What 's an example of something that was a problem for classical physics ?
Three - body problem has two distinguishable meanings in physics and classical mechanics : In its traditional sense , the three - body problem is the problem of taking an initial set of data that specifies the positions , masses and velocities of three bodies for some particular point in time and then determining the motions of the three bodies , in accordance with the laws of classical mechanics ( Newton 's laws of motion and of universal gravitation ) .