Of time and paradox

"The passage of time is probably one of the most basic facet of human perception, for we feel time slipping by in our innermost selves in a manner that is altogether more intimate than our experience of, say, space or mass. The passage of time has been compared to the flight of an arrow and to an ever rolling stream, bearing us inexorably from past to future. Evocative though these images may be, they run afoul of a deep and devastating paradox. Nothing known in physics corresponds to the passage of time. Indeed, physicists insist that time doesn't flow at all; it merely is. "
Paul Davies, Scientific American Special Edition - a Matter of Time

"We take for granted that time ticks by at the same rate for everyone. But Einstein's theory of relativity shows that this assumption is not strictly true. The classic case of time disparity involves twins - one of whom leaves Earth and travels round-trip to a star at nearly the speed of light, arriving back much younger than his brother. This aging difference is noticeable only when long distances are traveled at speeds approximating the speed of light. "
Ronald C. Lasky, Scientific American Special Edition - A Matter of Time