ABSTRACT
Past and future are alike to the physicist, differing only in direction, like east and west. But to the living person they are altogether different things. For man rolls up his past, as a tourist his' rug, and carries it with him wherever he goes. That is why Well’s ‘6 Time Machine ” and the reversed reels of the movies are so funny. There is nothing absurd about running a wheel backward but there is about running a man backward, t The physicist feels no reluctance about turning the stream of time backward for all physical phenomena are reversible under the proper conditions. If we interpret the universe as merely matter in motion and imagine at a certain instant that every individual particle reverses its motion and
goes in just the opposite direction at the same speed, then the whole history of the world would be reen acted in the opposite order and the earth would re turn to its primeval nebulae.
