evidence: Earth’s magnetic field is generated by the convection of molten iron in the planet’s core, around 1,800 miles (2896 km) beneath our feet. This superheated liquid generates electric currents that in turn produce electromagnetic fields. While the processes that drive pole reversal are comparatively less understood, computer simulations of planetary dynamics show that the reversals arise spontaneously. This is supported by observation of the Sun’s magnetic field, which reverses approximately every 11 years. Our own magnetic field came into existence at least 4 billion years ago, and Earth’s magnetic poles have reversed many times since then. Over the last 2.6 million years alone, the magnetic field switched ten times — and, because the most recent occurred a whopping 780,000 years ago, some scientists believe we are overdue for another. But reversals are not predictable and are certainly not periodic. [...] Regardless, the seriousness of a magnetic reversal will depend on how long the reversal takes to complete. If it slowly shifts for many thousands of years, it is possible that migratory creatures, and mankind as well, will be able to adapt. In the meantime, we have much to learn about what is happening deep within our planet.