Time travel refers to the concept of moving between different points in time, much like moving between different points in space. The idea is often explored in science fiction, where characters use various means, such as time machines or faster-than-light travel, to journey to the past or the future. Theoretical physics also considers time travel, particularly in relation to the theory of relativity, which suggests that time is not a constant and can be affected by speed and gravity. Common themes in time travel narratives include altering historical events, encountering past or future versions of oneself, and the potential paradoxes that can arise from these interactions, such as the grandfather paradox. Time travel captures the imagination by challenging our understanding of time and the linear progression of events.