Time is not absolute but relative to the observer. It is a dimension that is interwoven with space to form spacetime. The passage of time is affected by the presence of mass and energy, with larger masses causing a slower passage of time. Time is also affected by the speed of an object, with faster-moving objects experiencing a slower passage of time.

Einstein's theory of relativity revolutionized our understanding of time. It showed that time is not a fixed entity but rather something that is relative to the observer. This has profound implications for our understanding of the universe, from the microscopic scale of quantum mechanics to the vastness of cosmology.