François Levrier
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François Levrier
@francoislevrier.bsky.social
120 followers 140 following 290 posts
Professeur d’astrophysique - ENS Paris - Responsable du Master AAIS - Coordinateur de l’action thématique PCMI (Physique et Chimie du Milieu Interstellaire)
(Photo ©A. Vergallo)
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John W. Strutt, Lord Rayleigh, was born #OTD in 1842. His many contributions, most notably in fluid mechanics, optics, and acoustics, are reflected in the large number of phenomena and laws that bear his name.
en.wikipedia.org/wiki/John_Wi...
November 12, 2025 at 5:29 AM
francoislevrier.bsky.social
Mildred Spiewak Dresselhaus was born #OTD in 1930. During her extensive career at MIT, she dedicated a great part of her research to the properties of nanostructures (fullerenes and nanotubes), ushering in new technologies.
en.wikipedia.org/wiki/Mildred...
November 11, 2025 at 7:41 AM
francoislevrier.bsky.social
Carl Sagan was born #OTD in 1934. A pioneer of exobiology, he assembled messages on the Pioneer and Voyager probes and was an early advocate for SETI. He was an outspoken science communicator, writing many books for the general public.
en.wikipedia.org/wiki/Carl_Sa...
November 9, 2025 at 8:20 AM
francoislevrier.bsky.social
Johannes Rydberg was born #OTD in 1854. The Rydberg formula gives the wavelength of light for an electronic transition in hydrogen atoms. In a Rydberg state, one electron is highly excited, making the spectrum hydrogen-like.
en.wikipedia.org/wiki/Johanne...
November 8, 2025 at 7:27 AM
francoislevrier.bsky.social
Edmund Halley was born #OTD in 1656. The second Astronomer Royal, he catalogued the southern hemisphere and computed the periodicity of the comet that bears his name. He demonstrated that stars, far from fixed, undergo proper motions.
en.wikipedia.org/wiki/Edmond_...
November 8, 2025 at 7:26 AM
francoislevrier.bsky.social
Marie Skłodowska-Curie was born #OTD in 1867. One of the most prominent scientists of her time, she pioneered studies of radioactivity, coining the term and discovering two new chemical elements, polonium and radium.
en.wikipedia.org/wiki/Marie_C...
November 7, 2025 at 5:40 AM
francoislevrier.bsky.social
Fred Lawrence Whipple was born #OTD in 1906. He discovered several comets, hypothesizing that their composition was that of an icy conglomerate. He also designed a device to protect spacecraft from the impact of small particles.
en.wikipedia.org/wiki/Fred_La...
November 5, 2025 at 6:38 AM
francoislevrier.bsky.social
Charles K. Kao was born #OTD in 1933. His work on optical fibers proved that attenuation could be significantly reduced by using high-purity fused silica, opening the path to the wide use of this technology in modern communications.
en.wikipedia.org/wiki/Charles...
November 4, 2025 at 5:40 AM
francoislevrier.bsky.social
Alfred Perot was born #OTD in 1863. Together with C. Fabry, he invented a new high-precision, N-wave interferometer made of two semi-reflective plates. The Fabry-Perot interferometer had many applications in spectroscopy.
en.wikipedia.org/wiki/Alfred_...
November 3, 2025 at 6:21 AM
francoislevrier.bsky.social
Harlow Shapley was born #OTD in 1885. Initially opposed to Hubble’s idea that « spiral nebulæ » were galaxies like our own, rather than Galactic objects, he later defended the idea that they are organized in superclusters.
en.wikipedia.org/wiki/Harlow_...
November 2, 2025 at 3:25 PM
francoislevrier.bsky.social
Hermann Bondi was born #OTD in 1919. An Austrian-British cosmologist, he defended the steady-sate model with F. Hoyle and T. Gold. He also explained the nature of gravitational waves and worked on accretion onto compact objects.
en.wikipedia.org/wiki/Hermann...
November 1, 2025 at 8:02 AM
francoislevrier.bsky.social
Galileo Ferraris was born #OTD in 1847. An Italian physicist and electrical engineer, he worked on induction processes, building one of the first polyphase alternators, although he never patented his work, unlike N. Tesla.
en.wikipedia.org/wiki/Galileo...
October 31, 2025 at 6:50 AM
francoislevrier.bsky.social
Homi Bhabha was born #OTD in 1909. He computed the cross-section of electron-positron scattering and described how primary cosmic rays interact with the atmosphere to produce air showers. Post-WWII, he led the Indian nuclear program.
en.wikipedia.org/wiki/Homi_J....
October 30, 2025 at 7:18 AM
francoislevrier.bsky.social
Laura Bassi was born #OTD in 1711. She popularized Newtonian mechanics in Italy. She was one of the first women to earn a PhD and the first to become a teacher at the University of Bologna.
en.wikipedia.org/wiki/Laura_B...
October 29, 2025 at 6:38 AM
francoislevrier.bsky.social
Wilhelm Anderson was born #OTD in 1880. A Russian-Estonian astrophysicist, he worked on the mass limit of white dwarf stars, providing a value that is slightly overestimated because of an invalid uniform-density hypothesis.
en.wikipedia.org/wiki/Wilhelm...
October 28, 2025 at 6:21 AM
francoislevrier.bsky.social
#Publicité #Famille
Une fiction interactive jouée, captée et diffusée en direct sur Twitch, Youtube, Arte.tv mais aussi dans 25 salles de cinéma simultanément, c’est « Les Burgers Sanglants » et c’est ce vendredi 31 octobre à 19h.
October 27, 2025 at 10:14 PM
francoislevrier.bsky.social
Henrietta Hill Swope was born #OTD in 1902. She worked with H. Shapley, then W. Baade, to study variable stars. Using the period-luminosity relation for Cepheids discovered by H. S. Leavitt, she determined the distance to M31.
en.wikipedia.org/wiki/Henriet...
October 26, 2025 at 6:21 AM
francoislevrier.bsky.social
Henry Norris Russell was born #OTD in 1877. An American astronomer who devised the HR diagram, paving the way for stellar evolution studies. With F. Saunders, he developed the L-S coupling scheme for spin-orbit interactions.
en.wikipedia.org/wiki/Henry_N...
October 25, 2025 at 6:33 AM
francoislevrier.bsky.social
Pierre-Gilles de Gennes was born #OTD in 1932. A specialist of « soft-matter » physics, his work on the properties of polymers and liquid crystals, in particular their phase transitions, earned him the 1991 Nobel Prize.
en.wikipedia.org/wiki/Pierre-...
October 24, 2025 at 6:36 AM
francoislevrier.bsky.social
Felix Bloch was born #OTD in 1905. He worked on ferromagnetism, the properties of electrons in solids, and nuclear magnetic induction, for which he received the 1952 Nobel Prize. He was the first Director-General of CERN.
en.wikipedia.org/wiki/Felix_B...
October 23, 2025 at 6:29 AM
francoislevrier.bsky.social
Ilya Frank was born #OTD in 1908. He was awarded the Nobel Prize in 1958. The Frank-Tamm formula gives the spectrum of Cherenkov radiation emitted, per unit length, by a charged particle as it moves faster than light in a material medium.
en.wikipedia.org/wiki/Ilya_Fr...
October 23, 2025 at 6:28 AM
francoislevrier.bsky.social
Karl Guthe Jansky was born #OTD in 1905. A radio engineer with Bell Labs, he investigated sources of static that might interfere with communications, and thus discovered the radio emission from our Galaxy in August 1931.
en.wikipedia.org/wiki/Karl_Gu...
October 22, 2025 at 6:56 AM
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Ingrid van Houten-Groeneveld was born #OTD in 1921. Along with Tom Gehrels and Cornelis Johannes van Houten, she is credited with discovering several thousand asteroids in the Palomar-Leiden survey.
en.wikipedia.org/wiki/Ingrid_...
October 21, 2025 at 6:12 AM
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James Chadwick was born #OTD in 1891. He was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron, identified as the unknown radiation produced through the interaction of alpha particles with beryllium.
en.wikipedia.org/wiki/James_C...
October 20, 2025 at 5:25 AM
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Marguerite Perey was born #OTD in 1909. She discovered francium, one of the rarest naturally-occurring elements, as a product of actinium’s alpha decay. She was the first woman elected to the French « Académie des Sciences ».
en.wikipedia.org/wiki/Marguer...
October 19, 2025 at 6:37 AM