You’re a polar explorer and you’ve just reached the north pole. The huskies are yapping, the cameras are ready and you’re just about to unfurl the flag when, all of a sudden, the north pole becomes the south pole. Imagine your chagrin. Okay, so it doesn’t really happen that fast, but it’s true that in the past the earth’s magnetic poles have switched places. In fact, it seems to happen roughly every 250,000 years or so. How do we know this? Learn more on this Moment of Science.
What's the biggest magnet ever? Find out on this Moment of Science.
Millions of monarch butterflies fly southwest from eastern Canada and the United States down to Mexico each autumn; then millions more fly back to the northeast in the spring.The one-way trip is as long as 2500 miles for some of these creatures.
Although dissection remains a staple of medical training, over the years we have developed less invasive ways of peering inside the body. One of the most revolutionary and successful is MRI, or magnetic resonance imaging.