OTD Science Tweets by Robert McNees (important info about this data)
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Jan-01 Satyendra Nath Bose, who established the proper state counting for indistinguishable and non-interacting particles that do not obey the Pauli Exclusion Principle, work which he sent to Einstein in 1924, was born #OTD in 1894. Image: Courtesy Falguni Sarkar/The S.N. Bose Project
Jan-01 Edwin Hubble announced that Andromeda and other spiral nebulae were separate galaxies outside the Milky Way, in a paper read to a @AAAS meeting by H.N. Russell #OTD in 1925. He built on observations by Slipher and relied on Henrietta Swan Leavitt’s studies of Cepheid variables.
Jan-02 Lynn Conway, electricial engineer and computer scientist, co-architect of the VLSI design revolution, and transgender activist, was born #OTD in 1938. She invented Dynamic Instruction Scheduling at IBM, but was fired when they learned she was transitioning. Photo: Lynn Conway
Jan-02 Isaac Asimov, a scientist and prolific popularizer of science, one of the greats of science fiction, may have been born #OTD in 1920. He couldn’t say for sure. But today is the date he chose to celebrate. Photo: Mondadori Portfolio/Getty Images
Jan-03 Artificial transmutation of elements! Ernest Rutherford began a series of experiments #OTD in 1919, with significant but sometimes misreported results. Credit: George Grantham Bain Collection (LOC)
Jan-04 Physicist and mathematician Isaac Newton was born #OTD in 1643. He revolutionized our understanding of mathematics, mechanics, gravity, and optics, and foiled counterfeiters as warden of the Royal Mint. Portrait: Barrington Bramley, after Godfrey Kneller
Jan-05 The dwarf planet Eris was discovered by astronomers Mike Brown, Chad Trujillo, and David Rabinowitz #OTD in 2005. There it is, the tiny moving dot on the left of the gif. More: https://t.co/VJeywnOpgj Image: Mike Brown (@plutokiller)
Jan-05 The German physicist Martin Brendel took the first photograph of an aurora #OTD in 1892, at Alta fjord in northern Norway.
Jan-06 Jean Bernard Léon Foucault experimentally demonstrated the rotation of the Earth #OTD in 1851, setting in motion a 2m-long pendulum with a 5kg brass bob, and observing the slow rotation of its plane of oscillation. Video: Foucault pendulum at @msichicago
Jan-07 Physicist Marguerite Perey discovered Francium #OTD in 1939. It was the last element to be found in a naturally occurring state, rather than synthesized. Image: Musée Curie/ACJC Collection
Jan-08 Alfred Russel Wallace, who independently conceived of a theory of evolution via natural selection that was presented alongside Darwin’s theory in a paper read to the Linnean Society in 1858, was born #OTD in 1823.
Jan-08 Alfred Russel Wallace, Bryce DeWitt, and Stephen Hawking were all born #OTD. Threads on Wallace and Hawking are up, will add DeWitt if I get a chance. Images: unknown; UT Physics History; Santi Visalli/Getty
Jan-08 Stephen Hawking was born #OTD in 1942. He developed theorems with Penrose that determine when general relativity produces singularities, established classical laws of black hole mechanics, and hypothesized that quantum effects make black holes radiate. Image: Santi Visalli/Getty
Jan-09 "I have read your paper with the greatest interest. I had not expected that one could formulate the exact solution of the problem so simply. The analytical treatment of the problem appears to me splendid." –– Einstein's letter to Schwarzschild, #OTD in 1916
Jan-10 Mathematician Ruth Moufang, known for extending Hilbert's axioms for plane geometry to projective geometry, was born #OTD in 1905. The Nazis dismissed her from teaching, but she later became the first German woman professor of mathematics. (Credit in image description)
Jan-10 Project Diana pointed an SCR-271 bed-spring radar antenna at the rising moon #OTD in 1946 and broadcast a series of short signals. Each signal echoed off the moon and returned about 2.5s later, proving that radio could penetrate the ionosphere.
Jan-11 Young astrophysicist Subrahmanyan Chandrasekhar presented his results on electron degeneracy pressure and the maximum mass of a stable white dwarf star to a meeting of the Royal Astronomical Society #OTD in 1935. Beyond that lies neutron stars and black holes. Photo: Getty Images
Jan-12 Gregorio Ricci-Curbastro, the Italian mathematician who invented tensor calculus, was born #OTD in 1853. His early work built on ideas of Gauss, Riemann, and Christoffel; later contributions were done primarily in collaboration with his student Tullio Levi-Civita. https://t.co/D81wXsyJRy
Jan-13 The British Parliament passed the “Act Against Multipliers” #OTD in 1404. The law forbid alchemists from creating precious metals like gold or silver. It was repealed in 1688 due to the efforts of Robert Boyle, whose work was laying the foundations of modern chemistry.
Jan-14 Happy Titanniversary! The intrepid Huygens probe descended through Titan's hazy atmosphere and landed on its surface #OTD in 2005. We’ll be back with a rotorcraft in 2034. Images: ESA/NASA/JPL/University of Arizona
Jan-14 Mathematician Alfred Tarski was born #OTD in 1901. The Banach-Tarski paradox asserts that a ball in three dimensions can be decomposed into a finite number of pieces which, after translation and rotation, can be reassembled into *two* distinct copies of the original ball.
Jan-15 Sofya Kovalevskaya was born #OTD in 1850. She was the first woman to earn a doctorate in mathematics in modern Europe, be appointed to a university chair, and join the editorial board of a scientific journal. She also won the Prix Bordin from the French Academy of Science.
Jan-15 John Cocke and Mike Disney made the first observation of an optical pulsar, in the Crab Nebula, #OTD in 1969. Barely a year after Jocelyn Bell Burnell's discovery of pulsars, it was strong evidence that a neutron star is the remnant of supernova. Image: Nature, Vol. 221 No. 5180
Jan-16 "Dear Sir, I beg to introduce myself to you as a clerk in the Accounts Department of the Port Trust Office at Madras..." The remarkable mathematician Srinivasa Ramanujan sent his letter to the Godfrey Harold Hardy at Cambridge #OTD in 1913.
Jan-16 Astronaut Group 8 was announced by NASA #OTD in 1978. This class of 35 astronauts included the first women, African Americans, and Asian American to travel into space for the US. Image: @NASA
Jan-17 Edwin Hubble submitted his paper "A relation between distance and radial velocity among extra-galactic nebulae" #OTD in 1929. It showed that "extra-galactic nebulae" were moving away from us with a velocity that increased linearly with distance. Image: Carnegie Observatories
Jan-18 The physicist Yoichiro Nambu (南部 陽一郎) was born #OTD in 1921. He developed a theory of spontaneous symmetry breaking to explain superconductivity, paving the way for electroweak symmetry breaking via the Higgs mechanism in the Standard Model. Image: AIP Emilio Segre Archives
Jan-19 A comic strip titled "Be Scientific with Ol' Doc Dabble" appeared in the Los Angeles Times #OTD in 1934, quoting Fritz Zwicky's prediction of neutron stars, supernova, and the origin of cosmic rays. Image: Associated Press, @latimes
Jan-19 Dolly Parton was born #OTD IN 1946. Primarily known as an entertainer, her Imagination Library program has distributed over 100 million free books to kids around the world. Parton has probably done more than any living person to advance childhood literacy.
Jan-20 Buzz Aldrin, pilot of the Apollo 11 Lunar Module and the second person to set foot on the Moon, was born #OTD in 1930.
Jan-20 Léon Rosenfeld told the Princeton Physics Journal Club about his work with Bohr on fission, after Meitner & Frisch's discovery but before its publication. Bohr immediately wrote a letter to Nature #OTD in 1939, asserting the priority of Meitner & Frisch.
Jan-22 Felix Klein lectured “On Hilbert’s first note on the foundations of physics" at the Mathematical Society of Göttingen #OTD in 1918. He included excerpts from letters in which he and Hilbert give priority to Emmy Noether’s results on conservation of energy in general relativity.
Jan-22 Lev Davidovich Landau, perhaps the most influential Soviet theoretical physicist of the 20th century, was born #OTD in 1908. He made foundational contributions to superfluidity, superconductivity, plasma physics, phase transitions, and quantum electrodynamics. Image: D. Gai, 1934
Jan-22 A little thread on Emmy Noether and giving credit. Felix Klein gave a lecture at the Mathematical Society of Göttingen #OTD in 1918. He included excerpts from letters in which he and Hilbert give priority to Emmy Noether’s results on conservation of energy in general relativity.
Jan-23 Gertrude B. Elion, who developed pharmaceuticals by focusing on differences in the biochemistry of healthy human cells and pathogens, co-winner of the 1988 Nobel Prize in Medicine, was born #OTD in 1918. Image: GlaxoSmithKline Heritage Center
Jan-23 The physicist Hideki Yukawa was born #OTD in 1907. In 1934 he predicted the existence of a boson with a mass approximately 200 times that of the electron, based on the range of the strong nuclear force between protons and neutrons in the nucleus. Image: The Asahi Shimbun
Jan-24 A total solar eclipse passed over Long Island and part of New York City #OTD in 1925. Astronomers recorded the event from the US Navy dirigible Los Angeles, positioned near Montauk Point. Video: US Navy footage,
Jan-25 The Swedish mathematician Niels Fabian Helge von Koch was born #OTD in 1870. He discovered the "Koch Snowflake," one of the first examples of a fractal curve.
Jan-25 Joseph Louis Lagrange, who developed the calculus of variations and used it to reformulate all of mechanics, and made foundational contributions to group theory and other areas of mathematics, was born #OTD in 1736. Image: The Wellcome Collection
Jan-26 A thread I wrote last year about the physicist Polykarp Kusch, who was born #OTD in 1911. He measured the magnetic moment of the electron and found a small deviation from the expected value, which is explained by Quantum Electrodynamics.
Jan-26 The Fifth Washington Conference on Theoretical Physics convened #OTD in 1938. The topic was supposed to be low-temperature physics. But Gamow opened the meeting by introducing Bohr, who announced Hahn & Strassmann's discovery and Meitner & Frisch's explanation of nuclear fission.
Jan-27 Einstein gave his "Geometry and Experience" lecture #OTD in 1921, for the Prussian Academy of Science's Leibniz Day. He proposed that the question of whether the Universe is spatially finite might be answered via *measurement*. Photo: Ferdinand Schmutzer/Musée Historique de Berne
Jan-28 Physicist Kathleen Yardley Lonsdale was born #OTD in 1907. She pioneered the used of X-ray diffraction to study the structure of crystals; one of her earliest results showed that Benzene's ring structure is flat. Image: University of Kent
Jan-29 The physicist Abdus Salam was born #OTD in 1926. He proposed the electroweak theory that unifies the electromagnetic & weak interactions, and did foundational work on grand unified theories that incorporate the strong interaction in a similar framework. Image: ICTP Photo Library
Jan-29 Isaac Newton was made aware of Jean Bernoulli's "brachistochrone" problem #OTD in 1697. He solved it later that evening, showing that the curve of fastest descent between two points was given by a portion of a cycloid. https://t.co/YGRD2KiwDG
Jan-30 Maurice Wilkins, Francis Crick, and James Watson stole Rosalind Franklin's data #OTD in 1953 when Wilkins, without Franklin's permission, shared her "photograph 51" with Watson. The Crick and Watson double helix paper was published in Nature about three months later.
Jan-30 Engineer and inventor Douglas Engelbart was born #OTD in 1925. His team at SRI developed or contributed to the computer mouse, hypertext, networked computers, and graphical interfaces, all of which were presented at the “Mother of All Demos” in 1968. Image: ARC Bootstrapper
Jan-31 HAM the chimpanzee became the first hominid in space #OTD in 1961, launched on a sub-orbital flight aboard Mercury-Redstone 2. His name was an acronym for Holloman Aerospace Medical Center and a nod to its commanding officer Lt Col Hamilton Blackshear. Image: NASA (Photo AA-984)
Jan-31 Anyway, Ham the space chimp did great on his mission! His short sub-orbital mission paved the way for Alan Shepard’s flight aboard Freedom 7 about three months later. Here's a photo of someone giving Ham an apple after he was pulled from the Atlantic #OTD in 1961. Source: NASA
Jan-31 Albert Einstein submitted his paper “Über Gravitationswellen” #OTD in 1918. "On Gravitational Waves" corrects an important mistake in his 1916 paper and gives the correct description of gravitational waves in general relativity.
Jan-31 Physicist Rudolph Mössbauer was born #OTD in 1929. He is best known for his eponymous scattering phenomenon in which gamma rays are absorbed without recoil by nuclei in a crystal lattice. This allows frequency measurements precise enough for tests of general relativity.
Feb-01 Nuclear physicist Melba Newell Phillips was born #OTD in 1907. Author of two standard textbooks and numerous articles on physics history, she worked tirelessly to promote the teaching of physics as an AAPT member. Photo: AIP Emilio Segrè Archives, Esther Mintz Collection
Feb-02 Paul Dirac's paper on the quantum emission and absorption of radiation, advancing the first truly quantum theory of electrodynamics, was submitted to the Royal Society #OTD in 1927. It is considered by many to mark the beginning of Quantum Field Theory.
Feb-03 The Soviet space probe Luna 9 landed on the Moon #OTD in 1966, touching down in the Ocean of Storms for the first successful soft landing on another celestial body. It sent back grainy tv camera images – the first pictures beamed to Earth from the surface of another world.. Image: NASA
Feb-04 Astronomer Clyde Tombaugh was born #OTD in 1906. He discovered Pluto in 1930, then traveled to it in 2015 when the New Horizons spacecraft made its flyby with some of his ashes onboard. Images: Lowell Observatory Archive; NASA/JHUAPL/SwRI
Feb-04 My favorite serendipitous alignment of author names and paper topic occurred #OTD in 1992, when Dr. D'Eath and Dr. Payne submitted 3 papers to Physical Review exploring the physics of black holes smashing into each other at relativistic speeds.
Feb-05 Maarten Schmidt recognized the Balmer series in the spectra of radio source 3C 273 #OTD in 1963. The large redshift meant the quasi-stellar object, or "quasar," was about 3 billion light years away & brighter than the brightest known galaxy! (J. McClanahan/Caltech Archive)
Feb-06 Mariner 10 took this ultraviolet image of Venus #OTD in 1974, during the first interplanetary gravitational slingshot maneuver. Image: NASA/UW Madison Archives
Feb-06 Alan Shepard: "I think I got more dirt than ball there." Houston: "That looked like a slice to me, Al." Astronaut Alan Shepard hit a golf ball on the moon #OTD in 1971. Footage: NASA
Feb-07 Bruce McCandless and Robert Stewart, mission specialists on the Space Shuttle Challenger during STS-41-B, performed the first untethered spacewalks #OTD in 1984. They used nitrogen-propelled maneuvering units. Images: NASA
Feb-07 Harvey Washington Banks, the first African American to receive a PhD in Astronomy, was born #OTD in 1923. His 1961 dissertation (Georgetown) was on the spectrum of Titanium. A professor at Delaware State & later Howard, he worked on spectroscopy, geodetics, & celestial mechanics.
Feb-08 Einstein submitted his paper "Cosmological Considerations in the General Theory of Relativity" to the Prussian Academy #OTD in 1917. It marked the birth of relativistic cosmology, and introduced a Cosmological Constant term into the field equations of GR.
Feb-09 Mathematician Irene Stegun was born #OTD in 1919. A major contributor to the Works Progress Administration’s Mathematical Tables Project, she’s probably best known as co-author of the classic “A Handbook of Mathematical Functions” — usually referred to as “Abramowitz and Stegun“.
Feb-09 The Hungarian mathematician Farkas Bolyai was born #OTD in 1775. He was obsessed with Euclid's 5th postulate and tried to prove it without success. His rebellious son János went in the opposite direction and became one of the founders, with Lobachevsky, of non-Euclidean geometry.
Feb-10 The Irish astronomer and science writer Agnes Mary Clerke was born #OTD in 1842. She wrote hundreds of articles and several books that she herself described as "popular," but that were highly regarded for their rigor. Image: Public domain/@smithsonian Institution
Feb-11 The @LIGO & @ego_virgo collaborations officially announced the first direct detection of gravitational waves #OTD in 2016. Today marks five years of this remarkable new tool for understanding the universe.
Feb-11 Lise Meitner and Otto Frisch's explanation of nuclear fission, "Disintegration of Uranium by Neutrons: A New Type of Nuclear Reaction," was published in the journal Nature #OTD in 1939.
Feb-11 Banting, Best, and Collip published their initial results on the use of insulin to treat diabetes #OTD in 1922. They later sold the patent to University of Toronto for $1 each, hoping the agreement would keep the lifesaving medication cheap and accessible.
Feb-12 The naturalist Charles Darwin, who laid out a theory of evolution driven by natural selection in his book “On the Origin of Species,” was born #OTD in 1809. Portrait: George Richmond
Feb-13 [Levon Helm voice] "There was a demon that lived in the air. They said whoever challenged him would die…The demon lived at Mach 1 on the meter, 750 miles an hour, where the air could no longer move out of the way." Chuck Yeager, who broke the sound barrier, was born #OTD in 1923
Feb-14 "That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives." —Carl Sagan Voyager 1 captured the "Pale Blue Dot" image thirty years ago, #OTD in 1990. Image: NASA/JPL-Caltech
Feb-14 The Pale Blue Dot was just one frame from a mosaic of 60 images recorded by the Voyager 1 cameras #OTD in 1990. Earth, Venus, Jupiter, Saturn, Uranus and Neptune are all visible, though Earth and Venus were each just a fraction of a pixel.
Feb-15 Emmy Noether sent a postcard to Felix Klein #OTD in 1918, explaining a special case of her second theorem. The full result was published later that year in her "Invariante Variationsprobleme" paper. Reproduction: "The Noether Theorems", Yvette Kosmann-Schwarzbach, Springer (2011)
Feb-15 Astronaut and former Detroit Lions wide receiver Leland Melvin (@astro_flow) was born #OTD in 1964. Here he is in the greatest photo that the US space program has ever produced.
Image: NASA
Feb-17 “There are then innumerable suns, and an infinite number of earths revolve around those suns, just as the seven we can observe revolve around this sun which is close to us.” –– Giordano Bruno, burned at the stake for heresy #OTD in 1600.
Feb-17 Mathematician Rózsa Péter was born #OTD in 1905. She was one of the founders of Recursion Theory –– also known as Computability Theory –– along with Godel, Church, and Turing.
Feb-18 Clyde Tombaugh discovered Pluto #OTD in 1930, while comparing photographic plates he had taken the previous month. The name Pluto was suggested a month later by Venetia Burney, an 11 year old girl from Oxford. Credit: Lowell Observatory Archives
Feb-19 Edwin Hubble sent a letter to Harlow Shapley #OTD in 1924, describing data that placed the Andromeda Nebula outside our Milky Way. Shapley, who had long argued such objects were inside our galaxy, said to Cecilia Payne-Gaposchkin: “Here is the letter that destroyed my universe.”
Feb-20 The Mercury-Atlas 6 mission launched #OTD in 1962. John Glenn became the first American to orbit Earth, circling 3 times in the Friendship 7 capsule. But Glenn didn’t trust the computer controlled trajectory until mathematician Katherine Johnson checked it by hand. Credit: NASA
Feb-20 Ludwig Boltzmann, who developed the statistical mechanics that describes how bulk properties of matter emerge from the behavior of its microscopic constituents, was born #OTD in 1844. Image: AIP Emilio Segré Visual Archives
Feb-21 The mathematician W.K. Clifford read a remarkable paper to the Cambridge Philosophical Society #OTD in 1870. "On the Space-Theory of Matter" speculated that space might on average be described by Euclidean geometry, but behave more like the geometry of Riemann on small scales.
Feb-22 Writer and illustrator Edward Gorey was born in Chicago, of all places, #OTD in 1925.
Feb-23 Light from supernova 1987A, the closest and brightest supernova in hundreds of years, reached Earth #OTD in 1987. The Hubble space telescope captured this spectacular image for the 30 year anniversary in 2017. Credits: NASA, ESA, R. Kirshner (Harvard-Smithsonian CfA, Gordon and Betty Moore Foundation), M. Mutchler and R. Avila (STScI)
Feb-24 Jocelyn Bell and Anthony Hewish announced their discovery of a “rapidly pulsating radio source” — what we now call a “pulsar” — with a paper in @nature #OTD in 1968.
Feb-24 Herb Greenlee, on behalf of DZero, and Mel Shochet, representing CDF, simultaneously submitted papers to Physical Review Letters #OTD in 1995, announcing that their collaborations had discovered the Top quark at @Fermilab.
Feb-25 A solar eclipse passed over Sudan #OTD in 1952. The National Geographic Society and Naval Research Lab sent a group to Khartoum to measure relativistic deflection of starlight. Their result was 1.70±0.10 arcseconds, which matches the value of 1.75 predicted by general relativity.
Feb-26 Physicist, astronomer, and mathematician François Arago was born #OTD in 1786. In 1818, while serving as head of a committee convened by the French Academy of Sciences, he made a marvelous observation confirming Fresnel's new wave theory of light. Images: Wellcome Trust
Feb-27 Medical researcher Charles Best, who identified insulin as a treatment for diabetes and tried to gift it to the world so that it couldn't be held hostage by pharmaceutical profiteers, was born #OTD in 1899.
Feb-27 Physicist Alan Guth, who pioneered the idea of cosmic inflation with Starobinsky and others, was born #OTD in 1947. Inflation posits a period of rapid expansion in the early Universe, explaining some large scale properties we see (or don’t see) today.
Feb-28 Chandrasekhara Venkata Raman discovered the inelastic scattering of light by molecules in various liquids #OTD in 1928. Unlike elastic scattering, which changes the direction but not the frequency of photons, Raman's effect produces a range of frequencies for the scattered light.
Feb-29 Finally, a leap year! [SHOWTURTLE] 🐢 That means we get a February 29th #OTD. [FORWARD 4] ----🐢 [DRAW BIRTHDAY CAKE] ----🎂🐢 Seymour Papert, co-inventor of LOGO, was born #OTD in 1928. [BACK 4] 🐢 🎂 This one’s for you, nerds of a certain age. Image: Cynthia Solomon
Mar-01 Robert Cornelius, who in 1839 was the first person in the U.S. to take a selfie, was born #OTD in 1809. Image: Robert Cornelius / Library of Congress
Mar-02 The Pioneer 10 spacecraft launched #OTD in 1972. It was a mission of firsts: passing through the asteroid belt, visiting Jupiter, crossing the orbits of Neptune and then Pluto. We detected a last, faint signal on January 23, 2003. Now it belongs to the cosmos. Images: NASA
Mar-02 The Pioneer 10 spacecraft, launched #OTD in 1972, famously features a gold-anodized aluminum plaque. It was suggested by science journalist Eric Burgess, designed by Carl Sagan and Frank Drake, and illustrated by Linda Salzman Sagan.
Mar-03 Happy 157th birthday to the National Academy of Sciences. The Senate and House passed a bill incorporating the @theNASciences and President Lincoln signed it into law #OTD in 1863. Image: Albert Herter’s 1924 painting of the 1863 signing ceremony
Mar-03 The mathematician Georg Cantor was born #OTD in 1845. He is the founder of set theory, and developed the concepts of cardinal and transfinite numbers. His shocking results led his former professor Kronecker to call him a "corrupter of youth." Image: Oberwolfach Photo Collection
Mar-04 Physicist & chemist Richard Chace Tolman, who showed that electricity in metal is due to the flow of electrons, developed relativistic applications of thermodynamics, & served as science advisor to Gen. Leslie Groves during WWII, was born #OTD in 1881. Image: Caltech/Oregon State
Mar-04 Tolman's pioneering approach to understanding cosmological history in terms of thermodynamics was extended by George Gamow in his work on big bang nucleosynthesis. Gamow was also born #OTD, in 1904! What are the odds!? (About 0.27%)
Mar-04 As I mentioned in my Tolman thread, George Gamow was also born #OTD. Here is a thread about the letter that Gamow sent to Bohr outlining his early work on Big Bang Nucleosynthesis.
Mar-05 Voyager 1 made its closest approach to Jupiter #OTD in 1979, passing just 172,000 miles above the cloud tops. This 3 minute exposure, taken from Jupiter's night side, shows aurora over the north pole and bright spots which are thought to be lightning. Image: NASA/JPL
Mar-06 Valentina Vladimirovna Tereshkova, the first woman and first civilian in space, was born #OTD in 1937. She orbited the Earth 48 times aboard the Vostok 6 spacecraft in 1963. Her three day flight was more time than all US astronauts had spent in space up to that point, combined.
Mar-06 "In these rude collections, which are only the gleanings of my private diversions in broken hours..." Henry Oldenburg published the first issue of "Philosophical Transactions of the Royal Society" #OTD in 1665. It was the world's first scientific journal.
Mar-07 What was expected to be the "comet of the century" was spotted #OTD in 1973 by Luboš Kohoutek. It eventually became bright enough to see, but Comet Kohoutek remained much dimmer than astronomers predicted and was considered a bust by the public ☄️ 🔭🙁 Image: Table Mountain Obs.
Mar-07 Hermann Weyl submitted "Gravitation and the electron" #OTD in 1929, a follow-up to his 1928 paper "Gruppentheorie und Quantenmechanik." It was the first use of the now-ubiquitous (in physics) term "gauge invariance" in the English language! Open Access:
Mar-08 Voyager 1 captured the first evidence of an extraterrestrial volcanic eruption #OTD in 1979. The plume in this image was discovered by astronomer Linda A. Morabito, working as a JPL engineer at the time, and announced a few days later. Image: NASA/JPL
Mar-08 In my #OTD threads I try my best to draw attention to important scientists who historically haven't received the same recognition as their peers. A science education involves a lot of lore: Stories and anecdotes meant to flesh out a narrative about the development of a field.
Mar-08 My education didn't teach me many of those stories. The anecdotes were always about someone who looked like the person telling the anecdote. So some of these #OTD threads are me making sure I can relate a coherent history of my field that all my students can see themselves in.
Mar-09 ☝️A short thread on Pound and Rebka's experimental test of the equivalence principle, submitted to @PhysRevLett 60 years ago #OTD.
Mar-10 Astronomers Edward Dunham, James Elliot, and Jessica Mink discovered the rings of Uranus #OTD in 1977 when they saw unexpected flickers in star SAO 158687 just before and after its occultation by the planet. Fig: Nature, 267, 328–330 (1977)
Mar-11 Vannevar Bush, an electrical engineer who built one of the first analog computers, was born #OTD in 1890. He headed the Office of Scientific Research and Development during WWII, proposed what became the @NSF, and devised an early hypertext system.
Mar-12 Astronomer Ellen Dorrit Hoffleit was born #OTD in 1907. She discovered more than 1,000 new variable stars over the course of her career, worked in the observatories of Harvard and Yale, and edited the Bright Star Catalog. Image: American Association of Variable Star Observers
Mar-13 Clyde Tombaugh's discovery of Pluto was announced #OTD in 1930. Here it is dashing across his photographic plates, alongside an image taken just after New Horizon's closest approach back in July 2015. Images: Lowell Observatory / National Geographic (July 1939); NASA/JHUAPL/SwRI
Mar-13 The announcement was made on that date for two reasons. First, to honor Percival Lowell, born #OTD in 1855. Lowell first hypothesized the existence of Pluto to explain irregularities in the orbit of Uranus.
Mar-13 And second, to commemorate the discovery of Uranus, smooth as an egg and monstrously featureless to the human eye, by William Herschel #OTD in 1781. Image: NASA/JPL
Mar-13 The other reason for making the announcement on March 13 was to celebrate the anniversary of Herschel's discovery of Uranus #OTD in 1781. After all, it was irregularities in that orbit of Uranus that prompted Lowell's search. Image: E. Scriven / Wellcome Collection
Mar-13 Erwin Schrödinger's "Quantisierung als Eigenwertproblem," the first of six remarkable papers laying out his wave formulation of quantum mechanics, was published in Annalen der Physik #OTD in 1926.
Mar-13 Haha, I tweeted an #OTD thread about the announcement of the discovery of Pluto, and then I got this promoted tweet.
Mar-14 Albert Einstein was born #OTD in 1879. This is my annual plea to help dig up info about this little-known figure. His contributions, while minor, are still of some interest to me personally. I’d appreciate your help tracking down any of his work. (Photo taken by Paul Ehrenfest)
Mar-15 Mathematician Grace Chisolm Young, author or co-author of a host of articles and books on set theory, geometry, topology, and calculus, and the first woman to officially earn a doctoral degree from the University of Göttingen, was born #OTD in 1868. Image: Sylvia Wiegand / MAA
Mar-15 Edwin Hubble's "A relation between distance and radial velocity among extra-galactic nebulae" appeared in the Proceedings of the National Academy of Sciences #OTD in 1929.
Mar-16 The astronomer Caroline Herschel was born #OTD in 1750. She discovered and catalogued comets, stars, and nebulae, and, along with Mary Somerville, was the first woman elected to the Royal Astronomical Society. Image: Artist unknown (
Mar-17 Albert Einstein, age 26, sent his paper "Concerning an Heuristic Point of View Toward the Emission and Transformation of Light" to Annalen der Physik #OTD in 1905. It explained the photoelectric effect and established the reality of quanta.
Mar-18 Schrödinger submitted "On the relation between the quantum mechanics of Heisenberg, Born, and Jordan, and that of Schrödinger" to Annalen der Physik #OTD in 1926. It demonstrated that the wave and matrix approaches to quantum mechanics are equivalent.
Mar-19 Astronomer Margaret Harwood, who studied variable stars & asteroids, and worked as a computer at the Harvard Observatory before serving for 41 years as director of the Maria Mitchell Observatory, was born #OTD in 1885. Image: Acc. 90-105, Smithsonian Institution Archives
Mar-20 Einstein submitted "The Foundations of the General Theory of Relativity” to Annalen der Physik #OTD in 1916. It collected his work from throughout 1915, presenting the broader scientific community with a complete and coherent account of general relativity.
Mar-21 The astronomer Antonia Maury was born #OTD in 1866. She devised an entirely new stellar classification system that accounted for the strength and width of spectral lines, and conducted spectroscopic studies of binary stars. Image: Vassar College senior year photograph
Mar-21 Jean Baptiste Joseph Fourier was born #OTD in 1768. Among his many contributions was the idea, first presented in "Théorie analytique de la chaleur" (1822), that functions (subject to conditions described by Dirichlet) on a finite interval can be expressed as a sum of sine waves.
Mar-22 The physicist Robert Millikan was born #OTD in 1868. He is best known for his “oil drop” experiment that measured the charge of the electron, but his next experiment may have been even more important. Image: APS
Mar-23 The mathematician Emmy Noether was born #OTD in 1882. She made groundbreaking advances in abstract algebra, and her eponymous theorems articulated the deep connection between symmetries and conserved quantities in physics. Image: Public domain, photographer unknown
Mar-24 Walter Baade, who with Fritz Zwicky introduced the term "supernova" and hypothesized the existence of neutron stars, was born #OTD in 1893. Image: George Stranahan / Caltech
Mar-25 Happy #Titanniversary! Huygens discovered Saturn’s moon Titan #OTD in 1655, using a telescope he built with his brother. This mosaic of near-infrared images was captured by the Cassini spacecraft in August 2014. Credit: NASA/JPL/Univ. Arizona/U. Idaho
Mar-25 Physicist Caroline Herzenberg was born #OTD in 1932. She is known for pioneering early work in Mössbauer spectroscopy, including an analysis of the first samples returned from the moon by the Apollo astronauts. Image: Herzenberg as Finalist in the 1949 Science Talent Search
Mar-26 A curious article titled “Four-dimensional space” appeared in Nature #OTD in 1885. The pseudonymous author “S” imagined a four-dimensional union of space and time, very much like the setting that Minkowski proposed in 1907-1908 for Einstein's relativity.
Mar-27 Wolfgang Pauli's "Über das Wasserstoffspektrum vom Standpunkt der neuen Quantenmechanik" was published #OTD in 1926, a tour-de-force calculation in which he used the new matrix formulation of quantum mechanics to compute the spectrum of the Hydrogen atom.
Mar-27 The French civil engineer Charles Joseph Minard was born #OTD in 1781. He was known for his contributions to information graphics, including his famous map of the losses suffered by Napoleon during the 1812 Russian campaign.
Mar-28 Happy 71st birthday to the name "Big Bang"! Fred Hoyle accidentally coined a term for the prevailing model of the early Universe #OTD in 1949. Defending his steady state theory on the BBC he criticized "the hypothesis that all matter of the universe was created in one big bang."
Mar-29 The Mariner 10 spacecraft made its closest approach to Mercury #OTD in 1974. It sent back photos that showed an unprecedented level of detail, taken from less than 6,000 km above the surface.
Mar-30 Physicist David Mermin was born #OTD in 1935. He has made contributions to condensed matter physics and QM, may have coined "shut up and calculate," and is a prolific writer of and about science. My favorite Merminism are these entries from the index of his solid state textbook.
Mar-31 The physicist Tomonaga Shin'ichirō (朝永 振一郎) was born #OTD in 1906. In 1943 he discovered renormalization using a formulation of Quantum Electrodynamics that he called "super-many-time theory", a result that preceded work by Schwinger and Feynman. Image: Bettmann/Corbis
Mar-31 Astrophysicist Joan Feynman was born #OTD in 1927. She explained the origin of auroras, discovered that coronal mass ejections could be identified by the amount of helium in the solar wind, and elucidated the structure of Earth's magnetosphere. Image: Charles Hirshberg
Apr-01 The particle physicist Mary Katharine Gaillard was born #OTD in 1939. She and Benjamin Lee predicted the mass of the charm quark in 1974, and she was the first tenured woman on the physics faculty at UC Berkeley. Image: Emilio Segre Visual Archives/AIP/SPL
Apr-01 Mathematician Marie-Sophie Germain was born #OTD in 1776. She established important early results in the study of both Fermat’s Last Theorem and the theory of elasticity, and was the first woman to win the Prix Extraordinaire of the Paris Academy of Sciences. Image: Wikimedia
Apr-02 The very first photograph of the sun was taken #OTD in 1845. It was a daguerreotype made with a 1/60 second exposure by the physicists Louis Fizeau and Léon Foucault.
Apr-03 The primatologist Jane Goodall was born #OTD in 1934. Her study of chimpanzees in the Gombe Stream Reserve in Tanzania, which began in 1960, became the longest running continuous study of animals in the wild. Image: Michael Neugebauer / Carnegie Science Center
Apr-03 I don't usually post an #OTD unless it is connected to physics, math, or astro, but there is a story I really like about Jane Goodall that I wanted to mention. You've probably all heard it before.
Apr-04 Shing-Tung Yau (丘成桐), Fields Medalist who proved Calabi's conjecture on the existence of unique metrics with certain properties on compact, complex Kähler manifolds, and who proved the positivity of ADM mass in general relativity, was born #OTD in 1949. Image: D. Ferus, Berlin
Apr-05 The physicist Louise Dolan, who authored a foundational paper on symmetries & phase transitions at finite temperature, and received the @APS Maria Goeppert-Mayer Award for discovering applications of Kac-Moody algebras in string and field theory, was born #OTD in 1950. Image: IAS
Apr-05 ☝️An #OTD thread from last year about physicist Hedwig Kohn.
Apr-06 The engineer and photographer Harold Edgerton was born #OTD in 1903. He pioneered various forms of high-speed photography using specialized cameras, strobe lighting, and other techniques. You’ve seen his work! Images: MIT; H. Edgerton
Apr-07 Astronauts Don Peterson and Story Musgrave performed the Space Shuttle Program's first spacewalk #OTD in 1983, during the shuttle Challenger's first mission. Image Credit: NASA
Apr-08 The astronomer Kent Ford was born #OTD in 1931. He is best known for his pioneering work on imaging tubes for capturing astronomical data electronically, and collaborations with Vera Rubin that helped build the case for the existence of Dark Matter. Image: Michael Lucibella / APS
Apr-09 Mathematician and aerospace engineer Mary Jackson was born #OTD in 1921. She worked at the National Advisory Committee for Aeronautics until it was succeeded by NASA in 1958. Jackson then became the first black woman to work as a NASA engineer.
Apr-10 Einstein, fascinated by mathematically elegant but physically unsatisfactory theories put forward by Mie, Hilbert, and Weyl, read his paper "Do gravitational fields play an essential role in the structure of elementary particles?" to the Prussian Academy #OTD in 1919.
Apr-11 The chemist Reatha Clark King was born #OTD in 1938. Her calorimetry work on gaseous fluorine compounds at the National Bureau of Standards contributed to NASA's investigations of various rocket fuels for the space program. Image: Reatha Clark King / Science History Institute
Apr-12 Cosmonaut Yuri Gagarin became the first human to travel into space #OTD in 1961, completing one orbit of the Earth during a flight that lasted one hour and 48 minutes. Image: Popperfoto/Getty Images
Apr-13 Mathematician Stanislaw Ulam was born #OTD in 1909. He co-discovered cellular automata with von Neumann, proposed the nuclear pulse propulsion that led to Project Orion, and unfortunately may have pitched the idea that led Teller to the hydrogen bomb. Image: Amer. Phil. Soc.
Apr-13 For the last several years of his life, Albert Einstein suffered from an abdominal aortic aneurysm. It ruptured #OTD in 1955. But Einstein declined life-saving surgery, telling his doctors "I have done my share, it is time to go."
Apr-14 John Cockcroft and Thomas Walton used their new accelerator to achieve the "disintegration of Lithium by swift protons" #OTD in 1932. It was the first entirely artificial splitting of a nucleus.
Apr-15 "After dinner, the weather being warm, we went into the garden and drank thea, under the shade of some apple trees." Isaac Newton met with the writer William Stukeley #OTD in 1726, recounting a story of a falling apple that Stukeley would later publish.
Apr-15 Physicist Robert L. Mills was born #OTD in 1927. With his officemate C. N. Yang, he developed a relativistic field theory based on the principle of local invariance under a non-abelian symmetry group. Yang-Mills theory is the framework for the Standard Model of particle physics.
Apr-16 Biochemist Marie Maynard Daly, who studied correlations between heart attacks and cholesterol, and between smoking and lung disease, was born #OTD in 1921. She was the first African American woman to receive a chemistry PhD in the US. Image: National Institutes of Health
Apr-17 Robert R. Wilson, first director of Fermilab, famously testified in front of the Congressional Joint Committee on Atomic Energy #OTD in 1969. In making the case for building Fermilab he delivered a lovely justification for a national commitment to basic science. Image: Fermilab
Apr-18 Albert Einstein passed away #OTD in 1955. Complications from a ruptured abdominal aneurysm. Doctors recommended surgical intervention but Einstein declined. “I have done my share; it is time to go. I will do it elegantly." Here’s his office as he left it. Image: R. Morse/LIFE
Apr-19 “Albert Einstein Lived Here” Herb Block's cartoon memorializing Einstein appeared #OTD in 1955, the day after Einstein’s death, in the @washingtonpost. Image: Herb Block / Library of Congress
Apr-19 NASA announced the crews for the 7th and 8th space shuttle flights #OTD in 1982. They included Dr. Sally Ride, the first American woman in space, and Dr. Guion Bluford (Lieutenant Colonel, USAF), the first African American in space.
Apr-19 Here’s an #OTD thread from a few years ago that is really a story about something I have in common with my grandfather, who was my first scientific role model.
Apr-20 Gravity Probe B launched #OTD in 2004. The satellite-based experiment used four exquisitely polished gyroscopes coated with superconducting niobium to test the Lense-Thirring (frame dragging) and geodetic effects predicted by general relativity. Image:
Apr-22 Julius Robert Oppenheimer, the physicist best known for directing scientific work at Los Alamos during the Manhattan Project, was born #OTD in 1904. His important contributions to quantum mechanics, astrophysics, and relativity are not as well known! Image: Ed Westcott
Apr-23 "We had observed the oldest and largest structures ever seen in the early universe." George Smoot and the Cosmic Background Explorer (COBE) team announced the detection of minute anisotropies in the 2.7 K cosmic background radiation #OTD in 1992. Image:
Apr-24 The Hubble Space Telescope was launched #OTD in 1990. Happy 30th birthday @NASAHubble! #Hubble30 The nebulas NGC 2014 and NGC 2020, which make up an enormous star forming region in the Large Magellanic Cloud. Image: NASA, ESA, and STScI
Apr-25 Wolfgang Pauli was born #OTD in 1900. He postulated a "non-classically describable two-valuedness" of electrons which led to the idea of spin and his eponymous Exclusion Principle, made important contributions to quantum mechanics and QFT, and proposed the neutrino. Image: CERN
Apr-26 Naturalist and ornithologist John James Audubon was born #OTD in 1785. Go outside and look at some good birbs. Or watch them out your window — whichever way feels safest to you and in keeping social distancing directives. But look at some birds. Portrait: John Syme
Apr-27 Final telemetry data was received from the Pioneer 10 spacecraft #OTD in 2002, over 30 years after launch. It sent a few more whispers after that, but a year later its power source could no longer support transmissions and it quietly sailed off* into endless dark. *At 30,000 mph
Apr-27 Lord Kelvin delivered his lecture "Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light” to the Royal Institution of Great Britain #OTD in 1900. In it, he spelled out two major problems that 19th century physics seemed unable to address.
Apr-28 The physicist, mathematician, and electrical engineer Hertha Ayrton was born #OTD in 1854. She conducted foundational studies of electrical arcs, as well as the dynamics of ripple formation in sand. Portaint: Helena Arsène Darmesteter, Girton College
Apr-29 Physicist Marietta Blau was born #OTD in 1894. She pioneered the use of nuclear emulsion plates for particle detection, and discovered "disintegration stars" produced by cosmic rays interacting with nuclei in the plates. Photo: Agnes Rodhe
Apr-30 Albert Einstein submitted his dissertation “A New Determination of Molecular Dimensions“ to the University of Zürich #OTD in 1905. It was only 21 pages long! His committee complained that it was a little short.
Apr-30 Actually, I should have been more careful. Einstein *completed* the dissertation #OTD in 1905, but I don't think he officially submitted it until July 20. It was approved not long after, and Annalen der Physik received an edited version for publication on August 19.
Apr-30 Electrical engineer and computer scientist Harriet Rigas was born #OTD in 1934. Among other contributions, she developed the basic ideas that enable patching software without having to replace the entire program. Image: Washington State University
May-01 The first program written in Beginner’s All Purpose Symbolic Instruction Code — BASIC — ran #OTD in 1964. The language was designed by John G. Kemeny, Thomas E. Kurtz and Sister Mary Kenneth Keller. The program was: 10 PRINT 2+2 20 END Image: Dartmouth College
May-01 James Van Allen announced the discovery of radiation belts surrounding the Earth #OTD in 1958. Random anecdote: When I was a kid we had a picnic table that Van Allen helped build. His name was carved on the bottom with a wood-burning tool. Image: NASA
May-03 Physicist Steven Weinberg was born #OTD in 1933. His 1967 paper "A Model of Leptons" presented a unified theory of the electromagnetic and weak nuclear interactions, and is the most cited paper in particle physics. Image: AIP Emilio Segrè Visual Archives
May-04 Mathematician William Clifford was born #OTD in 1845. He introduced the notion of geometric algebra, and in 1870 - 45 years before general relativity - he proposed that space might deviate from Euclid's geometry according to some dynamics. Image: National Portrait Gallery, London
May-05 Alan Shepard became the first American in space #OTD in 1961, in a flight that lasted 15 minutes and took him 101 miles above the Earth. His Freedom 7 capsule was launched atop a Redstone missile, along a trajectory calculated by mathematician Katherine Johnson. Image: NASA
May-06 The physicist and astronomer Willem de Sitter was born #OTD in 1872. He is best known for his work in Cosmology, applying Einstein’s general relativity to the dynamics and history of the universe. Image:
May-06 Incoming #OTD that I started last year, but was then interrupted. Don't have much time for it but would like to say more than I managed to last year...
May-06 The physicist Robert H. Dicke was born #OTD in 1916. An accomplished theorist and experimentalist, he invented the lock-in amplifier & microwave radiometer, performed delicate tests of general relativity, and predicted the existence of the Cosmic Microwave Background Image: AIP
May-07 Supposedly, Isaack Fubine of the Hague managed to patent macaroni #OTD in 1660. What I need you to know is that there used to be a trade pub called “Macaroni Journal" with headlines like "Macaroni is Fashionable" and "A Big Program for Busy Business Men."
May-08 Sir David Attenborough was born #OTD in 1926. I’d happily listen to him narrate the instructions for a stack of tax return forms. Image: BBC
May-09 Einstein, touring the U.S. to raise funds for Hebrew University in Jerusalem, arrived in Princeton #OTD in 1921 to deliver a week of lectures on his still-controversial theory of general relativity. Those lectures were the basis for his book "The Meaning of Relativity."
May-10 Astronomer Cecilia Payne-Gaposchkin was born #OTD in 1900. She decoded spectral lines of stars to deduce their elemental composition (concluding they are mostly H and He) and was the first woman to be made full professor and department chair at Harvard. Image: Harvard Observatory
May-11 Physicist Sau Lan Wu was born #OTD in 1940. She was co-discoverer of three jet events in the TASSO experiment at DESY (considered evidence for the existence of gluons), was on the team that discovered the J/Ψ particle, and works on the ATLAS experiment at CERN. Image: UW-Madison
May-12 Biochemist Dorothy Crowfoot Hodgkin was born #OTD in 1910. She used X-ray crystallography and related techniques to discovered the structure of penicillin, vitamin B₁₂, and insulin. Image: Daily Herald Archive/National Science & Media Museum/SSPL
May-12 Happy 90th birthday to @AdlerPlanet! They first opened their doors to the public #OTD in 1930.
May-12 Florence Nightingale was born #OTD in 1820. Though she is best known as a nurse –– perhaps a gendered interpretation of her contributions –– she did pioneering work applying statistics to public health. Image: The National Archives (UK)
May-13 Seismologist Inge Lehmann, one of the first women to work as a geophysicist, was born #OTD in 1888. In 1936 she discovered the existence of a solid core at the center of the Earth, via careful analysis of global seismic records from a 1929 earthquake. Image: Royal Danish Library
May-14 Skylab, the first US space station, was launched from Kennedy Space Center’s Complex 39 atop a Saturn V rocket #OTD in 1973. Image: NASA
May-15 Astronomer Williamina Fleming, who developed a system to classify stars according to their spectra; cataloged over 10k stars; and discovered numerous novae, nebulae, and variable stars; was born #OTD in 1857. Image: Harvard College Observatory
May-16 The physicist Roy Kerr was born #OTD in 1934. He constructed an exact solution of general relativity that describes astrophysical, rotating black holes. As far as we know it describes spacetime around every black hole in our Universe.
May-16 The physicist Joe Polchinski was born #OTD in 1954. He made deep and important contributions to field theory, string theory, and problems at the intersection of gravity and quantum mechanics. He was a great guy who was unfailingly nice to people. Image: Kimberly White/Getty
May-16 Astronomer Nancy Grace Roman was born #OTD in 1925. She was @NASA’s first Chief of Astronomy, established the agency’s space astronomy program, and is often referred to as “Mother of the Hubble” for her work planning and overseeing the development of the telescope. Image: NASA
May-17 The physicist Joseph Weber was born #OTD in 1919. He pioneered lasers & masers, and made a controversial claim of evidence for gravitational waves. @LIGO incorporates many of his ideas, and Kip Thorne described him as the founder of the field. Image: U Maryland Archives
May-18 Apollo 10 launched #OTD in 1969 from Launch Complex 39-B at Kennedy Space Center. The Lunar Module approached within 16 km of the surface before the crew returned to Earth. The next mission would deliver astronauts to the surface. Images: NASA
May-19 Physicist Helen Quinn was born #OTD in 1943. She is best known for Peccei-Quinn theory, a proposed explanation of the Strong CP problem of quantum chromodynamics. It implies a very light particle –the axion– which may be a component of dark matter. Image: H. Quinn/@QuantaMagazine
May-20 The Hubble Space Telescope sent its first image back to Earth #OTD in 1990. Ground Image: E. Persson (Las Campanas Observatory, Chile)/Observatories of the Carnegie Institution of Washington Hubble Image: NASA, ESA, and STScI
May-21 Andrei Sakharov, who turned away from his work on nuclear weapons to fight proliferation and advocate for human rights, was born #OTD in 1921. He applied particle physics to cosmology, proposing a framework to explain the matter-antimatter asymmetry of the universe. Image: AIP
May-22 “I have not all my facts yet but I do not think there are any insuperable difficulties. Still, it is an error to argue in front of your data. You find yourself insensibly twisting them round to fit your theories.” Sir Arthur Conan Doyle was born #OTD in 1859
May-23 Physicist and chemist Esther Conwell, whose work with Weisskopf on the scattering of electrons by impurities in semiconductors was essential to understanding transistors and the development of integrated circuits, was born #OTD in 1922. Images: AIP, Ryan K. Morris Photography
May-23 Edward Lorenz was born #OTD in 1917, a tiny event that had a surprisingly large impact on mathematics.
May-24 William Gilbert was born #OTD in 1544. His book "De Magnete" (1600) belongs in the pantheon of works that we associate with the beginnings of the scientific method.
May-26 Physicist and astronaut Sally Ride, the first American woman and youngest American in space, was born #OTD in 1951. After NASA she worked on arms control and physics, investigated the Columbia and Challenger disasters, and promoted STEM through Sally Ride Science. Image: NASA
May-27 Accelerator physicist Helen Edwards was born #OTD in 1936. She was the lead scientist overseeing the design, construction, and operation of the Tevatron at Fermilab. Image: @Fermilab
May-28 Astronomer Frank Drake was born #OTD in 1930. N ≈ R×fp×ne×fl×fi×fc×L R = ⭐️ formation rate fp = fraction of ⭐️ with 🌎 ne = 🌎 per ⭐️ on avg that could support life fl = frac with life fi = frac of life becoming intelligent fc = frac that 📡 into 🌌 L = how long they broadcast
May-29 The deflection of starlight by the gravitational field of the sun was observed during a solar eclipse #OTD in 1919, an important piece of evidence supporting a central prediction of Einstein's theory of general relativity. Image: Arthur Eddington
May-30 Polymer chemist Henry Aaron Hill was born #OTD in 1915. After finishing his organic chemistry PhD at MIT, Hill became a research scientist & later vice president at North Atlantic Research Corporation. In 1977 he was elected president of the American Chemical Society. Image: ACS
Jun-02 The Surveyor 1 spacecraft touched down on the moon #OTD in 1966. It was the first soft landing by a US spacecraft on an extraterrestrial body, an important early step towards future crewed missions to the moon. Images: NASA/JPL
Jun-03 James Hutton, the founder of modern geology, was born #OTD in 1726. He proposed the idea of Uniformitarianism, that geological processes occurring now are the same as ones occurring in the past, unseating catastrophism and implying the Earth was much older than Biblical accounts.
Jun-05 The physicist Rudolph Peierls was born #OTD in 1907. He contributed across the breadth of 20th century physics, from quantum field theory to nuclear physics to statistical mechanics. Image: Atomic Heritage Foundation
Jun-07 "Every baby born in a modern hospital anywhere in the world is looked at first through the eyes of Virginia Apgar." Virginia Apgar was born #OTD in 1909. She devised a simple, effective method for assessing the health of newborn infants. Image: Mount Holyoke, Special Collections
Jun-07 Prince Rogers Nelson was born #OTD in 1958. Maybe the coolest human to ever __________.
Jun-08 Computer scientist and engineer Tim Berners-Lee was born #OTD in 1955. He proposed a global hypertext experiment at CERN in 1989 and now we all live in it. Image: CERN
Jun-08 Astronomer Giovanni Cassini was born #OTD in 1625. He discovered Saturn’s moons Iapetus, Rhea, Tethys, & Dione; observed the gap in Saturn’s rings that bears his name & suggested the rings were not solid; and measured the rotational period of Mars. Image: Wellcome Collection
Jun-09 "On a Heuristic Point of View Concerning the Production and Transformation of Light," Einstein's paper that asserted the reality of quanta to explain the photoelectric effect, was published #OTD in 1905.
Jun-12 Astrophysicist Margherita Hack was born #OTD in 1922. Known for her contributions to stellar spectroscopy and radio astronomy, she was the first woman to serve as director of the Trieste observatory. Hack was famous in Italy as a popularizer of science through books and TV.
Jun-12 Ken Wilson submitted his landmark paper "Confinement of Quarks" #OTD in 1974. It described a mechanism for why quarks must appear in bound states, and introduced Euclidean lattice gauge theory as a numerical tool for studying strongly coupled theories.
Jun-13 James Clerk Maxwell was born #OTD in 1831. He showed that electric and magnetic fields are aspects of a single phenomenon, determined the equations that govern it, and concluded that light and other forms of radiation are electromagnetic waves. Image: J.C. Maxwell Foundation
Jun-14 Mathematician Louise Hay was born #OTD in 1935. She worked on logic, recursive functions, and complexity theory; was a founding member of @AWMmath; and was the only women heading a math department at a US research institution (@thisisUIC) in the late 70s-early 80s. Image: AWM
Jun-15 Early employees and Atomic Energy Commission staff moved into @Fermilab's first offices #OTD in 1967. There they would oversee development of the facility that discovered the top & bottom quarks, tau neutrino, CP violation, and a zoo of baryons & mesons.
Jun-15 The Astronomy Picture of the Day website posted its first picture #OTD in 1995 — a computer-generated image of how Earth would warp the passage of light if it had the density of a neutron star. Happy 25th birthday @apod!
Jun-16 Valentina Tereshkova became the first woman in space #OTD in 1963. She orbited the Earth 48 times aboard Vostok 6. At the end of her flight, which lasted nearly three days, she had spent more time in space than all the US astronauts up to that point combined.
Jun-17 Astronomer William Parsons, 3rd Earl of Rosse, was born #OTD in 1800. He built several large telescopes and was the first person to discern that some nebula –– actually distant galaxies –– had spiral structure. Credit: Wellcome Collection; his sketch of M51 (the Whirlpool Galaxy)
Jun-18 Sally Ride became the first US woman in space #OTD in 1983. She was one of three mission specialists aboard the Space Shuttle Challenger for STS-7. Image: NASA
Jun-18 An Aerobee rocket carrying 3 geiger counters was launched from White Sands #OTD in 1962. Intended to measure the flux of X-rays reflected by the moon, it instead found the sky aglow: the galactic center, a bright binary star in Scorpius, a blazing source in Cygnus dubbed XR-1.
Jun-19 NASA creates many technologies, but occasionally it gets credit for something it only popularizes. Swiss electrical engineer George de Mestral was born #OTD in 1907. He got the idea for ~Velcro~ in 1941 after seeing prickly seeds stick to his dog’s fur during a walk in the Alps.
Jun-19 Astronomers Robert McMath and Robert Petrie used McMath-Hulbert observatory's spectroheliokinematograph to capture the first real movie of an erupting solar prominence #OTD in 1934. Credit: "A Short-Lived Solar Disturbance," Petrie and McMath, AAS (1936)
Jun-20 President Carter added water-heating solar panels to the White House #OTD in 1979, to demonstrate an ambitious long term commitment to renewable energy. A few years later, Reagan would order their removal in one of his first acts as president.
Jun-21 Physicist and mathematician Siméon Denis Poisson was born #OTD in 1781. He made foundational contributions to mechanics, optics, and more. No time for a thread today, I just wanted to mark the birthday of my great-great-great-great-great-great-great grand advisor.
Jun-22 Physicist William Caswell was born #OTD in 1947. He was the first person to calculate the QFT beta function to two-loop order in non-abelian gauge theory, work that is still relevant for interpreting particle physics experiments and considering physics beyond the Standard Model.
Jun-22 Mathematician Hermann Minkowski was born #OTD in 1864. He proposed a unified four-dimensional spacetime as the proper arena for the work of Maxwell, Lorentz, and Einstein. Image: MacTutor History of Mathematics Archive
Jun-23 Mathematician and computer scientist Alan Turing was born #OTD in 1912. He established the theoretical foundation for just about every modern computing device. He had a hand in you reading this right now. Image: The Guardian
Jun-23 Friends, here is a fun little physics story. The Navigation Technology Satellite 2 (NTS-2) was launched into orbit #OTD in 1977, an early step in establishing the GPS NAVSTAR network. The first satellite to carry a Cesium atomic clock into orbit! Image: Institute of Navigation
Jun-24 Fred Hoyle, who proposed a steady state model of the Universe and coined the name "Big Bang" to ridicule a rival theory, was born #OTD in 1915. He pioneered nucleosynthesis, but advocated unscientific theories about the origin of life and was known to make strange racist claims.
Jun-26 William Thomson, the Lord Kelvin, was born #OTD in 1824. With Faraday, he introduced the idea of fields in electromagnetism, laying a foundation for Maxwell's work. He is largely responsible for the modern formulation of thermodynamics as it emerged in the mid-1800s. Image: BBC
Jun-28 Physicist Maria Goeppert Mayer was born #OTD in 1906. She developed the nuclear shell model of the nucleus, for which she was awarded the 1963 Nobel Prize in Physics. Image: APS
Jun-28 My papaw did *something* #OTD in 1956, but I couldn't tell you what it was.
Jun-29 Alexander Friedmann submitted "On the Curvature of Space" to Zeitschrift für Physik #OTD in 1922. He described a homogeneous and isotropic universe that expands over time according to its matter and energy content, the arena for all of modern cosmology.
Jun-29 Albert Einstein memorialized Karl Schwarzschild before the Prussian Academy #OTD in 1916. Schwarzschild had passed away a month earlier, from an illness he contracted while serving in the German army on the Russian front.
Jun-30 The Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft launched from pad 17B at Kennedy Spaceflight Center #OTD in 2001, the start of a three month journey to the L2 Lagrange point 1.5 million km from Earth. Credit: NASA / Kennedy Space Flight Center
Jul-01 Charles Lyell and J.D. Hooker read excerpts from the work of Charles Darwin and an essay by Alfred Russel Wallace to the Linnaean Society of London #OTD in 1858, presenting for the first time the theory of evolution by natural selection.
Jul-02 The nuclear physicist Harriet Brooks, who was probably the first person to notice the recoil of an atomic nucleus due to emissions during nuclear decay, was born #OTD in 1876. Credit: Notman Archives/Musée McCord
Jul-03 The chemist Dr. Samuel P. Massie Jr., who worked on liquid uranium compounds for the Manhattan Project, helped develop compounds to fight numerous diseases, and was the first Black professor at the US Naval Academy, was born #OTD in 1919. Image: Massie family photo
Jul-04 The astronomer Henrietta Swan Leavitt was born #OTD in 1868. She established the period-luminosity relation for Cepheid variable stars. It is an essential tool for understanding the scale of our Universe. Image: Harvard-Smithsonian Center for Astrophysics
Jul-05 Happy 333rd birthday to Newton’s Principia, published #OTD in 1687.
Jul-06 Albert Einstein resigned his position at the Swiss patent office #OTD in 1909. A few months later he would assume a position as a professor in Zurich.
Jul-08 It wasn’t aliens #OTD in 1947.
Jul-09 Voyager 2 made its closest approach to Jupiter #OTD in 1979. This pic, with Io, is one of the images it sent back. (Image: NASA/JPL-Caltech)
Jul-09 The physicist John Archibald Wheeler was born #OTD in 1911. A giant of 20th century physics, he introduced the S-Matrix; developed the first general theory of fission (with Bohr); coined "worm hole" and popularized “black hole”; trained Feynman, Everett, Thorne, and many others.
Jul-10 Medical physicist and radiologist Edith Quimby was born #OTD in 1891. One of the founders of nuclear medicine, she developed diagnostic applications for X-rays and radioisotopes. Her research on the penetrating power of radiation established safe levels for its use in treatments.
Jul-11 Joseph Larmor was born #OTD in 1857. A prominent figure during a transitional period in physics, he made a number of contributions that were saddled by adherence to 19th century ideas yet figured prominently in important developments of the 20th century. Image: Royal Society
Jul-13 Aerospace researcher Sheila Widnall was born #OTD in 1938. She ran the MIT Fluid Dynamics Research laboratory, was the first chairwoman of the MIT faculty (1979), and became the first woman to head a branch of the military as Secretary of the Air Force (1993-97). Image: MIT
Jul-14 It’s grainy and hard to make out, but the Mariner 4 spacecraft took the first close-up photo of Mars #OTD in 1965.
Jul-14 Physicist Gertrude Scharff Goldhaber was born #OTD in 1911. In 1942 she discovered that spontaneous fission is associated with the emission of neutrons, and in 1948 she identified beta rays as atomic electrons. Image: Brookhaven National Lab
Jul-14 New Horizons made its closest approach to Pluto #OTD in 2015. Credit: NASA / Johns Hopkins / New Horizons
Jul-15 Astrophysicist Jocelyn Bell Burnell was born #OTD in 1943. As a grad student at Cambridge in 1967, she discovered an entirely new type of celestial object: Pulsars! Photo: National Science & Media Museum / Science & Society Picture Library
Jul-16 The Apollo 11 mission launched #OTD in 1969, carrying Neil Armstrong, Michael Collins, and Buzz Aldrin to the Moon. It was one of the most remarkable scientific collaborations in history, taking humans from Earth to the surface of another world. Images: NASA
Jul-16 Today is also the 75th anniversary of the Trinity Test, held #OTD in 1945. The result of scientific collaboration on an unprecedented scale, most participants came to regret what they had unleashed. After the test Kenneth Bainbridge remarked “Now we are all sons of bitches.”
Jul-16 And finally, Fragment A of comet Shoemaker-Levy 9 plunged into the atmosphere of Jupiter #OTD in 1994. It was moving at about 60 km/s, and produced a 3000km-high fireball that reached temperatures in excess of 20,000 K. Image: HST Science Team
Jul-16 Aerodynamics engineer Irmgard Flügge-Lotz was born #OTD in 1903. She advanced the understanding of aerodynamic pressure on wings and turbine blades, pioneered the theory of discontinuous control systems, and was the first woman named full professor of engineering at Stanford.
Jul-17 Physicist and astronomer Georges Lemaître was born #OTD in 1894. In 1927 he proposed a model of an expanding Universe. Then, in 1931, he ran the clock backwards and hypothesized its origin in a “unique atom” or “unique quantum,” paving the way for modern ideas about the Big Bang.
Jul-17 Astronomer Wendy Freedman was born #OTD in 1957. She was co-PI on the Hubble Space Telescope Key Project, which reported the value of the Hubble Constant as H₀ = 72 ± 8 km/sec/Mpc back in December of 2000.
Jul-18 "Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen," Einstein's work on Brownian motion and the second of his four “Miracle Year” papers, was published in Annalen der Physik #OTD in 1905.
Jul-18 The Dutch physicist Hendrik Antoon Lorentz was born #OTD in 1853. Here he is on the right next to an unidentified German scientist, probably one of his many admirers. Photo: Paul Ehrenfest (1921), via Museum Boerhaave, Leiden
Jul-19 Medical physicist Rosalyn Yalow was born #OTD in 1921. She won the 1977 Nobel for Physiology or Medicine, for developing the radioimmunoassay technique. Image: James J. Peters Va Medical Center
Jul-20 Humans first set foot on the Moon fifty-one years ago, #OTD in 1969. Images: NASA
Jul-20 As long as we’re talking about first landing and lovely photos... Viking 1 was the first probe to land on Mars, #OTD in 1976. Here is the first image of the surface that it sent back. Image Credit: NASA
Jul-21 In a letter to @nature #OTD in 1904, Harriet Brooks noted an unusual volatile behavior in active radium samples removed from their emanation. She was the first person to observe recoil of an atomic nucleus due to emissions during nuclear decay. Image: Notman Archives/Musée McCord
Jul-22 Astronomer, physicist, and mathematician Friedrich Bessel was born #OTD in 1784. Best known for his eponymous functions, he was also the first to publish a parallax calculation of the distance to another star (61 Cygni, estimated by Bessel at 10.3 ly). Image: Wellcome Collection
Jul-23 The astronomer Vera Rubin was born #OTD in 1928. Her work on galactic rotation curves became one of the main pieces of evidence for the existence of dark matter, and she deserved a Nobel Prize for it. Image: Vassar College / Emilio Segrè Visual Archives
Jul-23 The mathematician Emmy Noether gave a talk titled “Invariante Variationsprobleme” to the Göttingen Mathematical Society #OTD in 1918, explaining the two celebrated theorems that she published in a paper of the same name later that year. Happy 102nd birthday to Noether’s Theorems!
Jul-24 The first test of "Operation Moon Bounce" took place #OTD in 1954, when Naval Research Laboratory engineer James Trexler spoke into a microphone, bounced the signal off the moon, and received the return signal a few seconds later. Image: Plans from Trexler's notebook, APS History
Jul-25 Rosalind Franklin was born #OTD in 1920. Her X-ray diffraction work established the helical nature of DNA. Image: Vittorio Luzzati / Jewish Women’s Archive
Jul-26 Happy Rotating Black Hole Day! Roy Kerr submitted his breakthrough paper describing the spacetime around a rotating black hole #OTD in 1963. Physicists had been searching for this solution for decades.
Jul-27 Baron Loránd Eötvös was born #OTD in 1848. His delicate torsion balance experiments precisely demonstrated the equivalence between gravitational and inertial mass, a foundational insight for Einstein during the development of general relativity. Image: Tomory Lajos Múzeum
Jul-28 President Andrew Johnson signed the Metric Act #OTD 1.54 hectoyears ago (1866) making metric measurement legally acceptable for US commerce.
Jul-30 Geologist Marie Tharp was born 100 years ago, #OTD in 1920. She built the first accurate map of the Atlantic Ocean floor, discovering the Mid-Atlantic Ridge that provided evidence for seafloor spreading and plate tectonics. Image: Lamont-Doherty Earth Observatory
Jul-30 The @NASAPersevere rover launched today and is on its way to Mars. It’s also the anniversary of the Apollo 15 mission landing on the Moon, #OTD in 1971! It was the first mission with a lunar rover, which traveled more than 17 miles. Pretty good if you like Moon Cars! Image: NASA
Jul-31 Chemist Stephanie Kwolek was born #OTD in 1923. She invented Kevlar, used in high-strength/low-weight applications like body armor and airplane parts. She also invented the Nylon Rope Trick demo! Images: DuPont/Stephanie Kwolek
Aug-01 Astronomer Helen Sawyer Hogg was born #OTD in 1905. She was an authority on variable stars and globular clusters, and a pioneer of communicating science to the public. Image: University of Toronto, Department of Astronomy and Astrophysics
Aug-02 Mathematician Mina Rees was born #OTD in 1902. She coordinated work by mathematicians at OSRD during WWII, drove the development of computers and numerical science as head of mathematics at the Office of Naval Research, and was the first woman to serve as @AAAS president.
Aug-03 The physicist George Francis FitzGerald was born #OTD in 1851. He proposed length contraction as an explanation for the null result of the Michelson-Morley experiment. The phenomenon is real, but his justification for it was wrong. Image: National Library of Ireland
Aug-04 William Rowan Hamilton was born #OTD in 1805. His reformulation of classical Newtonian mechanics via the principle of stationary action is one of the most beautiful ideas in all of physics, and is at the heart of nearly every modern theory in physics.
Aug-05 Astronaut Neil Armstrong, the first US civilian in space and the first human to set foot on the moon, was born #OTD in 1930. Images: NASA / Project Apollo on Flickr
Aug-06 The @MarsCuriosity rover touched down at Bradbury Landing #OTD in 2012. Happy landing day, little robot. (Image: NASA/JPL-Caltech/Univ. of Arizona; NASA)
Aug-08 Paul Dirac (1902, discovered the relativistic equation for the wave function of fermions), Ernest Lawrence (1901, invented the cyclotron), and Roger Penrose (1931, developed the global view of spacetime and much of what we know about singularities in GR) were all born #OTD.
Aug-08 Mathematical physicist Roger Penrose was born #OTD in 1931. He is best known for the innovative mathematical techniques he introduced to relativity, and his results on singularities. Image: Science Photo Library
Aug-08 Penrose did his math PhD at Cambridge. His first advisor was Hodge, but he didn’t find the work interesting so he switched to Todd. He took some physics courses, which he found fascinating. One was Dirac’s (also born #OTD) QM course. Another was Bondi’s course on relativity.
Aug-09 Nuclear physicist Leona Woods Marshall Libby was born #OTD in 1919. She helped direct the development of the Hanford site reactors during the Manhattan Project, was the only woman on Enrico Fermi's Chicago Pile team, and was present when Chicago Pile-1 went critical.
Aug-11 Cell biologist Elaine Diacumakos, who developed techniques for inserting & removing material from cells, was born #OTD in 1930. In 1979, Diacumakos and Anderson were first to insert a functioning gene into a defective (mouse) cell to correct a genetic defect. Image: Rockefeller U
Aug-11 The South African cosmologist George F. R. Ellis was born #OTD in 1939. He co-authored "The Large Scale Structure of Space-Time" with Stephen Hawking in 1973, and was an anti-apartheid activist throughout the 1970s-80s. Image: David Sillitoe/Guardian News
Aug-12 Erwin Schrödinger was born #OTD in 1887. He developed the wave formulation of quantum mechanics, and hoped that his work might somehow reconcile the surprising conclusions of QM with our classical intuition about Nature. But it was not to be! Image: Science Source / @NatGeo
Aug-12 Happy 30th birthday (Rebirthday? Excavationday?) to @SUEtheTrex, discovered #OTD in 1990 by paleontologist Sue Hendrickson. Image: Connie Ma / Wikimedia
Aug-14 The physicist Hans Christian Ørsted was born #OTD in 1777. In 1820 he demonstrated an unexpected connection between electric and magnetic phenomenon, believed by many to be unrelated, initiating the development of the theory of electromagnetism. Image: Danmarks Tekniske Museum
Aug-15 Louis Victor Pierre Raymond de Broglie, the 7e duc de Broglie, was born #OTD in 1892. He postulated that matter must have wave-like properties, one of the defining features of quantum mechanics. Image: APS
Aug-16 The Mexican American microbiologist Sarah Stewart, a pioneer of viral oncology who showed that viruses could cause cancer in mammals, was born #OTD in 1905. Image: Georgetown University News Service
Aug-17 Software engineering pioneer Margaret Hamilton, who led NASA's in-flight software team for the Apollo mission, was born #OTD in 1936. Image: NASA
Aug-19 Milton La Salle Humason was born #OTD in 1891. He dropped out of the eighth grade and had almost no formal education, but he had a knack for difficult observations and collected much of the data used to establish what we now call Hubble’s Law. Image: Emilio Segrè Visual Archives
Aug-20 The Voyager 2 spacecraft launched #OTD in 1977. It is currently 11.5 billion miles from Earth, hurtling through interstellar space at over 34,000 mph with respect to the sun. Given everything happening on Earth rn, it probably feels pretty good about this. Image: NASA/JPL-Caltech
Aug-21 Nuclear physicist Noemie Benczer Koller, best known for her work on hyperfine interactions of nuclei and developing new techniques for studying magnetic properties of nuclei, was born #OTD in 1933. Koller was the first woman hired as faculty in the Physics Department at Rutgers.
Aug-22 “I was to sweep for comets, and by my Journal No.1, I see that I began August 22, 1782, to write down and describe all remarkable appearances I saw in my sweeps (which were horizontal)." Caroline Herschel began her "Book of Observation" #OTD in 1782.
Aug-23 Lunar Orbiter 1 took the first photo of the Earth from the Moon #OTD in 1966. (Image: NASA)
Aug-24 Voyager 2 made its closest approach to Neptune #OTD in 1989, the last stop on its Grand Tour of the outer planets. We haven’t been back there since. Images: NASA/JPL
Aug-24 Mathematician Karen Keskulla Uhlenbeck was born #OTD in 1942. She is known for her work on PDEs, calculus of variations, topology, and gauge theory, and was the second woman (after Emmy Noether!) to give the plenary lecture to the International Congress of Mathematicians.
Aug-24 The International Astronomical Union demoted Pluto to dwarf planet status #OTD in 2006. Never forget. (Pluto Image: NASA/Johns Hopkins APL/SW Research Institute)
Aug-25 Physiologist and biophysicist Alice Mary Stoll was born #OTD in 1917. She studied the effects of high speed flight and large accelerations on the body, and her work on exposure to heat and thermal radiation led to new fire-retardant materials. Image: Society of Women Engineers
Aug-25 Mathematician Katherine Johnson, whose orbital mechanics calculations played a vital role in so many NASA missions, was born #OTD in 1918. John Glenn trusted her calculations more than his onboard flight computer. Image: NASA
Aug-27 Geneticist Liane Russell was born #OTD in 1923. She pioneered the study of mutagenesis & teratogenesis due to radiation, and identified the role of the Y chromosome in sex determination. Her work led to diagnostic x-ray safety standards for women of childbearing age. Image: @ORNL
Aug-28 The first issue of Scientific American was published by Rufus Porter #OTD in 1845. Happy birthday @sciam! Image: Wikipedia
Aug-28 Meteorologist, atmospheric scientist, & climate researcher Warren Washington was born #OTD in 1936. He was awarded the National Medal of Science in 2010, and was the first African American president of the American Meteorological Society.
Aug-29 Michael Faraday first demonstrated the phenomenon of electromagnetic induction #OTD in 1831. He coiled insulated wire around two sides of an iron ring, then observed a brief current in one as he connected the other to a battery. Image: The Royal Institution, Paul Wilkinson
Aug-30 Physicist Ernest Rutherford was born in Brightwater, New Zealand #OTD in 1871. He discovered the nucleus, proton, α, and β particles; explained nuclear decay; and was the first person to successfully transmute one element into another. Image: George Grantham Bain Collection, LOC
Aug-31 During a solar eclipse #OTD in 1932, Karl Jansky saw no change in the intensity of the faint radio hiss he'd been monitoring. This meant that the sun wasn’t the source. He soon attributed what he called "star noise" to large clouds of ionized gas near the center of the Milky Way.
Aug-31 Scientists didn’t show much interest at the time. Even Jansky didn't really appreciate that he had invented the field of Radio Astronomy #OTD in 1932. 📡🌌 Image: Bell Telephone Laboratories
Sep-01 Pioneer 11, the first human-made probe to reach Saturn, made its closest approach #OTD in 1979. Image: NASA/University of Arizona Lunar & Planetary Laboratory
Sep-01 Roy Kerr's groundbreaking paper describing rotating black holes appeared in Physical Review Letters #OTD in 1963.
Sep-01 The first solar flare observations were made #OTD in 1859 by Carrington & Hodgson, preceding one of the largest geomagnetic storms on record. Both amateur astronomers made their observations independently, and published them simultaneously in MNRAS.
Sep-02 Teacher and astronaut Christa McAuliffe, selected as the first American civilian to go into space, was born #OTD in 1948. She was one of the seven crew members onboard the Space Shuttle Challenger when it was lost in 1986. #TeacherOnBoard Image: NASA
Sep-03 Physicist Carl Anderson was born #OTD in 1905. He developed an improved cloud chamber and used it to identify the positron – the antiparticle of the electron, which was first theorized by Dirac. Image: Lawrence Berkeley National Laboratory
Sep-04 Astrophysicist Dr. Jaqueline Hewitt, known for pioneering work on gravitational lensing, was born #OTD in 1958. In 1987 she led the team of observers at the Very Large Array that discovered the first Einstein ring. Images: Hewitt et al, Nature 333, 537 (1988)
Sep-05 Space probe Voyager 1 launched from NASA’s Kennedy Space Center at Cape Canaveral #OTD in 1977. Now it is nearly 14 billion miles from Earth – the most distant human-made object – and racing away from us at over 38,000 miles per hour with respect to the sun. Images: NASA/KSC/JPL
Sep-08 Epidemiology pioneer John Snow, who doubted the prevailing miasma theory for the spread of a cholera outbreak in London, traced infections and spoke to locals to pinpoint a public water pump as the source. The town removed its handle #OTD in 1854, helping to end to the outbreak.
Sep-08 This, from last year, is one of my favorite #OTD threads. Especially the part about the Kaiser and the Devilfish.
Sep-09 The mathematician Marjorie Lee Browne, whose work focused on linear algebra, topology, and the properties of classical groups, was born #OTD in 1914. She was one of the first Black women to earn a PhD in mathematics from a US university.
Sep-10 The first of beam of protons was successfully circulated around the Large Hadron Collider #OTD in 2008.
Sep-10 Physicist Arthur Compton was born #OTD in 1892. In 1923 he explained the behavior of X-rays scattered from electrons by treating the X-rays as massless particles in a relativistic collision, a compelling piece of evidence for the reality of quanta as proposed by Einstein in 1905.
Sep-11 Astronomer Mary Watson Whitney was born #OTD in 1847. She was known for her work on variable stars and measurements via photographic plates. One of Maria Mitchell’s first students, Whitney succeeded her as director of the Vassar Observatory and head of the astronomy department.
Sep-12 Dr. Mae Jemison, the first Black woman to go into space, headed into orbit on the shuttle Endeavour #OTD in 1992. (Image: NASA)
Sep-12 Irène Joliot-Curie was born #OTD in 1897. She was known for her work on radioactivity, and was awarded the 1935 Nobel Prize in Chemistry for demonstrating the artificial radioactivity of stable elements bombarded with alpha particles. Image: Robert Doisneau
Sep-13 Some of the last images taken by @CassiniSaturn, as it swept its cameras around #OTD in 2017. Two days later it would plunge into Saturn's atmosphere, ending its twenty year mission. Images: NASA/JPL-Caltech
Sep-14 Happy birthday to gravitational wave astronomy! @LIGO made the first detection of gravitational waves #OTD in 2015, 100 years after they were predicted by Einstein. The discovery was announced the following February. Figures: @LIGO
Sep-15 Physicist Murray Gell-Mann was born #OTD in 1929. He developed the Eightfold Way for explaining the properties of mesons and baryons, and postulated the existence of quarks as the building blocks of these particles. Image: Gell-Mann with particle theorist Mary Gaillard, CERN
Sep-15 Astronomer Judith Sharn Young was born #OTD in 1952. Recipient of the Maria Goeppert-Mayer award for physics and the Annie Jump Cannon prize in astronomy, she was known for her work mapping galactic distributions of carbon monoxide and other gases associated with star formation.
Sep-17 Uh, if you are a nerd of a certain age and want to feel old, the Dungeons & Dragons animated series debuted #OTD 37 years ago.
Sep-17 Mathematician Bernhard Riemann was born #OTD in 1826. He made deep contributions to complex analysis and number theory, but is best remembered by physicists for his work on the foundations of geometry that would one day provide the mathematical framework for general relativity.
Sep-18 The Voyager 1 spacecraft, 7.25 million miles away and speeding towards Jupiter, looked homeward #OTD in 1977 and captured the first picture of the entire Earth and Moon together in the same frame. Image: NASA / JPL
Sep-19 Austrian physicist Victor Weisskopf was born #OTD in 1908. He helped shape quantum mechanics and quantum field theory, establishing results that set the stage for Quantum Electrodynamics. Image: Duscha Scott Weisskopf / Physics Today
Sep-20 Paul Erdős had a fantasy that he'd die giving a lecture: He'd prove a result, someone would ask about a generalization, he'd say "I'll leave that to the next generation," and then he'd die. He passed away at a conference in Warsaw #OTD in 1996, just after proving a new result.
Sep-21 The Galileo spacecraft plunged into Jupiter #OTD in 2003, after spending 8 years studying the Jovian system. Like Cassini, it was destroyed to prevent possible contamination of moons in the system by terrestrial microbes! Images: NASA/JPL
Sep-22 Michael Faraday, who made foundational discoveries about electromagnetism and was an inspiration for both Maxwell and Einstein, was born #OTD in 1791. Portrait: Thomas Phillips
Sep-23 Physicist Clifford Shull, who developed techniques for studying the structure of matter via neutron diffraction, was born #OTD in 1915. Image: @ORNL
Sep-23 Johann Galle first identified the planet Neptune #OTD in 1846. He had been told where to look for it by Urbain Le Verrier, whose calculations were based on irregularities in the orbit of Uranus. Image: NASA
Sep-24 Astrophysicist Charlotte Moore Sitterly, who compiled extensive data on optical and later UV spectra, was born #OTD in 1898. Her spectroscopic tables are still in use today. Image: AIP Emilio Segrè Visual Archives, Gift of Michael A. Duncan
Sep-25 Danish astronomer Ole Rømer was born #OTD in 1644. His observations of Jovian moons confirmed that light propagates at finite speed. This was a profound conceptual shift that opened the door for work by Huygens, Fresnel, and Maxwell. Portrait: Jacob Conring / Wikimedia Commons
Sep-26 Happy 115th birthday to special relativity! "On The Electrodynamics Of Moving Bodies,” Einstein’s paper laying out special relativity, was published in Annalen der Physik #OTD in 1905. Original manuscript:
Sep-27 If there’s one physics formula everyone knows, it’s E = mc². Einstein proposed mass-energy equivalence in his second special relativity manuscript, submitted to Annalen der Physik #OTD in 1905. His first relativity paper had appeared the day before.
Sep-28 Astronomer and mathematician Pierre-Louis Moreau de Maupertuis, exact date of birth unknown, was born around this time in 1698 and baptized #OTD. He was among the first to articulate the Principle of Least Action, one of the most beautiful ideas in physics. Image: Wellcome Trust
Sep-29 Enrico Fermi, one of the foremost experimental *and* theoretical physicists of the 20th century, was born #OTD in 1901. Now estimate how many new physicists will be born today. Image: New York Public Library
Oct-01 Happy birthday, @NASA! The National Aeronautics and Space Administration began operations #OTD in 1958. Congress passed the act creating it on July 16 of that year, and President Eisenhower signed it a few weeks later.
Oct-01 Astrophysicist Dr. George Carruthers was born #OTD in 1939. He developed an ultraviolet spectrograph, launched on a sounding rocket in 1970, that confirmed the existence of interstellar hydrogen, and a similar device placed on the moon by Apollo 16. Image: US Naval Research Lab
Oct-02 I was going to post the following last night, before [sweeps arm in grand gesture] all of this. Consider this a retroactive #OTD post.
Oct-04 The Space Age began #OTD in 1957 when Sputnik 1, the first satellite made by humans, was launched into low Earth orbit. Image: NSSDC, NASA
Oct-05 Physicist Robert Goddard, a pioneer of rocketry and space flight, was born #OTD in 1882. @NASA's Goddard Space Flight Center in Maryland is named in his honor. Image: Clark University Robert H. Goddard Archive
Oct-06 VAR! In the early morning hours #OTD in 1923, Edwin Hubble took a photo plate of M31 showing a Cepheid variable star. Using Henrietta Swan Leavitt’s distance-luminosity relationship, Hubble concluded that M31 is another galaxy outside the Milky Way. Image: Carnegie Observatories
Oct-07 The Danish physicist Niels Bohr was born #OTD in 1885. He applied the nascent quantum theory to the structure of the Hydrogen atom, offering an explanation for an outstanding problem that classical physics could not account for. Image: Atomic Heritage Foundation
Oct-08 Astronomer Ejnar Hertzsprung was born #OTD in 1873. Emoji H-R diagram: 🔵 🔵 ⚪️ ⚪️ 🟡🟡 🟠🟠 🔴 🔴 ⚫️
Oct-09 The physicist and astronomer Karl Schwarzschild was born #OTD in 1873. In 1915, while serving in the German army on the Russian front, he found the first (well, besides empty space) exact solution of Einstein’s theory of general relativity: a non-rotating black hole!
Oct-10 The Very Large Array, part of @TheNRAO, was formally dedicated #OTD in 1980. It was renamed the "Karl G. Jansky Very Large Array" in 2012. Happy 40th birthday, VLA! (Be sure to click the image if you can’t see the whole thing.)
Oct-12 Guralnik, Hagen, and Kibble submitted their paper "Global Conservation Laws and Massless Particles" to Physical Review Letters #OTD in 1964. It was one of three important papers, by three groups of authors, developing what we now call the Higgs Mechanism.
Oct-13 Charles Messier discovered the Whirlpool galaxy #OTD in 1773. The designation M51 refers to its entry in the catalog he produced. Pretty good galaxy. Credit: NASA/ESA/S. Beckwith (STScI)/HHT (STScI/AURA)
Oct-14 [Levon Helm voice] "There was a demon that lived in the air. They said whoever challenged him would die…The demon lived at Mach 1 on the meter, 750 miles an hour, where the air could no longer move out of the way." @GenChuckYeager flew faster than the speed of sound #OTD in 1947
Oct-15 The most energetic single particle ever detected, a cosmic ray dubbed the "Oh-My-God" particle, was observed by the Fly's Eye Cosmic Ray Detector #OTD in 1991. It had an energy of about 3 x 10²⁰ eV ~ 48 J, equivalent to a baseball moving at almost 60 mph.
Oct-16 Crossing Brougham Bridge in Dublin #OTD in 1843, William Hamilton had a flash of insight. He finally understood how to multiply quaternions after puzzling over the problem for years. He scratched the result into the stone: i² = j² = k² = ijk = -1 Image: Wikimedia
Oct-17 “I just always assumed, despite the fact that the U.S. hadn’t sent any women up and there, or people of color, that I was going to go.” Dr. Mae Jemison was born #OTD in 1956. Doctor, peace corps volunteer, first Black woman in space, first astronaut on Star Trek.
Oct-18 Annual reminder that there are 20th century physicists who I will not write about in an #OTD post because, while their work may be important, they were literally Nazis.
Oct-18 The mathematician Dusa McDuff, known for her work in symplectic geometry as well as topology, was born #OTD in 1945. She's a Fellow of the Royal Society, a recipient of the Satter Prize from @amermathsoc, and gave the 1998 Emmy Noether Lecture for @AWMmath.
Oct-19 Subrahmanyan Chandrasekhar was born #OTD in 1910. He established an upper limit on the mass of stars that end their lives as white dwarfs. Above this Chandrasekhar Limit – about 1.44 solar masses – they eventually explode and then collapse into a neutron star or black hole.
Oct-21 Physicist and astronaut Ronald McNair was born #OTD in 1950. He spent about 8 days in space aboard Challenger in 1984 during STS-41-B. McNair was one of the seven crew members who lost their lives in the 1986 Challenger disaster. Image: NASA
Oct-22 Physicist Karl Jansky was born #OTD in 1905. While searching for the source of radio hiss that interfered with transatlantic phone calls for Bell Labs, he discovered that astrophysical objects emit radio waves. It was the birth of radio astronomy. Credit: NRAO/AUI/NSF
Oct-23 Astronomer Emma Williams (Vyssotsky) was born #OTD in 1894. After completing her astronomy PhD at Harvard, she studied stellar motions and the kinematics of the Milky Way at UVA's McCormick Observatory. In 1946 she received the @AAS_Office’s Annie Jump Cannon Award.
Oct-24 George Gamow sent a belated birthday letter to Niels Bohr #OTD in 1945. He explained that he was starting to think about the origin of light elements in the very early universe by examining nuclear physics in the relativistic setting of the hot big bang.
Oct-26 Astronomer Henrietta Hill Swope was born #OTD in 1902. She discovered thousands of variable stars, made precise measurements of the Cepheid period-luminosity relation, and gave the most accurate result for the distance to M31. Image: Charles Reyne, via Harvard College Obs.
Oct-27 A timely (imo) #OTD coming up.
Oct-27 The very first U.S. astronomical expedition, led by Harvard mathematician Samuel Williams, viewed an almost-total eclipse #OTD in 1780. They were allowed to conduct their observations behind British lines even though the Revolutionary War was in full swing.
Oct-28 The virologist and medical researcher Jonas Salk was born #OTD in 1914. In 1955 he developed the first inactivated vaccine for polio, a trivalent vaccine that induces resistance to all three types of poliovirus. Image: University of Pittsburgh Digital Archives / The Owl
Oct-29 The first message between two computers on ARPANET was sent #OTD in 1969. The “LO” of “LOGIN” was transmitted before one system crashed. Charles Kline’s IMP Log: “Talked to SRI host to host.” Image: UCLA Kleinrock Center for Internet Studies
Oct-30 “That is why you do well to follow your heart and your passion. Bare reason is likely to lead you astray.” Mathematician & Fields Medalist Bill Thurston was born #OTD in 1946. Read his lovely answer to the question “How can one contribute to mathematics?”
Oct-31 The mathematician Karl Weierstrass was born #OTD, Halloween, in 1815. The fools at the academy all said he was mad, but in 1872 he announced that he had succeeded in creating a ~monster~. Image: Smithsonian Institution Libraries
Nov-03 The very good girl Laika, a scrappy three-year-old stray from Moscow, was sent into space aboard Sputnik II #OTD in 1957. The first animal to orbit Earth, she became a national hero. This was cold comfort, since the mission wasn’t designed to return her to Earth.
Nov-06 There's a lot going on, so I haven't really been doing any #OTD threads, but here's a pretty good 'un from last year.
Nov-07 Physicist Lise Meitner was born #OTD in 1878. She discovered fission in uranium and was the first person to understand both its mechanics and implications. Image: Atomic Heritage Foundation (photographer unknown)
Nov-09 Carl Sagan was born #OTD in 1934. He was a planetary scientist, a dedicated science communicator, and a tireless advocate for the humanizing power of science. This passage of his has weighed heavily on me for the last four years; a little less so this morning. Image: NASA
Nov-10 Igor Dmitriyevich Novikov, who introduced the concept of the white hole in 1964, was born #OTD in 1935. He also introduced a self-consistency principle for time-travel...
Nov-11 The physicist Hugh Everett III was born #OTD in 1930. His “relative state” formulation of quantum mechanics, which we now call the “Many Worlds Interpretation,” was published in 1957.
Nov-12 John William Strutt, Lord Rayleigh, was born #OTD in 1842. He discovered argon, worked out the wavelength-dependence of elastic scattering of light by small particles that explains blue skies and red sunsets, and described the spectral radiance of a blackbody at long wavelengths.
Nov-13 When Einstein proposed general relativity he laid out three tests: the precession of Mercury's perihelion, deflection of light by the sun, and gravitational redshift. Irwin Shapiro proposed a fourth test #OTD in 1964: the gravitational time delay of light.
Nov-15 Einstein used my signature move #OTD in 1915 when he pretended to be sick so he could skip a seminar by a colleague (Hilbert) and stay home to work on his own theory. (From "David Hilbert and the Axiomatization of Physics" by L. Corry)
Nov-15 Leon Cooper's letter showing how pairs of electrons might form bound states in some metals at low temperature was published in Physical Review #OTD in 1956. Six months later, Cooper, Bardeen, and Schrieffer published their full theory of superconductivity.
Nov-15 Astronomer Johannes Kepler died #OTD in 1630. I usually don't do "died on this day" posts but I'll make an exception to quote the epitaph he wrote for himself: "I measured the skies, now the shadows I measure Skybound was the mind, earthbound the body rests." Image: Wikimedia
Nov-16 The "Arecibo Message" was beamed towards globular cluster M13 #OTD in 1974, during the dedication of an upgrade to the radio telescope. It was the first message sent with the intention of alerting extraterrestrials to life on earth.
Nov-17 Possibly where the #OTD tweets peaked.
Nov-17 The physicist Eugene Wigner was born #OTD in 1902. He made essential contributions to quantum mechanics and nuclear physics, including foundational work on the ways fundamental symmetries constrain physical laws. Image: New York Public Library
Nov-18 Einstein presented "Explanation of the Perihelion Motion of Mercury from the General Theory of Relativity" #OTD in 1915. He used his nearly-complete theory of general relativity to explain the 43 arc-second per century anomalous precession of Mercury.
Nov-19 NASA astronaut Eileen Collins was born #OTD in 1956. She was the first woman to pilot the space shuttle (1995) and the first woman to command a shuttle mission (1999).
Nov-19 Hilbert's postcard congratulating Einstein, #OTD in 1915: "If I could calculate as rapidly as you, in my equations the electron would correspondingly have to capitulate, and simultaneously the hydrogen atom would have to produce its note of apology about why it does not radiate."
Nov-19 The physicist and mathematician Tatyana Ehrenfest-Afanassjewa was born #OTD in 1876. She co-authored an important early survey on the foundations of statistical mechanics, and wrote papers on the role of randomness and probability in physics. Image: Smithsonian Libraries
Nov-20 Edwin Hubble was born #OTD in 1889. He established spiral nebulae as separate galaxies, and combined distance measurements with Slipher’s galaxy redshift data to obtain a linear relation between distance & recession velocity - now understood as evidence for an expanding universe.
Nov-21 Einstein’s paper “Does the Inertia of a Body Depend Upon Its Energy-Content?" appeared in Annalen der Physik #OTD in 1905. It contains his first published statement of the equivalence of mass and energy, the basis for the well-known formula E = mc².
Nov-22 Guion Stewart Bluford Jr was born #OTD in 1942. Engineer, computational fluid dynamicist, decorated Air Force pilot, veteran of four shuttle missions, and the first Black American in space. Image: NASA
Nov-23 Geneticist and microbiologist Rita Rossi Colwell was born #OTD in 1934. She was the first researcher in the US to use computers to analyze bacteriological data, and the first woman to serve as director of the @NSF.
Nov-23 The chemist Rachel Fuller Brown was born #OTD in 1898. She discovered the antifungal antibiotic nystatin while doing research for the NY State Department of Health, hence the name. Image: Smithsonian Institution
Nov-24 Charles Darwin's "On the Origin of Species by Means of Natural Selection" was published #OTD in 1859.
Nov-25 Einstein presented "The Field Equations of Gravitation" to the Prussian Academy #OTD in 1915. After years of work that culminated in a frenzied month-long race against David Hilbert, he finally had the correct form of the field equations for general relativity.
Nov-25 In any case, there's no need to include a cosmological constant as a separate term in the equations, as in the 1917 paper. It can just as well reside in the stress energy tensor on the right hand side of the equations Einstein presented #OTD in 1915.
Nov-27 The Reverend John Michell read a paper before the Royal Society #OTD in 1783 that included the first prediction of what, given the understanding of gravity at the time, might be called a Black Hole.
Nov-28 Jocelyn Bell Burnell transformed astronomy when she made the first observation of a pulsar #OTD in 1967. She and advisor Antony Hewish initially dubbed the object LGM-1 (“Little Green Men”) for its regular signal, but soon identified it as a rotating, magnetized neutron star.
Nov-29 Enos the chimpanzee became the second chimp in space and the third hominid (after Gagarin and Titov) to orbit the Earth #OTD in 1961. Image: NASA
Nov-29 If you check, you’ll find that Erwin Schrödinger’s paper “Die gegenwärtige Situation in der Quantenmechanik (The present situation in quantum mechanics)," which contained his famous cat paradox, was published #OTD in 1935. Translation:
Nov-30 Ernst Florens Friedrich Chladni, considered a pioneer of the field of acoustics, was born #OTD in 1756. He studied the mathematical theory of sound waves, the speed of sound in various materials, and eponymous complex patterns formed by vibrational modes of solid objects.
Dec-01 The mathematician Nikolai Ivanovich Lobachevsky was born #OTD in 1792. He developed a non-Euclidean geometry that shows up in areas ranging from relativity to the designs of M.C. Escher. Portrait: Lev Kryukov (wikimedia)
Dec-02 The United States Environmental Protection Agency was established #OTD in 1970. For the last four years it has been under assault by anti-science extremists, industries intent on harming the environment, and its own directors: a climate science denier and a fossil fuel lobbyist.
Dec-02 Enrico Fermi and collaborators initiated the world’s first artificial self-sustained nuclear reaction #OTD in 1942. Chicago Pile-1 was hidden under Stagg Field at the University of Chicago. Image: Melvin Miller/Argonne
Dec-02 Anyway, things moved pretty quickly after that. #OTD in 1957 — 15 years later, to the day — the reactor at the Shippingport Atomic Power Station went critical. It was the first full-scale atomic electric plant in the US, and remained in operation until 1982. Image: @ANS_org
Dec-04 “Dear Radioactive Ladies and Gentlemen” Wolfgang Pauli sent a letter to a group of nuclear physicists #OTD in 1930, proposing a new and hard-to-detect particle to explain energy that went missing in some beta decays. He dubbed them “neutrons” but we now call them “neutrinos.”
Dec-06 Physicist Nishina Yoshio (仁科 芳雄) was born #OTD in 1890. He spent time at Cambridge and Copenhagen in the 1920s, where he contributed to the development of quantum electrodynamics, then returned to Japan and established a national program of modern physics research.
Dec-07 Apollo 17, the last mission that took humans to the Moon (or beyond low Earth orbit), launched from Kennedy Space Center #OTD in 1972. Images: NASA (
Dec-07 ...and the last episode aired #OTD in 1985.
Dec-07 Neat paper published #OTD in 1999 by Falcke, Melia, and Agol in The Astrophysical Journal. They showed that imaging the supermassive black hole at the center of our galaxy with VLBI might be feasible. A real how it started / how it's going! Image: Event Horizon Telescope Collab
Dec-08 Astrophysicist Margaret Geller was born #OTD in 1947. She is known for her work on the distribution of galaxies and clusters, which showed that the Universe is full of unexpected structures and great voids, and for helping the public visualize our place in the cosmos. Image: AIP
Dec-09 Computer science pioneer and United States Navy rear admiral Grace Hopper was born #OTD in 1906. As far as I’m aware, she is the only person who has both a supercomputer and a US Navy destroyer named after her. Image: Computer History Museum
Dec-10 Ada Lovelace, née Augusta Ada Byron, was born #OTD in 1815. A mathematician and the first published computer programmer, she offered a prescient vision of what computing would become. Portrait: Margaret Sarah Carpenter (1836)
Dec-11 Astronomer Annie Jump Cannon was born #OTD in 1863. She was a pioneer of stellar classification and co-creator of the Harvard Classification Scheme. Over her lifetime she *manually* classified around 350,000 stars. Image: Harvard University, Radcliffe Archives
Dec-11 Physicist Max Born was...born... #OTD in 1882. In 1926 he formulated a rule for the statistical likelihood of a measurement on a quantum system yielding a particular outcome. Born’s rule says the probability is the square of an amplitude obtained from the system’s wave function.
Dec-12 Io hanging over Jupiter, casting its shadow on the clouds below. An image captured #OTD in 2000 by @CassiniSaturn as it flew by en route to Saturn. Credit: NASA/JPL/University of Arizona
Dec-13 The last moonwalk began #OTD in 1972. No one has set foot on the moon since Apollo 17 astronauts Eugene Cernan and Harrison Schmitt, 48 years ago. Images: NASA
Dec-14 Max Planck presented work on blackbody radiation to the German Physical Society #OTD in 1900. His novel “quantum hypothesis” suggested that light of frequency f should be treated as if emission and absorption by matter occurs only in discrete chunks of energy E=hf. Image: AIP
Dec-14 Now, something that isn’t widely known is that “h” is not the only fundamental constant that was introduced during Planck’s presentation to the German Physical Society #OTD in 1900!
Dec-15 Physicist Freeman Dyson was born #OTD in 1923. He was known for his work in quantum electrodynamics and –– among many other things –– his eschatological musings about physics and the prospects for life in the far-flung future. Photo: Heka Davis / AIP
Dec-15 I’ve seen a few tweets today about Wolfgang Pauli, on the anniversary of his death. I don’t usually do #OTD tweets on the date someone passed away, but...
Dec-17 Émilie du Châtelet, who hypothesized conservation of energy, established kinetic energy as distinct from momentum and proportional to (speed)², and combined Newton, Leibniz, and her own original ideas in "Institutions de Physique," was born #OTD in 1706. Portrait: M.Q. de La Tour
Dec-17 Sister Mary Kenneth Keller was born #OTD in 1913. She designed Beginner’s All Purpose Symbolic Instruction Code — BASIC — with John G. Kemeny and Thomas E. Kurtz, and was the first woman in the US to earn a PhD in Computer Science. 10 PRINT “HAPPY BIRTHDAY” 20 GOTO 10
Dec-18 J.J. Thomson was born #OTD in 1856. He discovered the electron, developed experimental techniques that led to mass spectroscopy, trained physicists like Rutherford and Bohr, but was ~betrayed~ by his own son in the ultimate act of filial physics rebellion.
Dec-19 An #OTD from last year about Albert Michelson, aether, gravitational waves, and... the TV show Bonanza?
Dec-20 Carl Sagan passed away #OTD in 1996. In his final interview he left us with two messages that are still relevant today: one emphasizing the importance of a science literate public, the other a warning about how hard it is to extract ourselves when we’ve been conned.
Dec-21 Here’s a thread from last year about mathematical physicist Cécile DeWitt-Morette. I was very fond of Cécile — a truly kind and generous person — so this is one of my favorite #OTD threads.
Dec-22 Chemist & educator St. Elmo Brady was born #OTD in 1884. He was the first Black American to receive a PhD in Chemistry (University of Illinois, 1916). Brady worked on organic acids, infrared spectroscopy, and halogen compounds, and he expanded chem programs at four schools.
Dec-22 Radio engineer, amateur astronomer, and Chicagoan Grote Reber was born #OTD in 1911. After reading about Karl Jansky’s accidental discovery of galactic radio emissions, he built a 9m radio telescope *in his back yard* and carried out the first radio survey of the sky. Image: NRAO
Dec-23 Brattain, Bardeen, and Shockley demonstrated their rudimentary point-contact transistor at Bell Labs #OTD in 1947. It had a gain of about 18, amplifying an audio signal by a factor of ~100. The underlying principle is central to all modern technology. Image: AT&T Archives
Dec-24 The Apollo 8 astronauts performed lunar orbit insertion #OTD in 1968. Frank Borman, Jim Lovell, and Bill Anders became the first humans to orbit the moon, the first to see an earthrise, fifty-two years ago today. Image: NASA
Dec-26 Mathematician John Conway was born #OTD in 1937. He made broad and profound contributions across all of mathematics, but he is maybe best known by the general public for his "game of life" cellular automaton. Conway died earlier this year from COVID-19.
Dec-28 Astronomer Maarten Schmidt was born #OTD in 1929. In 1963 he recognized the highly redshifted Balmer series in the spectra of radio source 3C 273. This meant the quasi-stellar object, or "quasar," was about 3 billion light years away and brighter than the brightest known galaxy!
Dec-28 The great polymath John von Neumann — mathematician, physicist, computer scientist — was born #OTD in 1903. He considered his contributions to quantum mechanics to be most important, but to get a sense of the breadth of his work look at his Wikipedia “known for” list.
Dec-29 The first photo of the Andromeda galaxy, then thought to be a nebula, was taken by astronomer Isaac Roberts #OTD in 1888. The image, captured with his 20" reflector, revealed a clear spiral structure. But scientists assumed M31 was a gas cloud in our galaxy. Image: Isaac Roberts
I've noticed that sometimes a link returned by a search is a dead link, even though twitter returned it from their own query. When I see instances of that, I search for an active link to include in this web page. However, there's so much data, I'm sure there will be some dead links in the above. When that happens, you could still find an active link by using the twitter search with keywords, e.g., twitter.com/search?q=from:mcnees%20OTD%20uhlenbeck