Seemingly independent visual or mental images that are considered concurrently may inspire unique ideas. According to his own story (and in contradiction to the story of being hit on the head by a falling apple), Newton conceived the concept of universal gravitation when he observed an apple falling and at the same time noticed the moon in the sky. These simultaneous images inspired him to speculate if the same laws governed the falling apple and the moon orbiting the earth. This in turn led him to develop the laws of mechanics and established mathematical analysis and modeling as the principal foundations of science and engineering.