You can sense the Earth's magnetic field!

Everybody knows that many animals, such as migratory birds, can tap into the Earth’s magnetic field to navigate for long distances. In fact, magnetic sensory systems seem to occur in virtually all organisms. Scientists have often wondered whether humans also tap into the Earth’s magnetic field. As one scientist said, “If we don’t have it, we would need to explain how we lost it.” Apparently, we haven’t lost it.

Recently, some Cal Tech scientists set up an experiment that shows how we sense magnetic fields. To do this, they built a cube that shielded unwanted electromagnetic radiation but that mimicked the Earth’s magnetic field in a way that scientists could manipulate. Study participants sat for an hour in the dark and quiet cube, wearing EEG caps that t allowed the scientists to eavesdrop on their brains. (As a control, the scientists also set up a similar-looking cube that was devoid of the magnetic fields.)

What the scientists discovered were changes in participants’ alpha waves. Our alpha waves are always present but are more prominent when we’re at rest. Whereas beta waves represent the arousal of an actively-engaged mind, alpha waves represent non-arousal. They are slower than beta waves and higher in amplitude. In the experiment, when the magnetic field was downward-oriented and swept counterclockwise, the scientists observed a significant decrease in the alpha wave amplitude. In some cases, the brain’s rhythm dropped by up to 60 percent before returning to normal. One scientist interpreted the dip as the brain "freaking out” upon realizing that the magnetic field has moved while the body didn’t. (Not all magnetic wave conditions elicited this change.)

Basically, what this experiment shows is that we unconsciously sense the Earth’s magnetic field. The scientists haven’t figured out how it works, but they do conclude that “the brain evolved over half a billion years to pull out information from the magnetic field just like any other sensory system.” Now what?

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