Researchers have identified a period of sluggish magnetic field flipping for planet Earth, some 40 million years ago – raising big questions about how long these reversals actually take, and how we might be affected by the next one. Magnetic field flips are thought to happen fairly regularly, as far as geological timescales go. There have been some 540 reversals across the last 170 million years, and it seems they've been happening for billions of years . But something was different 40 million