The awnser is a because it is the best awnser
Answer:
That is much less often than in the last 150 million years, when the field has flipped every 600,000 years. In the last 10-20 million years it has sped up even more, to once every 200,000-250,000 years. "The evidence points to a more stable field in the very far past and fewer reversals," says Veikkolainen.
