For questions relating to travel in time. Such travel often involves FTL travel; consider also using the [tag:faster-than-light] tag.
Time travel is a much debated premise in science and science fiction. It is theorised that travelling faster than light would cause the object in question to also move backwards in time, due to Einstein's theory of relativity. There are also several other theoretical ways of moving backwards in time, including wormholes and Einstein-Rosen bridges.
Please consider also using any relevant tags for your method of time travel. For example, if you plan for time travel to be possible through FTL travel, use the faster-than-light tag.