Do you see the same apparition doing the same things all the time? Do you hear the same noises, possibly at the same time of day, each time they are heard? Does that ghost seem to not even realize that you are there? If the answer is yes to any of these, you may be witnessing what is known as a residual haunting. Some of the most famous hauntings appear to be residual ones.
A residual haunting is a playback of a past event. The apparitions involved are not spirits, they are "recordings" of the event. I believe that this will be the first type of haunting that main stream researchers will recognize and study. There are numerous theories on how these residual hauntings come to be. The main one will be discussed here.
Video and audio tapes capture sounds and images on a film of special material that has been oxidized or rusted. Certain building materials, such as slate used in older castles and stone structures and iron nails used in many older buildings, have properties similar to that of the tapes. When a traumatic event occurs or a time of heightened emotions, these materials record the event for future playback. Everything is made up of energy and energy cannot be destroyed. The materials store the energy created by these traumatic events and plays them back at a later time. The Tower of London's ghost of Anne Boleyn and the Brown Lady of Raynham Hall are two famous examples of residual hauntings. We are not sure what causes the playback of the events, that still remains a mystery. Is it the right weather conditions, the witness's energy or sensitivity or some type of energy release? That is the question that we as researchers are trying to answer.
As I said, in a residual haunting, there is no spirit involved. This type of event is not dangerous at all so if you ever have the chance to witness one, do so without fear and enjoy it. This type of haunting has to be considered when investigating a haunting. When my group goes to a haunted location, we spend the first hour split into two teams. One team maps out the area, noting any EMF readings and Temperature readings so we have guidelines to judge other readings by. We also make note of how the building is constructed and set up. The other team is conducting interviews with witnesses. The questions are setup to find out if the activity sounds like a spirit, poltergeist, residual haunting, etc. If we feel the activity is a residual haunting we will set up a stakeout in the location the ghost is often seen or heard. This is the best way to observe and possibly capture evidence of the event. It may take many return trips and hours of sitting there staring at nothing. It is very tedious but if it something occurs, you will forget very quickly about all the time you sat waiting for it to happen.