A new study shows that the human brain can detect Earth’s magnetic field, as published in the online scientific journal eNeuro. Animals like salmon, birds, turtles, whales, and bats use it to help them navigate. Learn about another way we experience Earth’s magnetic field—the auroras.
The recent scientific experiment was conducted to determine if there is magnetoreception in the human brain. The results are summarized in the abstract of the published paper outlining the experiment. “Biophysical tests showed that the neural response [in test subjects] was sensitive to the static components of the magnetic field,” the report said. “The neural response was also sensitive to the polarity of the magnetic field.” This experiment ruled out the influence of electrical induction and other factors on the brain and proved that the brain responds to, as the report said, “ecologically-relevant rotations of Earth-strength magnetic fields.” While our understanding of human magnetoreception is still in its infancy, one of Earth’s most beautiful, natural phenomena—the auroras—has been studied for some time. The science behind auroras helps us understand the Earth’s magnetic field and what it means for the planet.
Planetary Magnetism, the Auroras’ First Component
“Earth’s magnetic field looks roughly like the dipolar field from a bar magnet,” said Dr. Michael E. Wysession, Associate Professor of Earth and Planetary Sciences at Washington University in St. Louis. “The field is actually much more complex than this, however, because there isn’t a big bar magnet inside the Earth.” Nobody knows exactly why we have a magnetic field, but scientists have a strong indication.
Dr. Wysession explained that Earth has a liquid iron outer core that reaches 5,000 degrees Celsius. As the heat rises to the Earth’s mantle, it cools. “Also, as the core crystallizes out, it tends to crystallize more pure iron and nickel, and it leaves a chemically lighter, more buoyant fluid,” Dr. Wysession said. Finally, the planet’s rotation, affects the iron in the outer core. These three processes—cooling, crystallizing, and the planet’s rotation—cause convection and likely create Earth’s magnetic field. Since the magnetic field is all around us all the time, it’s easy to understand how animals and even humans can respond to it.
Solar Wind, the Second Component of Auroras
The magnetic field isn’t enough to cause the auroras on its own. The Aurora Borealis (in the Northern Hemisphere), known as the “Northern Lights,” and the Aurora Australis (in the Southern Hemisphere), known as the “Southern Lights,” are actually phenomena of space weather—specifically, solar wind. What causes solar wind? Compared to most of the sun, in “the outer layers of the sun, the corona, there are fewer atoms, but they are millions of degrees hot,” Dr. Wysession said. “These incredibly high-temperature ionized particles get thrown off the layers of the sun at a variety of giant, great speeds.”
When solar wind hits Earth’s magnetic field, the process that forms the auroras begins. Solar wind particles warp and shape the magnetic field along its lines. However, they warp the lines so much that the lines can fold back over on themselves and snap. As this happens, solar wind travels around and past our planet then doubles back along those snapped lines. As the particles travel down to Earth, they travel along the broken magnetic field lines and cause ribbons of shimmering light to appear in the sky—the auroras.
Science and medicine haven’t proven any human relation to the broken magnetic field lines that cause the auroras, but these incredible lights in the sky lend a visible example of the immensity of the magnetic field to which our brains respond.
Dr. Michael E. Wysession contributed to this article. Dr. Wysession is Associate Professor of Earth and Planetary Sciences at Washington University in St. Louis. Professor Wysession earned his Sc.B. in Geophysics from Brown University and his Ph.D. from Northwestern University.