Principle of inertia
Principio de inercia
- Date
- 1632 · confidence high
- Place
- Florence, Italy
- Credited to
- Galileo Galilei; René Descartes
- People
- 👤 Galileo Galilei1564–1642👤 René Descartes1596–1650
- Field
- Cosmos & Earth
⚠️ Disputed: the sources disagree.
What was discovered
A body free of forces maintains its state of rest or uniform motion indefinitely; motion needs no cause to persist, only to change. It breaks with the Aristotelian idea that all motion requires a mover.
Galileo states it for horizontal (circular) motions in the 'Dialogue' (1632); Descartes formulates it as rectilinear in 'Principia philosophiae' (1644); Newton generalises it in 1687.
What it led to
- Newton's first law
- Concept of an inertial reference frame
- Classical mechanics
- Galilean and special relativity
Built on
- Avicenna's theory of impetus (mayl)c. 1027
- Impetus theory (Buridan)
- Inclined-plane experiments
Made possible
- Celestial mechanics
- Inertial navigation (20th century)