Isaac Newton did not discover gravity on a single exact date; instead, he developed his ideas about gravity over many years, especially around 1665–1666, and then published his full law of universal gravitation in 1687.

Quick Scoop: The real timeline

  • Around 1665–1666, during the plague years when Cambridge closed and Newton returned to the countryside, he began formulating the idea that the same force that pulls objects to Earth also governs the Moon and planets.
  • The famous “falling apple” story is linked to this period, but historians see it more as a symbolic anecdote than a literal eureka moment under a tree.
  • In 1684, Newton wrote De motu corporum in gyrum (“On the motion of bodies in an orbit”), laying out the physics that connect Kepler’s planetary laws with a central gravitational force.
  • On 5 July 1687, he published his major work Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), which formally presented the law of universal gravitation to the world.

So if you’re looking for a “when did Isaac Newton discover gravity” type answer for quick reference:

  • Concept takes shape: about 1665–1666 (plague years, apple legend).
  • Official publication of the law: 1687 in the Principia.

In modern terms, gravity wasn’t a one-night discovery; it was a two-decade journey from a curious question about falling objects to a precise mathematical law that explained both apples and planets.

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