~Henri Poincaré

The 198th day of the year; 198 is a Harshad number, divisible by the sum of its digits. A Harshad number, or Niven number in a given number base, is an integer that is divisible by the sum of its digits when written in that base. Harshad numbers were defined by D. R. Kaprekar, a mathematician from India. The word "Harshad" comes from the Sanskrit harṣa (joy) + da (give), meaning joy-giver. The Niven numbers take their name from Ivan M. Niven from a paper delivered at a conference on number theory in 1997.

(Students might try to find a pair of consecutive numbers greater than 10 which are harshad numbers)

198 nines followed by a one is prime 9999...... 91. *Derek Orr@Derektionary

198 is between the twin primes 197 and 199. If you multiply 198 by its reversal, 891, you get 176,418 which is between the twin primes 176,417 and 176,419. Is there another example of this curiosity?

More Math Facts for every year date here

**EVENTS**

**In 709 BC**, the earliest record of a confirmed total solar eclipse was written in China. From: Ch'un-ch'iu, book I: "Duke Huan, 3rd year, 7th month, day jen-ch'en, the first day (of the month). The Sun was eclipsed and it was total." This is the earliest direct allusion to a complete obscuration of the Sun in any civilisation. The recorded date, when reduced to the Julian calendar, agrees exactly with that of a computed solar eclipse. Reference to the same eclipse appears in the Han-shu ('History of the Former Han Dynasty') (Chinese, 1st century AD): "...the eclipse threaded centrally through the Sun; above and below it was yellow." Earlier Chinese writings that refer to an eclipse do so without noting totality.*TIS

**In 1778,** David Rittenhouse observed a total solar eclipse in Philadelphia. In a letter to him, dated 17 Jul 1778, Thomas Jefferson wrote that "We were much disappointed in Virginia generally on the day of the great eclipse, which proved to be cloudy." Rittenhouse (1732-1796) was not only an American astronomer, but also a mathematician and public official. He is reputed to have built the first American-made telescope and was the first director of the U.S. Mint (1792-1795).*TIS

Jefferson was an excellent applied mathematician and had contacted Rittenhouse on another occasion. Travelling through France ten years later, " in 1788, he noticed peasants near Nancy ploughing, and fell to wondering about the design of the moldboard, that is, the surface which turns the earth: he spent the next ten years working on this, on and off, wondering how to achieve the most efficient design, both offering least frictional resistance, and which also would be easy for farmers out in the frontiers to construct, far from technical help. He consulted the Pennsylvania mathematician Robert Patterson (born in Ireland in 1743), and consulted also another Philadelphia luminary, the self-taught astronomer and mathematical instrument-maker David Rittenhouse (1732-1796)." Jefferson also communicated with Thomas Paine about bridge design, suggesting the use of catenary arches. Jefferson is believed to be the first person ever to use the term "catenary" in English.

**1831 ** This is the date of birth of the man who would produce the birth of the modern slide rule, Victor Mayer Mannheim. The slide rule began with the creation of a single wooden logarithmic scale, the Gunter scale, a few decades after their creation by Napier. Within a half dozen years William Oughtred came up with the first paired scales, a pair of linear log scales, and another that were circular. Minor changes happened to the scale for over two hundred years. For example, Peter Mark Roget whose name is associated so closely with the thesaurus, in 1815 added the log-log scale (the logarithm of the logarithm of the number on the C and D scales... ) on the slide rule which facilitated finding powers and roots of numbers. Finally, in 1850, Mannheim would add the sliding runner, the hair line that ties together the various scales. Some suggest Newton may have created a single earlier version when he had a rule made to solve cubics requiring alignments of three log scales, but no written or physical evidence of such has been found.

**1850 **Vega became the first star (other than the Sun) to be photographed, when it was imaged by William Bond and John Adams Whipple at the Harvard College Observatory. The photo was a daguerreotype. *Wik

**1860** Four years before his death, partly due to his wife, Mary, (following the recommendations of a doctor who advocated homeopathic cold water cures) made Boole lie shivering for hours between cold wet sheets, George Boole wrote a letter to Augustus DeMorgan about his belief in homeopathy. George was a follower of homeopathic practices, but perhaps with a little less enthusiasm than his wife.

**1879**It was announced in Nature that Kempe had proved the four-color conjecture. A correct proof, based on Kempe’s ideas, had to wait another century. [N. L. Biggs, et al., Graph Theory 1736–1936, p. 94] *VFR

**1935**The ﬁrst problem was entered into the Scottish Book, a large bound notebook that Stefan Banach brought to the Scottish Cafe in LLw´ow for mathematicians to record research problems. Many of the problems oﬀered prizes to the solver. They ranged from “2 small beers” to “100 grammes of caviar.” This book has been translated into English and edited by R. D. Mauldin. (below) *VFR ..(A PDF file of the book is now available, thanks to a tip from Robin Whitty at theoremoftheday.org )in the 1930s and 1940s, mathematicians from the Lwów School collaboratively discussed research problems, particularly in functional analysis and

topology. Stanislaw Ulam recounts that the tables of the café had marble tops, so they could write in pencil, directly on the table, during their discussions. To keep the results from being lost, and after becoming annoyed with their writing directly on the table tops, Stefan Banach's wife provided the mathematicians with a large notebook, which was used for writing the problems and answers and eventually became known as the Scottish Book. The book—a collection of solved, unsolved, and even probably unsolvable problems—could be borrowed by any of the guests of the café. For problem 153, which was later recognized as being closely related to Stefan Banach 's "basis problem", Stanislaw Mazur offered the prize of a live goose. This problem was solved only in 1972 by Per Enflo, who was presented with the live goose in a ceremony that was broadcast throughout Poland.

The café building now houses the Universal Bank at the street address of 27 Taras Shevchenko Prospekt.*Wik

**1962**The first potential US women in space, often called the Mercury 13 in comparison to the original Mercury 7 astronauts would get a hearing in congress beginning on this day. The house convened public hearings before a special Subcommittee on Science and Astronautics. Significantly, the hearings investigated the possibility of gender discrimination a two full years before the Civil Rights Act of 1964 made that illegal, making these hearings a marker of how ideas about women's rights permeated political discourse even before they were enshrined in law. The hearings would abruptly be terminated at lunch the next day. In less than a year, Soviet cosmonaut Valentina Tereshkova became the first woman in space on June 16, 1963. In response, Clare Boothe Luce published an article in Life criticizing NASA and American decision makers. By including photographs of all thirteen Lovelace finalists, she made the names of all thirteen women public for the first time. (The Time issue is available at Google Books here. Astronaut Sally Ride became the first American woman in space in 1983 on STS-7. *Wik

1969 New York Times Apologizes for ridicule of Robert H. Goddard. and his report, “A Method of Reaching Extreme Altitudes,” published by the Smithsonian press in 1920.

In a famously nasty 1920 editorial, The New York Times ridiculed his ideas about rocketry, declaring that his claim that a rocket could fly in the vacuum of space would “deny a fundamental law of dynamics, and only Dr. Einstein and his chosen dozen, so few and fit, are licensed to do that.”*discovermagazine.com

(On July 17, 1969, as Apollo 11 was racing moonward, the Times published a gently self-mocking correction: “Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th Century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error.”)

**1997**"You DON'T have mail"... A programming error temporarily threw the Internet into disarray in a preview of the difficulties that inevitably accompany a world dependent on e-mail, the World Wide Web, and other electronic communications.

At 2:30 a.m. Eastern Daylight Time, a computer operator in Virginia ignored alarms on the computer that updated Internet address information, leading to problems at several other computers with similar responsibilities. The corruption meant most Internet addresses could not be accessed, resulting in millions of unsent e-mail message. *This Day in History, Computer History Museum

**2011**NASA's Dawn Spacecraft Enters Orbit Around Vesta

NASA's Dawn spacecraft on Saturday became the first probe ever to enter orbit around an object in the main asteroid belt between Mars and Jupiter. *NASA

**1698 Pierre Louis de Maupertuis**, (Saint-Malo, 17 July 1698 – Basel, 27 July 1759) developer of the principle of least action. *VFR a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Berlin Academy of Science, at the invitation of Frederick the Great.

Maupertuis made an expedition to Lapland to determine the shape of the earth. He is often credited with having invented the principle of least action; a version is known as Maupertuis' principle – an integral equation that determines the path followed by a physical system. His work in natural history has its interesting points, since he touched on aspects of heredity and the struggle for life.*Wik (he died in the home of Johann II Bernoulli, whose death occurred on this same date, (see Deaths)

John S. Wilkins@john_s_wilkins pointed out in a tweet that "Maupertuis was the first scientific evolutionist, 7 years after first edition of Systema Naturae."

**1752 Barnaba Oriani**(July 17 1752 - November 12 1832) Italian geodesist, astronomer and scientist. After getting his elementary education in Carignano, he went on to study at the College of San Alessandro in Milan, under the tutelage and with the support of the Order of Barnabus, which he later joined. After completing his studies in the humanities, physical and mathematical sciences, philosophy, and theology, he was ordained as a priest in 1775.

Oriani was a devoted friend of the Theatine monk, Giuseppe Piazzi, the discoverer of Ceres. Oriani and Piazzi worked together for thirty-seven years, cooperating on many astronomical observations.For his work in astronomy, Oriani was honored by naming asteroid (4540) "Oriani". This asteroid had been discovered at the Osservatorio San Vittore in Bologna, Italy on November 6, 1988. *TIA

**1831 Victor Mayer Amédée Mannheim**(17 July 1831 – 11 December 1906) was the inventor of the modern slide rule. Around 1850, he introduced a new scale system that used a runner to perform calculations. This type of slide rule became known under the name of its inventor: the Mannheim.*Wik

**1837 Wilhelm Lexis**(July 17, 1837, Eschweiler – October 25, 1914, Göttingen), studied data presented as a series over time thus initiating the study of time series.*SAU Although the author of an

*Allgemeine Volkswirtschaftslehre*(general economics book) (1910) and certainly a distinguished economist, even a pioneer of Law and Economics thinking and of the study of consumption and crises, Lexis is today primarily known as a statistician, partially due to his creation of the Lexis ratio. His reputation as a demographer is underlined by the ubiquity of Lexis Diagrams, which are named for him, although primary credit for their invention belongs to Gustav Zeuner and O. Brasche

^{}(a notable example of Stigler's law of eponymy). He is also one of the founding fathers of the interdisciplinary, professional study of insurance. A

*Kathedersozialist*, he was closely affiliated with academic policy makers in Prussia and one of Friedrich Althoff’s experts and the editor of important works on German higher education, most famously the six-volume

*Das Unterrichtswesen im Deutschen Reich*, compiled for the St. Louis World's Fair of that year and still the key reference work for that time. *Wik

**1863 Herbert Richmond**(17 July 1863 in Tottenham, Middlesex, England - 22 April 1948 in Cambridge, England) studied at Cambridge and spent his whole career there, His main interest was in Algebraic Geometry. He became an honorary member of the EMS in 1930.*SAU

**1868 Peter Comrie**(17 July 1868 in Muthill, near Crieff, Perthshire, Scotland

Died: 20 Dec 1944 in Edinburgh, Scotland) graduated from St Andrews and after a series of teaching posts became Rector of Leith Academy. He was much involved in the EMS, becoming Secretary in 1911 and President in 1916 and 1917.*SAU

**1894 Georges Henri Joseph Édouard Lemaître**(17 July 1894 – 20 June 1966) was a Belgian priest, astronomer and professor of physics at the Catholic University of Louvain. He was the first person to propose the theory of the expansion of the Universe, widely misattributed to Edwin Hubble.[1][2] He was also the first to derive what is now known as the Hubble's law and made the first estimation of what is now called the Hubble constant, which he published in 1927, two years before Hubble's article.[3][4][5][6] Lemaître also proposed what became known as the Big Bang theory of the origin of the Universe, which he called his 'hypothesis of the primeval atom' *Wik

**1909 Geoffrey Walker**(17 July 1909 - 31 March 2001) studied at Oxford and Edinburgh. He taught at Imperial College London, Liverpool and Sheffield before returning to Liverpool as Professor of Pure Mathematics. He worked on Differential Geometry, Relativity and Cosmology.*SAU Walker was an accomplished geometer, but he is best remembered today for two important contributions to general relativity. Together with H. P. Robertson, the well known Robertson-Walker metric for the Friedmann-Lemaître-Robertson-Walker cosmological models, which are exact solutions of the Einstein field equation. Together with Enrico Fermi, he introduced the notion of Fermi-Walker differentiation.*Wik

**1920 Gordon Gould**(July 17, 1920 – September 16, 2005) American physicist who coined the word "laser" from the initial letters of "Light Amplification by Stimulated Emission of Radiation." Gould was inspired from his youth to be an inventor, wishing to emulate Marconi, Bell, and Edison. He contributed to the WWII Manhattan Project, working on the separation of uranium isotopes. On 9 Nov 1957, during a sleepless Saturday night, he had the inventor's inspiration and began to write down the principles of what he called a laser in his notebook Although Charles Townes and Arthur Schawlow, also successfully developed the laser, eventually Gould gained his long-denied patent rights. *TIS

**1975 Terence "Terry" Chi-Shen Tao**FAA FRS (17 July 1975, Adelaide - ), is an Australian mathematician working in harmonic analysis, partial differential equations, additive combinatorics, ergodic Ramsey theory, random matrix theory, and analytic number theory. He currently holds the James and Carol Collins chair in mathematics at the University of California, Los Angeles. In August 2006, at the 25th International Congress of Mathematicians in Madrid, he became one of the youngest persons, the first Australian, and the first UCLA faculty member ever to be awarded a Fields Medal. *Wik

**1790 Johann II Bernoulli**died (28 May 1710 in Basel, Switzerland - 17 July 1790 in Basel, Switzerland) Johann II Bernoulli (also known as Jean), the youngest of the three sons of Johann Bernoulli. He studied law and mathematics, and, after travelling in France, was for five years professor of eloquence in the university of his native city. In 1736 awarded the prize of the French Academy for his suggestive studies of Aether On the death of his father he succeeded him as professor of mathematics. He was thrice a successful competitor for the prizes of the Academy of Sciences of Paris. His prize subjects were, the capstan, the propagation of light, and the magnet. He enjoyed the friendship of P. L. M. de Maupertuis, who died under his roof (July 27, 1759) while on his way to Berlin. He himself died in 1790. His two sons, Johann and Jakob, are the last noted mathematicians of the Bernoulli family. *Wik

**1912 Jules Henri Poincare**(29 April 1854 – 17 July 1912) died very suddenly from an embolism while dressing, in his 59th year. *VFR French mathematician, theoretical physicist, engineer, and a philosopher of science. He is often described as a polymath, and in mathematics as The Last Universalist, since he excelled in all fields of the discipline as it existed during his lifetime.

As a mathematician and physicist, he made many original fundamental contributions to pure and applied mathematics, mathematical physics, and celestial mechanics. He was responsible for formulating the Poincaré conjecture, one of the most famous problems in mathematics. In his research on the three-body problem, Poincaré became the first person to discover a chaotic deterministic system which laid the foundations of modern chaos theory. He is also considered to be one of the founders of the field of topology.

Poincaré introduced the modern principle of relativity and was the first to present the Lorentz transformations in their modern symmetrical form. Poincaré discovered the remaining relativistic velocity transformations and recorded them in a letter to Dutch physicist Hendrik Lorentz (1853–1928) in 1905. Thus he obtained perfect invariance of all of Maxwell's equations, an important step in the formulation of the theory of special relativity.

The Poincaré group used in physics and mathematics was named after him.*Wik

His Poincaré Conjecture holds that if any loop in a given three-dimensional space can be shrunk to a point, the space is equivalent to a sphere. Its proof remains an unsolved problem in topology.*TIS

His family gravestone at Cimetière de Montparnasse in Paris is covered with coins, flowers, and notes. One telling him that "It has been proven."

**1917 Giuseppe Veronese**(7 May 1854 – 17 July 1917) Although his work was severely criticised as unsound by Peano, he is now recognised as having priority on many ideas that have since become parts of transfinite numbers and model theory, and as one of the respected authorities of the time, his work served to focus Peano and others on the need for greater rigor.

He is particularly noted for his hypothesis of relative continuity which was the foundation for his development of the first non-archimedean linear continuum.*SAU

**1944 William James Sidis**(April 1, 1898 – July 17, 1944) an American child prodigy with exceptional mathematical and linguistic abilities. He became famous first for his precocity, and later for his eccentricity and withdrawal from the public eye. He avoided mathematics entirely in later life, writing on other subjects under a number of pseudonyms. The difficulties Sidis encountered in dealing with the social structure of a collegiate setting may have shaped opinion against allowing such children to rapidly advance through higher education in his day.*Wik

**1963 Bevan Braithwaite Baker**(1890 in Edinburgh, Scotland - 1 July 1963 in Edinburgh, Scotland) graduated from University College London. After service in World War I he became a lecturer at Edinburgh University and was Secretary of the EMS from 1921 to 1923. He left to become Professor at Royal Holloway College London.*SAU

**1998 Sir Michael James Lighthill**(23 January 1924 – 17 July 1998) was a British mathematician who contributed to supersonic aerofoil theory and, aeroacoustics which became relevant in the design of the Concorde supersonic jet, and reduction of jet engine noise. Lighthill's eighth power law which states that the acoustic power radiated by a jet is proportional to the eighth power of the jet speed. His work in nonlinear acoutics found application in the lithotripsy machine used to break up kidney stones, the study of flood waves in rivers and road traffic flow. Lighthill also introduced the field of mathematical biofluiddynamics. Lighthill followed Paul Dirac as Lucasian professor of Mathematics (1969) and was succeeded by Stephen Hawking *TIS

Credits :

*CHM=Computer History Museum

*FFF=Kane, Famous First Facts

*NSEC= NASA Solar Eclipse Calendar

*RMAT= The Renaissance Mathematicus, Thony Christie

*SAU=St Andrews Univ. Math History

*TIA = Today in Astronomy

*TIS= Today in Science History

*VFR = V Frederick Rickey, USMA

*Wik = Wikipedia

*WM = Women of Mathematics, Grinstein & Campbell

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