On January 25, 1736, Italian mathematician and astronomer Joseph-Louis Lagrange (1736-1813) was born. He was instrumental in developing number theory and contributed greatly to the fields of classical and celestial mechanics. Lagrange is often considered the greatest mathematician of the eighteenth century, primarily due to his work on wave progagation and the maxima and minima of curves. In 1788, he wrote the textbook “MÃ©canique Analytique” (“Analytic Mechanics”), which is considered the basis for all further studies within the field. Joseph-Louis Lagrange’s biography is presented at: https://www.andrews.edu/~calkins/math/biograph/biolagra.htm.
Irish chemist, physicist, inventor, and natural philosopher Robert Boyle (1627-1691) was born on January 25, 1627. He is famous for his early work on gases, having Boyle’s Law named after him. (Boyle’s law states that with constant temperature the product of the pressure (P) and volume (V) of a fixed quantity of an ideal gas is constant (k): PV = k.) Boyle is considered to have been the first modern chemist. His writing “The Sceptical Chymist”, laid the foundation for the field of chemistry. A biography of Robert Boyle appears at: https://www.bbk.ac.uk/boyle/biog.html.
On January 25, 1974, South African cardiac surgeon Christian Barnard (1922-2001) transplanted a human heart without removing the original heart. A BBC news story about Christian Barnard appears at: https://news.bbc.co.uk/1/hi/health/1470356.stm.
On January 25, 1945, Grand Rapids, Michigan became the first U.S. city to add fluoride to its drinking water, introducing fluoridation into U.S. society. More information about the history of fluoridation occurs at: https://www.nidcr.nih.gov/HealthInformation/DiseasesAndConditions/Fluoride/StoryFluoride.htm.
On January 25, 1915, Alexander Graham Bell, from New York City, Thomas A. Watson, in San Francisco, and Theodore N. Vail (the first president of the American Telephone & Telegraph Company [AT&T]), from Jekyll Island, Georgia, opened the first transcontinental telephone line for commercial service across the United States. More information on the event is found at: https://www.glynncounty.com/cgi-bin/oaktree.pl?dbf=data.txt&ID=00014547.