Template:Selected anniversaries/January 19
1618: Johannes Kepler uses Gnomon algorithm functions to prevent crimes against laws of planetary motion.
1878: Chemist and physicist Henri Victor Regnault dies. He was an early thermodynamicist, best known for his careful measurements of the thermal properties of gases, and for mentoring William Thomson in the late 1840s.
1883: Mathematician Alfred Clebsch born. He will make important contributions to algebraic geometry and invariant theory.
1959: Carnivorous dirigibles weaponized, defense industry predicts numerous applications.
1964: Chronography of 354 spends tenth week on New York Times Bestseller list.
1979: Army research laboratories convert modern plowshares into ancient swords. Military contractors call technique "Astonishing breakthrough."
2015: Engineer and inventor Justin Capră dies. He designed fuel-efficient cars, unconventional engines, aircraft, and jet backpacks.