The Famous Apple Incident
There exists the famous story of how Newton whilst sitting underneath an apple tree, got hit on the head by a falling apple. And he suddenly thought of the Universal Law of Gravitation. However what really happened is something less animated and more realistic, as is explained by one of Newton's friends:
... we went into the garden, & drank there under the shade of some appletrees; only he, & my self. 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 earths centre? 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 earths center, not in any side of the earth. Therefore does this apple fall perpendicularly, or toward the centre. 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."
This account gives us the more realistic approach to Newton's thought on Gravity. As the apple falls to the ground, it accelerates and as per Newton's Second Law of Motion there must be a force that causes the apple to accelerate and this force he later concluded as gravity.
... we went into the garden, & drank there under the shade of some appletrees; only he, & my self. 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 earths centre? 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 earths center, not in any side of the earth. Therefore does this apple fall perpendicularly, or toward the centre. 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."
This account gives us the more realistic approach to Newton's thought on Gravity. As the apple falls to the ground, it accelerates and as per Newton's Second Law of Motion there must be a force that causes the apple to accelerate and this force he later concluded as gravity.