... But he went home from Cambridge one summer in 1665, thought a lot about the physical nature of the world, and came back two years later with a revolutionary understanding of mathematics, gravitation, and optics. Apollo 17: Boulder on the Moon . ... These fleeting events are only visible to those in the path of the Moon's shadow as it races across the Earth. Dark Sky, Bright Sun . ... Five hundred light years from Earth, in the constellation Aquarius, a sun-like star is dying. ...