Radio waves become a terrifying disturbance of the psyche in the new horror film Shortwave. In the film’s new trailer, it’s supposed to be good news when Josh, a scientist, has a “breakthrough involving a cryptic shortwave radio signal and its universal origin,” two years after his child’s mysterious disappearance. But when his wife Isabel hallucinates an encounter with her child in the woods after turning on one of his radios, we know his work is little more sinister than the average science experiment. Fortunately, the disturbing science doesn’t hold up IRL.
Isabel believes the short radio waves hold the key to finding their missing daughter, and later, they lead to her lying on a bloody shower floor. These paranormal events suggest that the “universal origin” of these wave is connected to a freaky Upside Down-like universe, which is great for plot but isn’t very realistic: In real life, we already know the atmospheric reason why short wave radio transmission works.
The transmission of short wave — or high-frequency — radio is dependent on the existence of the ionosphere, the layer of the Earth’s atmosphere 50 miles above the ground. Because the ionosphere is so electron-dense, it reflects radio waves, preventing them from shooting off into space. Bouncing off the ionosphere and back to Earth, the signals travel on short wave bands. When Isabel turns on the radio in our world, it’s not a dark force controlling the radio waves — it’s an atmospheric layer.
Her sensitivity to radio waves, however, isn’t unheard of IRL. While her visual hallucinations are unique to the horror plot, some people (and, sure, Superman too) can “hear” radio wave signals as well, though they don’t sound like the screech Isabel experiences — rather, they resemble a tiny click, hiss, knock, or chirp. The people who experience this pick up radio frequencies at a range of about five kilohertz, which then stimulate the cochlear nerve; in turn, the nerve shoots auditory information to the brain. It’s not a phenomenon that would cause visual hallucinations, but it has been found to cause irritability and depression.
Shortwave is gaining steady notoriety on the festival circuit for its terrifying use of tension and sound. The science may not exactly be right, but it’s a terrifying twist of the facts we know to be true.