英语听力：自然百科 地球力场 Earth's Force Field—4

 Scientists believe that the South Atlantic Anomaly, is a sign of a global decline in the magnetic field. Evidence of this comes from a surprising source. 

 

Dr. Mimi Hill uses pottery¹ to uncover the secrets of earth's magnetic past. Ancient pots tell us about our distant ancestors, but they also tell us how our magnetosphere has changed over thousands of years. 

 

I'm very interested in ancient pottery because it's a really a good recorder of what the earth's magnetic field has done at the time when the pot was fired. 

 

Clay contains tiny particles of magnetic iron-based mineral called magnetite. Normally, these are randomly² orientated³. When clay is fired at high temperatures, they start to move around. 

 

All the little magnetic minerals will align⁴ up with the earth’s magnetic field, when it cools down, it's locked in. 

 

As the clay cools and hardens, these minerals become re-magnetized by the earth's magnetic field, locking in a precise record of the strength of the field at that moment. 

 

What we are doing is, taking a tiny little core from an ancient pot and put this small core into a microwave air archetype system. 

 

Hill measures the magnetite from an ancient pot. She uses this measurement to calculate the extract strength of earth's magnetic field at the time the pot was fired. 

 

And, yes, we'll go on to microwaving. 

 

She compares this to samples taken from several pots over the last 400 years. 

 

We know this is dated about 1640 to 1670 and can tell from the experiment that the magnetic field strength was stronger by about 10 percent. 

 

Hill's research indicates that our magnetic protection is fading at an alarming rate.

1 pottery   

n.陶器，陶器场

参考例句：

• My sister likes to learn art pottery in her spare time.我妹妹喜欢在空余时间学习陶艺。
• The pottery was left to bake in the hot sun.陶器放在外面让炎热的太阳烘晒焙干。

2 randomly   

adv.随便地，未加计划地

参考例句：

• Within the hot gas chamber, molecules are moving randomly in all directions. 在灼热的气体燃烧室内，分子在各个方向上作无规运动。 来自辞典例句
• Transformed cells are loosely attached, rounded and randomly oriented. 转化细胞则不大贴壁、圆缩并呈杂乱分布。 来自辞典例句

3 orientated   

v.朝向( orientate的过去式和过去分词 )；面向；确定方向；使适应

参考例句：

• He orientated himself by finding a familiar landscape. 他寻见一处熟悉的景色，从而确定自己所处的方位。 来自《简明英汉词典》
• They orientated the tennis court north and south. 他们把网球场定为南北向。 来自辞典例句

4 align   

vt.使成一线，结盟，调节；vi.成一线，结盟

参考例句：

• Align the ruler and the middle of the paper.使尺子与纸张的中部成一条直线。
• There are signs that the prime minister is aligning himself with the liberals.有迹象表明首相正在与自由党人结盟。