英语听力：自然百科 地球力场 Earth's Force Field—8（在线收听） |
Easily confused by this idea, there has a big thawed iron inner core, so that I think it's just the bar magnet, just permanent magnet frozen in nad, and that's where causes all the magnetic field. But it's too hot inside the Earth, that can't happen when the temperature gets hot enough, magnets turn off. Permanent magnets stop working at 1,200 degrees Fahrenheit. So some other process must be generating Earth's magnetic field. To find out more, professor Dan Lathrop embarks on a very ambitious experiment. At the University of Maryland, he and his team build a 10-foot mechanical model of the Earth's core.
I think we want to understand is why some planets generate magnetic field, and why others have no magnetic field. So, by building experiments, we could hope to understand the conditions when it works and when it doesn't. What's the switch / why sometimes a planet comes alive magnetically and why sometimes they will mean dead.
Inside this sphere, is a solid iron bowl, surrounded by 13 tons of churning liquid metal. Lathrop uses molten sodium instead of iron, because of its lower melting point. So we get a rotating outer sphere, holds liquid sodium and its man-to-man mixed iron and the Earth's core..
o limit Earth's rotation. Those drive the outer sphere of the vas, 4 revolutions per second and inner core of the vas, 15 revolutions per second.
So, let's go, give it a spin. If it succeeds, Lathrop's experiment will advance our understanding of how our magnetic field is generated. Looks good, seeing 26 turns of rotatings, metal on liquids up close to the sound, so really had no idea with a big deal like that. That is, it's wavering turns.
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| 原文地址：http://www.tingroom.com/lesson/zrbaike/2011/259940.html |