Time has been a major subject of religion, philosophy, and science, but defining it in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars. Time perception is a field of study within psychology, cognitive linguistics, and neuroscience that refers to the subjective experience of time, which is measured by someone's own perception of the duration of the indefinite and unfolding of events. The perceived time interval between two successive events is referred to as perceived duration. Another person's perception of time cannot be directly experienced or understood, but it can be objectively studied and inferred through a number of circumstances. One of such question is that: what is time? Newton came up with simple and comprehensible answer is that "Time is absolute and universal". But Einstein came up with the theory which says "Time is relative" contrary to Newton's. Now the new question evolved from the theory of relativity that "is time travel possible?" this question may look simple but answer is quite subtle. This book helps you to understand the meaning of this question.