For as long as humans have had language to articulate you, we’ve been recounting tales of ghosts, haunting, and terror beyond the world of the living. Since the age of reason, most scientists have tried to distance themselves from such claims, but what happens when scientists themselves see ghosts?

Well, as luck would have it: this actually happened. The story starts in a medical laboratory in England, where Vic Tandy worked along with several other people in the late 1990s. Soon after people began working in the lab, rumors began that it was haunted. Tandy, a hard-nosed engineer, refused to accept ghosts as the answer to the various accounts of the room being haunted.

People were claiming to have seen, and felt, an otherworldly presence in the room. Tandy set about figuring out what was so special about this room, and ruling out things like pranksters and animals. What he came across though, was beyond our perception, but still within our material world: he found standing waves of a very low-frequency.

Standing waves are waves that peak and slump at very specific points, appearing to “stand” still at those points. The most famous and cool demonstration of these kind of waves are seen on a chaldini plate:

So to get back to the story: Tandy found standing waves of a sub-audible level in the lab, coming from a ventilator. The frequency of the waves was what is now known as “infrasound,” which is below 20 hertz (here it was 19Hz). Changing the ventilator in the lab effectively ended all ghost related experiences in the laboratory. Efforts to prove this effect, using a concert experiment, effectively showed over 1/5 of people to be sensitive to these frequency of waves (17Hz in the experiment) and experience fear and anxiety when exposed.

Because frequencies around 18-19Hz are not audible, but still major enough to trigger a physical response, and even jiggle your eyes. The frequency generates both a feeling of unease and anxiety, as well as making vision less clear. In such a circumstance, the eye may try to focus on “floaters” (which are really just protein in your eyes) and perceive them as menacing due to additional emotional influence of the waves. This also finally explains why ghosts are so often seen as white,transparent, and whispy.

The funny thing about low-frequency waves is that they can also put our fires, which could explain the “candles going out” in haunted places. When accompanied with cold spots and a little imagination, these kind of waves can lead to a characteristically haunted house. So, how many of you still believe in ghosts after reading this?