One theory which may explain residual hauntings is the "stone tape theory". A number of paranormal researchers believe that buildings and materials are able to absorb energy from living things. The belief is that tragic events, grief and other strong emotions can be imprinted at a location and replay like a tape. According to popular belief there is no intelligent ghost or spirit involved in this type of haunting, only the energy left behind from a past event. The Tower of London is believed to be the site of one of the most famous residual hauntings.
What causes one to be able to see this type of haunting is still up for debate and not everyone is convinced that this theory holds any truth.