Why heavy bodies fall: driven to the center of the spheres
A cosmological argument on gravity and the center of the elements
A text-only page of natural philosophy argues that the circles of the celestial spheres, together with the elements, equally drive every heavy body away from themselves toward the center, where it must come to rest. Leonardo concludes that falling bodies are pushed down from above rather than pulled from the center. He offers a thought-experiment: if the earth's place could be filled with air, a stone thrown into it would halt at the center of the two elements and the spheres.
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Heavy bodies are thrust to the center, not pulled
Leonardo reasons that the celestial spheres and the elements equally repel every heavy thing, so each must gather and settle at their common center. From this he concludes that objects falling toward the center are driven from above rather than drawn downward by the center itself. The note is a speculation on the cause of weight and fall.
Thought-experiment: a stone at the center of the spheres
He imagines the place occupied by the earth being emptied and filled with air. A stone thrown from our world into that air would, he says, come to rest at the center of the two elements and of the spheres. The image dramatizes his idea of a natural center within the cosmos.