Explorers have long trusted compasses to navigate Earth’s land and oceans, using our planet’s global magnetic field as their guide.
But what happens when you take a compass beyond Earth — into orbit, to the Moon, to other planets, or even beyond our solar system? Would it still point north, or would it aimlessly spin in the absence of a dominant magnetic field? The answer depends on where you are in the cosmos and what other magnetic fields are at play.
On Earth, a compass needle aligns with our planet’s geomagnetic field, which is generated by the movement of molten iron in Earth’s outer core. This strong, bullet-shaped global magnetic field extends far beyond the surface of our planet. But as you venture farther and farther into space, the compass behavior can change.
A Compass in Earth's Orbit
Earth’s magnetic field, called the magnetosphere, bubbles out thousands of miles beyond Earth’s surface. But in low Earth orbit (LEO) — where the International Space Station (ISS) circles the planet at an altitude of about 250 miles — Earth’s magnetic field is nearly as strong as it is on the surface.
