Proposed in the 1970s as a possible explanation for ghosts. The Stone Tape Theory speculates that inanimate materials can absorb energy from living beings. In other words a ‘recording’ or track is laid down during moments of high tension, such as murder. This stored energy can consequently be released, resulting in a display of the recorded activity. The replay can take the form of a full manifestation or partial sounds such as voices or footsteps. Paranormal investigators commonly refer to such phenomena as residual hauntings. Ghosts are not spirits but non-interactive recordings similar to the registration capacities of an audiotape machine that can playback previously recorded events. While the theory may explain some ghostly sightings, no one knows what the recorded energy actually is. However, the possibility that it could be composed by our natural electric and magnetic fields is one of the explanations that the Stone Tape Theory advances.