I have never seen a ghost, nor have I ever had an encounter reported to me by someone who claimed to have seen such an apparition. I don't know if ghosts exist and I certainly would have to be convinced by hard evidence before I could accept that they do exist.
However, I know that strange things do happen and that apparently normal people "see" or otherwise experience the presence of ghosts. These phenomena are under active objective examination by various psychical associations. Many of the people who work in this area are seeking natural explanations (reviewed by Andy Coghlan, New Scientist, December 1998).
Most investigators are unable to see ghosts themselves. They usually visit "haunted" sites accompanied by professional psychics, who claim to be able to see and experience the spirits They point the investigators to the spot where the apparition/phenomenon is occurring. The investigator then makes technical measurements at this spot, e.g. magnetic and electrical measurements.
We are all familiar with the stereotypical idea of a ghost, a sort of whitish-grey fog arranged in an overall human configuration. If I saw such an apparition, I would, as a scientist, be interested in knowing things such as the chemical composition of the fog; is it emitting or absorbing energy; does it have associated electrical/magnetic fields; is its temperature greater or less than room temperature; is it radioactive? and so forth. I would also be keenly interested in photographing the image, in taking a moving video film of the apparition and in making an audio recording.
The questions I listed in the previous paragraph occurred to me right off as my probable first reaction on seeing the ghost but, interesting as these technical questions are, they are probably inadequate as a first human response to seeing a ghost. I would prefer to think that my first reaction would be to try to communicate with the apparition. I would ask if it was the spirit of a dead person and, if so, of whom.
I would ask if it was having a problem and, if so, to tell me about it so I could try to help. I would ask what it was like to be a spirit and what happened immediately after the body's death. I would ask if it had contact with other spirits. I would ask about God.
A sharply fluctuating magnetic field is one of the most consistent effects reported by investigators who make technical measurements at spots where ghosts appear. Much higher magnetic measurements are reported at these spots. Magnetic fields are measured in units called milligauss.
Normal background levels are of the order of one to two milligauss. Up against your PC screen you will measure about five milligauss. At a haunted spot, wildly fluctuating measurements peak at about 100 milligauss. The ghostly magnetic field doesn't stay put but floats about from one room to the next.
Temperature measurements made in these ghostly magnetic fields are also reported to show intense cold, between 20C and 35C colder than ambient room temperature. Other investigators have reported detecting gamma ray emissions from these ghostly spots. Gamma rays indicate radioactivity.
The most common instrument in the toolkit of the technical investigator of ghostly phenomena is the camera. It can be loaded with ordinary film or with film that is sensitive to infra red or to ultraviolet radiation. The latter two can record data which the human eye cannot see.
Elaborate apparatus can be set up in "haunted" locations with batteries of cameras loaded with various types of film and connected to sensors of electrical and magnetic fields. When the sensors detect unusual electromagnetic activity, they automatically trigger the cameras to start taking photographs. Conventional ghostly images have been captured on these films and also white streaks. In most cases it is difficult (or impossible) to rule out glitches in film-processing as the real cause of the ghostly picture.
The weight of the scientific evidence in fav our of ghosts is not very heavy, I'm afraid. The enhanced magnetic field measurements indicate that something is happening at "haunted" sites, but this can be interpreted in two ways. Believers interpret the findings as corroborating their own belief, while sceptics interpret the measurements as freak natural phenomena that are capable of inducing hallucinations.
The work of Michael Persinger of the Laurentian University, Ontario, Canada, supports this latter interpretation. Persinger has shown that hallucinations, impressions of alien abductions, hauntings and out-of-body experiences can be induced in volunteers by subjecting their brains to electromagnetic fields (New Scientist, November 19th, 1994, p29).
Other workers have correlated reports of hauntings since the mid-1800s with peaks in sunspot activity that can trigger magnetic storms on Earth. (Proceedings of Journal of Physical Research, vol. 57, p275).
Investigators who believe in the reality of ghosts are unperturbed by this negative evidence. They believe that ghosts are electromagnetic in nature, are etched into the environment and that high levels of electromagnetic activity, during sunspot cycles for example, provide the "fuel" to trigger sleeping ghosts to show themselves. Some ghosts are passive and just appear, others apparently interact with the person who beholds them. But the evidence for all of this is even more ghostly than the apparitions themselves.
William Reville is a senior lecturer in biochemistry and director of microscopy at UCC
The Irish Times has recently published a collection of Dr Reville's articles with additional material from him. Understanding the Natural World, illustrated, £14.99 from bookshops. Information available by phoning (01) 679-2022, ext. 8271