Stone Tape theory

The Stone Tape theory was a speculative explanation for ghosts. It speculated that physical matter, especially stone, could absorb energy from living beings, thus " recording" them. Under certain circumstances, those stored echoes could be played back. Sarah Jane Smith, who did not believe that ghosts were the souls of the departed, was a proponent of that theory. While investigating the case of Ashen Hill Manor, Sarah briefly explained the theory to her young companions Rani Chandra and Clyde Langer. (TV: The Eternity Trap) She also mentioned it to Emily Morris during a time-travelling trip in 1889. On that occasion, Sarah discovered that the fabric of a building could transmit echoes not only from the past, but also from the future. (TV: Lost in Time)