Readingmaterial
阅读理解
1.Unlesswespendmoneytospot(认出，发现)andpreventasteroids(小行星)now,onemightcrashintoEarthanddestroylifeasweknowit,saysomescientists.
Asteroidsarebiggerversionsofthemeteoroids(流星体)thatraceacrossthenightsky.MostorbitthesunfarfromEarthanddon'tthreatenus.ButtherearealsothousandsofasteroidswhoseorbitsputthemonacollisioncoursewithEarth.
But$500millionworthofnewtelescopesrightnow,thenspend$10millionayearforthenext25yearstolocatemostofthespacerocks.Bythetimewespotafatalone,thescientistssay,we'llhaveawaytochangeitscourse.
Isitworthit?Twothingsexpertsconsiderwhenjudginganyriskare(i)Howlikelytheeventis;(2)Howbadtheconsequencesiftheeventoccurs.ExpertsthinkanasteroidbigenoughtodestroylotsoflifemightstrikeEarthonceevery500,000years.Soundsprettyrarebutifonedidfall.Itwouldbetheendoftheworld."Ifwedon'ttakecareofthesebidasteroids,they'lltakecareofus,"saysonescientist."it'sthatsimple."