ABSTRACT Light-pulse atom interferometry, where light pulses are used as atom beam splitters, has led to extremely sensitive and accurate quantum sensors that offer many applications in fundamental physics, geosciences and inertial navigation. Until recently, light-pulse atom interferometry had only exploited continuous-wave (cw) laser sources. During this talk, I will present atom interferometers where the beam splitters are realized with pulsed lasers, or more specifically frequency-comb lasers [1]. This technique, which we demonstrated in the visible spectrum on rubidium (Rb) atoms, paves the way for extending light-pulse interferometry to other wavelengths (e.g. deep-UV to X-UV) and therefore to new species, since one can benefit from the high peak intensity of the ultrashort pulses which makes frequency conversion in non-linear media efficient. [1] C. Solaro et al., “Atom interferometer driven by a picosecond frequency comb”, Physical Review Letters 129, 173204 (2022).

Attempts at estimating by astronomical means the longitude of newly discovered lands had an enormous increment in the early sixteenth century. The reason behind these efforts was not navigational safety nor the desire for improved geographical knowledge, but quite more prosaically the ambitions of imperial expansion. In this presentation I will provide an overview of the measurements of longitude in the first decades of the 16th century. I will show how the results of these measurements clashed with nautical cartography of the period thus leading to heated scientific and diplomatic debates. I will also argue that the problems created by long distance oceanic voyages and the need for more accurate geographical descriptions led to the development of mathematical cosmography.

The celestial navigation skills of early modern Arab pilots in the Indian Ocean are as legendary as vaguely and partially known. In this talk I will draw directly from the two known late medieval sources, Ahmad ibn Mājid and particularly Sulaymān al-Mahrī —who remains mostly untranslated— to paint a fuller picture, including their astronomical framework, the techniques they used and their relation to scholarly astronomy. Working on an initial question, “What could be tabulated from their works?”, I expect to be able to delineate with some precision their craft, and so to furnish interested astronomers with clear elements for comparison and reflection.

The Ferrara humanist Celio Calcagnini (1479-1541), an Italian contemporary of Nicolaus Copernicus (1473-1543), wrote around 1518 an apology for the motion of the Earth, Quod caelum stet, terra moveatur vel de perenni motu terrae (That the Hevens Stand Still, and the Earth Moves, or on the Earth’s Constant Motion). It is a short but dense treatise, philosophically complex and sophisticated in style, on a topic of great interest in the history of cosmology. Yet, it has not so far received adequate consideration in the history of science. In his talk, Pietro Daniel Omodeo presents the publication of its first translation into a modern language, edited by Alberto Bardi and himself (Castelvecchi 2022).

Partant de l'analyse critique du Procès Verbal qui constate le travail fait par le Citoyen Verniquet, auteur du Plan de Paris, pour la vérification de toutes les Opérations Trigonométriques, qui ont servi pour les positions des principaux Monuments de Paris (Lalande, Lacroix : 1795), nous nous efforcerons de retracer ces opérations et d'en évaluer la cohérence et la qualité, depuis les levés sur le terrain jusqu'aux stratégies de calcul qui ont permis à Edme Verniquet et son équipe d'établir un système de référence de coordonnées de Paris et un plan de la ville d'une précision inédite. Nous nous appuierons pour cela sur le corpus très riche mais dispersé d'archives relatives à l'histoire et à la mise au point de son célèbre Atlas du plan général de la ville de Paris publié en 1793-1799.

Upon the establishment of the Ming dynasty, the first emperor ordered the translation and adaptation of the Hijri Islamic calendar and its related calculation methods and ushered in a new era in the application of Islamicate mathematical astronomy in early modern China. To coordinate the Hijri and the Chinese calendrical systems, as well as to make use of these calendrical systems for its political causes, the Ming court devised algorithms that established reference points, including the Hijri Epoch (li yuan 曆元) and Year 1 of the Hexadecimal Cycle (jiazi nian 甲子年). In the case of the Hijri Epoch factor, lack of attentiveness to a required coordination of the solar and lunar systems led a flawed algorithm and subsequently a flawed result. This talk will explore the impact of such a flaw on the application of astronomy at the court and outside of it between the 14th and 17th centuries. The set of astronomical algorithms and reference points that were established during the late 14th century continued to be used, with some modification, as factors in the various astronomical calculations and adjustments taken in the Chinese courts up to the 17th century. They impacted the way Islamic astronomy was implemented at the Chinese courts, its level of accuracy and eventually its inferiority vis-à-vis European astronomical predictions. As such, the calculation of these factors became a subject of debate among Chinese astronomers that lingered even long after the Hijri calendar fell out of grace at the Chinese court. At the same time, these calculated factors greatly shaped the cultural and religious identities of China's Islamic communities by producing a flawed timeframe for the history of Islam in China

In its reception of ideas from the Marāgha and Samarqand schools, Sanskrit astronomy of early modern Mughal India adapted Islamicate (Arabic and Persian) concepts to suit the linguistic and logical requirements of its own changing episteme.The practical, physical, and philosophical forces that influenced this change are being investigated by the Gerda Henkel Stiftung-funded project Changing Episteme in Early Modern Sanskrit Astronomy (CEEMSA, 2022─23, Grant Agreement № AZ 21/F/21). In this talk, the project PI Anuj Misra and project postdoc Jean Arzoumanov will jointly present some of the latest developments of the project; in particular, those that have emerged in comparing the canons from two 17th century astronomical table-texts composed near-contemporaneously: the Persian Zīj-i Shāh Jahānī of Mullā Farīd and its Sanskrit translation, the Siddhāntasindhu of Nityānanda.

Victorine de Chastenay (1771-1855), issue d’une famille de la noblesse bourguignonne, est l’autrice de traductions et ouvrages littéraires, de Mémoires réédités à plusieurs reprises, mais aussi d’une importante production de correspondances et de notes de lecture portant sur les domaines les plus variés : littérature, histoire, linguistique, chimie, astronomie, physique, botanique, géographie. Pour assouvir sa soif de savoirs, elle côtoie les plus grands savants de son temps, comme François Arago dont elle obtient un cours privé (1811-1812). Elle assiste ensuite (à partir de 1821) au cours public proposé à l’Observatoire de Paris, prenant en notes ses cours et ses observations dans des cahiers, conservés par les Archives départementales de la Côte d’Or, qui font l’objet d’un projet d’édition numérique.

L’importance de l’astronomie dans l’œuvre d’Auguste Comte est à la mesure de la place fondatrice qu’il lui accorde dans sa propre classification des sciences que constitue le Cours de philosophie positive. Comte dispense même un cours populaire d’astronomie, dont l’objectif n’est pas de former à l’astronomie mais à la « saine philosophie » positive. D’où le regard philosophique qu’il porte sur elle comme l’indique son Traité philosophique d’astronomie populaire. Pour Comte, l’astronomie est donc tout à la fois, un modèle de science positive et un faire-valoir de la philosophie positive et même de l’engagement positiviste, quitte à restreindre assez fortement son champ d’étude.

Dans la seconde moitié du XIXe siècle, tous les observatoires astronomiques de premier plan s’équipent d’un cercle méridien, les observatoires français ne font pas exception et de 1877 à 1890 ils acquièrent auprès d’une même dynastie de mécaniciens des instruments comparables. Ces cercles sont certes conçus suivant le même modèle mais chacun d’eux profite des défauts du précédent, des remarques des utilisateurs et des savoir-faire cumulés des constructeurs. Dans notre intervention, nous reviendrons sur la mise en place de ce réseau instrumental, nous essaierons de présenter les transformations et renouvellements des instruments, de leurs accessoires et de leurs horloges en parallèle des usages et travaux scientifiques menés par les personnels des services méridiens des observatoires. Fait exceptionnel, un siècle et demi plus tard, tous les instruments ont été conservés, nous dresserons un constat d’état de leur conservation, protection et valorisation.

Résumé à venir