What are ghosts? My thoughts.
Assuming that ghosts actually exist in some form or other and all reported sightings and experiences are not just figments of people's imaginations, hallucinations, cases of mistaken identity and so on there are two main hypotheses as to what they may be. The first is that ghosts are the surviving intelligences of humans (and some animals) after physical death. The second is that they're products of the human brain caused by electromagnetic stimulation of the temporal lobe. My opinion is that both of these hypotheses may be correct.
(By the way, a hypothesis is just another name for an idea or a wild-arsed guess, but it's a guess that attempts to rationally explain collected evidence and observations. A theory is the combination of a hypothesis, the evidence and observations that support it, and any experimentation with its results that also supports the hypothesis. For example, Einsteinian theory says (among other things) that energy and matter are related, in that the energy of a thing equals its mass multiplied by a constant and the product squared . This has been proven by experimentation in the area of atomic and nuclear weaponry. At present we have no theories as yet about what "ghosts" really are, only hypotheses. We lack enough evidence to support any given hypotheses to the extent that it becomes a valid theory. "Hypothesis" is the singular form, "hypotheses" is the plural.)
Ghosts as survivors of the self after death:
One popular hypothesis amongst believers in ghosts is that they are indeed the survival of the "self" after physical death. This hypothesis has been believed in since the dawn of mankind, as evidenced by archeological digs of Paleolithic and Neolithic burials. There is actually scientific theory in support of this belief. The argument goes that humans are composed of a combination of matter and energy, the energy being the electrical impulses of the human brain, spinal core and nervous system. Einstein says that energy as such can never be destroyed: it can only continue to exist in some state or other or else be converted into matter based on the above formula.
The idea is that when this bonding of matter and energy become separated on the occurrence that we call "death", the energy continues to exist. Furthermore, this energy is thought by some to include our personality, our very "self". This, say the followers of this particular hypothesis, is what "ghosts" or "spirits" are. This hypothesis is at this time supported mainly by observational (eyewitness and anecdotal) evidence and how such evidence fits the hypothesis. Other evidence includes bursts or spikes of electromagnetic energy in supposedly haunted areas, as recorded on appropriate meters, sometimes if not often accompanying other observational evidence of haunting activity such as a feeling of being watched, manipulation of physical objects in the immediate area, recordings of supposed EVPs and/or anomalous photographs. Most amateur paranormal investigative groups are attempting to provide evidence to support this hypothesis.
This hypothesis may explain why investigators experience the sudden draining of their equipment's batteries, as the ghost or spirit tries to boost its own energy level in order to attempt to manifest itself. It may also explain why EMF meters show higher levels of electromagnetic energy in the alleged presence of a ghost- it's detecting the energy that ghosts are composed of. It may also point the way to explaining how EVPs happen, if the energy is able to affect audio recording equipment directly in some way that we don't yet understand. Some experimenters mentioned that they were able to continue recording EVPs after unplugging the microphone, indicating possible direct manipulation of the recording device.
Ghosts as natural products of the human brain:
A more recent hypothesis is that so-called ghostly experiences are caused by the stimulation of a part of the human brain called the temporal lobe by external sources of energy, possibly including electricity, magnetism, a combination of the two, ultrasonic and/or subsonic energy. The sources of these forms of energy could include nearby electrical appliances, power lines, even geologic fault zones where crystalline rock structure combined with tectonic movement generates a piezoelectric effect.
Unlike the other hypothesis, laboratory experiments have been able to recreate seemingly-paranormal effects in volunteers by means of placing devices on their heads which, when coupled to machines, stimulate the temporal lobe with energy. These volunteers have reported experiencing the feeling of "a presence" in the room, or even seeing a "ghostly" apparition. Even poltergeist symptoms such as moving objects have been recreated in laboratory settings via the application of energy to a building or room.
Evidence and observations:
Let's take a look at the various common categories of ghosts or hauntings as observed or witnessed.
Crisis apparitions are manifestations of people, usually appearing to friends , family or other loved ones, when the person is undergoing some crisis such as (but not necessarily) death.. These can include apparitions, lucid or vivid dreams, phantom telephone calls,.among other things. These apparitions often interact with the witnesses and try to communicate with them, often sending messages of comfort, saying "I'm OK".
Post-mortem manifestations are, as the name implies, manifestations of a dead person known to the living witness. These may also be in the form of apparitions, dreams or electronic communications from the dead. Similar to crisis apparitions they often convey messages of comfort or assurances that the dead individual is watching out for the witness and possibly the witnesses family.
Residual or anniversary haunting are recurring apparitions or other haunting effects (sounds, smells, etc.) associated with a traumatic event in the life of a deceased person, such as a violent death. These haunting appear to be unaware of the presence of the witness(es) and simply act as though a videotape or hologram of the original event is being replayed. Many think that the great emotional trauma of certain events somehow imprint themselves into nearby rock or metal, or mineral-rich soil, similarly to the way audio or video impressions get recorded onto iron oxide-impregnated Mylar video or audio tapes, and under certain conditions these recordings get replayed.
Poltergeist activity (from the German for "noisy ghost") consists of noises and/or manipulation of physical objects by seemingly paranormal means, including but not limited to rapping on walls, floors of ceilings (that may interact with observers' answering raps or verbal commands); movement of objects (even including furniture in some cases); apparent materialization of objects out of nowhere (called "apports") or disappearances of objects ; toilets flushing by themselves; water taps turning on or off; radios or Tvs changing channels or adjusting volume; and/or the setting of small fires. This type of phenomenon is thought to be associated with unconscious pcychokinetic activity on the part of a resident of the location, often but nit necessarily a child going through puberty or someone in a dysfunctional household.
EVP (Electronic Voice Phenomena) is thought to be the ability of recording devices such as recording phonographs, wire and tape recorders, and electronic voice recorders to be able to record voices, purportedly of the dead, that we are unable to hear with the naked ear. These voices, only heard when playing the recording afterward, sometimes seem to interact with the people present: answering questions or injecting comments into conversation. A common EVP motif, recorded during paranormal investigations, is a voice commanding the investigators to "get out!".
Past residents of a dwelling may linger on and manifest themselves to current occupants. These manifestations may take the form of poltergeist-type activities, a feeling of being watched, the sound of footsteps when no one is around to cause them, EVPs and/or apparitions. This is one of the more commonly-reported types of haunting and seems to be the type that causes the most fear in witnesses. This may be because the ghost often acts in a manner to try to repel what it considers intruders in its home. Other people simply fear an unknown "person" in their household, not knowing what it may do or how it will react as they don't know the individual.
Hypotheses vs. evidence/observations:
The first hypothesis, the survival of "self" after physical death of the material body, seems to explain most of the haunting types above except perhaps for poltergeist activity and residual/anniversary haunting.s. The latter may be explained if we assume that apparitions and haunting effects are products og the energy-self's "mind". As humans, we often rerun "tapes" of traumatic events over and over in our minds. If a ghost or spirit is able to manifest itself to the living on sheer mind-power, it being composed of pure energy rather than an energy-matter marriage, perhaps when it plays its tapes it inadvertently causes what's on them to manifest itself to us as well?
The second hypothesis, that paranormal phenomena are the product of energy-stimulation of a part of our brain, explains most of the haunting types except again for the residual/anniversary haunting, the EVPs, and to an extent the details of the post-mortem and past resident haunting. To explain: there are reports of small children playing with an older person which only they can see. Afterwards the child is able to identify the person in an old family photo album, and it turns out to be a relative who died before the child was even born. There are reports of people seeing the apparition of a past resident who they were only later able to identify via historical records and photographs, or family photo albums belonging to the descendants of that resident.
Conclusion: my views:
I think that the two hypotheses may be able to be combined into one. If a ghost is the surviving energy of a person's brain, cerebral cortex and nervous system and if it retains the original person's intelligence and personality, that energy may affect witnesses' temporal lobes in a controlled manner, causing them to see, hear, smell or feel what the ghost or spirit desires them to. This would explain both how scientists are able to induce fake haunting activity, or the perception of it, in their volunteer subjects as well as how the same things take place in supposedly haunted locations. Ghosts may gain this ability on becoming pure energy, similar to how a blind person gains exceptional hearing. This may also explain, to an extent, how various psi effects may work. Some individuals may learn or have a natural ability to affect outside objects and people through their own internal energy levels.
Researching this "Grand Unified Theory" (hypothesis, actually) would require the combined efforts of paranormal researchers/investigators, physicians (to monitor brain activity), parapsychologists and physicists. Getting such a team together would probably require enlisting a sponsor with deep pockets, as the promise of money may be the only way to enlist the cooperation of professionals in the various fields mentioned, or at least graduate students in these areas. If any multimillionaires are reading this, feel free to get such a team together and begin this research.