p style=\"text-align:justify\"><span style=\"font-variant:small-caps\">First edition of this thesis. Copy nscribed to the mathematician Henri Poincar\u00e9 (1854\u20131912) on the half-title page: &#8221; &nbsp;<\/span><i><span style=\"font-variant:small-caps\">\u00e0 M. Henri Poincar\u00e9, respectueux hommages &#8220;.&nbsp;<\/span><\/i><\/p>\n<p style=\"text-align:justify\">Focusing on the optical properties of X-rays, discovered by Wilhelm R\u00f6ntgen in 1895, this dissertation\u2014defended in Paris in December 1900\u2014examines their propagation, scattering, and absorption through a strictly optical approach. His research notably demonstrated the existence of secondary rays derived from X-rays.<\/p>\n<p style=\"text-align:justify\">The significance of this copy also lies in its provenance. A former student of Poincar\u00e9 (1854\u20131912) at the \u00c9cole Normale Sup\u00e9rieure, where he notably took his courses on Hertzian oscillations between 1892 and 1893, Sagnac naturally dedicated his dissertation to the man he recognized as one of the leading scientific authorities of his time. Like many young academics, Sagnac wished to have his work recognized by his peers, whose approval was of paramount importance. The letter highlights an academic connection between the two men, a connection that would be sustained through several scientific exchanges.<\/p>\n<p style=\"text-align:justify\">This relationship is documented in particular by correspondence predating the submission of his dissertation, including a letter\u2014now held in the National Archives\u2014regarding the research conducted by W. Nicolai\u00e8ve, dated 1899. In their correspondence, Georges Sagnac and Henri Poincar\u00e9 discuss fundamental questions of electromagnetism, such as the role of the magnetic field, the mechanisms of electromagnetic action transmission, and the principle of action and reaction.<\/p>\n<p style=\"text-align:justify\">These exchanges took place within a particularly active scientific network centered around Poincar\u00e9, founded on interdisciplinarity and the sharing of knowledge. Thus, between 1878 and 1912, he corresponded with more than sixty scientists, physicists, chemists, and engineers, among whom was George Sagnac.<\/p>\n<p style=\"text-align:justify\">The debates between the two scholars found particular expression in the development of Einstein\u2019s theory, to which Poincar\u00e9 made a major contribution by introducing the principles of simultaneity and the relativity of time, notably in \u201cLa mesure du temps,\u201d published in 1898 in the <i>Revue de m\u00e9taphysique et de morale.<\/i><\/p>\n<p style=\"text-align:justify\">If Sagnac\u2019s name is particularly well known in the scientific community, it is primarily because of the discovery that bears his name, which is still used in engineering today. Convinced by Fresnel\u2019s theory of the ether, Sagnac conducted optical experiments aimed at demonstrating the existence of a time delay in the reception of two signals traveling along opposite paths. He interpreted the results of his experiment as contradicting Einstein\u2019s theory of relativity. In reality, Sagnac had just discovered a deeper aspect of the phenomenon of relativity, which would be correctly interpreted in 1921 by Paul Langevin.<\/p>\n<p style=\"text-align:justify\">Sending his work to Poincar\u00e9 was thus part of a vital network of scholars, within which ideas and knowledge circulated, influenced one another, and helped foster a scientific debate essential to progress. This work, one of his earliest scientific publications, marked his first step toward joining the circle of scholars who shaped modern science in the early 20<sup>th<\/sup> century.<\/p>\n<p style=\"text-align:justify\">Front printed cover and spine missing, paper loss on the remaining back cover.<\/p>\n","protected":false},"excerpt":{"rendered":"<p style=\"text-align:justify\">8vo (253 x 162 mm), 2 unn.l. (half-title and title), 166pp. Sewed, un-opened.&nbsp;<\/p>\n","protected":false},"featured_media":91767,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[],"product_cat":[550],"product_tag":[1450,1264,1335],"class_list":{"0":"post-91832","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-science","7":"product_tag-first-edition","8":"product_tag-inscription","9":"product_tag-physics","10":"pa_auteur-sagnac-georges-2","11":"pa_type-de-livre-printed-book","13":"first","14":"outofstock","15":"shipping-taxable","16":"purchasable","17":"product-type-simple"},"acf":{"artist":"SAGNAC Georges","chapeau":"","adresse_bibliographique":"Paris, Gauthier-Villars, 1900","book_type":"Printed book","provenance":"","afficher_prix":"oui"},"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>SAGNAC Georges De l&#039;optique des rayons de R\u00f6ntgen et des rayons secondaires qui en d\u00e9rivent. - Libairie Clavreuil<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.librairieclavreuil.com\/en\/sagnac-georges-de-loptique-des-rayons-de-rontgen-et-des-rayons-secondaires-qui-en-derivent\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"SAGNAC Georges De l&#039;optique des rayons de R\u00f6ntgen et des rayons secondaires qui en d\u00e9rivent. - Libairie Clavreuil\" \/>\n<meta property=\"og:description\" content=\"8vo (253 x 162 mm), 2 unn.l. 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