January 19

Born in 1683, Jean-Pierre Christin was a versatile scientist whose work spanned physics, mathematics, and astronomy. In 1743, he proposed reversing Anders Celsius's temperature scale to designate 0° for the freezing point and 100° for boiling water, a system that became the centigrade scale. Christin conducted precise experiments on thermometry and contributed to early studies of magnetism. As an active member of the French Académie des Sciences, he published observations on comets, eclipses, and mathematical theories. His innovations in measurement and instrumentation played a key role in advancing 18th-century scientific practice. He passed away in 1755, leaving a lasting impact on the standardization of temperature measurement.

Thomas Ruddiman was born in 1674 near Boyndie, Scotland, and educated at Marischal College in Aberdeen. He gained renown for his 'Rudiments of the Latin Tongue' (1714), a Latin grammar that became a standard educational text across Europe. Ruddiman served as the King's Chief Librarian at the Advocates' Library in Edinburgh, curating and expanding its collections. He produced critical editions of classical authors such as Cicero and Horace, demonstrating meticulous scholarship. His work in philology and bibliography significantly influenced the study and teaching of classical languages in the 18th century. Ruddiman died on January 19, 1757, remembered as a pillar of Scottish scholarship.

Jonathan Toup was born in 1713 in Cornwall and educated at Exeter College, Oxford. He excelled as a headmaster and later devoted himself to textual criticism of Latin poets, producing meticulous editions of Cicero, Juvenal, and Horace. His multi-volume 'Epistolarum libri duo' (1766) offered critical letters that advanced scholarly debate on classical texts. Toup's sharp wit and extensive knowledge made him a leading figure in 18th-century literary circles. Despite his reclusive nature, his work significantly influenced the standards of accuracy and annotation in classical philology. He died on January 19, 1785, leaving behind a legacy of rigorous scholarship.

Born in Stuttgart in 1773, Karl Faber pursued historical studies at the University of Tübingen. He became a professor of history at the University of Heidelberg, where he taught for decades. Faber's seminal works analyzed the constitutions and political systems of classical Greece in meticulous detail. His research combined rigorous source criticism with a clear narrative style, influencing future generations of historians. He died in 1853, leaving behind a legacy of scholarship that reshaped the study of ancient political history.

Born in Stuttgart-Bad Cannstatt in 1788, Carl Reichenbach studied chemistry and metallurgy at the University of Tübingen. He conducted groundbreaking experiments on essential oils, creosote, and the properties of coal tar compounds. Reichenbach later proposed the existence of the 'Odic force,' an energy he believed permeated all living things. Although his claims were met with skepticism, they sparked debates at the intersection of science and the occult. He held academic posts in Basel and Leipzig and left a mixed but enduring legacy in both chemistry and parapsychology.

Born in Aix-en-Provence in 1810, Henri Victor Regnault studied chemistry under Gay-Lussac in Paris. He conducted meticulous experiments on the thermal expansion and conductivity of gases, leading to the formulation of Regnault's law. Regnault's work on the specific heat of gases and vapor pressure advanced the emerging field of thermodynamics. He served as director of the scientific instrument workshop at the Paris Observatory and later became a pioneer in ceramic manufacturing. His death in 1878 marked the loss of one of France's most exacting experimentalists.

Frank P. Ramsey was born in Cambridge in 1903 and displayed extraordinary intellectual abilities from a young age. At Trinity College, Cambridge, he contributed groundbreaking work to mathematical logic, influencing the development of modern set theory. His 1927 essay on probability laid the groundwork for subjective probability theory and decision making. In economics, Ramsey introduced optimal taxation theory, now known as the Ramsey problem, which remains central in public finance. He also made important contributions to philosophy, particularly on truth and belief in his early work. Tragically, Ramsey's career was cut short by his death from liver disease in 1930 at the age of 26. Despite his brief life, his interdisciplinary achievements continue to shape multiple fields.

Born in 1885, Theodor Kaluza studied mathematics and physics at the University of Königsberg. In 1921, he extended Einstein's general theory of relativity to a fifth dimension, proposing what is now known as Kaluza's theory. This groundbreaking idea laid the foundation for later developments in unified field theories and string theory. Kaluza's academic career included professorships at several German universities where he taught mathematics and theoretical physics. He published research on differential geometry, number theory, and potential theory. Despite limited recognition during his lifetime, Kaluza's work gained prominence posthumously, influencing generations of physicists exploring higher-dimensional models. He passed away in 1954, but his five-dimensional approach remains a fundamental concept in modern theoretical physics.

Hidetsugu Yagi was a pioneering Japanese electrical engineer and professor. He co-developed the Yagi-Uda antenna, transforming radio and television broadcasting. Yagi's antenna design offered high directionality and gain with simple construction. He published influential research and taught at several prestigious universities. His work laid foundations for modern wireless communication systems. Yagi's invention remains one of the most widely used antenna designs globally.

Lawrence Kohlberg was a professor at Harvard University who revolutionized the study of moral reasoning. Drawing inspiration from Jean Piaget, he proposed six stages of moral development grouped into three levels. He conducted extensive research using moral dilemmas such as the Heinz dilemma to explore how individuals justify ethical decisions. His work influenced education, psychology, and ethics by highlighting the role of cognitive processes in moral growth. Kohlberg published several seminal works and founded research centers dedicated to moral education. He died in 1987, yet his theoretical framework remains a cornerstone in developmental psychology.

Marcel Chaput earned a doctorate in biochemistry and worked in research before turning to politics and journalism. In the 1960s, he co-founded the Ralli du Québec, a movement advocating for Quebec sovereignty. He wrote extensively in newspapers and pamphlets, combining scientific rigor with political activism. His efforts helped lay the groundwork for the modern Quebec independence movement. Chaput also lectured widely and remained committed to social and cultural causes. He died in 1991, remembered as a pioneer in Quebec's struggle for self-determination.

Hedy Lamarr (1914–2000) was a Hollywood film star celebrated for her beauty and performances in classics like Algiers and Samson and Delilah. Beyond her acting career, she co-invented a frequency-hopping spread spectrum technology during World War II, intended to protect Allied torpedoes from jamming. Although the patent was initially overlooked, her work pioneered techniques later used in Wi-Fi, Bluetooth, and GPS. A self-taught mathematician, Lamarr held a U.S. patent for the invention and was posthumously inducted into the National Inventors Hall of Fame. Her dual legacy as a glamorous actress and innovative thinker continues to inspire filmmakers, scientists, and inventors worldwide.