Astrophysicien au CEA (Commissariat à l'énergie atomique et aux énergies alternatives)

Photo © G. Lhériteau
Joined January 2010
Montargis se souvient. Depuis 2016, il existe un Musée Historique de l’Amitié Franco-Chinoise avec des documents intéressants comme la carte d'ouvrier de Deng à l'usine Hutchinson, où il est mentionné "refuse de travailler. Ne pas reprendre" et une stèle sur le parvis de la gare.
Suite à mon post sur Deng Xiaoping ouvrier en France, plusieurs abonnés chinois ont commentés et écrit que le Parti communiste chinois avait été fondé en France, à Montargis. J'ai vérifié, et la réalité est assez intéressante. Je laisse les spécialistes confirmés :) Le PCC tient son premier congrès à partir du 23 juillet 1921 à Shanghai, dans la concession française d'ailleurs, même si la Chine célèbre officiellement sa naissance le 1er juillet. Mais l'idée, elle, semble bien partir d'une petite ville du Loiret. En 1919, un groupe de jeunes du Hunan, des amis proches de Mao, s'installe à Montargis dans le cadre du mouvement Travail-Études. Les garçons vont au collège de la ville, les filles au collège du Chinchon dirigé par Mme Dumont, la mère de l'agronome René Dumont, et en juillet 1920 tout ce petit monde se réunit au jardin Durzy pour débattre de l'avenir de la Chine. Mao, lui, est resté au pays. Parmi eux, il y a Cai Hesen, le théoricien du groupe. Le 13 août 1920, depuis Montargis, il écrit à Mao pour lui proposer de créer un Parti communiste chinois, qu'il voit comme l'avant-garde de la révolution. Mao lui répond le 1er décembre qu'il est d'accord. À Paris, Zhou Enlai rejoint au printemps 1921 le groupe communiste chinois de la capitale. De 1922 à 1924, il vit dans une chambre minuscule au 17 rue Godefroy dans le 13e, qui sert aussi de base aux jeunes communistes chinois en Europe, et le jeune Deng Xiaoping y travaille avec lui en tirant leur revue à la ronéo. Donc non, le parti n'est pas né à Montargis, mais une bonne partie de ses fondations intellectuelles a été posée là-bas, dans des lettres écrites entre deux cours et deux journées d'usine, et c'est pour ça que Le Monde a pu titrer « Montargis, berceau de la Chine nouvelle ». Je trouve fou qu'une petite sous-préfecture du Loiret ait joué un rôle pareil dans l'histoire d'un pays aussi immense que la Chine, et que la plupart des Français qui passent par Montargis n'en sachent absolument rien. Encore une fois, un lien entre les 2 pays.
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This blew my mind: between 1403 and 1407, the Ming Dynasty emperor commissioned an encyclopedia - now called the Yongle encyclopedia, after the emperor - that was so vast in scale (around 400 million Chinese characters) that the only other encyclopedia that finally exceeded it was Wikipedia in 2007, 6 years after its launch! This is yet another example of West-centric our sense of intellectual history is: in French education we're taught that encyclopedias as a concept started with Diderot and d'Alembert's "Encyclopédie" in the mid-18th century, which we're told was the first attempt in history to gather all of human knowledge in one place. Not only was the Yongle encyclopedia completed 350 years earlier, and not only is it 20 times larger than L'Encyclopédie, but it was itself a very late entry in a Chinese tradition of encyclopedias which started with the Huanglan - more than 8 million characters in length - compiled around 220 AD (en.wikipedia.org/wiki/Huangl…). Unfortunately much of the encyclopedia has been lost: out of the original 11,095 volumes, only around 400 are known to have survived (300-ish of which are in China). But we sometimes find new ones, like two volumes that surfaced in 2020 in the attic of a French family, descendants of a naval officer who had received them as a gift from corrupt Chinese officials in the 1870s. They went to auction in Paris with a starting price of 5,000 euros and sold for 8.12 million to a Chinese textile entrepreneur, Jin Liang, who donated them to China's National Archives of Publications this summer (sixthtone.com/news/1019031).
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Philip II was King of Macedon and the father of Alexander the Great. At his death (336 BC) the king was buried with a royal ceremonial under the Great Tumulus in Vergina. It is fortunate that this truly monumental tomb was never plundered and was unearthed in 1977 by renowned Greek archaelogist Manolis Andronikos, making it a worldwide sensation. Among the grave findings of the Tomb II was an impressive suit of armour, which, given unique body form of the wearer described in ancient texts, most probably belonged to Phillip personal atire. At present the fully restored armour is displayed at the underground Archaelogical Museum at Aigai which has been designed and constructed so as to preserve the authenticity of the royal tombs of that era. It is in fact a modern tumulus-shaped shelter built to cover the original cluster of royal tombs. After the ceremonial cremation of body, suit of armour was placed inside the main chamber, suit of armour was placed inside the main chamber of Tomb II, next to Phillip’s golden funeral box (larnaka) to accompany him in his journey to after-life. Archaeologists managed to assemble scattered elements of the suit and were able to fully restore it to its original condition. The excellence of their work enabled a serious attempt at a reproduction. The main body of the suit is made of iron, in seven anatomical shaped plates securely connected between them with long, vertical and horizontal hinges. It is obvious that it was designed to resemble the basic structure of a Linothorax i.e. with upper shoulder pads (epomides), main body corselet and double row of leather pteryges for the lower body and groin. The two long flaps at the shoulder, the epomides, also cover the wearer’s neck areas bending over the top to latch onto the upper part of the chest area. Two horizontally arranged hinges in bronze (the originals were made of gold) connect iron bases of flaps with sizable dorsal plate. Lion-shaped bronze rings are rivetted at the ends of each of these. Purple leather is used to embellish the external surfaces of the epomides as well as all external rims, together with a delicate, narrow bronze band with embossed lesbian ornaments. The front area bears Royal Sun emblem from Vergina handstiched of pure silk. All the plates are manufactured with the hammered technique to conform to a curved anatomical shape of the short, round body. The lower half of the right side plate bears an embossed depiction of goddess Athena. The other half, on the front, bears a floral decoration in silk copied from Phillip’s funeral box, while the upper half has a pair of stylized lion rings fitted. On the left side there are two more identical pairs of lion-shaped bronze rings also fastened horizontally. Finally, the upper curved section of the back plate bears a silk panel consisting of three blue margarita blossoms, copied once again from the King’s treasury. All inner surfaces have been padded with wool and silk. Two rows of narrow leather strips with fringe decorations are attached to the rim of the cuirass, enabling freedom of movement along with protection for the groin and thighs. The pair of bronze greaves have been recreated using traditional techniques from an example found in same chamber of Tomb II, next to the suit of armour. The extra decorative elements (external leather, silk decoration and padding) were included by the artist in his attempt to restore the thorax to its full glory. The suit offers a glimpse into the luxurious royalty of ancient Macedon. Museum of the Royal Tombs of Aigai #archaeohistories
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It is impossible to project a globe onto a sheet of paper without compromise. Distances, areas, directions and angles cannot all be preserved at once. Something must be sacrificed when three dimensions are forced into two. Hence, there is nothing improper about preferring one map projection over another. But the quarrel over the Mercator projection soon becomes identity politics. And so it inherits every vice of that style of argument: it is anachronistic, reductionist, and charged with unspoken insinuations about colonial guilt and the inherited sin of white people. The Mercator projection of 1569 was a stroke of genius for the purpose it was meant to serve. Mercator’s map was a navigational instrument. Its decisive property was that it rendered directions and angles truly: a line of constant compass bearing appears as a straight line. To secure that property, a faithful representation of area had to be given up. But as already said: one cannot have everything when a sphere must be drawn as a plane. One has to choose. It is therefore almost intolerable to hear the insinuation that Mercator was some kind of racist, intent on striking Africans with an inflated Greenland. We should honour Gerardus Mercator for what he was: one of the great cartographers in the history of the craft. The author of a projection whose charts, for centuries, helped generations of seafarers across the open ocean - long before longitude could be determined with any reliability at sea.
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Tiré de "Géants de Science : Voir l'intérieur de la Matière" youtube.com/watch?v=3fYC2hXG… Réalisation : Jérôme Blumberg Auteur : Jean-Marc Bonnet-Bidaud, Production CEA - CNRS Images (2018) images.cnrs.fr/video/6495
Bertrand Goldschmidt a été le premier à révéler que, dès le début, le projet Manhattan avait pour but de construire deux bombes atomiques pour bombarder l'Allemagne ET le Japon. Le prétexte de la reddition du Japon n'a été qu'une raison de dernière minute.
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Bertrand Goldschmidt a été le premier à révéler que, dès le début, le projet Manhattan avait pour but de construire deux bombes atomiques pour bombarder l'Allemagne ET le Japon. Le prétexte de la reddition du Japon n'a été qu'une raison de dernière minute.
📽️ En 1984, Bertrand Goldschmidt, pionnier du nucléaire français au CEA, revient sur sa participation aux États-Unis, pendant la Seconde Guerre mondiale, aux travaux qui ont conduit à l’isolement du plutonium par l’équipe de Glenn T. Seaborg.
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Regard sur… 𝐋𝐞 𝐌𝐮𝐬𝐞́𝐞 𝐟𝐫𝐚𝐧𝐜̧𝐚𝐢𝐬 𝐝𝐞 𝐥𝐚 𝐫𝐚𝐝𝐢𝐨𝐥𝐨𝐠𝐢𝐞 𝐞𝐭 𝐝𝐞 𝐥’𝐢𝐦𝐚𝐠𝐞𝐫𝐢𝐞 𝐦𝐞́𝐝𝐢𝐜𝐚𝐥𝐞 (Paris, France) Par Jean-Philippe Bricka Situé dans une petite rue du XIIIᵉ arrondissement de Paris, (./.)
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In 1930, a 19-year-old student sat on a steamship traveling from India to England, scribbling math equations in a notebook to pass the time. By the time the ship reached port, the teenager had mathematically proven that the most massive stars in the universe do not die peacefully. Instead, they are destined to collapse into infinitely dense, terrifying monsters. He had just discovered the mathematical trigger for black holes. But when he arrived at Cambridge and presented his work, the leading astronomer of the Western world publicly mocked him, calling his mathematics a stellar joke. His name was Subrahmanyan Chandrasekhar. It would take nearly 50 years for the scientific establishment to admit they were wrong and award him the Nobel Prize for the math he did on that ship when he was nineteen. His struggle against scientific elitism is the ultimate lesson in what happens when rigid dogmas clash with undeniable mathematical reality. In the early 20th century, astronomers believed they understood the life cycle of stars. They knew that when a star runs out of fuel, gravity tries to crush it. But quantum mechanics offered a beautiful safety net: a force called "electron degeneracy pressure" would push back against gravity. The star would shrink into a stable, peaceful, glowing ember called a White Dwarf. The entire scientific establishment agreed: every star, no matter how big, would eventually settle into this quiet retirement. It was a neat, comforting formula. But on that ship, Chandra realized the establishment had left a massive variable out of their equations: Albert Einstein’s Special Relativity. Chandra recalculated the math, factoring in what happens when the collapsing particles inside a dying star approach the speed of light. What he found shattered the comforting consensus. He proved that if a dying star is more than 1.44 times the mass of our Sun (a boundary now immortalized as the Chandrasekhar Limit), the quantum safety net snaps. The gravity becomes so intense that the electrons cannot push back. The star cannot form a peaceful White Dwarf. There is no formula to stop it. It must keep collapsing, falling inward forever, crushing itself into a single point of infinite density. When Chandra presented this at the Royal Astronomical Society, Sir Arthur Eddington,the most powerful physicist in Britain, literally stood up, tore Chandra’s paper to pieces, and ridiculed the idea of stars collapsing into nothingness. Eddington’s ego couldn't accept a universe with such violent, unpredictable geometry. Chandra was completely isolated. The establishment closed ranks around Eddington. Instead of fighting a toxic, biased system, Chandra quietly shifted his focus to other areas of physics, leaving his flawless math in the journals for a future generation to find. Decades later, when advanced telescopes finally spotted real neutron stars and black holes in deep space, the world realized the 19-year-old kid on the boat had been right all along. The philosophical blueprint Chandrasekhar left behind is a vital truth for navigating gatekeepers and institutional pushback: Comforting illusions will always be more popular than harsh, disruptive truths. Trust the math anyway. Most of us approach our careers and projects seeking the validation of the current experts or the established guard. When we propose a radical new idea or try to change a broken system, and the authorities tell us we are wrong, our instinct is to assume our logic is flawed. We abandon our data to fit the consensus. But Chandrasekhar’s legacy proves that institutional authority is not the same thing as truth. Gatekeepers are human; they protect their own theories, their own legacies, and their own comfort. What is an idea, a project, or a direction you’ve abandoned just because an expert or a boss told you it wouldn't work? What happens if you stop looking for their permission and trust the structural integrity of your own work?
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#univers 🌌 | Sommes-nous seuls dans l’Univers ? Exoplanètes, James Webb, océans cachés sous les lunes glacées… Le docu 📺"Secrets de la Science " nous plonge dans les dernières avancées scientifiques avec @astro_allan aux côtés de chercheurs du CEA. 👀👉france.tv/documentaires/docu…
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The multiwavelength observatory INTEGRAL operated for 22 yrs and facilitated progress across a breadth of astrophysical topics. The Project Scientist and team outline some of INTEGRAL's key achievements and its legacy in a Review article: dlvr.it/TSYXZx #astrosci
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🚨Avis aux étudiants de l'@IPSA🚨 Ne manquez pas la conférence exceptionnelle de #RolandLehoucq, astrophysicien au @CEA_Officiel qui aura lieu le mardi 5 mai de 18h00 au 19h30 à l'amphithéâtre de l'#IPSA de Paris-Ivry. Le thème de sa conférence sera "Voyage interstellaire : entre science & imagination". Inscriptions obligatoires pour assister à la conférence à cette adresse mail : [email protected] La conférence sera retransmise sur Youtube à cette adresse : youtube.com/live/A9OqZZuVXCY Image : IPSA
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Conférence passionnante, mercredi soir, de @jmbobi au @LeCnam à #Paris, dans le cadre des conférences mensuelles de la #SociétéAstronomiquedeFrance. Intitulée « Les rêves de l’origine », cette conférence a captivé son public. Image : Joris Bossard
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A propos du livre "Les Rêves de l'Origine" bonnetbidaud.free.fr/cosmo/p… Conférence de la Société Astronomique de France donnée au CNAM- Paris le 8 avril 2026 accessible sous : youtube.com/watch?v=2gB2rAYS…
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Première cartographie thermique de planètes tempérées de taille terrestre: TRAPPIST-1 b et c irfu.cea.fr/Phocea/Vie_des_l…
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L’œuf d'or n'est pas un œuf de Pâques. C'est la vision cosmologique traditionnelle en Inde. Illustrations de Guillaume Duprat dans le livre "Les rêves de l'Origine" bonnetbidaud.free.fr présenté au Conservatoire Arts et Métiers (CNAM le 8 avril 2026)
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Le Big Bang face aux cosmologies anciennes. D'après le livre «Les Rêves de l'origine : Récits extraordinaires de la création du Monde" par Jean-Marc Bonnet-Bidaud, Illustrations Guillaume Duprat (Edition Tana 2025) bonnetbidaud.free.fr/cosmo/p… CNAM Arts et Métiers
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La fin de l'Univers : scénarios pour le dernier acte youtu.be/qDZoLF8XE5w?si=HA4g… via @YouTube
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SVOM and the Civilization of the Transient Sky in China youtu.be/GyxqRUOF7kc?si=Zkd1… via @YouTube
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Part of #CosmicVision, @ESA_Smile is a joint European–Chinese mission that will give us a global picture of the interaction between the Sun and Earth. By improving our understanding of geomagnetic storms, solar wind and space weather, Smile will help keep our technology & astronauts safe. 1/ #CM25
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