Can We Sense Magnetic Fields?

April 12, 2016

In 2006, an Arizona body-hacker named Steve Haworth sliced open Quinn Norton’s ring finger, slipped a small rare-earth magnet into the incision, and then sewed her up.

“If I pick up a cord or I ran my hand over my laptop, certain parts of it would just make my finger tingle,” she said in an interview with NPR’s All Things Considered (she originally wrote about it for Wired.)

“I’d reach over towards something and I’d have this very sudden tingling in my finger from a live phone cord. Phone cords aren’t particularly high voltage but they’re also not very shielded. So I could really feel them,” she said.

Norton’s purpose wasn’t to invoke some superheroic ability to move objects like Magneto from Marvel’s X-Men comics. The idea was that the implanted magnet might allow her to detect the presence of magnetic fields.

Here’s how it works: our fingertips are packed to the brim with sensory receptors, the nerve endings that inform your brain about whatever it is you’re touching. When exposed to a magnetic field, that implanted magnet might move or vibrate just enough to activate those nerve endings.

We’re all of course continuously bathed in a swirling soup of magnetic fields: from the Earth, the Sun, our refrigerators, light bulbs, smartphones and television remotes. Because electricity and magnetism are inextricably linked, anything that produces an electrical current also creates a magnetic field, and vice versa.

The sort of bodyhacking that Haworth and Norton involved themselves with a decade ago was not meant to pick up on all those magnetic fields. As Norton explained in the radio interview, she usually had to make physical contact with an object to detect the magnetic fields radiating from it.

Animals don’t have to try so hard. Scientists have known since the late 1960s that some birds navigate by taking advantage of the Earth’s magnetic fields. For them, it’s thanks to biology and evolution, rather than minor surgery. Robins, for example, have molecules in their eyes called cryptochrome which, when stimulated by magnetic fields, can overlay magnetic information onto the birds’ perception of the world by making some parts of its visual field brighter and other parts darker.

They’re not the only ones. Pigeons have neurons that are sensitive to magnetic fields, and loggerhead sea turtles use magnetic fields to migrate. Foxes seem able to rely on the small magnetic fields that betray the presence of hidden prey. Dogs apparently prefer to do their business with their bodies aligned on a north-south axis, and zoologists can’t quite agree on whether or not herds of cows and deer prefer to orient themselves along the Earth’s magnetic field lines.

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