The meaning of time and motion is discussed, at first tracing conceptu
al changes from Aristotle to Galileo/Newton to Einstein. Different vie
ws of 'time' in 20th century physics are then examined, with primary f
ocus on the revolutionary changes that came with the theory of general
relativity. Implications of its new view in all domains of physics ar
e discussed - from elementary particles to cosmology. The special role
of Hamilton's quaternion calculus in equations of motion in general r
elativity is shown.