Jean-Baptiste Biot was born #OTD in 1774. He is usually remembered for his works on electromagnetism and polarization of light, but he also uncovered the extraterrestrial origin of meteorites, in support of Chladni’s theory.
en.wikipedia.org/wiki/Jean-Ba...
Richard von Mises was born #OTD in 1883. He worked on mechanics of solids and fluids, and made several contributions to probability theory. The von Mises distribution is the equivalent of the Gaussian for circular variables.
en.wikipedia.org/wiki/Richard...
Leonhard Euler was born #OTD in 1707. One of the greatest mathematicians of all time, he developed analysis, number theory, and graph theory. In physics, he made contributions in optics, elasticity, and fluid mechanics.
en.wikipedia.org/wiki/Leonhar...
Christiaan Huygens was born #OTD in 1629. Among his many achievements, he proposed a wave theory of light later championed by Fresnel, invented the pendulum clock, and discovered Titan while studying the rings of Saturn.
en.wikipedia.org/wiki/Christi...
Edward Walter Maunder was born #OTD in 1851. He observed that sunspots tend to migrate towards the equator during the 11-year cycle, and discovered the occurrence of a prolonged minimum in the late 17th century.
en.wikipedia.org/wiki/Edward_...
He was also a keen observer of solar eclipses, and were it not for unfortunate circumstances, he would probably have preceded Eddington in confirming Einstein’s theory through the deflection of light rays past the Sun.
William Wallace Campbell was born #OTD in 1862. A pioneer of astronomical spectroscopy, he made many measurements of stellar radial velocities. He was the director of Lick Observatory.
en.wikipedia.org/wiki/William...
Thomas Johann Seebeck was born #OTD in 1770. His study of the relation between heat, electricity and magnetism, following Ørsted’s experiments, led to the discovery of the effect that bears his name, used in thermocouples.
en.wikipedia.org/wiki/Thomas_...
Guillaume Bigourdan was born #OTD in 1851. A French astronomer at Toulouse and Paris Observatory, he traveled to observe transits of Venus and solar eclipses, and published a large catalogue of nebulae.
en.wikipedia.org/wiki/Guillau...
Donald Lynden-Bell was born #OTD in 1935. The first director of the Institute of Astronomy, his most influential works bear on the dynamics of gravitational systems. He also predicted the IR excess from disks around T Tauri stars.
en.wikipedia.org/wiki/Donald_...
William Watson was born #OTD in 1715. Primarily a botanist, he suggested, independently from Benjamin Franklin, that the two « types » of electricity identified were actually surpluses of positive or negative charges.
en.wikipedia.org/wiki/William...
Sophie Germain was born #OTD in 1776. A French mathematician and physicist, she overcame prejudices against women in the sciences. Mostly known for her mathematical work in number theory, she is also a pioneer of elasticity theory.
en.wikipedia.org/wiki/Sophie_...
Bravo à Guillaume Vigoureux, 1er prix du jury de la finale PSL de "Ma thèse en 180 secondes" !
www.youtube.com/watch?v=aurf...
Adriaan van Maanen was born #OTD in 1884. He discovered the nearest solitary white dwarf. His erroneous measurement of stellar motions was one of Shapley's arguments in the debate about the extragalactic nature of spiral nebulæ.
en.wikipedia.org/wiki/Adriaan...
Tullio Levi-Civita was born #OTD in 1873. His theory of tensor calculus was the mathematical foundation of Einstein's development of general relativity. He also contributed to the three-body problem and Dirac's equation.
en.wikipedia.org/wiki/Tullio_...
Douglas Hartree was born #OTD in 1897. He developed differential analysers that prefigured computers. The Hartree-Fock method is an approach to solve self-consistently for the wavefunctions and energies of multi-electron atoms.
en.wikipedia.org/wiki/Douglas...
Wilhelm Röntgen was born #OTD in 1845. In 1895, he produced and detected the first electromagnetic radiation in the wavelength range known as X-rays. He was the first laureate of the Nobel Prize in Physics in 1901.
en.wikipedia.org/wiki/Wilhelm...
Nicolaas Hartsoeker was born #OTD in 1656. A Dutch physicist, he made contributions to the development of microscopy and is credited for discovering spermatozoids, although a priority dispute exists with van Leeuwenhoek.
en.wikipedia.org/wiki/Nicolaa...
Christopher Clavius was born #OTD in 1538. A German Jesuit and astronomer, he built on the work of Lilius to propose the reform that would be adopted under Pope Gregory XIII to bring about the Gregorian calendar in use today.
en.wikipedia.org/wiki/Christo...
Josef Stefan was born #OTD in 1835. Stefan's law, stating that the total power radiated by a blackbody goes as the fourth power of the temperature, is widely used in astronomy. A Stefan problem is a PDE problem with moving boundary.
en.wikipedia.org/wiki/Josef_S...
Peter Debye was born #OTD in 1884. A Dutch-born American physicist, he improved on Einstein's model of the heat capacity of solids by estimating the phonon contribution. With E. Hückel, he modelled the conductivity of electrolytes.
en.wikipedia.org/wiki/Peter_D...
Walter Baade was born #OTD in 1893. A German astronomer, he discovered the first Centaur in the Solar System, 944 Hidalgo, and established the existence of distinct stellar populations, the younger Pop. I, and the older Pop. II.
en.wikipedia.org/wiki/Walter_...
Pierre-Simon Laplace was born #OTD in 1749. A French polymath, he made vast contributions to analysis, probability theory, and to physical questions pertaining to celestial mechanics, fluid mechanics, and thermodynamics.
en.wikipedia.org/wiki/Pierre-...
Emmy Noether was born #OTD in 1882. She made vast contributions to algebra and mathematical physics. Noether's theorem states that symmetries of the action imply conservation laws, such as those of energy, linear and angular momenta.
en.wikipedia.org/wiki/Emmy_No...
Norman Robert Pogson was born #OTD in 1829. He spent much of his career at the Madras observatory and is best known for formalising mathematically, on a logarithmic scale, the Hipparchian system of stellar magnitudes.
en.wikipedia.org/wiki/N._R._P...
Millikan’s association to the eugenics movement led very recently to his name being removed from several buildings in California.
Interestingly, Millikan found an estimate for e that was off because he had used an incorrect value for the viscosity of the air. Feynman pointed out that it took a while for physicists to acknowledge that, a case of psychological bias in scientific methodology.
Robert Millikan was born #OTD in 1868. He measured the elementary electric charge e using an experiment that relies on the equilibrium between viscous, gravitational, and electric forces on charged oil droplets.
en.wikipedia.org/wiki/Robert_...
Antonia Maury was born #OTD in 1866. A member of the « Harvard computers » under Edward Pickering and Annie Cannon, she built a catalogue of stellar spectra and designed a classification that is at the base of the one still used.
en.wikipedia.org/wiki/Antonia...
Guillermo Haro was born #OTD in 1913. He was an important figure in the development of astronomy in Mexico. Herbig-Haro objects are small patches of bright emission formed when a protostellar jet collides with the ambient medium.
en.wikipedia.org/wiki/Guiller...