evidence: During a pole reversal, Earth’s magnetic north and south poles swap locations. While that may sound like a big deal, pole reversals are common in Earth’s geologic history. Paleomagnetic records tell us Earth’s magnetic poles have reversed 183 times in the last 83 million years, and at least several hundred times in the past 160 million years. The time intervals between reversals have fluctuated widely, but average about 300,000 years, with the last one taking place about 780,000 years ago. During a pole reversal, the magnetic field weakens, but it doesn’t completely disappear. The magnetosphere, together with Earth’s atmosphere, continue protecting Earth from cosmic rays and charged solar particles, though there may be a small amount of particulate radiation that makes it down to Earth’s surface. The magnetic field becomes jumbled, and multiple magnetic poles can emerge in unexpected places. [...] Plant and animal fossils from the period of the last major pole reversal don’t show any big changes. Deep ocean sediment samples indicate glacial activity was stable. In fact, geologic and fossil records from previous reversals show nothing remarkable, such as doomsday events or major extinctions.