【導讀】oneknowsexactlyhowtheearthbegan,asithappenedsolongago.However,acordingtoawidelyacceptedtheory,theuniversebeganwitha“BigBang“thatthrewmaterinaldirections.Afterthat,atomsbegantoformandbingtocreatestarsandotherbodies.Forseveralbilionyearsafterthe“BigBang“,theearthwasstiljustacloudofdust.Whatitwastobeewasuncertainuntilbetween4.5and3.8billionyearsagowhenthedustsettledintoasolidglobe.Theearthenwarebecam

　　

【正文】 ghtl essl y around i n our spaceshi p cabi n watchi ng the earth be e sm al er and the m oon larger. When we got there, I wanted to expl ore im medi atel y. “ Com e on,” I sai d. “ If you are ri ght, m y m ass wi l be l ess than on the earth because the moon i s smal er and I wil l be abl e to move m ore freel y. I m i ght even grow tal l er i f I stay here l ong enough. I shal l certai nl y wei gh l ess!” I l aughed and cl im bed down the steps from the spaceshi p. But when I tri ed to step forward, I found I was cari ed twi ce as far as on the earth and fel over. “ O h dear, ” I cri ed, “ wal ki ng does need a bit of practi ce now that gravi ty has changed. ” After a whi l e I got the hang of i t and we began to enjoy ourselves. Leavi ng the m on’s gravity was not as painful as l eavi ng the earth’s. But returni ng to the earth was very fri ghteni ng. We watched, am azed as fi re broke out on the outsi de of the spaceship as the earth’s gravi ty increased. Agai n we were pushed back hard i nto our seats as we cam e back to l and. “ That was very exhausti ng but very exciti ng too, ” I sai d. “N ow I know m uch m ore about gravi ty! Do you thi nk we coul d bisi t som e stars next ti m e?” “O f course,” he sm il ed, “ whi ch star woul d you l i ke to go to?” Caught by a bl ack hol e The spaceship warned Li Yanpi ng and m e to be ready as we were approachi ng the “black hol e”. We coul d see som e fai nt l i ghts around what l ooked li ke an em pty space. Li Yanpi ng sai d, “ That em pty hole i s l i ke a m outh al ways needi ng to be fed. Those l i ghts are thi ns that are being pul ed i nto tim e by the gravity of the hol e.” We watched with i nterest and am azem ent at the li ghts whi ch seem ed to be goi ng fai nter and fai nter round the edge of the black hol e. Just then the l i ghts on our spaceshi p went our the and the puter stopped worki ng. What was happeni ng? I tri ed to turn the spaceshi p away from the hol e but i t woul d not m ove. Woul d it eat us too? Suddenl y the spaceshi p jum ped and began to m ove round the edge of trhe hol e too. The gravi ty of the “bl ack hol e” was pul ing us i nto i ts “m outh”. As the spaceshi p m oved round the bl ack hol e, I fel t rather si ck. My m outh went dry and I cl osed m y eyes. Al l the stori es about what happened when you were caught by the gravi ty of a “black hol e” seem to be true. But then the spaceshi p jum ped agai n. Thi s tim e i t m oved si deways and away from this edge of the “black hol e”. Som eone watchi ng m e woul d have seen the spaceshi p fl yi ng l ike a bird away from the “black hol e”. But we fel t nothi ng. At l ast we were abl e to l ook around us. Lucki l y the puter had started worki ng agai n. We real i zed that we had di scovered som ethi ng new about “bl ack hole”. If you go i nsi de the edge of a “bl ack hol e”, i t wi l “eat” you and there is no escape。 but i f you do not, you may have an opportuni ty to escape. H ow exci ti ng! Unit 5 A tri p on “ The True North” Li Dai yu and her cousi n Li u Qi an were on a tri p to Canada to bi si t their cousi ns i n Montreal on the Atl anti c coast. Rather than take the aeropl ane al the way, they deci ded to fl y to Vancouver and then take the trai n west to east acros Canada. The though that they coul d cross the whol e continent was exci ti ng. Thei r fri end, Danny Li n, was waiti ng at the ai rport. H e was goi ng to take them and thei r baggage to catch “The True N orth”, the cross Canada train. O n the way to the stati on, he chated about thei r tri p. “You’re goi ng to see som e great scenery. Goi ng eastward, you’l l pass m ountai ns and thousands of l akes and forests, as wel l as wi de ri vers and l arge ci ti es. Som e peopl e have the i dea that you can cross Canda i n l ess than fi ce days, but they fet the fact that Canada i s 5500 ki l om eters from coast to coast. H ere i n Vancouver, you’re in Canada’s warm est part. Peopl e say i t i s Canada’s m ost beauti ful ci ty, surrounded by m ountains and the Paci fi c O cean. Ski ng i n the Rocky Mountai ns and sai li ng i n the harbour m ake Vancouver one of Canada’s m ost popul ar ci ti es to l ive i n. Its popul ati on i s i ncreasi ng rapi dl y. The coast north of Vancouver has som e of the ol dest and m ost beauti ful forests i n the worl d. It is so wet there that the trees are extrem el y tal, som e m easuri ng over 90 m etres. ” That afternoon aboard the trai n, the cousi ns settl ed down i n thei r seats. Earl i er that day, when they crossed the Rocky Mountai ns, they m anaged to catch si ght of som e m ountai n goats and even a gri zzl y bear and an eagl e. Thei r next stop was Cal gary, whi ch i s fam ous for the Cal gary Stam pede. Cowboys from al l over the worl d e to pete i n the Stam pede. Many of them have a gi ft for ri di ng wi l d horses and can wi n thousands of dol l ars i n pri zes. After two days’ travel , the gi rl s began to real i ze that Canada i s qui te em pty. At school , they had l earned that m ost Canadi ans l i ve wi thi n a few hundred ki l om etres of the USA border, and Canada’s popul ati on i s onl y sl i ghtl y over thi rty m i l l i on, but now they were am azed to see such an em pty country. They went through a wheatgrowi ng provi nce one knows exactl y how the earth began, as i t happened so long ago. H owever, acording to a wi del y accepted theory, the universe began wi th a “ Bi g Bang “ that threw m ater i n al di recti ons. After that, atoms began to form and bi ng to create stars and other bodi es. For several bi l i on years after the “ Bi g Bang “, the earth was sti l just a cl oud of dust. What i t was to be e was uncertai n unti l between 4. 5 and 3. 8 bil li on years ago when the dust settl ed i nto a soli d gl obe. The earthenware becam e so vi olent that i t was not cl ear whether the shape woul d l ast or not. It expl oded l oudl y wi th fi re and rock.