If you believe in ghosts, you're not alone: A 2005 Gallup poll found that 37 percent of Americans believe in haunted houses, and about one-third believe in ghosts. Tens of thousands of people around the world actively search for ghosts as a hobby. Researcher Sharon Hill of the Doubtful Newsblog counted about 2,000 active amateur ghost-hunting groups in America.
Ghosts have been a popular subject for millennia, appearing in countless stories, from "Macbeth" to the Bible, and even spawning their own folklore genre: ghost stories. Ghosts are perhaps the most common paranormal belief in the world. Part of the reason is that belief in ghosts is part of a larger web of related paranormal beliefs, including near-death experience, life after death, and spirit communication.
The idea that the dead remain with us in spirit is an ancient one, and one that offers many people comfort; who doesn't want to believe that our beloved but deceased family members aren't looking out for us, or with us in our times of need? Most people believe in ghosts because of personal experience; they have seen or sensed some unexplained presence.
The science and logic of ghosts
Personal experience is one thing, but scientific evidence is another matter. Part of the difficulty in investigating ghosts is that there is not one universally agreed-upon definition of what a ghost is. Some believe that they are spirits of the dead who for whatever reason get "lost" on their way to The Other Side; others claim that ghosts are instead telepathic entities projected into the world from our minds.
Still others create their own special categories for different types of ghosts, such as poltergeists, residual hauntings, intelligent spirits and shadow people. Of course, it's all made up, like speculating on the different races of fairies or dragons: there are as many types of ghosts as you want there to be.
There are many contradictions inherent in ideas about ghosts. For example, are ghosts material or not? Either they can move through solid objects without disturbing them, or they can slam doors shut and throw objects across the room. Logically and physically, it's one or the other. If ghosts are human souls, why do they appear clothed and with (presumably soulless) inanimate objects like hats, canes, and dresses — not to mention the many reports of ghost trains, cars and carriages?
If ghosts are the spirits of those whose deaths were unavenged, why are there unsolved murders, since ghosts are said to communicate with psychic mediums, and should be able to identify their killers for the police. And so on; just about any claim about ghosts raises logical reasons to doubt it.
Ghost hunters use many creative (and dubious) methods to detect the spirits' presences, often including psychics. Virtually all ghost hunters claim to be scientific, and most give that appearance because they use high-tech scientific equipment such as Geiger counters, Electromagnetic Field (EMF) detectors, ion detectors, infrared cameras and sensitive microphones. Yet none of this equipment has ever been shown to actually detect ghosts.
Other people take exactly the opposite approach, claiming that the reason that ghosts haven't been proven to exist is that we simply don't have the right technology to find or detect the spirit world. But this, too, can't be correct: Either ghosts exist and appear in our ordinary physical world (and can therefore be detected and recorded in photographs, film, video, and audio recordings), or they don't. If ghosts exist and can be scientifically detected or recorded, then we should find hard evidence of that — yet we don't. If ghosts exist and cannot be scientifically detected or recorded, then all the photos, videos, and other recordings claimed to be evidence of ghosts cannot be ghosts. With so many basic contradictory theories — and so little science brought to bear on the topic — it's not surprising that despite the efforts of thousands of ghost hunters on television and elsewhere for decades, not a single piece of hard evidence of ghosts has been found.
Why many believe
Many people believe that support for the existence of ghosts can be found in no less a hard science than modern physics. It is widely claimed that Albert Einstein suggested a scientific basis for the reality of ghosts; if energy cannot be created or destroyed but only change form, what happens to our body's energy when we die? Could that somehow be manifested as a ghost?
It seems like a reasonable assumption — unless you understand basic physics. The answer is very simple, and not at all mysterious. After a person dies, the energy in his or her body goes where all organisms' energy goes after death: into the environment. The energy is released in the form of heat, and transferred into the animals that eat us (i.e., wild animals if we are left unburied, or worms and bacteria if we are interred), and the plants that absorb us. There is no bodily "energy" that survives death to be detected with popular ghost-hunting devices.
While most ghost hunters engage in harmless (and fruitless) fun, there can be a darker side. In the wake of popular ghost-hunting TV shows, police across the country have seen a surge in people being arrested, injured, and even killed while looking for ghosts. In 2010, a man died while ghost-hunting with a group of friends hoping to see the ghost of a train that crashed years earlier. The ghost train did not appear — but a real train came around a bend and killed one man.
The evidence for ghosts is no better today than it was a year ago, a decade ago, or a century ago. There are two possible reasons for the failure of ghost hunters to find good evidence. The first is that ghosts don't exist, and that reports of ghosts can be explained by psychology, misperceptions, mistakes and hoaxes. The second option is that ghosts do exist, but that ghost hunters are simply incompetent. Ultimately, ghost hunting is not about the evidence (if it was, the search would have been abandoned long ago). Instead, it's about having fun with friends, telling stories, and the enjoyment of pretending they are searching the edge of the unknown. After all, everyone loves a good ghost story.
Benjamin Radford is deputy editor of "Skeptical Inquirer" science magazine and author of six books, including "Scientific Paranormal Investigation: How to Solve Unexplained Mysteries." His website is www.BenjaminRadford.com.