Christiaan Huygens, in his posthumously published book Cosmotheros, argues that other planets in the solar system are inhabited, starting a debate that extends into the 20th century.
The piano is invented by Italian Bartolomeo Cristofori, originally named the "piano et forte" (meaning "soft and loud").
A metronome is developed as a machine to measure musical tempo.
Events
November - Tani Jinzan, astronomer and calendar scholar, observes a fire destroy Tosa in Japan at the same time as a Leonidmeteor shower, taking it as evidence to reinforce belief in the "Theory of Areas".