Space mysteries: Why do Earth's magnetic poles flip?  

 Every so often, Earth's magnetic poles completely flip. Why causes this to happen? And how do these reversals affect life on Earth?  

https://cdn.mos.cms.futurecdn.net/nRxyGrDk93kNfgfsXJfm75.jpg

https://www.space.com/space-mysteries-why-do-earths-magnetic-poles-flip