美国有线新闻 CNN 地磁北极在快速由加拿大移向俄罗斯(在线收听) |
CARL AZUZ: Which of these places is located the farthest north? Anchorage, Alaska, USA; St. Petersburg, Russia; Reykjavik, Iceland; or Oslo, Norway? The northernmost city on this list, that's 64 degrees north latitude is the capital of Iceland. But they're all in latitudes north of 55 degrees which means their smart phone maps could be effected by a shift in the magnetic north pole. There's the True North Pole and the Magnetic North. The True North Pole is geographic. It's the northernmost point on the planet. The Magnetic North Pole is where compass needles point. Historically, it's been located in the Canadian artic, several hundred miles away from the True north. And it's moving. Scientists say it's always done that slowly. But in recent years, the Magnetic North Pole has been speeding up, traveling about 34 miles per year in the direction of Russia. Why is this happening? No one knows for sure. Many scientists think it's because the Earth's magnetic field is tied to a liquid outer core deep inside the planet. When the liquid flows, it could pull the Magnetic North with it. Will compasses still point north? For the most part, they will. But this could cause some navigational trouble above 55 degrees north latitude, so for people who live in the cities mentioned in the 10 Second Trivia. What can be done about it? Well there's something called the world magnetic model. It k?eeps track of the Earth's magnetic poles, and it's used by militaries, North American and European countries and civilian navigation systems. Officials usually update it every five years so it can stay accurate. But they just took steps to update it sooner than that, so it can keep up with the faster moving Magnetic North. |
原文地址:http://www.tingroom.com/lesson/cnn2019/3/471379.html |