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Isaac Newton and the falling apple story
The aforementioned tale of Isaac Newton’s discovery of the law of gravitation provides additional information about happenstance as a common experience in technical-scientific achievement and how it has been used by innovators and historians alike to explain them. Much has been written about Newton’s falling apple legend and, according to research by the Royal Society of London, the source of the tale is now well-known to have been none other than Isaac Newton himself. Although he left no written record of it, the English mathematician, physicist, astronomer, theologian and author was twenty-three years old in 1666 when the famous “moment” of gravity’s discovery was to have taken place.
There are at least four known instances in which Newton—who was born on January 4, 1643 in Lincolnshire and died on March 31, 1727 in the London borough of Kensington—told the anecdote toward the end of his life. The most complete account of Newton telling his story is provided by William Stukeley, a younger scientist from Lincolnshire who befriended the old man and published the first biography of the scientist called Memoirs of Sir Isaac Newton’s Life in 1752. The two men met often as members of the Royal Society and a conversation about the apple took place on April 15, 1726, a year before Newton’s death, as Stukeley recorded it in his handwritten memoir:
After dinner, the weather being warm, we went into the garden & drank thea under the shade of some apple tree; only he & myself. Amid other discourse, he told me, he was just in the same situation, as when formerly the notion of gravitation came into his mind. Why sh[oul]d that apple always descend perpendicularly to the ground, thought he to himself; occasion’d by the fall of an apple, as he sat in contemplative mood.
Although Stukeley describes the fruit descending “perpendicularly to the ground” and not upon the scientist’s head, he confirms that the falling apple story—in which “the notion of gravitation came into his mind”—was told to him directly by Isaac Newton. Stukeley goes on to describe how Newton explained the fruit of his contemplation:
Why sh[oul]d it not go sideways, or upwards? But constantly to the Earth’s centre? Assuredly the reason is, that the Earth draws it. There must be a drawing power in matter. And the sum of the drawing power in the matter of the Earth must be in the Earth’s centre, not in any side of the Earth.
Therefore does this apple fall perpendicularly or towards the centre? If matter thus draws matter; it must be proportion of its quantity. Therefore the apple draws the Earth, as well as the Earth draws the apple.
From this account, it appears that Newton used the falling apple tale for two reasons. The first was to explain how he came upon his breakthrough scientific theory of the “drawing power in matter” that later become known as the universal law of gravitation. The second reason was so that he could review the basic principles of his theory in a manner that could be understood by nearly anyone. Since the notion that “the apple draws the Earth, as well as the Earth draws the apple” is—to say the least—counterintuitive, Newton was giving a practical example of how “matter thus draws matter” and that this power in matter is in “proportion of its quantity.”
The historical record contains other contemporary accounts from people with whom Newton shared the apple tale in the final year of his life. One further example to be related here comes from the French philosopher Voltaire, who said he was told about the falling fruit by the husband of Newton’s niece, John Conduitt. According to Voltaire, Conduitt told him the event had taken place in “the country near Cambridge” where the scientist had withdrawn in 1666 because of the plague.
Commenting recently on the falling apple legend, Keith Moore, the Librarian of the Royal Society said, “The story was certainly true, but let’s say it got better with the telling.” Newton’s story was thus embellished over time and the apple “falling upon his head” was most likely added over years of the “better” telling and retelling of the legend. There was a need for both Newton to tell—and his audience to hear—about the theory of universal gravitation and the apple story became the vehicle through which the new discovery was explained, with some degree of scientific detail supported by an explanation in popular form.
In both the displacement method of volume measurement discovered by the mathematician Archimedes and the law of gravitation discovered by Newton, it is evident that the legends of Eureka moments—whether they actually occurred or not—are historically important and that there has been a need for such tales to be told. They have helped fix these events in public consciousness by presenting a twist of fate or seemingly inexplicable series of events as a stroke of luck. Through the “magic” of happenstance, people from the era of Archimedes and Newton—who otherwise had no scientific explanation as to where their ideas came from—could explain complicated ideas and concepts that appeared to contradict common sense.
In his introduction to Serendipity, Roberts quotes an important comment from Nobel laureate Paul Flory upon receiving the Priestley Medal of the American Chemical Society:
Significant inventions are not mere accidents. The erroneous view [that they are] is widely held, and it is one that the scientific and technical community, unfortunately, has done little to dispel. Happenstance usually plays a part, to be sure, but there is much more to invention than the popular notion of a bolt from the blue. Knowledge in depth and in breadth are virtual prerequisites. Unless the mind is thoroughly charged beforehand, the proverbial spark of genius, if it should manifest itself, probably will find nothing to ignite.
While it is of course decisive to recognize the role of the individual scientist and his or her desires and intentions—the content of Flory’s concept of a mind that is “thoroughly charged” in advance of the accidental moment—there is also the broader technical, social and even political environment that must also be recognized as foundational to the discovery, without which the individual scientist or inventor could not have been prepared and the serendipitous moment could not have been recognized. We see here—with Flory’s reference to “mere accidents” as though they somehow are of secondary significance—an overemphasis on the knowledge, mind and motivation of the individual innovator as the singular primary factor.
In the case of Newton, did the law of gravitation actually come to him both “suddenly” and “all at once” with the fall of an apple in a garden in 1666? As explained by F.E.L. Priestley of the University of Toronto English Department in his 1987 essay Newton and the Apple, “The more vulgar popular versions of the legend feel no qualms about suggesting that the sight of the falling apple suddenly equipped the genius Newton with all he needed to write the Principia, apart from minor details.” Clearly, aside from the broader societal context within which Newton lived, worked and thought—he was part of a generation of what were known at the time as philosophers who were preoccupied with the subject of the paths of falling bodies—he could not have had his falling apple moment.
Priestley goes on to explain that in the 1660s there were various theories being discussed regarding “the paths followed by bodies falling toward the centre of the earth” along with experiments that are “fully illustrated in detailed accounts of the controversies.” The works of Galileo Galliliae, Johan Georg Locher and Johannes Kepler were being studied as the topic was being debated and ideas exchanged. Priestley writes, “Newton himself took part in the discussions so he hardly needed to watch an apple to become aware of the problem of the fall of theories of attraction or the law of inverse squares.” It would take Newton another twenty years of experimentation and mathematical calculations to complete his work on the law of gravitation.
Furthermore, Priestley explains the decisive element in the historical circumstances surrounding the genesis of Newton’s apple tale, i.e., the predominating outlook among the scientific and academic community during his lifetime. Priestley writes:
It is very difficult, in our own secular and materialist age, to recapture the whole intellectual atmosphere of Newton’s world, and it is almost as difficult, in this age of scientific specialization and professionalism, to grasp Newton’s attitude towards science—which he called “philosophy.” … One gets a truer picture of Newton in his historical context by thinking of him as primarily religious and philosophical than by seeing him in terms of a modern professional scientist. … For Newton, spirit is the active substance, matter the inactive, inert substance. … The source of all motion, of all activity, is the active substance, spirit. Both substances are extended in infinite space; matter is finitely extended: spirit, at least the divine spirit, is infinitely extended. … The mathematical, hence rational, order, Newton sees as evidence of the divine creation of the world system, of the divine ordering and dominion constantly active in it.
So, while Newton and his contemporaries were studying the science of the law governed movement of bodies, they had a very limited and unscientific understanding of where the impulse for matter in motion came from. Given that it would be another three hundred years after Newton sat in his mother’s garden to establish by means of observation the source of all motion in the universe, it goes without saying that even less was understood in the late 1600s about serendipity and the source of revolutionary scientific and technical ideas. Some have speculated that Newton’s legendary apple story employs Judeo-Christian symbolism of the Biblical forbidden fruit from the Garden of Eden deliberately. It was far more likely—whether the apple actually did fall on his head or not—that Newton saw his own discovery as a moment of divine inspiration rather than merely a stroke of good luck.