Sketches found inside Leonardo da Vinci's sketchbooks, show that he had already grasped the essence of Einstein’s 1907 ‘Equivalence Principle’ centuries before the physicist.

Da Vinci’s sketches, which were forgotten for decades, show triangles formed by sand-like particles pouring from a jar. These falling grains depicted experiments to show that gravity was a form of acceleration more than 400 years before Einstein did, a new study argues.