A time machine is a hypothetical device that allows individuals to travel through time, either to the past or the future. The concept has been popularized in science fiction, with famous examples including the DeLorean from the movie Back to the Future and the TARDIS from the television series Doctor Who. While time travel remains a theoretical idea, some scientific theories, like Einstein's theory of relativity, suggest that time is not a fixed entity and could potentially be manipulated. However, no practical time machine has been created, and the laws of physics as we understand them currently do not support the feasibility of time travel.