资源描述：
《某饲料厂年产50000吨饲料加工项目可行性研究报告》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、achancetomakeatripintospacewithmyfriendLiYanping,anastronomer.Wevisitedthemooninourspaceship! Beforeweleave,LiYanpingexplainedtomethattheforeceofthegravitywouldchangethreetimesonourjourneyandthatthefirstchangewouldbethemostpowerful.Thenwewereoff.Astherocketroseintotheair,wewerepushe
2、dbackintoourseatsbecauseweweretryingtoescapethepulloftheearth’sgravity.Itwassohardthatwecouldnotsayanythingtoeachother.GraduallytheweightlessenedandIwasabletotalktohim.“Whyisthespaceshipnotfallingbacktotheearth?OntheearthifIfallfromatreeIwillfalltoground.”Iasked.“Wearetoofarfromthee
3、arthnowtofeelitspull,“heexplained,“sowefeelasifthereisnogravityatall.Whenwegetclosertothemoon,weshallfeelitsgravitypullingus,butitwillnotbeasstrongapullastheearth’s.“Icheeredupimmediatelyandfloatedweightlesslyaroundinourspaceshipcabinwatchingtheearthbecomesmallerandthemoonlarger. Wh
4、enwegotthere,Iwantedtoexploreimmediately.“Comeon,”Isaid.“Ifyouareright,mymasswillbelessthanontheearthbecausethemoonissmallerandIwillbeabletomovemorefreely.ImightevengrowtallerifIstayherelongenough.Ishallcertainlyweighless!”Ilaughedandclimbeddownthestepsfromthespaceship.ButwhenItried
5、tostepforward,IfoundIwascarriedtwiceasfarasontheearthandfellover.“Ohdear,”Icried,“walkingdoesneedabitofpracticenowthatgravityhaschanged.”AfterawhileIgotthehangofitandwebegantoenjoyourselves. Leavingthemoon’sgravitywasnotaspainfulasleavingtheearth’s.Butreturningtotheearthwasveryfrigh
6、tening.Wewatched,amazedasfirebrokeoutontheoutsideofthespaceshipastheearth’sgravityincreased.Againwewerepushedbackhardintoourseatsaswecamebacktoland.“Thatwasveryexhaustingbutveryexcitingtoo,”Isaid.“NowIknowmuchmoreaboutgravity!Doyouthinkwecouldbisitsomestarsnexttime?”“Ofcourse,”hesmi
7、led,“whichstarwouldyouliketogoto?” Caughtbyablackhole ThespaceshipwarnedLiYanpingandmetobereadyaswewereapproachingthe“blackhole”.Wecouldseesomefaintlightsaroundwhatlookedlikeanemptyspace.LiYanpingsaid,“Thatemptyholeislikeamouthalwaysneedingtobefed.Thoselightsarethinsthatarebeingpull
8、edintotimebythegrav
