#PHYSICS
NEWTON’S APPLE
A MAGGOT-INFESTED MYTH?
During my undergraduate physics days, there
was an awful lot of stuff to learn. Quantum
mechanics, relativity, particle physics – they
were all subjects that I tried (and often failed) to
wrap my head around. But there was one topic
that we never broached: a fabled event that you
could say actually kick-started modern physics.
I’m talking, of course, about Isaac Newton’s
famous apple. Did Newton really develop his
theory of gravity after seeing a cascading Cox?
Or is the whole tale just a maggot-infested myth
that’s been passed down through the years? I
thought it was finally the time to find out.
Probably the most obvious place to start looking
for evidence would be Isaac Newton’s own
journals and notebooks. But, alas, I discovered
that 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. It is here
that we find some revealing clues to the truth of
the apple event.
The case for the fruity legend
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 the University of Cambridge
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.”
JAMES LLOYD • PHYSICS GURU
So Conduitt may not describe Newton taking
an apple to the head, or even that the scientist
actually observed the falling fruit, but he at
least makes a pretty strong reference to it.
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 we find 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”). But there on page 15, in a beautifully
handwritten script, is an anecdote that makes
the mouth water more than a freshly-baked
apple pie:
One spring day in April 1726, Stukeley visited
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Previous Page: (Filoli Gardens - Apple Orchard) Flickr • Jill Clardy, (Whole Earth) NASA, (My Newton tree) Flickr • DailyPic
NEWTON’S APPLE
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 motion 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? Physics
Guru James Lloyd finds out.
an 83-year-old Newton in Kensington, London.
Unlike today’s London district, Kensington was
then situated in the countryside, so the elderly
scientist had rented a house there in the hope
that the fresh air would improve his declining
health. The two men spent the day together, and
their conversations carried 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, 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,
NEWTON’S APPLE
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
important fact that Newton was deeply interested in religion, so the nod to the Garden of
Eden’s forbidden fruit might have appealed to
him.
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. 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.
As for the apple itself, the tree at Woolsthorpe
Manor produces a rare variety of cooking apple
known as ‘Flower of Kent’, which has been
described as mealy, sharp, and quite flavorless.
So if Newton really did see one fall to the
ground, he probably didn’t enjoy eating it.
Ultimately, we’ll perhaps 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…
Physics Guru’s notepad:
how Newton discovered gravity
Even if Newton did observe a falling 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.
His universal law of gravitation was published some 20
years after the alleged apple incident. In Philosophiæ
Naturalis Principia Mathematica (1687), Newton
explains that the gravitational force between two objects
is inversely proportional to the square of the distance
between them, and directly proportional to the product of
their masses. In other words, if you double the distance
BELOW:
Woolsthorpe
Manor.
between two objects you reduce the gravitational force by
a factor of four; triple the distance and you reduce it by a
factor of nine.
Using this law, Newton was able to show that the orbits
of the planets around the Sun – and the Moon around
the Earth – can be explained by the bodies’ mutual
gravitational attraction. It’s the very same effect that
pulls a falling apple towards the ground.
ABOVE:
This apple tree
at Woolsthorpe
Manor grew
up from the
fallen trunk of
another apple tree
that existed in
Newton’s day.
Links
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•
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Read more here about Newton’s Universal Law of Gravitation
Read William Stukeley’s apple anecdote
Woolsthorpe Manor
James Lloyd studied physics at university and recently finished a climate science PhD.
He’s now swapped semiconductors for semicolons, writing about science and blogging
at The Soft Anonymous. James enjoys music making, hill walking and trying to find
the perfect flapjack. Find him on Twitter @jbb_lloyd.
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(Newton’s Apple Tree) Flickr • dexter_mixwith, (Vintage Memo Notepad) Flickr • Calsidyrose
(Woolsthorpe Manor) Flickr • David Ireland
NEWTON’S APPLE