时差N小时:海洋独特的磁场

Last time, we talked about “motional induction,” aphenomenon by which the ocean generates a magnetic field.

上次，我们提到过动生电磁感应：海洋产生磁场的一种现象。

It works like this: earth has its own magnetic field.

地球有自己的磁场，

The oceanhas plenty of charged atoms in it, in the form of dissolved salt.

海洋有无数溶解盐形式的带电原子，

These atoms are in motion because the ocean flows.

随着海洋运动而运动。

Charged atoms moving through a magnetic field will induce an electric current.

在磁场中运动的带电原子会引起电流，

And an electriccurrent will, in turn, create another magnetic field.

而电流反过来又回形成另一个磁场。

The ocean should generate its own magneticfield.

这样海洋应该就形成了自己的磁场。

You said should. How could we know this “motional induction” is happening?

你说“应该”，我们怎么知道这种动生电磁感应确有其事?

Direct evidence came in 2003 from scientists working at the University of Washington and aresearch institute in Potsdam, Germany.

直到2003年，华盛顿大学和德国波兹坦的某研究学院。

These researchers used a magnetometer on board anorbiting satellite.

研究人员将磁力计放在轨道卫星上，证实海洋的磁场真是存在。

First, they figured out what the magnetic field of the planet should be.

最初，磁力计上的数据让科学家以为是地球磁场作用的。

After subtracting thisfigure, they found there was still some leftover magnetic field.

而后，他们发现除去这个因素后，仍然有磁场存在。

Next, the team made a computer model of what kind of magnetic field the ocean shouldgenerate through motional induction.

研究人员又电脑模拟在动生电磁感应让海洋产生哪种磁场，

Sure enough, their prediction matched the excessmagnetic field measured by the satellite.

当然，科学家的推论和卫星上测出的“另一个”磁场吻合。

The satellite also found that magneticintensity over the oceans peaked every twelve and a halfhours, but not over the land. Can you guess why?

卫星还发现，海洋磁场每隔12个半小时就会出现高峰，但是地球磁场不受影响。你能猜到原因吗?

Every twelve hours…Oh, I get it— tides!

每隔12个半小时?我知道了!答案是潮汐。

Exactly right!

完全正确!

The tides rise and fall every twelve and half hours, just as that extra magneticenergy swells and diminishes.

潮汐每隔12个半小时潮起潮落，正好和“另一个”磁场高低峰吻合。

This is very strong evidence that motional induction is real… andthe ocean has its own magnetism.

这正是磁场感应存在的真凭实据，海洋确实有自己独特的磁力。