Great Idea 4

Idea 4: Newton’s universal law of gravitation

        In 1687 English physicist Sir Isaac Newton (1642-1727) published a law of universal gravitation in his important and influential work Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy).  Newton's law of universal gravitation states that bodies with mass attract each other with a force that varies directly as the product of their masses and inversely as the square of the distance between them.  It is more precisely expressed with the equation F = Gm1m2/r2, where m1 and m2 are masses, r is the distance between them, and G is universal gravitation constant.

    Newton discovered the relationship between the motion of the Moon and the motion of a body falling freely on Earth. By his dynamical and gravitational theories, he explained Kepler’s laws and established the modern quantitative science of gravitation. Newton assumed the existence of an attractive force between all massive bodies, one that does not require bodily contact and that acts at a distance
    Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. Gravity creates stars and planets by pulling together the material from which they are made.
    
     Newton’s universal law of gravitation showed that the same laws of physics that govern the fall of an apple also govern the motions of the moon and planets. It began the search for laws of nature that were precise, simple to express, and applied equally to all parts of the universe.