What would it be like if the Earth’s magnetic pole switched? Migrating animals and hikers would certainly need to reset their compasses, but could it play real havoc with life on Earth? Analysing the rings of an ancient tree pulled from a bog in New Zealand, researchers have been investigating what happened the last time north and south flipped – 42,000 years ago. Nicola Davis speaks to Prof Chris Turney about how it changed the chemistry of the atmosphere and, if combined with a period of lower solar activity, what impact this could have had on the environment and evolution. Help support our independent journalism at <a href="https://www.theguardian.com/sciencepod">theguardian.com/sciencepod</a>
