Did an apple fall on Newton's head?

The claim, and the verdict

The claim: a young Isaac Newton was sitting under a tree when an apple dropped on his head, and in that instant he discovered gravity.

The verdict: the apple is real in the sense that Newton told the story himself; the bump on the head is invented; and the “instant discovery” is wrong. People knew things fall long before Newton. His insight was that the pull which brings an apple down might be the same force that holds the Moon in its orbit, and it took him about twenty years of mathematics to show it, in the Principia of 1687.

The setting is believable. In 1665 and 1666 plague closed the University of Cambridge, and Newton, then in his early twenties, spent long stretches at his family's farmhouse, Woolsthorpe Manor near Grantham. Those months are when he worked out early versions of calculus, his theory of colours and his first ideas on gravity.

What the evidence shows: the earliest sources

Every early version traces back to Newton's own telling, more than fifty years after the event, when he was in his eighties and famous. That is the main reason for caution: it is a memory, possibly polished, not a note made at the time.

Stukeley describes visiting Newton at his lodgings in Kensington on 15 April 1726. After dinner, in warm weather, they went into the garden and drank tea under the shade of some apple trees. Newton told him he was in just the same situation as when the notion of gravitation first came into his mind, set off by the fall of an apple as he sat in a contemplative mood. Stukeley then reports Newton's question to himself:

Conduitt's notes, made in 1727 and 1728, give the same scene with the idea that matters: while musing in a garden, it came into Newton's thought that the power of gravity, which brought an apple from the tree to the ground, was not limited to a certain distance from the Earth, and might reach as far as the Moon. Neither writer says anything about Newton's head.

How the story grew into a bump on the head

Voltaire did more than anyone to spread the apple. He lived in England from 1726 to 1728, admired Newton, and repeated the story in two books aimed at a European readership. From there it became a fixture of popular science writing in the eighteenth and nineteenth centuries.

The bump on the head came later, in children's books, cartoons and comic retellings, because it makes a better picture: a single blow, a single flash of genius. It turns a slow piece of reasoning into a joke about luck. No source from Newton's lifetime or the decades after supports it.

Some historians have wondered whether Newton told the story to make his discovery look early and simple, at a time when he was fighting Robert Hooke and Gottfried Leibniz over who thought of what first. That is a reasonable suspicion, not a proven fact. Most biographers, including Richard Westfall, accept that an apple may well have fallen and that Newton linked it to his thinking, while stressing that the real work came after.

What Newton actually worked out

The key step was the Moon. Newton asked whether the force that pulls an apple down could also keep the Moon curving round the Earth instead of flying off in a straight line, if that force grew weaker with distance. In his memorandum of about 1714 he recalled that in 1666 he compared the two forces using the rule that gravity falls off with the square of the distance:

“Pretty nearly” is honest. His figures did not match well, partly because he used a poor value for the size of the Earth, and he set the problem aside. In August 1684 the astronomer Edmond Halley visited him in Cambridge and asked what path a planet would follow under an inverse square force. That question led to the Philosophiae Naturalis Principia Mathematica, published in July 1687, where universal gravitation is set out with full proofs. Even then Newton refused to guess what gravity is. In the General Scholium added in 1713 he said he did not frame hypotheses about its cause.

If you want to hear Newton explain this himself, you can ask Isaac Newton in Yuga, by voice or text. It is an AI recreation built from his writings and the historical record, not Newton, and it can make mistakes, so quote the Principia and his letters in an essay, not the app.

Is Newton's apple tree still alive?

Yes, probably. An old apple tree of the Flower of Kent variety stands in front of Woolsthorpe Manor, now cared for by the National Trust. Tradition holds that it is the tree Newton watched. It blew down in a storm in the early nineteenth century but rerooted, and it still grows and fruits. Grafts and cuttings from it have been planted at Trinity College, Cambridge, and at universities and observatories around the world.

No one can prove that this exact tree dropped the famous apple. Stukeley's account says only that Newton was in a garden, and Conduitt places it at Woolsthorpe. But the tree's age fits, and the National Trust is careful to present it as the tree of the story rather than a certified relic.

How to check a science legend like this

1. Find the first written source, and note who told it and when. Here, Newton himself, about sixty years after the event.
2. Separate the core from the decoration. The apple and the garden are in the early sources; the head is not.
3. Ask what the person had to gain. Newton was defending his priority in old age.
4. Check the science against the person's own papers. Newton's memorandum puts the Moon, not the apple, at the centre.

The same method works for Archimedes and “Eureka” and Franklin's kite. For the full checklist see how to check if a quote is real, and for interview ideas see questions to ask Isaac Newton.