Fiction about time travel can be used to impart information both about dimensions and about history, as in Alan Moore's Jerusalem (London, 2016). The ghost John thinks that Prince Rupert was Charles I's son, not his nephew.
Ghosts make excellent time travelers. See here. Being invisible and intangible, they cannot alter past events. Thus, Oliver Cromwell writing a letter to his wife is unaware that John is reading it over his shoulder. (Cromwell's statue (see image) holds a Bible and a sword, representing theory and practice.)
In Jerusalem, a suicide bomber spends eternity in his exploding form. Other ghosts give him a wide berth.
Cromwell and suicide bombers: two phases of our history.