triking Back at Lightning With LasersSeldom is the weather more dramatic than when thunderstormsstrike. Their electrical fury inflicts death or serious injury on around500 people each year in the United States alone. As the clouds roll ina leisurely round of golf can become a terrifying dice with death - outin the open, a lone golfer may be a lightning bolt's most invitingtarget. And there is damage to property too. Lightning damage costsAmerican power companies more than $100 million a year.But researchers in the United States and Japan are planning to hitback. Already in laboratory trials they have tested strategies forneutralising the power of thunderstorms, and this winter they wil!brave real storms, equipped with an armoury of lasers that they willbe pointing towards the heavens to discharge thunderclouds beforelightnina can strike.
The idea of forcing storm clouds to discharge their lightning oncommand is not new.In the early 1960s,researchers tried firingrockets trailing wires into thunderclouds to set up an easy dischargepath for the huge electric charges that these clouds generate. Thetechnique survives to this day at a test site in Florida run by theUniversity of Florida , with support from the Electrical Power ResearchInstitute (EPRl), based in California. EPRl, which is funded by powerc儂鸕摣倥齜能係彫戍糧Å襲筽﹏洵戗俟腙粨忄设乜闸鎳肟辰寓使蓯磁窓杷违ies,is looking at ways to protect the United States'powergrid from lightning strikes. "We can cause the lightning to strike wherewe want it to using rockets,says Ralph Bernstein,manager olightning projects at EPRl. The rocket site is providing precisemeasurements of lightning voltages and allowing engineers to checkhow electrical equipment bears up.Bad behaviour
But while rockets are fine for research, they cannot provide theprotection from lightning strikes that everyone is looking for. Therockets cost around $1,200 each, can only be fired at a limitedfrequency and their failure rate is about 40 per cent. And even whenthey do trigger lightning, things still do not always go according toplan,'Lightning is not perfectly well behaved,'says Bernstein.Occasionally,it will take a branch and go someplace it wasn'supposed to go.'
And anyway,who would want to fire streams of rockets in apopulated area? "What goes up must come down, 'points out Jean-Claude Diels of the University of New Mexico. Diels is leading aproject, which is backed by EPRl, to try to use lasers to dischargelightning safely
and safety is a basic requirement since no one wants to putthemselves or their expensive equipment at risk. With around$500,000 invested so far, a promising system is just emerging fromthe laboratory.The idea began some 20 years ago, when high-powered lasers wererevealing their ability to extract electrons out of atoms and createions. lf a laser could generate a line of ionisation in the air all the wayup to a storm cloud, this conducting path could be used to guidelightning to Earth , before the electric field becomes strong enough tobreak down the air in an uncontrollable surge. To stop the laser itselfbeing struck, it would not be pointed straight at the clouds. Instead itwould be directed at a mirror, and from there into the sky. The mirrorwould be protected by placing lightning conductors close by. ldeallythe cloud-zapper (gun)would be cheap enough to be installedaround all key power installations, and portable enough to be takento international sporting events to beam up at brewing storm clouds.
A stumbling block
However, there is still a big stumbling block. The laser is no niftyportable: it's a monster that takes up a whole room. Diels is trying tocut down the size and says that a laser around the size of a smalltable is in the offing. He plans to test this more manageable systemon live thunderclouds next summer.Bernstein says that Diels's system is attracting lots of interest fromthe power companies. But they have not yet come up with the $5million that EPRl says will be needed to develop a commercial system,by making the lasers yet smaller and cheaper. l cannot say l havemoney yet, but l'm working on it,’says Bernstein. He reckons thatthe forthcoming field tests will be the turning point - and he’ shoping for good news. Bernstein predicts 'an avalanche of interestand support'if all goes well. He expects to see cloud-zapperseventually costing $50,000 to $100,000 each.Other scientists could also benefit. With a lightning 'switch' at theirfingertips, materials scientists could find out what happens whenmighty currents meet matter, Diels also hopes to see the birth of'interactive meteorology'- not just forecasting the weather butcontrolling it. 'f we could discharge clouds, we might affect theweather, ' he says.
And perhaps, says Diels,we'll be able to confront some othermeteorological menaces. "We think we could prevent hail by inducinglightning’he says. Thunder, the shock wave that comes from alightning flash, is thought to be the trigger for the torrential rain thatis typical of storms. A laser thunder factory could shake the moistureout of clouds, perhaps preventing the formation of the gianthailstones that threaten crops. With luck, as the storm clouds gatherthis winter, laser-toting researchers could, for the first time, strikeback.
Questions 7-10Complete the summary using the list of words, A-l, below.Write the correct letter, A-l in boxes 7- 10 on your answer sheet.In this method, a laser is used to create a line of ionisation by1. This laser is thenremoving electrons from 7directed at 8 .. 2 in order to control electrical charges, amethod which is less dangerous than using 9.......... 3 As aprotection for the lasers, the beams are aimed firstly at 10...4
storm clouds
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8cloud-zappersatomsA
E
F
ions
Dmir羋覺獤兇甦;rs
technique
GrocketsH
thunder
conductors