Priroda nikada ne krši svoje zakone. - Leonardo da Vinci

Weight, force and casual impulse, together with resistance, are the four external powers in which all the visible actions of mortals have their being and their end.

I find that any luminous body when seen through a dense and thick mist diminishes in proportion to its distance from the eye. Thus it is with the sun by day, as well as the moon and the other eternal lights by night. And when the air is clear, these luminaries appear larger in proportion as they are farther from the eye.

Impetus is a power of the mover applied in a movable thing which causes the movable thing to move after it is separated from its mover.