英语听力：自然百科 地球力场 Earth's Force Field—4
时间：2019-01-22 作者：英语课 分类：自然百科2011年
英语课
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 pottery 1 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 randomly 2 orientated 3. When clay is fired at high temperatures, they start to move around.
All the little magnetic minerals will align 4 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.
n.陶器，陶器场
- 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。
adv.随便地，未加计划地
- 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
v.朝向( orientate的过去式和过去分词 )；面向；确定方向；使适应
- 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