It Wasn't the Apple that Newton Used to Discover Gravity

Science finds order and meaning in our experience, and sets about this in quite a different way. It sets about it as New¬ ton did in the story which he himself told in his old age, and of which the schoolbooks give only a caricature. In the year 1665, when Newton was twenty-two, the plague broke out in southern England, and the University of Camb] idge was closed. Newton therefore spent the next eighteen months at home, removed from traditional learning, at a time when he was impatient for knowledge and, in his own phrase, 'I was in the prime of my age for invention.' In this eager, boyish mood, sitting one day in the garden of his widowed mother, he saw an apple fall. So far the books have the Story right; we think we even know the kind of apple; tradition has it that it was a Flower of Kent. But now they miss the crux of the story. For what struck the young New¬ ton at the sight was not the thought that the apple must be drawn to the earth by gravity; that conception was older than Newton. What struck him was the conjecture that the same force of gravity, which reaches to the top of the tree, might go on reaching out beyond the earth and its air, endlessly into space. Gravity might reach the moon: this was Newton's new thought; and it might be gravity which holds the moon in her orbit. There and then he calculated what would hold the moon. anH rr^mr^c>r-f^A it T»ritV. tUt^ Vnr^xAm would hold the moon, and compared it with the known force of gravity at tree height. The forces agreed; Newton says laconically, 'I found them answer pretty nearly.' Yet they agreed only nearly: the likeness and the approximation go together, for no likeness is exact. In Newton's sentence modern science is full grown.

It grows from a comparison. It has seized a likeness between two unlike appearances; for the apple in the summer garden and the grave moon overhead are surely as unlike in their movements as two things can be. Newton traced in them two expressions of a single concept, gravitation: and the concept (and the unity) are in that sense his free creation.

Gravity was already known, Newton's vision was extending the force of gravity up to the Moon.