Template:Selected anniversaries/September 21
1576: Gerolamo Cardano dies. He was one of the most influential mathematicians of the Renaissance.
![1781: Joseph-Louis Lagrange writes to d'Alembert: "It appears to me also that the mine [of mathematics] is already very deep and that unless one discovers new veins it will be necessary sooner or later to abandon it." This view is prevalent at the end of the eighteenth century.](/w/images/thumb/c/c8/Joseph-Louis_Lagrange.jpg/107px-Joseph-Louis_Lagrange.jpg)
1781: Joseph-Louis Lagrange writes to d'Alembert: "It appears to me also that the mine [of mathematics] is already very deep and that unless one discovers new veins it will be necessary sooner or later to abandon it." This view is prevalent at the end of the eighteenth century.
1792: French Revolution: The National Convention declares France a republic and abolishes the absolute monarchy.
1853: Physicist and academic Heike Kamerlingh Onnes born. He will receive widespread recognition for his work, including the 1913 Nobel Prize in Physics for "his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium".
2018: Signed first edition of Spiral used in high-energy literature experiments unexpectedly develops spontaneous artificial intelligence.