We all know the story. A young Isaac Newton is sitting in his garden when – plonk! – an apple falls onto his head. As the scientist rubs his sore scalp, an idea enters his mind – could the same force that brought the apple plummeting to the ground also explain the motions of the Moon and the planets? In that instant the theory of gravity is born! At least that’s how the story goes. But did this cranial collision ever really happen?
Is Newton’s apple just a maggot-infested myth? (credit: dreamiurg)
Newton’s famous apple incident is an event that – if true – pretty much kick-started modern science. By inspiring Newton’s theory of gravity, it laid the foundations upon which countless great minds have built their ideas. But did Newton really develop his theory after seeing a cascading apple? Or is the whole tale just a maggot-infested myth that’s been passed down through the years? I decided to find out.
The case for the fruity legend
Probably the most obvious place to look for evidence would be Isaac Newton’s own journals and notebooks. But alas, Newton never mentioned the apple in any of his writings. Instead, we must turn to a man named John Conduitt, who wrote about the incident some 60 years later. Conduitt, a politician by trade, was Newton’s assistant at the Royal Mint and the husband of Newton’s beloved half-niece, Catherine Barton.
In his Draft account of Newton’s life at Cambridge, Conduitt describes a fresh-faced, 23-year-old Isaac Newton returning to his mother’s Lincolnshire home in 1666 – not because he missed his mum’s cooking, but because the plague had forced Cambridge University to shut down. There, Conduitt wrote, “whilst he was musing in a garden it came into his thought that the same power of gravity (which made an apple fall from the tree to the ground) was not limited to a certain distance from the Earth but must extend much farther than was usually thought…”
So Conduitt may not describe Newton taking an apple to the head, nor even that the scientist actually observed the falling fruit, but he at least makes a pretty strong reference to it.
Woolsthorpe Manor – Newton’s Lincolnshire birthplace (credit: David Ireland)
Around the same time, the French philosopher Voltaire was also helping to perpetuate the fruity legend. In An Essay Upon the Civil Wars of France (1727), he wrote: “Sir Isaac Newton walking in his gardens, had the first thought of his system of gravitation, upon seeing an apple falling from a tree.” Voltaire probably heard the story from Catherine Barton, whom he described as Newton’s “very charming niece”, when he visited England in the 1720s.
But the strongest evidence for Newton’s apple comes from another of Sir Isaacs’s close friends, an antiquarian called William Stukeley. In 1752, a quarter of a century after Newton’s death, Stukeley published his Memoirs of Sir Isaac Newton’s Life. Truth be told, it’s a rather drab and long-winded account of the scientist’s life (though we do find out what the great scientist had for breakfast: “an infusion of orange peel in boiling water”, apparently, “with bread & butter” – functional yet tangy). But there on page 15, in a beautifully handwritten script, is an anecdote that waters the mouth more than a freshly-baked apple pie…
William Stukeley’s handwritten apple anecdote
One spring day in April 1726, Stukeley visited an 83-year-old Newton in Kensington, London – at that time situated in the countryside. The two men spent the day together, profiting from the fresh air and chatting on into the evening.
“After dinner, the weather being warm, we went into the garden, and drank thea [sic] under the shade of some apple trees…,” recalled Stukeley. “Amidst 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, occasion’d by the fall of an apple, as he sat in a contemplative mood. ‘Why should it not go sideways or upwards but constantly to the Earth’s centre?’”
So, while drinking this cup of ‘thea’ in the dusky evening light, an elderly Sir Isaac actually recounted the falling apple story to his friend Stukeley. The famous apple! From the horse’s mouth!
A mouldy tale?
But can we really trust Stukeley? After all, he was a very good friend of Newton and may have been tempted to mythologise the scientist. As Scott Berkun, author of The Myths of Innovation, writes: “biographers, certainly in 1720, are not objective reporters running around checking facts. They are often fans of their subjects, as Stukeley was of Newton.”
And why would Newton have waited 60 years before sharing the story with someone? One explanation may be that he saw a falling apple in his youth and gradually embellished the story over time. It’s easy to see why it’d be such an attractive tale: a simple visual metaphor for his “Eureka!” moment; a humorous way to explain how gravity works. And then there’s the fact that Newton was deeply interested in religion, so the nod to the Garden of Eden’s forbidden fruit might have appealed to him.
But even if Newton did observe a tumbling apple in 1666, it’s highly unlikely that he developed his theory of gravity right there on the spot. At some point, though – and this is what fits in nicely with the apple story – he came to realise that the same force which governs the acceleration of objects towards the ground also reaches far out into space. It wasn’t until 1687, some 20 years after the alleged apple incident, that Newton published his universal law of gravitation, showing that the orbits of the planets around the Sun – and the Moon around the Earth – could be explained by the bodies’ mutual gravitational attraction.
The Moon’s orbit – beautifully explained by Newton’s law of universal gravitation (credit: wvs)
One thing we can be sure of is that the apple never struck Newton on the head. That detail was added by a later writer, Isaac D’Israeli, who evidently had a penchant for slapstick comedy. But that hasn’t stopped the story from entering popular consciousness. Woolsthorpe Manor, Isaac Newton’s birthplace and the home he returned to in 1666, has since become something of a pilgrimage site for starry-eyed physicists. In the house’s garden, visible from Newton’s old bedroom window, is said to be the very apple tree that the young scientist sat under nearly 350 years ago.
The apple tree under which Newton is said to have sat. The tree was reportedly re-rooted after a storm toppled it in 1816 (credit: dexter_mixwith)
As for the apple itself, the tree at Woolsthorpe Manor produces a rare variety of green cooking apple known as ‘Flower of Kent’, which has been described as mealy, sharp, and quite flavourless. So if Newton really did see one fall to the ground, he probably didn’t enjoy eating it.
Ultimately, perhaps we’ll never know the full truth behind Newton’s apple. Maybe we should trust those anecdotes provided by his friends. Maybe, in the grand scheme of things, it doesn’t really matter. After all, Newton went on to develop his theory of gravity in the end, apple or not. One thing’s for sure though – we should be glad that it was Newton sitting under that tree. Anyone else would have required a whole barrel full of fruit…
This blog post is based on an article published in the June/July 2013 edition of Guru magazine… download the magazine for free here!