Time travel in science fiction is a popular concept that explores the possibility of moving through time, either to the past or future. It raises intriguing questions about **causality**, free will, and the consequences of altering events. Common themes include the **grandfather paradox**, where changing the past could erase the time traveler's existence, and **alternate timelines**, where changes create parallel universes. Iconic works like H.G. Wells’ *The Time Machine* and films like *Back to the Future* delve into these ideas. While time travel remains speculative, it allows science fiction to explore complex philosophical and scientific questions about the nature of time.