March 31: René Descartes

René Descartes

March 31, 1596 – February 11, 1650

René Descartes was a French philosopher, mathematician, scientist, and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the "Father of Modern Philosophy," and much of subsequent Western philosophy is a response to his writings, which continue to be studied closely to this day. In particular, his Meditations on First Philosophy continues to be a standard text at most university philosophy departments. Descartes' influence in mathematics is also apparent, the Cartesian coordinate system allowing geometric shapes to be expressed in algebraic equations being named for him. He is accredited as the father of analytical geometry. Descartes was also one of the key figures in the Scientific Revolution.

Descartes was a major figure in 17th century continental rationalism, later advocated by Hobbes, Baruch Spinoza and Gottfried Leibniz, and opposed by the empiricist school of thought consisting of Locke, Berkeley, and Hume. Leibniz, Spinoza and Descartes were all well versed in mathematics as well as philosophy, and Descartes and Leibniz contributed greatly to science as well. As the inventor of the Cartesian coordinate system, Descartes founded analytic geometry, the bridge between algebra and geometry, crucial to the discovery of calculus and analysis. His most famous statement is: Cogito ergo sum (I think, therefore I am).

Descartes' theory provided the basis for the calculus of Newton and Leibniz, by applying infinitesimal calculus to the tangent line problem, thus permitting the evolution of that branch of modern mathematics. This appears even more astounding considering that the work was just intended as an example to his Discours de la méthode pour bien conduire sa raison, et chercher la verité dans les sciences (Discourse on the Method to Rightly Conduct the Reason and Search for the Truth in Sciences, better known under the shortened title Discourse on Method).

Descartes' rule of signs is also a commonly used method to determine the number of positive and negative zeros of a polynomial.

Descartes created analytic geometry, and discovered an early form of the law of conservation of momentum (the term momentum refers to the momentum of a force). He outlined his views on the universe in his Principles of Philosophy.

Descartes also made contributions to the field of optics. He showed by using geometric construction and the law of refraction (also known as Descartes' law) that the angular radius of a rainbow is 42 degrees (i.e. the angle subtended at the eye by the edge of the rainbow and the ray passing from the sun through the rainbow's centre is 42°). He also independently discovered the law of reflection, and his essay on optics was the first published mention of this law.

One of Descartes most enduring legacies was his development of Cartesian geometry which uses algebra to describe geometry. He also invented the notation which uses superscripts to show the powers or exponents, for example the 2 used in x^2 to indicate squaring.

March 30: Bernhard Schmidt

Bernhard Woldemar Schmidt
March 30, 1879 – December 1, 1935

Bernhard Schmidt was an Estonian Swedish optician who spent his adult life in Germany. In 1930 he invented the Schmidt telescope which corrected for the optical errors of spherical aberration, coma, and astigmatism, making possible for the first time the construction of very large, wide-angled reflective cameras of short exposure time for astronomical research.

When he was 15 years old, he experimented with gunpowder. He packed an iron pipe with a charge, but through a mistake with the fuse the pipe exploded, and he lost the thumb and index finger of his right hand. Despite his mother's attempts to clean and bandage the wounds, surgeons in Tallinn later amputated the whole hand. This event appears to have deepened his reserve and introspection, qualities well noted by his contemporaries in later life.

Schmidt developed an early interest in astronomy and optics. Gradually, he found his true calling, namely the grinding and polishing of highly precise optics for astronomical applications. He seems to have begun the grinding of mirrors sometime around 1901, and thereafter began to sell some of his products to amateur astronomers. By March 1904, he had made so much progress in his new endeavor that after finishing his studies, he was soon in contact with professionals at the major observatories in Germany. His business rapidly took off when noted astronomers such as Hermann Carl Vogel, and Karl Schwarzschild realized the excellence of Schmidt's mirrors for their researches.

During 1927 and 1929, Schmidt participated in two solar eclipse expeditions mounted by the Hamburg Observatory, the first to northern Sweden and the second to the Philippines. It was during this second trip that Schmidt announced to his companion, the astronomer Walter Baade, the most important invention of Schmidt's lifetime, indeed an invention that revolutionized astronomy and optical design in the second half of the 20th century, namely his wide-angle reflective camera.

According to Baade, he had abandoned at least one solution already, when finally he hit upon his ultimate design, which involved a novel, indeed bold departure from traditional optical designs. Schmidt realized that by employing a large spherically shaped mirror (instead of the normal paraboloidal mirror of a reflector telescope) and a smaller apertured diaphragm placed at the center of curvature of the mirror, he could at a stroke eliminate coma and astigmatism. He would be left, however, with spherical aberration which is just as damaging to image sharpness.

Schmidt built his first "Schmidtspiegel"(which came to be known as the Schmidt camera) in 1930, a breakthrough which caused a sensation around the world. He employed a very clever method (the so-called "vacuum pan" method) to make the difficult "corrector plate," so that the system gave superb images. The vacuum pan involved carefully warping the glass lens under partial vacuum and then polishing a smooth curve into it. After release of the vacuum, the lens would spring back into the "Schmidt shape" needed for the camera. No one had ever made a lens in this way before.

Schmidt fell ill at the end of November 1935 and died on December 1. Soon after his death, through the advocacy of Walter Baade when he arrived at the Mount Wilson Observatory in the United States, the Schmidt telescope idea took off. An 18" Schmidt was produced in 1938 and then ten years later, the famous 48" Samuel Oschin Schmidt-telescope was built at Mount Palomar Observatory. This last telescope produced a flood of new observations and information. It proved the brilliance of the Schmidt concept beyond doubt.

Subsequently at Bergedorf in 1955 a large, well-constructed Schmidt was dedicated. The 2-meter Schmidt telescope of the Karl Schwarzschild Observatory was built later and remains the largest Schmidt camera in the world, although more technologically advanced versions have since been produced. The Bergedorf Schmidt was moved to Calar Alto Observatory in 1976.

The Lunar crater Schmidt is named, in part, in his honor.

March 29: Tullio Levi-Civita

Tullio Levi-Civita

March 29, 1873 — December 29, 1941

Tullio Levi-Civita was an Italian mathematician, most famous for his work on absolute differential calculus (tensor calculus) and its applications to the theory of relativity but who also made significant contributions in other areas. He was a pupil of Gregorio Ricci-Curbastro, the inventor of tensor calculus. His work included foundational papers in both pure and applied mathematics, celestial mechanics (notably on the three-body problem) and hydrodynamics.

In 1900 he and Ricci-Curbastro published the theory of tensors in Méthodes de calcul différentiel absolu et leurs applications which Albert Einstein used as a resource to master the tensor calculus, a critical tool in Einstein's development of the theory of general relativity. Levi-Civita's series of papers on the problem of a static gravitational field were also discussed in his 1915–1917 correspondence with Einstein. The correspondence was initiated by Levi-Civita, as he found mathematical errors in Einstein's use of tensor calculus to explain theory of relativity. Levi-Civita methodically kept all of Einstein's replies to him, and even though Einstein hadn't kept Levi-Civita's, the entire correspondence could be re-constructed from Levi-Civita's archive. It's evident from these letters that, after numerous letters, the two men had grown to respect each other. 

In one of the letters, regarding Levi-Civita's new work, Einstein wrote

"I admire the elegance of your method of computation; it must be nice to ride through these fields upon the horse of true mathematics while the like of us have to make our way laboriously on foot".

In 1933 Levi-Civita contributed to Paul Dirac's equations in quantum mechanics as well.

His textbook on tensor calculus, The Absolute Differential Calculus (originally a set of lecture notes in Italian co-authored with Ricci-Curbastro), remains one of the standard texts more than a century after its first publication, with several translations available.

The 1938 race laws enacted by the Italian Fascist government deprived Levi-Civita of his professorship and of his membership of all scientific societies. He died isolated from the rest of the scientific world in his apartment in Rome in 1941.

Later on, when asked what he liked best about Italy, Einstein said "spaghetti and Levi-Civita".

Analytic dynamics was another aspect of Levi-Civita's studies: many of his articles examine the three body problem. He wrote articles on hydrodynamics and on systems of differential equations. He is credited with improvements to the Cauchy-Kowalevski theorem, on which he wrote a book in 1931. In 1933, he contributed to work on the Dirac equation. He developed the Levi-Civita field, a system of numbers that includes infinitesimal quantities.

The Royal Society awarded him the Sylvester Medal in 1922 and elected him as a fellow in 1930. He became an honorary member of the London Mathematical Society, of the Royal Society of Edinburgh, and of the Edinburgh Mathematical Society, following his participation in their colloquium in 1930 at the University of St Andrews. He was also a member of the Accademia dei Lincei and the Accademia Pontificia.

The Lunar crater Levi-Civita is named in his honor.

March 28: Dinsmore Alter

Dinsmore Alter

March 28, 1888 – September 20, 1968

Dinsmore Alter was an American astronomer and meteorologist. He was born in Colfax, Washington, and attended college at Westminster College in Pennsylvania. Dinsmore performed his graduate studies at the University of Pittsburgh, and earned a master's in astronomy with additional studies in the field of meteorology. In 1911 he became an instructor at the University of Alabama, teaching physics and astronomy. The following year he became an assistant professor, then an adjunct professor in 1913.

In 1914 he moved to the University of California in Berkeley, teaching astronomy while also studying for his doctorate. He gained his Ph.D. in astronomy in 1916. By 1917 he became an assistant professor of astronomy at the University of Kansas. However, when the United States entered World War I he took time off to serve as a major in the United States Army.

After returning home following the war, he rejoined the University of Kansas, and would remain at that institution for nearly 20 years. He was promoted to assistant professor in 1919, then professor in 1924.

From 1925 until 1927 he served as the vice-president of the American Meteorological Society. He was then awarded a Guggenheim Fellowship scholarship and spent two years studying astronomy in Britain. In 1935 he took a leave from the University of Kansas and became director of the Griffith Observatory. A year later he resigned his professorship to remain director at the observatory. He also served as a research associate at Caltech in Pasadena during the same period.

After the U.S. entered the Second World War, Dr. Alter took a leave from his position to serve in the armed forces for four years. He became a colonel and served in a transport division. He remained a member of the army reserve following the war, training at Fort MacArthur, Los Angeles.

His earlier studies had focused on solar observation, but after the war he became increasingly concentrated on the Moon. As his expertise increased, he became an authority on the geology of the Moon, including its surface and history. He also remained involved in astronomy research, and in 1950 he served a term as president of the Astronomical Society of the Pacific.

In 1956 he used the 60" reflector at the Mount Wilson Observatory to observe a peculiar obscuration on part of the floor of Alphonsus crater, which brought him worldwide notice. This is a class of events now called a transient lunar phenomenon.

During 1958 he reached mandatory retirement age, and was officially retired on March 31. However he remained active during his retirement, writing several books on astronomy and performing consulting services. He also served as Director Emeritus for the Griffith Observatory.

The Lunar crater Alter is named in his honor.

March 27: Wilhelm Röntgen

Wilhelm Conrad Röntgen

March 27, 1845 – February 10, 1923

Wilhelm Röntgen was a German physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range today known as x-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901.

In 1888, he obtained the physics chair at the University of Würzburg, and in 1900 at the University of Munich, by special request of the Bavarian government. Röntgen had family in Iowa in the United States and at one time planned to emigrate. Although he accepted an appointment at Columbia University in New York City and had actually purchased transatlantic tickets, the outbreak of World War I changed his plans and he remained in Munich for the rest of his career.

During 1895 Röntgen was investigating the external effects from the various types of vacuum tube equipment —apparatus from Heinrich Hertz, Johann Hittorf, William Crookes, Nikola Tesla and Philipp von Lenard —when an electrical discharge is passed through them. In early November he was repeating an experiment with one of Lenard's tubes in which a thin aluminium window had been added to permit the cathode rays to exit the tube but a cardboard covering was added to protect the aluminium from damage by the strong electrostatic field that is necessary to produce the cathode rays. He knew the cardboard covering prevented light from escaping, yet Röntgen observed that the invisible cathode rays caused a fluorescent effect on a small cardboard screen painted with barium platinocyanide when it was placed close to the aluminium window. It occurred to Röntgen that the Hittorf-Crookes tube, which had a much thicker glass wall than the Lenard tube, might also cause this fluorescent effect.

In the late afternoon of 8 November 1895, Röntgen determined to test his idea. He carefully constructed a black cardboard covering similar to the one he had used on the Lenard tube. He covered the Hittorf-Crookes tube with the cardboard and attached electrodes to a Ruhmkorff coil to generate an electrostatic charge. Before setting up the barium platinocyanide screen to test his idea, Röntgen darkened the room to test the opacity of his cardboard cover. As he passed the Ruhmkorff coil charge through the tube, he determined that the cover was light-tight and turned to prepare the next step of the experiment. It was at this point that Röntgen noticed a faint shimmering from a bench a meter away from the tube. To be sure, he tried several more discharges and saw the same shimmering each time. Striking a match, he discovered the shimmering had come from the location of the barium platinocyanide screen he had been intending to use next.

Röntgen speculated that a new kind of ray might be responsible. 8 November was a Friday, so he took advantage of the weekend to repeat his experiments and make his first notes. In the following weeks he ate and slept in his laboratory as he investigated many properties of the new rays he temporarily termed X-rays, using the mathematical designation for something unknown. Although the new rays would eventually come to bear his name in many languages where they became known as Röntgen Rays, he always preferred the term X-rays. Nearly two weeks after his discovery, he took the very first picture using x-rays of his wife's hand, Anna Bertha. When she saw her skeleton she exclaimed "I have seen my death!"

The idea that Röntgen happened to notice the barium platinocyanide screen misrepresents his investigative powers; he had planned to use the screen in the next step of his experiment and would therefore have made the discovery a few moments later.

At one point while he was investigating the ability of various materials to stop the rays, Röntgen brought a small piece of lead into position while a discharge was occurring. Röntgen thus saw the first radiographic image, his own flickering ghostly skeleton on the barium platinocyanide screen. He later reported that it was at this point that he determined to continue his experiments in secrecy, because he feared for his professional reputation if his observations were in error.

Röntgen's original paper, "On A New Kind Of Rays" (Über eine neue Art von Strahlen), was published 50 days later on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen's discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He published a total of 3 papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology, the medical specialty which uses imaging to diagnose disease.

In 1901 Röntgen was awarded the very first Nobel Prize in Physics. The award was officially "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him". Röntgen donated the monetary reward from his Nobel Prize to his university. Like Pierre Curie several years later, Röntgen refused to take out patents related to his discovery. He did not even want the rays to be named after him.

The Lunar crater Röntgen is named in his honor. In November 2004 IUPAC named element number 111 roentgenium (Rg) in his honor.

March 26: Nathaniel Bowditch

Nathaniel Bowditch

March 26, 1773 – March 16, 1838

Nathaniel Bowditch was an early American mathematician remembered for his work on ocean navigation. He is often credited as the founder of modern maritime navigation; his book The New American Practical Navigator, first published in 1802, is still carried onboard every commissioned U.S. Naval vessel.

In 1787, aged fourteen, Bowditch began to study algebra and two years later he taught himself calculus. He also taught himself Latin in 1790 and French in 1792 so he was able to read mathematical works such as Isaac Newton's Philosophiae Naturalis Principia Mathematica. At seventeen, he wrote a letter to a Harvard University professor pointing out an error in the Principia; at eighteen, he copied all the mathematical papers he found in the Transactions of the Royal Society of London. Among his many significant scientific contributions would be a translation of Pierre-Simon Laplace's Méchanique céleste, a lengthy work on mathematics and theoretical astronomy.

Bowditch's mathematical and astronomical work earned him a significant standing, including election to the American Academy of Arts and Sciences in 1799 and the American Philosophical Society in 1809. He was offered the chair of mathematics and physics at Harvard in 1806, but turned it down. In 1804, an article on his observations of the Moon was published and in 1806 he published naval charts of several harbors, including Salem. More scientific publications followed, including a study of a meteor explosion (1807), three papers on the orbits of comets (1815, 1818, 1820) and a study of the Lissajous figures created by the motion of a pendulum suspended from two points (1815).

As well as Harvard, the United States Military Academy and the University of Virginia offered Bowditch chairs in mathematics. Bowditch again refused these offers, perhaps (in the case of the University of Virginia) because the $2,000 salary offered was two-thirds of the salary he received as president of the insurance company.

Bowditch's translation of the first four volumes of Laplace's Traité de mécanique céleste was completed by 1818. Publication of the work, however, was delayed for many years, most likely due to cost. Nonetheless, he continued to work on it with the assistance of Benjamin Peirce, adding commentaries that doubled its length.

By 1819, Bowditch's international reputation had grown to the extent that he was elected as a member of the Royal Societies of Edinburgh and London and the Royal Irish Academy.

The Oceanographic Survey Ship USNS Bowditch and the Lunar crater Bowditch are named in his honor.

March 25: Giovanni Battista Amici

Giovanni Battista Amici

March 25, 1786 - April 10, 1863

Giovanni Amici was an Italian astronomer and microscopist who invented the dipleidoscope, an  instrument used to determine true noon.

Amici was born in Modena, Italy. After studying at Bologna, he became professor of mathematics at Modena, and in 1831 was appointed inspector-general of studies in the duchy. A few years later he was chosen director of the observatory at Florence, where he also lectured at the museum of natural history.

His name is best known for the improvements he effected in the mirrors of reflecting telescopes and especially in the construction of the microscope. The Amici prism, a combination of three prisms, is still used in refracting spectroscopy. He was also a diligent and skillful observer, and busied himself not only with astronomical subjects but also with biological studies. 

In astronomy, Amici studied double stars, Jupiter's moons and designed improvements to reflecting telescope mirrors including grinding several 10-inch and 12-inch metal mirrors. With his own micrometer design, Amici made accurate measurements of the polar and equatorial diameters of the Sun. Combining botany interests with innovative advances in compound microscopes, the Italian scientist made important discoveries about the circulation of sap in plants and the processes of plant reproduction, including many details of orchid pollination and seed development.

The Lunar crater Amici is named in his honor.

March 24: Joseph Stefan

Joseph Stefan

March 24, 1835 – January 7, 1893

Joseph Stefan was a physicist, mathematician and poet of Slovene mother tongue and Austrian citizenship.

After having graduated top of his class in high school he briefly considered joining the Benedictine order but his great interest in physics prevailed. He left for Vienna in 1853 to study mathematics and physics. His professor of physics in gymnasium was Karel Robida who wrote the first Slovene physics textbook. Stefan then graduated in mathematics and physics at the University of Vienna in 1857. During his student years, he also wrote and published a number of poems in Slovene. He taught physics at the University of Vienna, was Director of the Physical Institute from 1866, Vice-President of the Vienna Academy of Sciences and member of several scientific institutions in Europe.

He published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences, and he is best known for originating a physical power law in 1879 stating that the total radiation from a black body j* is proportional to the fourth power of its thermodynamic temperature T.

Stefan deduced the law from experimental measurements made by the Irish physicist John Tyndall. In 1884 the law was derived theoretically in the framework of thermodynamics by Stefan's student Ludwig Boltzmann and hence is known as the Stefan-Boltzmann law. Boltzmann treated a heat engine with light as a working matter. This law is the only physical law of nature named after a Slovene physicist. 

Today we derive the law from Planck's law of black body radiation and is valid only for ideal black objects. With his law Stefan determined the temperature of the Sun's surface and he calculated a value of 5430 °C. This was the first sensible value for the temperature of the Sun.

Stefan provided the first measurements of the thermal conductivity of gases, treated evaporation, and among others studied diffusion, heat conduction in fluids. For his treatise on optics he received the Richard Lieben award from the University of Vienna. Flow from a droplet or particle that is induced by evaporation or sublimation at the surface is now called Stefan flow because of his early work in calculating evaporation and diffusion rates.

Very important are also his electromagnetic equations, defined in vector notation, and works in the kinetic theory of heat. He was among the first physicists in Europe who fully understood Maxwell's electromagnetic theory and one of the few outside of England who expanded on it. He calculated inductivity of a coil with a quadratic cross-section, and he corrected Maxwell's miscalculation. He also researched a phenomenon called the skin effect, where high-frequency electric current is greater on the surface of a conductor than in its interior.

The Lunar crater Stefan is named in his honor.

March 23: Norman Robert Pogson

Norman Robert Pogson
March 23, 1829 – June 23, 1891

Norman Robert Pogson was an English astronomer. By the time he was 18 years old, he had computed the orbits of two comets. He became an assistant at Radcliffe Observatory in Oxford, England in 1851. In 1860 he traveled to Madras, India, becoming the government astronomer. At the Madras Observatory he produced the Madras Catalog of 11,015 stars.

In 1861, Pogson was appointed the government astronomer at Madras, India. He was the Director from 1861 to 1891. When he arrived he had to work under harsh conditions. He found the instruments in a bad shape and there were no proper staff to assist him. In spite of all these he began a series of observations which lasted until his death 30 year later. He was credited with 50,000 observations, most of which were published by Michie Smith after Pogson's death. During his stay in Madras he discovered several minor planets and detected large number of variable stars. He named his daughters after the minor planets he discovered. He was also well known for his work in comets and solar eclipses.

His most notable contribution was to note that in the stellar magnitude system introduced by the Greek astronomer Hipparchus, stars of the first magnitude were about a hundred times as bright as stars of the sixth magnitude. His suggestion in 1856 was to make this a standard, so each decrease in magnitude represented a decrease in brightness equal to the fifth-root of 100 (or about 2.512). The Pogson Ratio became the standard method of assigning magnitudes. The magnitude relation is given as follows:

m₂ − m₁ = − 2.5log¹⁰(L₂ / L₁)

where m is the stellar magnitude and L is the luminosity, for stars 1 and 2.

In 1868 and 1871, Pogson joined the Indian solar eclipse expeditions. During his career he discovered a total of eight asteroids and 21 variable stars. He headed the Madras Observatory for 30 years until his death.

The Lunar crater Pogson and asteroid 1830 Pogson are named in his honor.

March 22: Ulugh Beg

Ulugh Beg

March 22, 1394 – October 27, 1449

Ulugh Beg was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler." Ulugh Beg was also notable for his work in astronomy-related mathematics, such as trigonometry and spherical geometry.

The teenaged ruler set out to turn the city into an intellectual center for the empire. In 1417-1420 he built a madrasa ("university" or "institute") on Registan Square in Samarkand, and invited numerous Islamic astronomers and mathematicians to study there. The madrasa building still survives. Ulugh Beg's most famous pupil in mathematics was Ghiyath al-Kashi (circa 1370 - 1429).

His own particular interests concentrated on astronomy, and in 1428 he built an enormous observatory, called the Gurkhani Zij, similar to Tycho Brahe's later Uraniborg as well as Taqi al-Din's Istanbul observatory of al-Din. Lacking telescopes to work with, he increased his accuracy by increasing the length of his sextant; the so-called Fakhri Sextant had a radius of circa 36 meters (118 ft) and the optical separability of 180" (seconds of arc). Using it he compiled the 1437 Zij-i-Sultani of 994 stars, generally considered the greatest of star catalogues between those of Ptolemy and Brahe, alongside Abd al-Rahman al-Sufi's Book of Fixed Stars. The serious errors which he found in previous Arabian star catalogues (many of which had simply updated Ptolemy's work, adding the effect of precession to the longitudes) induced him to redetermine the positions of 992 fixed stars, to which he added 27 stars from Abd al-Rahman al-Sufi's catalogue Book of Fixed Stars from 964, which were too far south for observation from Samarkand. 

This catalogue, one of the most original of the Middle Ages, was edited by Thomas Hyde at Oxford in 1665 under the title Tabulae longitudinis et latitudinis stellarum fixarum ex observatione Ulugbeighi by G. Sharpe in 1767, and in 1843 by Francis Baily in vol. xiii. of the Memoirs of the Royal Astronomical Society.

In 1437 Ulugh Beg determined the length of the sidereal year as 365.2570370...d = 365d 6h 10m 8s (an error +58s). In his measurements within many years he used a 50 m high gnomon. This value was improved by 28s 88 years later in 1525 by Nicolaus Copernicus (1473-1543), who appealed to the estimation of Thabit ibn Qurra (826-901), which was accurate to +2s.

The above-ground portion of Ulugh Beg's observatory was destroyed shortly after his death; the surviving underground chamber was excavated in 1908 by primary school teacher and amateur archaeologist Vladimir Viyatkin, later Samarkand's director of antiquities.

In mathematics, Ulugh Beg (14th century) wrote accurate trigonometric tables of sine and tangent values correct to 8 decimal places.

The crater Ulugh Beigh on the Moon was named after him by the German astronomer Johann Heinrich von Mädler in his 1830 map of the Moon.

March 21: Antonia Maury

Antonia Caetana de Paiva Pereira Maury
March 21, 1866 – January 8, 1952

Antonia Maury was an American astronomer who worked at Harvard College Observatory (HCO) along with Williamina Fleming and Annie Jump Cannon. She published an important early catalog of stellar spectra.

Maury was the granddaughter of John William Draper and niece of Henry Draper, both pioneering astronomers. In 1840 her grandfather had made the first daguerreotype image of the moon, while in 1872 her uncle made the first photograph of a star, Vega, showing absorption lines—dark lines in the star's spectrum caused by the absorption of hot gases as they cool. On her father's side, Commander Matthew Fontaine Maury, the first director of the United States Naval Observatory (1842-61), was an astronomer and oceanographer, known as the "Pathfinder of the Seas".

Antonia Maury was educated at Vassar College, graduating in 1887. She was employed at Harvard College Observatory (HCO), where she observed stellar spectra and published a catalog of classifications in 1897 (Spectra of Bright Stars Photographed with the 11-inch Draper Telescope as part of the Henry Draper Memorial, Annals of Harvard College Observatory, vol. 28, pp.1-128).

Antonia Maury's uncle, Henry Draper, had devoted great time and effort to the study of stellar spectra, and he was in the process of cataloging over 100 stars through spectral analysis when he died, in 1882, at the age of 45. Three years later Edward Charles Pickering and Williamina Fleming had begun the monumental task at the Harvard College Observatory of cataloging, according to a color index they had devised, the prismatic spectra of some 10,000 stars.

In 1886, Maury's aunt, Anna Draper, who had worked with her husband on his catalog, had established the Henry Draper Memorial to fund it. Antonia Maury was the "computer" responsible for computing and cataloging stellar spectra for bright stars in the northern hemisphere, which entailed analyzing thousands of spectral photographs for minute differences. The average pay for the "computers"—sometimes referred to as "Pickering's Harem"—was 25 cents an hour, less than half the amount paid to men.

The director of HCO at the time, Pickering, disagreed with Maury’s system of classification and explanation of differing line widths, prompting her to leave HCO. However, Ejnar Hertzsprung realized the value of her classifications and used them in his system of identifying giant and dwarf stars.

Maury's efforts to refine the spectral categories were not appreciated. Doing original theoretical work not only conflicted with Pickering's expectations for her as a "computer," but they also slowed down the work on the Draper Catalogue. Her detailed measurements of width and sharpness put him behind schedule. "She was one of the most original thinkers of all the women Pickering employed", Hoffleit notes, "but instead of encouraging her attempts at interpreting observations, he was only irritated by her independence and departure from assigned and expected routine." Frustrated by this constriction of her work, Antonia Maury left Harvard in 1891 to teach in the Gilman School in Cambridge.

In 1908, Maury returned to HCO where she remained for many years. Her most famous work there was the spectroscopic analysis of the binary star Beta Lyrae, published in 1933 (The Spectral Changes of Beta Lyrae, Annals of Harvard College Observatory, vol. 84, no. 8).

Antonia Maury, surveying the vastness of the known universe, once observed

"but the human brain is greater yet, because it can comprehend it all."

In 1943, Antonia Maury was awarded the Annie Jump Cannon Award in Astronomy by the American Astronomical Society. The lunar crater Maury is co-named after her and Matthew Fontaine Maury.

March 20: David Lasser

David Lasser

March 20, 1902 – May 5, 1996

David Lasser was one of the most influential figures of early science fiction writing, working closely with Hugo Gernsback.

In the 1920s, Lasser moved to New York, where he pursued his interest in the nascent fields of rocketry and science fiction. On 4 April 1930, he became president of the American Interplanetary Society (renamed the American Rocket Society in 1934), which he founded with Gawain and Leatrice Pendray, both regular contributors to Science Wonder Stories.

Lasser used his expertise in science, engineering, and rocketry to write The Conquest of Space (1931). It was the first non-fiction English-language book to deal with spaceflight and detailed how man could one day travel into outer space. The book was an inspiration to a generation of science-fiction writers, including Arthur C. Clarke. From 1929 to 1933, Lasser worked as the Managing Editor of Hugo Gernsback’s Stellar Publishing Corporation. He was responsible for editing all the issues of Science Wonder Stories and Wonder Stories Quarterly, as well as identifying and retaining promising writers. Lasser also edited Gernsback’s Wonder Stories from June 1930 to October 1933 and remained involved in the science fiction realm throughout his life.

The American Institute of Aeronautics and Astronautics (AIAA) currently awards the Gardner-Lasser Aerospace History Literature Award to the best original non-fiction work dealing with aeronautics or aeronautical history. The award is named to honor David Lasser and Lester Gardner.

March 19: Franz von Gruithuisen

Baron Franz von Paula Gruithuisen

March 19, 1774 – 1852

Franz von Gruithuisen was a Bavarian physician and astronomer. He taught medical students before becoming a professor of astronomy at the University of Munich in 1826.

During his period of medical studies and instruction, he was noted for his contributions to urology and lithotrity. He developed ideas on safer methods to remove bladder stones transurethrally, and his instruments served as models for subsequent devices.

Like others before and since his time, Gruithuisen believed that the Earth's moon was inhabitable. He made multiple observations of the lunar surface that supported his beliefs, including his announcement of the discovery of a city in the rough terrain to the north of Schröter crater he named the Wallwerk. This region contains a series of somewhat linear ridges that have a fishbone-like pattern, and, with the small refracting telescope he was using, could be perceived as resembling buildings complete with streets. He published his observations in 1824, but they were greeted with much skepticism by other astronomers of the time. His claims were readily refuted using more powerful instruments.

He is also noted for the discovery of bright caps on the cusps of the crescent Venus, for being the first to suggest that craters on the Moon were caused by meteorite impacts and for his prolific rate of publication. He proposed that jungles on Venus grew more rapidly than in Brazil due to the proximity of the planet to the Sun, and that as a consequence the inhabitants celebrated fire festivals— the cause of the bright caps on Venus.

The crater Gruithuisen on the Moon is named in his honor.

March 18: Philippe de La Hire

Philippe de La Hire

March 18, 1640 — April 21, 1718

Philippe de La Hire was a French mathematician and astronomer. According to Bernard le Bovier de Fontenelle he was an "academy unto himself".

He was born in Paris, the son of Laurent de La Hire, a distinguished artist. In 1660, he moved to Rome to study painting. Upon his return to Paris, he began to study science and showed an aptitude for mathematics. He became a member of French Academy of Sciences in 1678, and subsequently became active as an astronomer, calculating tables of the movements of the Sun, Moon, and planets.

From 1679–1682 he made several observations and measurements of the French coastline, and in 1683 aided in mapping France by extending the Paris meridian to the north. In 1683 La Hire assumed the chair of mathematics at the Collège Royale. From 1687 onwards he taught at the Académie d’architecture.

La Hire wrote on graphical methods, 1673; on conic sections, 1685; a treatise on epicycloids, 1694; one on roulettes, 1702; and, lastly, another on conchoids, 1708. His works on conic sections and epicycloids were founded on the teaching of Desargues, of whom he was his favourite pupil. He also translated the essay of Manuel Moschopulus on magic squares, and collected many of the theorems on them which were previously known; this was published in 1705. He also published a set of astronomical tables in 1702. La Hire's work also extended to descriptive zoology, the study of respiration, and physiological optics.

Two of his sons were also notable for their scientific achievements: Gabriel-Philippe de La Hire (1677-1719), mathematician, and Jean-Nicolas de La Hire (1685-1727), botanist.

The mountain Mons La Hire on the Moon is named in his honor.

March 17: Thomas Maclear

Sir Thomas Maclear

March 17, 1794 – July 14, 1879

Thomas Maclear was an Irish-born South African astronomer who became Her Majesty's astronomer at the Cape of Good Hope.

Dr. Maclear had a keen interest in amateur astronomy, and would begin a long association with the Royal Astronomical Society, to which he would be named a Fellow. In 1833, when the post became vacant, he was named as Royal Astronomer at the Cape of Good Hope, and arrived there aboard the Tam O'Shanter with his wife and 5 daughters, to take up his new duties in 1834. He worked with John Herschel until 1834, performing a survey of the southern sky, and continued to perform important astronomical observations over several more decades. The Maclears and Herschels formed a close friendship, the wives drawn together by the unusual occupations of their husbands and the raising of their large families. Mary Maclear, like Margret Herschel, was a noted beauty and intelligent, though suffering from extreme deafness.

In 1750 Abbe Nicolas Louis de Lacaille had measured a triangulation arc northwards from Cape Town, to determine the shape of the earth and found that the curvature of the earth was less in southern latitudes than at corresponding northern ones. Sir George Everest visited the Cape in 1820 and visited the site of LaCailles measurements. From his experience in the Himalayas he believed that the presence of considerable mountain masses in the Cape could have caused false measurements to be made by LaCaille. Between 1841 and 1848 Maclear would be occupied in performing a geodesic survey for the purpose of recalculating the dimensions and shape of the Earth. He became close friends with David Livingstone, and they shared a common interest in the exploration of Africa. He performed many other useful scientific activities, including collecting meteorological, magnetic and tide data.

In 1861 his wife died. Two years later he was granted a pension, but did not retire from the observatory until 1870. He lived thereafter at Grey Villa, Mowbray. By 1876 he had lost his sight, and he died three years later in Cape Town, South Africa. He is buried next to his wife on the grounds of the Royal Observatory.

The Lunar crater Maclear is named in his honor.

March 16: Caroline Lucretia Herschel

Caroline Lucretia Herschel

March 16, 1750 – January 9, 1848

Caroline Herschel was a German-born English astronomer, the sister of astronomer Sir William Herschel with whom she worked throughout both of their careers. Her most significant contribution to astronomy was the discovery of several comets and in particular the periodic comet 35P/Herschel-Rigollet, which bears her name.

William's interest in astronomy started as a hobby to pass time at night. He took to retiring to bed as soon as he arrived home, taking "a bason of milk" and an astronomy book for company. At breakfast the next day he would give an impromptu lecture on what he had learned the night before. Caroline became as interested as William, stating that she was "much hindered in my practice by my help being continually wanted in the execution of the various astronomical contrivances." William became known for his work on high performance telescopes, and Caroline found herself supporting his efforts.

William's telescopes gained the attention of many in the field. When comparing observations with the Astronomer Royal, Nevil Maskelyne, William's telescope proved far superior. In March 1781 he made his first observation of what would eventually prove to be the planet Uranus. In 1782, William accepted the office of King's Astronomer to George III and moved to Datchet and subsequently to Observatory House near Slough, Berkshire. The new job proved to be a mixed blessing; although it left him with ample free time to continue his astronomical observations, it also meant a reduction in income and being called upon by the king for entertainment at any time. During this time William perfected his telescope making, building a series of ever larger devices that ultimately ended with his famous 40-foot focal length instrument. Caroline was his constant assistant in his observations, also performing the laborious calculations with which they were connected. During one such observation run on the large telescope in 1783, Caroline became caught on an iron hook and when she was helped off "...they could not lift me without leaving nearly 2 ouches of my flesh behind."

In 1778 William married a rich widow. Although his new wife made every effort to stay on friendly terms with Caroline it seems her life was considerably upset. Through this period she continued her observations on her own, and made many of her discoveries. She later reconciled with the couple, and took great delight in her new nephew, John Herschel.

During her leisure hours she occupied herself with sweeping the heavens with a 27-inch focal length Newtonian telescope and by this means detected a number of astronomical objects during the years 1783 - 87, including most notably an independent discovery of M110 (NGC 205), the second companion of the Andromeda Galaxy. During 1786 - 97 she also discovered eight comets, her first comet being discovered on August 1, 1786. She had unquestioned priority on five of the comets and had rediscovered Comet Encke in 1795. The following year she was granted an annual salary of £50 by George III for her work as William's assistant.

In 1797 William's observations had shown that there were a great many discrepancies in the star catalogue published by John Flamsteed, which was difficult to use due to its having been published as two volumes, the catalogue proper and a volume of original observations. William realised that he needed a proper cross-index in order to properly explore these differences but was reluctant to devote time to it at the expense of his more interesting astronomical activities. He therefore recommended to Caroline that she undertake the task. The resulting Catalogue of Stars was published by the Royal Society in 1798 and contained an index of every observation of every star made by Flamsteed, a list of errata, and a list of more than 560 stars that had not been included.

Caroline returned to Hanover in 1822 following her brother's death, but did not abandon her astronomical studies, continuing to verify and confirm William's findings and producing a catalogue of nebulae to assist John in his work.

In 1828 the Royal Astronomical Society presented her with their Gold Medal for this work - no woman would be awarded it again until Vera Rubin in 1996.

In 1835, along with Mary Somerville, she was elected to honorary membership of the Royal Astronomical Society; they were the first honorary women members. In 1838 she was also elected as a member of the Royal Irish Academy. In 1846 at the age of 96, she was awarded the Gold Medal for Science by the King of Prussia.

March 15: Nicolas Louis de Lacaille

Abbé Nicolas Louis de Lacaille

March 15, 1713 – March 21, 1762

Abbé Nicolas Louis de Lacaille was a French astronomer. He is noted for his catalogue of nearly 10,000 southern stars, including 42 nebulous objects. This catalogue, called Coelum Australe Stelliferum, was published posthumously in 1763. It introduced 14 new constellations which have since become standard. He also calculated a table of eclipses for 1,800 years.

In honor of his contribution to the study of the southern hemisphere sky, a 60-cm telescope at Reunion Island will be named La-Caille telescope.

Born at Rumigny, in the Ardennes, he was left destitute by the death of his father, who held a post in the household of the duchess of Vendôme. Therefore, his theological studies at the College de Lisieux in Paris were undertaken at the expense of the duke of Bourbon.

After he had taken deacon's orders, however, he concentrated on science, and, through the patronage of Jacques Cassini, obtained employment, first in surveying the coast from Nantes to Bayonne, then, in 1739, in remeasuring the French arc of the meridian, for which he is honored with a pyramid at Juvisy-sur-Orge. The success of this difficult operation, which occupied two years, and achieved the correction of the anomalous result published by J. Cassini in 1718, was mainly due to Lacaille's industry and skill. He was rewarded by admission to the Academy and the appointment of mathematical professor in Mazarin college, where he worked in a small observatory fitted for his use.

His desire to observe the southern heavens led him to propose, in 1750, an astronomical expedition to the Cape of Good Hope. This was officially sanctioned by Roland-Michel Barrin de La Galissonière. Among its results were determinations of the lunar and of the solar parallax (Mars serving as an intermediary), the first measurement of a South African arc of the meridian, and the observation of 10,000 southern stars. 

Lalande said of him that, during a comparatively short life, he had made more observations and calculations than all the astronomers of his time put together. The quality of his work rivalled its quantity, while the disinterestedness and rectitude of his moral character earned him universal respect.

The crater La Caille on the Moon is named in his honor. Asteroid 9135 Lacaille (AKA 7609 P-L and 1994 EK6), discovered on October 17, 1960 by Cornelis Johannes van Houten, Ingrid van Houten-Groeneveld, and Tom Gehrels at Palomar Observatory, was also named after him.