**Nature creates curved lines while humans create straight lines.**

The 23rd day of the year; 23 is the only number, n, such that n! is n digits long (decimal). 23 is also the answer to the classic Birthday Problem. (

*How many randomly selected people in a group makes the probability greater than 50% that two share a commmon birthdate.*)

**EVENTS**

**1656**Blaise Pascal wrote the ﬁrst of his eighteen Provincial Letters.

**1640**John Pell wrote Mersenne that Thomas Harriot (1560–1621) had found the law of refraction, now known as Snell’s law.*VFR

**1675**Christiaan Huygens drew a sketch in his notebook of a watch mechanism with a coiled spring regulator and then, “Eureka – I have found it”. He believed he had found a method of regulating a clock that would keep accurate time and not be affected by motion for use in attacking the problem of longitude. (Hooke had presented a watch regulated by a spring in the early 1660’s to the Royal Society for exactly the same goal in response to Huygen’s first pendulum clock. ) *Lisa Jardine, Ingenious Pursuits, pg 148

**1764**Fire gutted Harvard Hall, the last of Harvard’s original buildings. The job of replacing the valuable scientiﬁc instruments housed in the building fell to John Winthrop, the second Hollis professor of mathematics and natural philosophy at Harvard. He was also friend and advisor of George Washington. *VFR

1848 Gold discovered in California. Jonas Clark soon was on hand with a wagon load of shovels and so made a wagon load of money. He used it to found Clark University in Worcester, MA, which,in the early 1890’s, had the strongest mathematics department in the country. *VFR

In 1896, Wilhelm Roentgen first made a public lecture-demonstration of his X-ray device, in Würzburg, Germany. *TIS

1896 Two months after Rontgen discovered X-rays (the x was for unknonwn), Henri Poincare was sent photographs of these X-rays and was so amazed that he passed them on to two doctors and asked if they could duplicate Rontgen's work. On January 23 they would present a paper on their results at the French Academy with Henri Becquerel in the audience. Within months he would discover rays coming from Uranium. *Brody & Brody, The Science Class You Wished You Had

In 1911, Marie Curie's nomination to the French Academy of Sciences, having already won one Nobel Prize, is nevertheless voted down by the Academy's all-male membership. She went on to win a second Nobel Prize. *TIS

1930 Clyde Tombaugh photographed the planet Pluto, the only planet discovered in the twentieth century, after a systematic search instigated by the predictions of other astronomers. Tombaugh was 24 years of age when he made this discovery at Lowell Observatory in Flagstaff, Ariz. *TIS

*Northwestern University

1986 Science reported that a statistical analysis of word frequencies on a newly discovered poem attributed to Shakespeare concluded “There is no convincing evidence for rejecting the hypothesis that Shakespeare wrote it.” Otherwise said, the poem “ﬁts Shakespeare as well as Shakespeare ﬁts Shakespeare.” [Mathematics Magazine 59 (1986), p 183]. *VFR

1959 Robert Noyce Conceives the Idea for a Practical Integrated Circuit:

Robert Noyce, as a co-founder and research director of Fairchild Semiconductor, was responsible for the initial development of silicon mesa and planar transistors, which led to a commercially applicable integrated circuit. In 1968 Noyce went on to found Intel Corp. with Gordon Moore and Andy Grove.*CHM

**BIRTHS**

1719 John Landen (23 Jan 1719; died 15 Jan 1790) British mathematician who made important contributions on elliptic integrals. As a trained surveyor and land agent (1762-88), Landen's interest in mathematics was for leisure. He sent his results on making the differential calculus into a purely algebraic theory to the Royal Society, and also wrote on dynamics, and summation of series. Landen devised an important transformation, known by his name, giving a relation between elliptic functions which expresses a hyperbolic arc in terms of two elliptic ones. He also solved the problem of the spinning top and explained Newton's error in calculating the precession. Landen was elected a Fellow of the Royal Society in 1766. He corrected Stewart's result on the Sun-Earth distance (1771).*TIS

1785 Matthew Stewart (15 Jan 1717 in Rothesay, Isle of Bute, Scotland - 23 Jan 1785 in Catrine, Ayrshire, Scotland)was a Scottish geometer who wrote on geometry and planetary motion. Stewart's fame is based on General theorems of considerable use in the higher parts of mathematics (1746), described by Playfair as, "... among the most beautiful, as well as most general, propositions known in the whole compass of geometry." *SAU

1798 Karl Georg Christian von Staudt (January 24, 1798 – June 1, 1867) was a German mathematician born in the Free Imperial City of Rothenburg, which is now called Rothenburg ob der Tauber in Germany. From 1814 he studied in Gymnasium in Ausbach. He attended the University of Göttingen from 1818 to 1822 where he studied with Gauss who was director of the observatory. Staudt provided an ephemeris for the orbits of Mars and the asteroid Pallas. When in 1821 Comet Nicollet-Pons was observed, he provided the elements of its orbit. These accomplishments in astronomy earned him his doctorate from University of Erlangen in 1822.

The book Geometrie der Lage (1847) was a landmark in projective geometry. As Burau (1976) wrote, "Staudt was the first to adopt a fully rigorous approach. Without exception his predecessors still spoke of distances, perpendiculars, angles and other entities that play no role in projective geometry."

Furthermore, this book uses the complete quadrangle to "construct the fourth harmonic associated with three points on a straight line", the projective harmonic conjugate. *Wik (

*TIS gives birthdate as Jan 23*)

1806 Ernst Ferdinand Adolf Minding (23 Jan 1806 in Kalisz,Russian Empire (now Poland) - 3 May 1885 in Dorpat, Russia (now Tartu, Estonia))His work, which continued Gauss's study of 1828 on the differential geometry of surfaces, greatly influenced Peterson. In 1830 Minding published on the problem of the shortest closed curve on a given surface enclosing a given area. He introduced the geodesic curvature although he did not use the term which was due to Bonnet who discovered it independently in 1848. In fact Gauss had proved these results, before either Minding of Bonnet, in 1825 but he had not published them.

Minding also studied the bending of surfaces proving what is today called Minding's theorem in 1839. The following year he published in Crelle's Journal a paper giving results about trigonometric formulae on surfaces of constant curvature. Lobachevsky had published, also in Crelle's Journal, related results three years earlier and these results by Lobachevsky and Minding formed the basis of Beltrami's interpretation of hyperbolic geometry in 1868.

Minding also worked on differential equations, algebraic functions, continued fractions and analytic mechanics. In differential equations he used integrating factor methods. This work won Minding the Demidov prize of the St Petersburg Academy in 1861. It was further developed by A N Korkin. Darboux and Émile Picard pushed these results still further in 1878. *SAU

1840 Ernst Abbe (23 Jan 1840, 14 Jan 1905) German physicist who made theoretical and technical innovations in optical theory. He improved microscope design, such as the use of a condenser lens to provide strong, even illumination (1870). His optical formula, now called the Abbe sine condition, applies to a lens to form a sharp, distortion-free image He invented the Abbe refractometer for determining the refractive index of substances. In 1866, he joined Carl Zeiss' optical works, later became his partner in the company, and in 1888 became the owner of the company upon Zeiss' death. Concurrently, he was appointed professor at the Univ. of Jena in 1870 and director of its astronomical and meteorological observatories in 1878.*TIS

1853 Kazimierz Żorawski (June 22, 1866 – January 23, 1953) was a Polish mathematician. His work earned him an honored place in mathematics alongside such Polish mathematicians as Wojciech Brudzewski, Jan Brożek (Broscius), Nicolas Copernicus, Samuel Dickstein, Stefan Banach, Stefan Bergman, Marian Rejewski, Wacław Sierpiński, Stanisław Zaremba and Witold Hurewicz.[citation needed]

Żorawski's main interests were invariants of differential forms, integral invariants of Lie groups, differential geometry and fluid mechanics. His work in these disciplines was to prove important in other fields of mathematics and science, such as differential equations, geometry and physics (especially astrophysics and cosmology).*Wik

1857 Andrija Mohorovicic (23 Jan 1857; 18 Dec 1936) Croatian meteorologist and geophysicist who discovered the boundary between the Earth's crust and mantle, a boundary now named the Mohorovicic discontinuity. In 1901 he was appointed head of the complete meteorological service of Croatia and Slavonia, he gradually extended the activities of the observatory to other fields of geophysics: seismology, geomagnetism and gravitation. After the Pokuplje (Kupa Valley) earthquake of 8 Oct 1909, he analyzed the spreading of seismic waves with shallow depths through the Earth. From these, he was the first to establish, on the basis of seismic waves, a surface of velocity discontinuity separating the crust of the Earth from the mantle, now known as the Mohorovicic discontinuity.

*TIS

1862 David Hilbert (23 Jan 1862; 14 Feb 1943) German mathematician who reduced geometry to a series of axioms and contributed substantially to the establishment of the formalistic foundations of mathematics. In his book, Foundations of Geometry, he presented the first complete set of axioms since Euclid. His work in 1909 on integral equations led to 20th-century research in functional analysis (in which functions are studied as groups.) Today Hilbert's name is often best remembered through the concept of Hilbert space in quantum physics, a space of infinite dimensions.*TIS

He is recognized as one of the most influential and universal mathematicians of the 19th and early 20th centuries. Hilbert discovered and developed a broad range of fundamental ideas in many areas, including invariant theory and the axiomatization of geometry. He also formulated the theory of Hilbert spaces, one of the foundations of functional analysis.

Hilbert adopted and warmly defended Georg Cantor's set theory and transfinite numbers. A famous example of his leadership in mathematics is his 1900 presentation of a collection of problems that set the course for much of the mathematical research of the 20th century.

Hilbert and his students contributed significantly to establishing rigor and developed important tools used in modern mathematical physics. Hilbert is known as one of the founders of proof theory and mathematical logic, as well as for being among the first to distinguish between mathematics and metamathematics.*Wik

In Constance Reid's "Hilbert", she describes his mother thus: "She was an unusual woman-in the German way of expression, 'an original' - interested in philosophy and astronomy and fascinated by prime numbers."

1872 Paul Langevin (23 Jan 1872; 19 Dec 1946) French physicist who was the first to explain (1905) the effects of paramagnetism and diamagnetism (the weak attraction or repulsion of substances in a magnetic field) using statistical mechanics. He further theorized how the effects could be explained by how electron charges behaved within the atom. He popularized Einstein's theories for the French public. During WW I, he began developing a source for high intensity ultrasonic waves, which made sonar detection of submarines possible. He created the ultrasound from piezoelectric crystals vibrated by high-frequency radio circuits. In WW II, he spoke out against the Nazis, for which he was arrested and imprisoned, though he managed to escaped and fled to Switzerland.*TIS

1878 Edwin Plimpton Adams (23 Jan 1878 in Prague - 31 Dec 1956 in Princeton, USA) studied at Harvard, Göttingen and Cambridge and became Physics Professor at Princeton. He is best known for his translations of some of Einstein's lectures. *SAU

1907 Hideki Yukawa (23 Jan 1907; 8 Sep 1981) Japanese physician and physicist who shared the 1949 Nobel Prize for Physics for “his prediction of the existence of mesons on the basis of theoretical work on nuclear forces.” In his 1935 paper, On the Interaction of Elementary Particles*, he proposed a new field theory of nuclear forces that predicted the existence of the previously unknown meson. Mesons are particles heavier than electrons but lighter than protons. One type of meson was subsequently discovered in cosmic rays in 1937 by American physicists, encouraging him to further develop meson theory. From 1947, he worked mainly on the general theory of elementary particles in connection with the concept of the “non-local” field. He was the first Japanese Nobel Prize winner. *TIS (Yukawa donated a bronze crane that works as a wind chime when pushed against a traditional peace bell from which it is suspended at the Children's Peace Museum in Hiroshima. On the bell in his handwriting is the wish, "A Thousand Paper Cranes. Peace on Earth and in the Heavens."

1924 Sir Michael James Lighthill (23 Jan 1924, 17 Jul 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 (1989) *TIS

**DEATHS**

1810 Johann Wilhelm Ritter (16 Dec 1776, 23 Jan 1810) German physicist who discovered the ultraviolet region of the spectrum (1801) and thus helped broaden man's view beyond the narrow region of visible light to encompass the entire electromagnetic spectrum from the shortest gamma rays to the longest radio waves. After studying Herschel's discovery of infrared radiation, he observed the effects of solar radiation on silver salts and deduced the existence of radiation outside the visible spectrum. He also made contributions to spectroscopy and the study of electricity. *TIS

Credits

*VFR = V Frederick Rickey, USMA

*TIS= Today in Science History

*Wik = Wikipedia

*SAU=St Andrews Univ. Math History

*CHM=Computer History Museum

*FFF=Kane, Famous First Facts