Template:Selected anniversaries/January 20
1573: Astronomer Simon Marius born. He will discover the four largest moons of Jupiter, independently of Galileo Galilei.
1775: Physicist and mathematician André-Marie Ampère born. He will be one of the founders of the science of classical electromagnetism, which he will referr to as "electrodynamics".
1841: Adventurer Jørgen Jørgensen dies. He sailed to Iceland, declaring the country independent from Denmark and pronouncing himself its ruler, intending to found a new republic following the United States of America and France.
1901: Electrical engineer Zénobe Gramme dies. He invented the first usefully powerful electric motor.
1904: Mathematician Renato Caccioppoli born. Caccioppoli will contribute to mathematical analysis, including the theory of functions of several complex variables, functional analysis, and measure theory.
1959: Project SCORE satellite makes contact with orbital artificial intelligence AESOP.