MYTH: Sir Isaac Newton "discovered" gravity when an apple fell on his head.
Newton's apple legend isn't true, but like many urban legends, it's an embellished version of something that actually happened. An apple didn't fall on Newton's head, but Newton did start theorizing about gravity when he saw an apple falling from a tree and started thinking about it.
The very event was inscribed in Sir Isaac Newton's memoir, where he recalls going outside after dinner with a friend.
Of course, today our account of physics is far more precise than Newton's notion of gravity. He didn't account for General Relativity, theorized by Albert Einstein more than 200 years after Newton died, and developing ideas in Quantum Mechanics problematize Newton's theories even more.
we went into the garden, & drank thea under the shade of some appletrees, only he, & myself. 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 him self: occasion'd by the fall of an apple, as he sat in a comtemplative mood: "why should it not go sideways, or upwards? but constantly to the earths centre? assuredly, the reason is, that the earth draws it. there must be a drawing power in matter. & the sum of the drawing power in the matter of the earth must be in the earths center, not in any side of the earth. therefore dos this apple fall perpendicularly, or toward 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."