Newton Publishes the Principia Mathematica
Three laws of motion and universal gravitation explain why the planets stay in orbit at all
Quick facts
- Scientist
- Isaac Newton, 1643 to 1727
- Work
- Philosophiae Naturalis Principia Mathematica
- Published
- 5 July 1687
- Core law
- Universal gravitation, inverse-square with mass
What happened
Isaac Newton's Philosophiae Naturalis Principia Mathematica was published on 5 July 1687 under the Royal Society's imprimatur, with Edmond Halley funding the printing. The book set out three laws of motion: that a body at rest or in motion continues that way unless acted on by a force, that a force produces an acceleration proportional to its size and in its direction, and that every action has an equal and opposite reaction. Building on these, Newton stated the law of universal gravitation: every object attracts every other object with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Newton showed mathematically that this single law explained Kepler's three laws of planetary motion as consequences rather than separate rules, and that the same force governing a falling apple also governs the Moon's orbit and the ocean tides, which he showed result from the Moon's and Sun's gravitational pull on Earth's water.
Why it matters
The Principia unified terrestrial and celestial mechanics under one mathematical law for the first time, finishing the process Copernicus had started and Kepler and Galileo had advanced, of erasing the Aristotelian division between an imperfect Earth and a perfect, separately governed heaven. Its method, deriving testable, quantitative predictions from a small number of general laws, became the model other sciences aspired to for the next two centuries.
How we know
Original copies of the 1687 first edition of the Principia survive and have been studied continuously since publication; MacTutor's biography of Newton and NASA's Earth Observatory account of the history of orbital astronomy both describe the book's structure, its three laws, and its law of gravitation from the surviving text and Newton's own later editions and correspondence.
Sources
- NASA Earth Observatory. Planetary Motion: The History of an Idea That Launched the Scientific Revolution · Reputable sourceearthobservatory.nasa.gov · The domain "earthobservatory.nasa.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- MacTutor History of Mathematics, University of St Andrews. Isaac Newton · Reputable sourcemathshistory.st-andrews.ac.uk · The domain "mathshistory.st-andrews.ac.uk" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- The Enlightenment → · Newton's demonstration that a few general laws, tested by observation and expressed mathematically, could explain the whole visible universe became the model Enlightenment thinkers tried to apply to society, government, and the mind.