Most of us don't often think about Earth's magnetic field, but without it, humans and most other life would be unable to exist. Earth's magnetic field protects our planet from harsh radiation blasted out of the sun. It's essential to everything we think of as life on Earth. Scientists believe our magnetic field comes from the rotation of Earth's liquid iron core around a smaller, solid core (this is an effect called geodynamo). But the solid core hasn't always existed. What was the magnetic field like back then? This question has been a mystery for years, but a recently published paper in the journal Geophysical Research Letters by scientist Peter Driscoll seems to point to an answer. For most of history, the magnetic field has had two poles, north and south. Scientists have found proof of that in very old rocks that still show signs of the magnetic polarity of their times. The dipolarity of our planet seems to have remained consistent through much of Earth's 4.5 billion year history.