Hello again, Buzzkillers. In this week’s mini-myth, we tackle Isaac Newton’s famous apple – an object we all heard about in grade school that allegedly hit Sir Isaac Newton on the head some time in 1666, causing him to have a sudden epiphany about the universal law of gravitation.
So, did Sir Isaac really discover the secrets of the heavens because of a sudden, concussive insight under an apple tree, or is this just a fruity story, embellished over time by overzealous Newtonians?
As it turns out, there is to this day an apple tree growing just outside Isaac Newton’s old bedroom window at Woolsthorpe Manor in Lincolnshire. And another apple tree, grafted and descended from that one, grows in the botanical garden at Cambridge University. You can even visit them if you want to. Both are claimed to be descendants of the tree whose apple struck Newton and jolted him into having that penetrating insight into the mysteries of physics over 300 years ago.
Naturally, there is no certain proof that either of these trees is descended from the one that inspired Newton’s solution to the mystery of gravity. For that matter, there is no proof that Newton derived any of his inspiration from an apple falling. What we do have is a story Newton apparently told quite often, including to his first biographer, William Stukeley.
Like Newton, Stukeley was a man of science born in Lincolnshire. The two became friends late in Newton’s life, and socialized regularly. According to Stukeley, it was during an after dinner walk on April 15th, 1726 that Newton first related to him his encounter with the famous apple tree. Here is how Stukeley’s account reads:
After dinner, the weather being warm, we went into the garden & drank tea under the shade of some apple tree, only he and 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 should that apple always descend perpendicularly to the ground, thought he to himself, occasioned by the fall of an apple, as he sat in contemplative mood.
Why should it not go sideways, or upwards? But constantly to the Earth’s center? 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 center, not in any side of the Earth.
Therefore, does this apple fall perpendicularly or towards the center? If matter thus draws matter; it must be in proportion of its quantity. Therefore the apple draws the Earth, as well as the Earth draws the apple.
So, there we have the story of Newton’s apple, according to William Stukeley. There are other contemporary accounts of Newton telling this story, including one by John Conduitt, Newton’s assistant and relative by marriage; and another by Voltaire in his Essay on Epic Poetry of 1727, but Stukeley’s is the most complete account that we have. It is therefore safe to say that Stukeley’s Memoirs of Sir Isaac Newton’s Life is the best version of the apple story, and the ultimate source of the one we all know and love from grade school.
But Stukeley wrote his account in 1752 about a conversation he had with Newton in 1726, regarding an incident between Newton and an apple that occurred in 1666. That’s 86 years between the event in question and our best record of it. Newton was already an old man by the time this story became popular, so how can we be sure that it really happened? Any story can change a lot over time, and this one is no different.
It seems likely that there is some “core” of truth to Newton’s tale as recounted by Stukeley, but did you notice that something key was missing? At no point in Stukeley’s account does Newton have a sudden flash of insight after an apple strikes him on his head. So where did this colorful element of the Newton-hit-on-the-head-with-an-apple story come from?
Some biographers have noted that Newton was a very religious man, and that the first alleged “sudden insight” associated with an apple tree goes all the way back to the Biblical account of Adam and Eve. Though the Book of Genesis does not mention any fruit specifically, popular interpretations have long held that the Tree of Knowledge in the Garden of Eden was an apple tree. Could it be that the association between apple trees and knowledge was too tempting to resist?
Nobody can say for sure, but whatever the case, Buzzkillers, the keyword for today is “embellishment.” It is likely that the only reason any of us knows this story so well is because parts that were added (and embellished) over time, and that embellishment made it a better story. After all, it may be interesting that an apple inspired Newton’s theory of universal gravitation, but fruit falling from a tree at a safe distance is not nearly as memorable – not nearly as impactful, you might say – as the idea of sudden insight delivered from above and hitting you directly on the head.