Template:On This Day (nonfiction)/May 25
986: Astronomer Abd al-Rahman al-Sufi dies.
1555: Physician, mathematician, and cartographer Gemma Frisius dies. He created important globes, improved the mathematical instruments of his day, and applied mathematics to surveying and navigation in new ways.
1828: Mathematician Karl Mikhailovich Peterson born. He will discover equations which will subsequently be named the Gauss–Codazzi equations, fundamental to the theory of embedded hypersurfaces in a Euclidean space.
1889: Aircraft designer Igor Sikorsky born. He will pioneer both helicopters and fixed-wing aircraft.
1961: Apollo program: U.S. President John F. Kennedy announces before a special joint session of the Congress his goal to initiate a project to put a "man on the Moon" before the end of the decade.