Close your eyes, relax, and think of something pleasant. In this state, your brain is filled with alpha waves, a type of electrical brainwave associated with waking relaxation. Scientists at the California Institute of Technology have found evidence that changes in the Earth's magnetic field can suppress alpha waves in the human brain.
It has long been established that living things can sense magnetic fields. For example, bees, fish, turtles, birds, and bats use the geomagnetic field to orient themselves in space, and specially trained dogs can locate a magnet.
"Many animals feel it, so why don't we?" asks Connie Wang, a Caltech graduate student and lead author of the study.
To find out if humans can sense magnetic fields, the researchers built an isolated RF-shielded chamber where the participants sat in complete darkness for an hour. As the magnetic fields moved silently around the camera, the participants' brain waves were measured using electrodes on their heads.
In some of the 34 participants, alpha brain wave power decreased by as much as 60% in response to the shifting fields. The study co-authors argue that this is the first concrete evidence of yet another human feeling: magnetoreception.
Notably, participants who experienced the change reported not seeing anything. The unconsciousness of this effect has led researchers to speculate that it may be a remnant of the ancient ability of our ancestors to navigate using local magnetic signals.
Does this mean that humans can sense geomagnetic storms? It is not clear. When they hit the Earth, the planet's magnetic field begins to oscillate. The compass needles can move 4 or 5 degrees at mid-latitudes. However, the magnetic fields inside the test chamber were offset by about 90 degrees - much more than in a typical geomagnetic storm. Thus, it is not yet known whether the human magnetoreceptor is sensitive enough to detect the relatively small changes associated with space weather.
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The research is published in the journal eNeuro.
