VOA标准英语2015--马里兰大学实验室复刻地球磁场

Scientists Take on Earth’s Magnetic Field 马里兰大学实验室复刻地球磁场

WASHINGTON—

Most of us hardly ever think about the Earth's magnetic field. We might be aware that it helps guide birds as they migrate and ensures that our compasses point north, but not realize that it is one of the crucial components¹ that make life on Earth possible. Yet, the processes in the Earth’s core that create the magnetic field are poorly understood.

At a lab of University of Maryland, scientists are trying to replicate² the conditions that reign³ 3,000 kilometers below our feet.

Deep inside our planet, a 3,400 kilometer-wide sphere of molten iron and nickel, with a smaller solid iron ball at its center, creates the electric currents responsible for Earth’s magnetic field.

The most immediate⁴ benefit is its role in navigation.

But there’s more, says University of Maryland physics professor Daniel Lathrop.

“It’s an important part of what makes the Earth a habitable planeta because it shields us from a lot of the worst radiation from the sun,” he said.

Evidence shows that the Earth’s magnetic field is not stationary⁵. It wanders around and sometimes even ventures [expands?] far away.

“We do know the Earth’s magnetic field has reversed north-south hundreds of times in Earth’s history," said Lathrop. "Of course, the spin of the Earth stays the same, but where the magnetic pole is - moves and has actually reversed.”

In their laboratory, funded by the National Science Foundation, Lathrop and his team are trying to find out how and why that happens.

Spinning a ball of molten iron being somewhat impractical⁶, researchers built a suitable substitute: a 3-meter wide spinning steel ball filled with 12.5 tons of sodium⁷, a soft metal that melts at just under 100 degrees Celsius⁸.

A 1-meter-wide inner non-magnetic steel sphere substitutes for the solid core. Both can be rotated independently.

Spinning them slowly has not created the so-called dynamo effect, thought to be responsible for creating magnetic fields.

“We only see them when we impose small magnetic fields from the outside. But imposing⁹ small magnetic fields from outside we get a factor of 10 larger magnetic fields induced by the flow. We get large gain without the so-called dynamo. Now we’re aiming to go full speed,” said Lathrop.

Will these experiments prepare us for the possible reversal of the Earth’s magnetic field? Lathrop says it is difficult to predict changes that happen over thousands of years.

“One second of operation of the experiment models 5,000 years of evolution of the magnetic field. So the goal is to take data from the experiment to do mock predictions and then you can improve the predictions,” he said.

Lathrop notes that the intensity¹⁰ of our planet’s magnetic field has dropped about 10 percent in the last 170 years, so the reversal process may have already started.

Fortunately for us, the change is too slow to affect our regular lives.

1 components   

（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分

参考例句：

• the components of a machine 机器部件
• Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

2 replicate   

v.折叠，复制，模写；n.同样的样品；adj.转折的

参考例句：

• The DNA of chromatin must replicate before cell division.染色质DNA在细胞分裂之前必须复制。
• It is also easy to replicate,as the next subsection explains.就像下一个小节详细说明的那样，它还可以被轻易的复制。

3 reign   

n.统治时期，统治，支配，盛行；v.占优势

参考例句：

• The reign of Queen Elizabeth lapped over into the seventeenth century.伊丽莎白王朝延至17世纪。
• The reign of Zhu Yuanzhang lasted about 31 years.朱元璋统治了大约三十一年。

4 immediate   

adj.立即的；直接的，最接近的；紧靠的

参考例句：

• His immediate neighbours felt it their duty to call.他的近邻认为他们有责任去拜访。
• We declared ourselves for the immediate convocation of the meeting.我们主张立即召开这个会议。

5 stationary   

adj.固定的，静止不动的

参考例句：

• A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
• Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。

6 impractical   

adj.不现实的，不实用的，不切实际的

参考例句：

• He was hopelessly impractical when it came to planning new projects.一到规划新项目，他就完全没有了实际操作的能力。
• An entirely rigid system is impractical.一套完全死板的体制是不实际的。

7 sodium   

n.（化）钠

参考例句：

• Out over the town the sodium lights were lit.在外面，全城的钠光灯都亮了。
• Common salt is a compound of sodium and chlorine.食盐是钠和氯的复合物。

8 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

9 imposing   

adj.使人难忘的，壮丽的，堂皇的，雄伟的

参考例句：

• The fortress is an imposing building.这座城堡是一座宏伟的建筑。
• He has lost his imposing appearance.他已失去堂堂仪表。

10 intensity   

n.强烈，剧烈；强度；烈度

参考例句：

• I didn't realize the intensity of people's feelings on this issue.我没有意识到这一问题能引起群情激奋。
• The strike is growing in intensity.罢工日益加剧。