Add Yahoo as a preferred source to see more of our stories on Google. The cosmic microwave background, the faint afterglow of the Big Bang that fills all of space, passes through massive galaxy ...

Legend has it that Isaac Newton had the moment of inspiration that would lead to his theory of gravity when, on a warm afternoon, he saw an apple fall from a tree and wondered why it should fall down ...

Gravity behaves predictably in your daily life. Drop a ball, and it falls. Planets loop around stars. On paper, the same rules should also govern matter spread across the universe. But the farther ...