http://www.smithsonianmag.com/smart-...ria-180952016/
Previously, researchers estimated the field was weakening about 5 percent per century, but the new data revealed the field is actually weakening at 5 percent per decade, or 10 times faster than thought. As such, rather than the full flip occurring in about 2,000 years, as was predicted, the new data suggest it could happen sooner.
Read more:
http://www.smithsonianmag.com/smart-...BhDw6rDdBbX.99
Give the gift of Smithsonian magazine for only $12!
http://bit.ly/1cGUiGv
Follow us: @SmithsonianMag on Twitter