英语听力：自然百科 地球力场 Earth's Force Field—17

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“We drive them about 20 miles away to the North, and release them, and we track them as they try to fly back home.”

 

 

 

He’s up, OK.

 

 

 

Holland wants to see how the magnetic poles will affect their ability to navigate¹ home. Bats normally fly back to the barn in around 60 minutes, but what happens to those whose senses have been manipulated.

 

 

 

“Now, that's it, he's gone, he's gone. He's gone and he's headed North, so this guy he's had his polarity reversed, his magnetic compass will screw that he's gonna in the wrong direction, but eventually he'll correct it and will get back to the home route.

 

 

 

It takes the bat several hours to make it back, Holland believes that bats/ sense Earth's magnetic field lines, so when the magnetic field reverses, it’s as if they’re navigating² with an upside down map, inevitably³ they go the wrong way.

 

 

 

There is very clear behavioral evidence that animals use the magnetic field for a compass, certainly, and also possibly as a map.”

 

 

 

But fluctuations⁴ in the magnetic polarity/ don't just affect bats. For decades whale beaching has mystified scientists.  But in the 1980s, biologists noticed a correlation⁵ between the location of whale strandings and sudden magnetic anomalies on the seafloor. A weakening magnetic field could cause the leader of whale pod to misread its internal GPS, leading others into dangerously shallow water. 

 

 

 

“There is the potential for this to affect animals’ ability to locate their position using the magnetic field. The Earth's magnetic field is a mechanism⁶ of locating their position. It has just been vital for animals throughout the history of life on earth, and so it's hard to imagine life without the magnetic field.”

 

 

 

An absence of the magnetic poles could be disastrous⁷ for many species including us.

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