They’re ba-ack. With the release of Gil Kenan’s Poltergeist, a reboot of the original 1982 horror classic directed by Tobe Hooper and produced by Steven Spielberg, moviegoers will once again be propelled to wonder: Why doesn’t the plagued family just get a sublet?

Poltergeists don’t just haunt middle-class American homeowners—this myth dates back to the first century and crops up across a wide array of nations and cultures. And although there may be no scientific evidence that poltergeist, ghosts or undead spirits of any kind actually haunt our homes, that hasn’t stopped ghost hunters and other pseudo-scientific experts from trying to prove their existence.

To understand the various ways that science is brought to bear on ghosts, Sloan Science and Film spoke with Benjamin Radford, a scientific paranormal investigator, deputy editor of the Skeptical Inquirer, and author and co-author of several books, including Hoaxes, Myths, and Manias: Why We Need Critical Thinking and Scientific Paranormal Investigation: How to Solve Unexplained Mysteries.

Sloan Science and Film: First, let’s talk poltergeists. There’s a long history of people trying to prove the existence of poltergeists and ghosts. What do you see as the most recurrent ways that people have attempted to investigate these paranormal activities?

Benjamin Radford: Poltergeists are a subcategory of ghosts—which is a bit silly, like a subset of angels or dragons—but they are said to be malicious. This is different from other ghosts, which in many cases are benign. There are many people I’ve interviewed who believe that a ghost is in their home and it’s not terrifying; it’s a friendly, reassuring presence that makes itself known by occasionally flickering a light or making you lose your keys. Poltergeists—which means “noisy ghost” in German—came into their own in the 1600 and 1700s.

SF: So in terms of poltergeists or ghosts, in general, you’ve written that people use scientific tools to detect them, such as Geiger counters, EMF detectors, and ion detectors. But how are they supposed to work?

BR: When you look at the organized pursuit of evidence for spirits, that’s been going on for centuries. And it’s incredibly diverse. What you find, among ghost hunters, is essentially that anything can be taken for a ghost. If a room appears unusually warm or unusually cold, they’ll assume it’s a ghost. Smells, sights, sounds, lights, feelings, sensations, queasiness, fear—take your pick. There are no uniform criteria. Because the claims are so mundane—a flash of light or a dark spot—if you go to a location that is supposed to be “haunted,” you have expectations of the experience. So if you’re looking for ghostly phenomena, anything can be and will be interpreted as a ghost. One of the common ones is footsteps. Part of the problem is when you go to record these things, it’s not clear that there are actually footsteps. It can be cars outside or rodents. Or a plane flying overhead.

SSF: Another way people cite the existence of ghosts are light orbs. What’s the issue with light orbs? And what actually causes them?

BR: Orbs have plagued ghost-hunting for decades. They are one of the most common types of photographic evidence for ghosts. I’ve seen hundreds and hundreds of orb photos. I still get two or three ghost photos a month. Many of them are orbs. It’s typically a round or oval anomaly in the image. It’s usually white or sometimes transparent—it’s very easy to create. It can seem mysterious to people who don’t understand photography, because they are unseen at the time a photo is taken. The expectation is what you see in a photograph matches what you saw with your eyes. In the case of orb photographs, the mysterious orbs show up in the photographs after they are developed or are saved to a disk. Typically, the explanation for an orb is a flash reflection. That’s why you don’t see it with your eyes. There will often be some small element like dust, a bug or raindrops, or simply any reflective surface, which reflects the flash. It explains why they are usually white, because it’s the flash being reflected back to the camera.

SSF: Are there any other prevalent pieces of evidence that people point to as evidence of ghosts?

BR: The second most common type of evidence is EVPs, electronic voice phenomenon. These are recordings claimed to be of ghostly voices. Ghost hunters will go into a supposedly haunted location with high tech audio recording equipment and will sometimes turn it on and start asking questions of the empty room, such as “Is there a spirit here?” But if you wait long enough in silence, eventually, there are lots of things that can make sounds, such as the wind or the house settling. Other times, they’ll leave the equipment on for several hours and go away, and then come back to get their equipment, and then spend dozens of hours listening carefully to the recordings for anything that might be weird. So there’ll be hours and hours of silence and then there may be some knock or thud or a voice or any faint sound. Then they may hear what they believe are voices.

SSF: So what’s really causing it?

BR: Well, first of all, this gets to the heart of what is pseudoscientific about ghost investigations. If you leave a recording device and come back six hours or eight hours later, there’s no way to know what caused it. You weren’t there to investigate it. That’s not how scientists do research. By the time they’re combing through the audio, days or weeks may have lapsed, so there’s no way to possibly know what may have actually caused that sound.

SSF: Have you heard of infrasound as an explanation?

BR: It’s certainly possible that what is recorded is essentially ambient sounds. There are very few places in the world that have no sound. No matter where you are, there are ambient sounds. There are insects; there are electronics; there are animals; breathing makes a sound. Digestion makes a sound. The human body makes a sound. By the time they hear these so-called EVPs, they turn up the volume so high, any minor thing that no one would normally hear is magnified and examined, so it becomes an exercise in absurdity. And of course, there’s no confirmation that ghosts speak. Presumably, ghosts and disembodied spirits don’t have any physical way—the mechanical anatomy that creates speech—to speak.

So essentially, the process of EVPs is a version of what’s called pareidolia, which is when we create patterns in the world, such as when we see faces in clouds. That same process occurs with auditory phenomenon. We can hear phantom sounds; we can hear what appears to be language. A Canadian psychology professor named James Alcock has written about his ability to induce EVPs in people. He presents people with recordings of gibberish, and when that’s overlaid with static sound, people’s minds fill in what they believe or conjecture what’s going on and think that they hear something. The human brain pieces something together, even though it’s complete nonsense.

SSF: What about magnetic fields as an explanation for paranormal activity?

BR: There have been some claims, most notably from Michael Persinger, a Canadian neuroscientist, who says he may have found evidence that helps to explain ghosts. He created something called the “God Helmet," which he claims can induce hallucinations or the perception of ghostly phenomenon through the use of electromagnetic fields. The theory is that because we are surrounded by these electromagnetic fields, these might be a possible origin for ghostly phenomenon. If you’re near a cellphone or a computer or anything that gives off electro-magnetism, this might be the cause of hallucinations. But the fatal flaw is that the level of electromagnetic stimulation that he has induced is far greater in magnitude than in our natural environment.

SSF: Are you aware of any hard scientific research that has tried to determine whether ghosts exist?

BR: No. I’m not aware of any organized research programs that are doing evidence-based or science-based investigations of ghostly phenomena. There is no body of knowledge. There are misperceptions and anecdotes and personal experiences. It’s, “I saw something weird that I can’t explain and therefore it’s a ghost.” But that’s a logical fallacy. It doesn’t mean there is a ghost. It just means that you can’t explain it.