ACHANCETOMAKEATRIPINTOSPACEWITHMYFRIENDLIYANPING,ANASTRONOMERWEVISITEDTHEMOONINOURSPACESHIPBEFOREWELEAVE,LIYANPINGEXPLAINEDTOMETHATTHEFORECEOFTHEGRAVITYWOULDCHANGETHREETIMESONOURJOURNEYANDTHATTHEFIRSTCHANGEWOULDBETHEMOSTPOWERFULTHENWEWEREOFFASTHEROCKETROSEINTOTHEAIR,WEWEREPUSHEDBACKINTOOURSEATSBECAUSEWEWERETRYINGTOESCAPETHEPULLOFTHEEARTHSGRAVITYITWASSOHARDTHATWECOULDNOTSAYANYTHINGTOEACHOTHERGRADUALLYTHEWEIGHTLESSENEDANDIWASABLETOTALKTOHIM“WHYISTHESPACESHIPNOTFALLINGBACKTOTHEEARTHONTHEEARTHIFIFALLFROMATREEIWILLFALLTOGROUND”IASKED“WEARETOOFARFROMTHEEARTHNOWTOFEELITSPULL,“HEEXPLAINED,“SOWEFEELASIFTHEREISNOGRAVITYATALLWHENWEGETCLOSERTOTHEMOON,WESHALLFEELITSGRAVITYPULLINGUS,BUTITWILLNOTBEASSTRONGAPULLASTHEEARTHS“ICHEEREDUPIMMEDIATELYANDFLOATEDWEIGHTLESSLYAROUNDINOURSPACESHIPCABINWATCHINGTHEEARTHBECOMESMALLERANDTHEMOONLARGERWHENWEGOTTHERE,IWANTEDTOEXPLOREIMMEDIATELY“COMEON,”ISAID“IFYOUARERIGHT,MYMASSWILLBELESSTHANONTHEEARTHBECAUSETHEMOONISSMALLERANDIWILLBEABLETOMOVEMOREFREELYIMIGHTEVENGROWTALLERIFISTAYHERELONGENOUGHISHALLCERTAINLYWEIGHLESS”ILAUGHEDANDCLIMBEDDOWNTHESTEPSFROMTHESPACESHIPBUTWHENITRIEDTOSTEPFORWARD,IFOUNDIWASCARRIEDTWICEASFARASONTHEEARTHANDFELLOVER“OHDEAR,”ICRIED,“WALKINGDOESNEEDABITOFPRACTICENOWTHATGRAVITYHASCHANGED”AFTERAWHILEIGOTTHEHANGOFITANDWEBEGANTOENJOYOURSELVESLEAVINGTHEMOONSGRAVITYWASNOTASPAINFULASLEAVINGTHEEARTHSBUTRETURNINGTOTHEEARTHWASVERYFRIGHTENINGWEWATCHED,AMAZEDASFIREBROKEOUTONTHEOUTSIDEOFTHESPACESHIPASTHEEARTHSGRAVITYINCREASEDAGAINWEWEREPUSHEDBACKHARDINTOOURSEATSASWECAMEBACKTOLAND“THATWASVERYEXHAUSTINGBUTVERYEXCITINGTOO,”ISAID“NOWIKNOWMUCHMOREABOUTGRAVITYDOYOUTHINKWECOULDBISITSOMESTARSNEXTTIME”“OFCOURSE,”HESMILED,“WHICHSTARWOULDYOULIKETOGOTO”CAUGHTBYABLACKHOLETHESPACESHIPWARNEDLIYANPINGANDMETOBEREADYASWEWEREAPPROACHINGTHE“BLACKHOLE”WECOULDSEESOMEFAINTLIGHTSAROUNDWHATLOOKEDLIKEANEMPTYSPACELIYANPINGSAID,“THATEMPTYHOLEISLIKEAMOUTHALWAYSNEEDINGTOBEFEDTHOSELIGHTSARETHINSTHATAREBEINGPULLEDINTOTIMEBYTHEGRAVITYOFTHEHOLE”WEWATCHEDWITHINTERESTANDAMAZEMENTATTHELIGHTSWHICHSEEMEDTOBEGOINGFAINTERANDFAINTERROUNDTHEEDGEOFTHEBLACKHOLEJUSTTHENTHELIGHTSONOURSPACESHIPWENTOURTHEANDTHECOMPUTERSTOPPEDWORKINGWHATWASHAPPENINGITRIEDTOTURNTHESPACESHIPAWAYFROMTHEHOLEBUTITWOULDNOTMOVEWOULDITEATUSTOOSUDDENLYTHESPACESHIPJUMPEDANDBEGANTOMOVEROUNDTHEEDGEOFTRHEHOLETOOTHEGRAVITYOFTHE“BLACKHOLE”WASPULLINGUSINTOITS“MOUTH”ASTHESPACESHIPMOVEDROUNDTHEBLACKHOLE,IFELTRATHERSICKMYMOUTHWENTDRYANDICLOSEDMYEYESALLTHESTORIESABOUTWHATHAPPENEDWHENYOUWERECAUGHTBYTHEGRAVITYOFA“BLACKHOLE”SEEMTOBETRUEBUTTHENTHESPACESHIPJUMPEDAGAINTHISTIMEITMOVEDSIDEWAYSANDAWAYFROMTHISEDGEOFTHE“BLACKHOLE”SOMEONEWATCHINGMEWOULDHAVESEENTHESPACESHIPFLYINGLIKEABIRDAWAYFROMTHE“BLACKHOLE”BUTWEFELTNOTHINGATLASTWEWEREABLETOLOOKAROUNDUSLUCKILYTHECOMPUTERHADSTARTEDWORKINGAGAINWEREALIZEDTHATWEHADDISCOVEREDSOMETHINGNEWABOUT“BLACKHOLE”IFYOUGOINSIDETHEEDGEOFA“BLACKHOLE”,ITWILL“EAT”YOUANDTHEREISNOESCAPEBUTIFYOUDONOT,YOUMAYHAVEANOPPORTUNITYTOESCAPEHOWEXCITINGUNIT5ATRIPON“THETRUENORTH”LIDAIYUANDHERCOUSINLIUQIANWEREONATRIPTOCANADATOBISITTHEIRCOUSINSINMONTREALONTHEATLANTICCOASTRATHERTHANTAKETHEAEROPLANEALLTHEWAY,THEYDECIDEDTOFLYTOVANCOUVERANDTHENTAKETHETRAINWESTTOEASTACROSSCANADATHETHOUGHTHATTHEYCOULDCROSSTHEWHOLECONTINENTWASEXCITINGTHEIRFRIEND,DANNYLIN,WASWAITINGATTHEAIRPORTHEWASGOINGTOTAKETHEMANDTHEIRBAGGAGETOCATCH“THETRUENORTH”,THECROSSCANADATRAINONTHEWAYTOTHESTATIION,HECHATTEDABOUTTHEIRTRIP“YOUREGOINGTOSEESOMEGREATSCENERYGOINGEASTWARD,YOULLPASSMOUNTAINSANDTHOUSANDSOFLAKESANDFORESTS,ASWELLASWIDERIVERSANDLARGECITIESSOMEPEOPLEHAVETHEIDEATHATYOUCANCROSSCANDAINLESSTHANFICEDAYS,BUTTHEYFORGETTHEFACTTHATCANADAIS5500KILOMETERSFROMCOASTTOCOASTHEREINVANCOUVER,YOUREINCANADASWARMESTPARTPEOPLESAYITISCANADASMOSTBEAUTIFULCITY,SURROUNDEDBYMOUNTAINSANDTHEPACIFICOCEANSKIINGINTHEROCKYMOUNTAINSANDSAILINGINTHEHARBOURMAKEVANCOUVERONEOFCANADASMOSTPOPULARCITIESTOLIVEINITSPOPULATIONISINCREASINGRAPIDLYTHECOASTNORTHOFVANCOUVERHASSOMEOFTHEOLDESTANDMOSTBEAUTIFULFORESTSINTHEWORLDITISSOWETTHERETHATTHETREESAREEXTREMELYTALL,SOMEMEASURINGOVER90METRES”THATAFTERNOONABOARDTHETRAIN,THECOUSINSSETTLEDDOWNINTHEIRSEATSEARLIERTHATDAY,WHENTHEYCROSSEDTHEROCKYMOUNTAINS,THEYMANAGEDTOCATCHSIGHTOFSOMEMOUNTAINGOATSANDEVENAGRIZZLYBEARANDANEAGLETHEIRNEXTSTOPWASCALGARY,WHICHISFAMOUSFORTHECALGARYSTAMPEDECOWBOYSFROMALLOVERTHEWORLDCOMETOCOMPETEINTHESTAMPEDEMANYOFTHEMHAVEAGIFTFORRIDINGWILDHORSESANDCANWINTHOUSANDSOFDOLLARSINPRIZESAFTERTWODAYSTRAVEL,THEGIRLSBEGANTOREALIZETHATCANADAISQUITEEMPTYATSCHOOL,THEYHADLEARNEDTHATMOSTCANADIANSLIVEWITHINAFEWHUNDREDKILOMETRESOFTHEUSABORDER,ANDCANADASPOPULATIONISONLYSLIGHTLYOVERTHIRTYMILLION,BUTNOWTHEYWEREAMAZEDTOSEESUCHANEMPTYCOUNTRYTHEYWENTTHROUGHAWHEATGROWINGPROVINCEANDSAWFARMSTHATCOVEREDTHOUSANDSOFACRESAFRERDINNER,THEYWEREBACKINANURBANAREA,THEBUSYPORTCITYOFTHUNDERBAYATTHETOPOFTHEGREATLAKESBECAUSEOFTHEGREATLAKES,THEYLEARNED,CANADAHASMOREFRESHWATERTHANANYOTHERCOUNTRYINTHEWORLDINFACT,ITHASONETHIRDOFTHEWORLDSTOTALFRESHWATER,ANDMUCHOFITISINTHEGREATLAKESTHATNIGHTASTHEYSLEPT,THETRAINRUSHEDACROSSTHETOPOFLAKESUPERIOR,THROUGHTHEGREATFORESTSANDSOUTHWARDTOWADSTORONTO“THETRUENORTH”FROMTORONTOTOMONTREALTHENEXTMORNINGTHEBUSHESANDMAPLETREESOUTSIDETHEIRWINDOWWERERED,GOLDANDORANGE,ANDTHEREWASFROSTONTHEGROUND,CONFIRMINGTHATFALLHADARRIVEDINCANADAAROUNDNOONTHEYARRIVEDINTORONTO,THEBIGGESTANDMOSTWEALTHYCITYINCANADATHEYWERENOTLEAVINGFORMONTREALUNTILLATER,SOTHEYWENTONATOUROFTHECITYTHEYWENTUPTHETALLCNTOWERANDLOOKEDACROSSTHELAKEINTHEDISTANCE,THEYCOULDSEETHEMISTYCLOUDTHATROSEFROMTHEGREATNIAGARAFALLS,WHICHISONTHESOUTHSIDEOFTHELAKETHEWATERFLOWSINTOTHENIAGARARIVERANDOVERTHEFALLSONITSWAYTOTHESEATHEYSAWTHECOVEREDSTADIUM,HOMEOFSEVERALFAMOUSBASKETBALLTEAMSASTHEYWALKEDNORTHFROMTHEHARBOURAREA,LIDAIYUSAID,“LINFANG,ONEOFMYMOTHERSOLDSCHOOLMATES,LIVESHEREISHOULDPHONEHERFROMATELEPHONEBOOTH”THEYMETLINFEIAROUNDDUSKINDOWNTOWNCHINATOWN,ONEOFTHETHREEINTORONTOOVERDINNERATARESTAURANTCALLEDTHEPINKPEARL,THECOUSINSCHATTEDWITHLINFEI,WHOHADMOVEDTOCANADAMANYYEARSEARLIER“WECANGETGOODCANTONESEFOODHERE,”LINFEITOLDTHEM,“BECAUSEMOSTOFTHECHINESEPEOPLEHERECOMEFROMSOUTHCHINA,ESPECIALLYHONGKONGITSTOOBADYOUCANTGOASFARASOTTAWA,CANADASCAPITALITSAPPROXIMATELYFOURHUNDREDKILOMETERSNORTHEASTOFTORONTO,SOITWOULDTAKETOOLONG”THETRAINLEFTLATETHATNIGHTANDARRIVEDINMONTREALACHANCETOMAKEATRIPINTOSPACEWITHMYFRIENDLIYANPING,ANASTRONOMERWEVISITEDTHEMOONINOURSPACESHIPBEFOREWELEAVE,LIYANPINGEXPLAINEDTOMETHATTHEFORECEOFTHEGRAVITYWOULDCHANGETHREETIMESONOURJOURNEYANDTHATTHEFIRSTCHANGEWOULDBETHEMOSTPOWERFULTHENWEWEREOFFASTHEROCKETROSEINTOTHEAIR,WEWEREPUSHEDBACKINTOOURSEATSBECAUSEWEWERETRYINGTOESCAPETHEPULLOFTHEEARTHSGRAVITYITWASSOHARDTHATWECOULDNOTSAYANYTHINGTOEACHOTHERGRADUALLYTHEWEIGHTLESSENEDANDIWASABLETOTALKTOHIM“WHYISTHESPACESHIPNOTFALLINGBACKTOTHEEARTHONTHEEARTHIFIFALLFROMATREEIWILLFALLTOGROUND”IASKED“WEARETOOFARFROMTHEEARTHNOWTOFEELITSPULL,“HEEXPLAINED,“SOWEFEELASIFTHEREISNOGRAVITYATALLWHENWEGETCLOSERTOTHEMOON,WESHALLFEELITSGRAVITYPULLINGUS,BUTITWILLNOTBEASSTRONGAPULLASTHEEARTHS“ICHEEREDUPIMMEDIATELYANDFLOATEDWEIGHTLESSLYAROUNDINOURSPACESHIPCABINWATCHINGTHEEARTHBECOMESMALLERANDTHEMOONLARGERWHENWEGOTTHERE,IWANTEDTOEXPLOREIMMEDIATELY“COMEON,”ISAID“IFYOUARERIGHT,MYMASSWILLBELESSTHANONTHEEARTHBECAUSETHEMOONISSMALLERANDIWILLBEABLETOMOVEMOREFREELYIMIGHTEVENGROWTALLERIFISTAYHERELONGENOUGHISHALLCERTAINLYWEIGHLESS”ILAUGHEDANDCLIMBEDDOWNTHESTEPSFROMTHESPACESHIPBUTWHENITRIEDTOSTEPFORWARD,IFOUNDIWASCARRIEDTWICEASFARASONTHEEARTHANDFELLOVER“OHDEAR,”ICRIED,“WALKINGDOESNEEDABITOFPRACTICENOWTHATGRAVITYHASCHANGED”AFTERAWHILEIGOTTHEHANGOFITANDWEBEGANTOENJOYOURSELVESLEAVINGTHEMOONSGRAVITYWASNOTASPAINFULASLEAVINGTHEEARTHSBUTRETURNINGTOTHEEARTHWASVERYFRIGHTENINGWEWATCHED,AMAZEDASFIREBROKEOUTONTHEOUTSIDEOFTHESPACESHIPASTHEEARTHSGRAVITYINCREASEDAGAINWEWEREPUSHEDBACKHARDINTOOURSEATSASWECAMEBACKTOLAND“THATWASVERYEXHAUSTINGBUTVERYEXCITINGTOO,”ISAID“NOWIKNOWMUCHMOREABOUTGRAVITYDOYOUTHINKWECOULDBISITSOMESTARSNEXTTIME”“OFCOURSE,”HESMILED,“WHICHSTARWOULDYOULIKETOGOTO”CAUGHTBYABLACKHOLETHESPACESHIPWARNEDLIYANPINGANDMETOBEREADYASWEWEREAPPROACHINGTHE“BLACKHOLE”WECOULDSEESOMEFAINTLIGHTSAROUNDWHATLOOKEDLIKEANEMPTYSPACELIYANPINGSAID,“THATEMPTYHOLEISLIKEAMOUTHALWAYSNEEDINGTOBEFEDTHOSELIGHTSARETHINSTHATAREBEINGPULLEDINTOTIMEBYTHEGRAVITYOFTHEHOLE”WEWATCHEDWITHINTERESTANDAMAZEMENTATTHELIGHTSWHICHSEEMEDTOBEGOINGFAINTERANDFAINTERROUNDTHEEDGEOFTHEBLACKHOLEJUSTTHENTHELIGHTSONOURSPACESHIPWENTOURTHEANDTHECOMPUTERSTOPPEDWORKINGWHATWASHAPPENINGITRIEDTOTURNTHESPACESHIPAWAYFROMTHEHOLEBUTITWOULDNOTMOVEWOULDITEATUSTOOSUDDENLYTHESPACESHIPJUMPEDANDBEGANTOMOVEROUNDTHEEDGEOFTRHEHOLETOOTHEGRAVITYOFTHE“BLACKHOLE”WASPULLINGUSINTOITS“MOUTH”ASTHESPACESHIPMOVEDROUNDTHEBLACKHOLE,IFELTRATHERSICKMYMOUTHWENTDRYANDICLOSEDMYEYESALLTHESTORIESABOUTWHATHAPPENEDWHENYOUWERECAUGHTBYTHEGRAVITYOFA“BLACKHOLE”SEEMTOBETRUEBUTTHENTHESPACESHIPJUMPEDAGAINTHISTIMEITMOVEDSIDEWAYSANDAWAYFROMTHISEDGEOFTHE“BLACKHOLE”SOMEONEWATCHINGMEWOULDHAVESEENTHESPACESHIPFLYINGLIKEABIRDAWAYFROMTHE“BLACKHOLE”BUTWEFELTNOTHINGATLASTWEWEREABLETOLOOKAROUNDUSLUCKILYTHECOMPUTERHADSTARTEDWORKINGAGAINWEREALIZEDTHATWEHADDISCOVEREDSOMETHINGNEWABOUT“BLACKHOLE”IFYOUGOINSIDETHEEDGEOFA“BLACKHOLE”,ITWILL“EAT”YOUANDTHEREISNOESCAPEBUTIFYOUDONOT,YOUMAYHAVEANOPPORTUNITYTOESCAPEHOWEXCITINGUNIT5ATRIPON“THETRUENORTH”LIDAIYUANDHERCOUSINLIUQIANWEREONATRIPTOCANADATOBISITTHEIRCOUSINSINMONTREALONTHEATLANTICCOASTRATHERTHANTAKETHEAEROPLANEALLTHEWAY,THEYDECIDEDTOFLYTOVANCOUVERANDTHENTAKETHETRAINWESTTOEASTACROSSCANADATHETHOUGHTHATTHEYCOULDCROSSTHEWHOLECONTINENTWASEXCITINGTHEIRFRIEND,DANNYLIN,WASWAITINGATTHEAIRPORTHEWASGOINGTOTAKETHEMANDTHEIRBAGGAGETOCATCH“THETRUENORTH”,THECROSSCANADATRAINONTHEWAYTOTHESTATIION,HECHATTEDABOUTTHEIRTRIP“YOUREGOINGTOSEESOMEGREATSCENERYGOINGEASTWARD,YOULLPASSMOUNTAINSANDTHOUSANDSOFLAKESANDFORESTS,ASWELLASWIDERIVERSANDLARGECITIESSOMEPEOPLEHAVETHEIDEATHATYOUCANCROSSCANDAINLESSTHANFICEDAYS,BUTTHEYFORGETTHEFACTTHATCANADAIS5500KILOMETERSFROMCOASTTOCOASTHEREINVANCOUVER,YOUREINCANADASWARMESTPARTPEOPLESAYITISCANADASMOSTBEAUTIFULCITY,SURROUNDEDBYMOUNTAINSANDTHEPACIFICOCEANSKIINGINTHEROCKYMOUNTAINSANDSAILINGINTHEHARBOURMAKEVANCOUVERONEOFCANADASMOSTPOPULARCITIESTOLIVEINITSPOPULATIONISINCREASINGRAPIDLYTHECOASTNORTHOFVANCOUVERHASSOMEOFTHEOLDESTANDMOSTBEAUTIFULFORESTSINTHEWORLDITISSOWETTHERETHATTHETREESAREEXTREMELYTALL,SOMEMEASURINGOVER90METRES”THATAFTERNOONABOARDTHETRAIN,THECOUSINSSETTLEDDOWNINTHEIRSEATSEARLIERTHATDAY,WHENTHEYCROSSEDTHEROCKYMOUNTAINS,THEYMANAGEDTOCATCHSIGHTOFSOMEMOUNTAINGOATSANDEVENAGRIZZLYBEARANDANEAGLETHEIRNEXTSTOPWASCALGARY,WHICHISFAMOUSFORTHECALGARYSTAMPEDECOWBOYSFROMALLOVERTHEWORLDCOMETOCOMPETEINTHESTAMPEDEMANYOFTHEMHAVEAGIFTFORRIDINGWILDHORSESANDCANWINTHOUSANDSOFDOLLARSINPRIZESAFTERTWODAYSTRAVEL,THEGIRLSBEGANTOREALIZETHATCANADAISQUITEEMPTYATSCHOOL,THEYHADLEARNEDTHATMOSTCANADIANSLIVEWITHINAFEWHUNDREDKILOMETRESOFTHEUSABORDER,ANDCANADASPOPULATIONISONLYSLIGHTLYOVERTHIRTYMILLION,BUTNOWTHEYWEREAMAZEDTOSEESUCHANEMPTYCOUNTRYTHEYWENTTHROUGHAWHEATGROWINGPROVINCEANDSAWFARMSTHATCOVEREDTHOUSANDSOFACRESAFRERDINNER,THEYWEREBACKINANURBANAREA,THEBUSYPORTCITYOFTHUNDERBAYATTHETOPOFTHEGREATLAKESBECAUSEOFTHEGREATLAKES,THEYLEARNED,CANADAHASMOREFRESHWATERTHANANYOTHERCOUNTRYINTHEWORLDINFACT,ITHASONETHIRDOFTHEWORLDSTOTALFRESHWATER,ANDMUCHOFITISINTHEGREATLAKESTHATNIGHTASTHEYSLEPT,THETRAINRUSHEDACROSSTHETOPOFLAKESUPERIOR,THROUGHTHEGREATFORESTSANDSOUTHWARDTOWADSTORONTO“THETRUENORTH”FROMTORONTOTOMONTREALTHENEXTMORNINGTHEBUSHESANDMAPLETREESOUTSIDETHEIRWINDOWWERERED,GOLDANDORANGE,ANDTHEREWASFROSTONTHEGROUND,CONFIRMINGTHATFALLHADARRIVEDINCANADAAROUNDNOONTHEYARRIVEDINTORONTO,THEBIGGESTANDMOSTWEALTHYCITYINCANADATHEYWERENOTLEAVINGFORMONTREALUNTILLATER,SOTHEYWENTONATOUROFTHECITYTHEYWENTUPTHETALLCNTOWERANDLOOKEDACROSSTHELAKEINTHEDISTANCE,THEYCOULDSEETHEMISTYCLOUDTHATROSEFROMTHEGREATNIAGARAFALLS,WHICHISONTHESOUTHSIDEOFTHELAKETHEWATERFLOWSINTOTHENIAGARARIVERANDOVERTHEFALLSONITSWAYTOTHESEATHEYSAWTHECOVEREDSTADIUM,HOMEOFSEVERALFAMOUSBASKETBALLTEAMSASTHEYWALKEDNORTHFROMTHEHARBOURAREA,LIDAIYUSAID,“LINFANG,ONEOFMYMOTHERSOLDSCHOOLMATES,LIVESHEREISHOULDPHONEHERFROMATELEPHONEBOOTH”THEYMETLINFEIAROUNDDUSKINDOWNTOWNCHINATOWN,ONEOFTHETHREEINTORONTOOVERDINNERATARESTAURANTCALLEDTHEPINKPEARL,THECOUSINSCHATTEDWITHLINFEI,WHOHADMOVEDTOCANADAMANYYEARSEARLIER“WECANGETGOODCANTONESEFOODHERE,”LINFEITOLDTHEM,“BECAUSEMOSTOFTHECHINESEPEOPLEHERECOMEFROMSOUTHCHINA,ESPECIALLYHONGKONGITSTOOBADYOUCANTGOASFARASOTTAWA,CANADASCAPITALITSAPPROXIMATELYFOURHUNDREDKILOMETERSNORTHEASTOFTORONTO,SOITWOULDTAKETOOLONG”THETRAINLEFTLATETHATNIGHTANDARRIVEDINMONTREAL1第一部分我們的使命第一章健康、疾病與藥品在日常生活中，當身體出現(xiàn)發(fā)燒、頭痛等癥狀時，說明我們生病了，身體不再健康。受到了疾病的困擾，必須采取辦法治療疾病。俗語說得好“生病吃藥，藥到病除”，所以，治療疾病的辦法就是對癥下藥。辭海對健康的定義人體各器官系統(tǒng)發(fā)育良好、功能正常、體質(zhì)健壯、精力充沛，并具有健全的身心和社會適應(yīng)能力的狀態(tài)。通常用人體測量、體格檢查和各種生理和心理指標來衡量。辭海對疾病的定義指人體在一定條件下，由致病因素所引起的一種復(fù)雜而有一定表現(xiàn)形式的病理過程。此時，在不同程度上，人體正常生理過程遭到破壞，表現(xiàn)為對外環(huán)境變化的適應(yīng)能力降低、勞動力受到限制或喪失，并出現(xiàn)一系列臨床癥狀。疾病是致病因素對人體的損害和人體對抗這些損害的防御、代償?shù)茸饔玫拿堋＿@一矛盾的雙方，在整個疾病過程中不斷進行斗爭，直到疾病痊愈或人體死亡時才告終結(jié)。由此可見，藥品在維護我們的身體健康中起著不可替代的作用。我們身體一旦受到疾病的侵擾，都必須使用藥品予以調(diào)節(jié)或治療，才能恢復(fù)健康。大家想想，如果沒有藥品，當受到病患的侵擾時，我們將無力與疾病抗爭，任由病魔肆虐，疾病將奪去我們的健康甚至生命。因此，健康離不開藥品，我們的生活離不開藥品。ACHANCETOMAKEATRIPINTOSPACEWITHMYFRIENDLIYANPING,ANASTRONOMERWEVISITEDTHEMOONINOURSPACESHIPBEFOREWELEAVE,LIYANPINGEXPLAINEDTOMETHATTHEFORECEOFTHEGRAVITYWOULDCHANGETHREETIMESONOURJOURNEYANDTHATTHEFIRSTCHANGEWOULDBETHEMOSTPOWERFULTHENWEWEREOFFASTHEROCKETROSEINTOTHEAIR,WEWEREPUSHEDBACKINTOOURSEATSBECAUSEWEWERETRYINGTOESCAPETHEPULLOFTHEEARTHSGRAVITYITWASSOHARDTHATWECOULDNOTSAYANYTHINGTOEACHOTHERGRADUALLYTHEWEIGHTLESSENEDANDIWASABLETOTALKTOHIM“WHYISTHESPACESHIPNOTFALLINGBACKTOTHEEARTHONTHEEARTHIFIFALLFROMATREEIWILLFALLTOGROUND”IASKED“WEARETOOFARFROMTHEEARTHNOWTOFEELITSPULL,“HEEXPLAINED,“SOWEFEELASIFTHEREISNOGRAVITYATALLWHENWEGETCLOSERTOTHEMOON,WESHALLFEELITSGRAVITYPULLINGUS,BUTITWILLNOTBEASSTRONGAPULLASTHEEARTHS“ICHEEREDUPIMMEDIATELYANDFLOATEDWEIGHTLESSLYAROUNDINOURSPACESHIPCABINWATCHINGTHEEARTHBECOMESMALLERANDTHEMOONLARGERWHENWEGOTTHERE,IWANTEDTOEXPLOREIMMEDIATELY“COMEON,”ISAID“IFYOUARERIGHT,MYMASSWILLBELESSTHANONTHEEARTHBECAUSETHEMOONISSMALLERANDIWILLBEABLETOMOVEMOREFREELYIMIGHTEVENGROWTALLERIFISTAYHERELONGENOUGHISHALLCERTAINLYWEIGHLESS”ILAUGHEDANDCLIMBEDDOWNTHESTEPSFROMTHESPACESHIPBUTWHENITRIEDTOSTEPFORWARD,IFOUNDIWASCARRIEDTWICEASFARASONTHEEARTHANDFELLOVER“OHDEAR,”ICRIED,“WALKINGDOESNEEDABITOFPRACTICENOWTHATGRAVITYHASCHANGED”AFTERAWHILEIGOTTHEHANGOFITANDWEBEGANTOENJOYOURSELVESLEAVINGTHEMOONSGRAVITYWASNOTASPAINFULASLEAVINGTHEEARTHSBUTRETURNINGTOTHEEARTHWASVERYFRIGHTENINGWEWATCHED,AMAZEDASFIREBROKEOUTONTHEOUTSIDEOFTHESPACESHIPASTHEEARTHSGRAVITYINCREASEDAGAINWEWEREPUSHEDBACKHARDINTOOURSEATSASWECAMEBACKTOLAND“THATWASVERYEXHAUSTINGBUTVERYEXCITINGTOO,”ISAID“NOWIKNOWMUCHMOREABOUTGRAVITYDOYOUTHINKWECOULDBISITSOMESTARSNEXTTIME”“OFCOURSE,”HESMILED,“WHICHSTARWOULDYOULIKETOGOTO”CAUGHTBYABLACKHOLETHESPACESHIPWARNEDLIYANPINGANDMETOBEREADYASWEWEREAPPROACHINGTHE“BLACKHOLE”WECOULDSEESOMEFAINTLIGHTSAROUNDWHATLOOKEDLIKEANEMPTYSPACELIYANPINGSAID,“THATEMPTYHOLEISLIKEAMOUTHALWAYSNEEDINGTOBEFEDTHOSELIGHTSARETHINSTHATAREBEINGPULLEDINTOTIMEBYTHEGRAVITYOFTHEHOLE”WEWATCHEDWITHINTERESTANDAMAZEMENTATTHELIGHTSWHICHSEEMEDTOBEGOINGFAINTERANDFAINTERROUNDTHEEDGEOFTHEBLACKHOLEJUSTTHENTHELIGHTSONOURSPACESHIPWENTOURTHEANDTHECOMPUTERSTOPPEDWORKINGWHATWASHAPPENINGITRIEDTOTURNTHESPACESHIPAWAYFROMTHEHOLEBUTITWOULDNOTMOVEWOULDITEATUSTOOSUDDENLYTHESPACESHIPJUMPEDANDBEGANTOMOVEROUNDTHEEDGEOFTRHEHOLETOOTHEGRAVITYOFTHE“BLACKHOLE”WASPULLINGUSINTOITS“MOUTH”ASTHESPACESHIPMOVEDROUNDTHEBLACKHOLE,IFELTRATHERSICKMYMOUTHWENTDRYANDICLOSEDMYEYESALLTHESTORIESABOUTWHATHAPPENEDWHENYOUWERECAUGHTBYTHEGRAVITYOFA“BLACKHOLE”SEEMTOBETRUEBUTTHENTHESPACESHIPJUMPEDAGAINTHISTIMEITMOVEDSIDEWAYSANDAWAYFROMTHISEDGEOFTHE“BLACKHOLE”SOMEONEWATCHINGMEWOULDHAVESEENTHESPACESHIPFLYINGLIKEABIRDAWAYFROMTHE“BLACKHOLE”BUTWEFELTNOTHINGATLASTWEWEREABLETOLOOKAROUNDUSLUCKILYTHECOMPUTERHADSTARTEDWORKINGAGAINWEREALIZEDTHATWEHADDISCOVEREDSOMETHINGNEWABOUT“BLACKHOLE”IFYOUGOINSIDETHEEDGEOFA“BLACKHOLE”,ITWILL“EAT”YOUANDTHEREISNOESCAPEBUTIFYOUDONOT,YOUMAYHAVEANOPPORTUNITYTOESCAPEHOWEXCITINGUNIT5ATRIPON“THETRUENORTH”LIDAIYUANDHERCOUSINLIUQIANWEREONATRIPTOCANADATOBISITTHEIRCOUSINSINMONTREALONTHEATLANTICCOASTRATHERTHANTAKETHEAEROPLANEALLTHEWAY,THEYDECIDEDTOFLYTOVANCOUVERANDTHENTAKETHETRAINWESTTOEASTACROSSCANADATHETHOUGHTHATTHEYCOULDCROSSTHEWHOLECONTINENTWASEXCITINGTHEIRFRIEND,DANNYLIN,WASWAITINGATTHEAIRPORTHEWASGOINGTOTAKETHEMANDTHEIRBAGGAGETOCATCH“THETRUENORTH”,THECROSSCANADATRAINONTHEWAYTOTHESTATIION,HECHATTEDABOUTTHEIRTRIP“YOUREGOINGTOSEESOMEGREATSCENERYGOINGEASTWARD,YOULLPASSMOUNTAINSANDTHOUSANDSOFLAKESANDFORESTS,ASWELLASWIDERIVERSANDLARGECITIESSOMEPEOPLEHAVETHEIDEATHATYOUCANCROSSCANDAINLESSTHANFICEDAYS,BUTTHEYFORGETTHEFACTTHATCANADAIS5500KILOMETERSFROMCOASTTOCOASTHEREINVANCOUVER,YOUREINCANADASWARMESTPARTPEOPLESAYITISCANADASMOSTBEAUTIFULCITY,SURROUNDEDBYMOUNTAINSANDTHEPACIFICOCEANSKIINGINTHEROCKYMOUNTAINSANDSAILINGINTHEHARBOURMAKEVANCOUVERONEOFCANADASMOSTPOPULARCITIESTOLIVEINITSPOPULATIONISINCREASINGRAPIDLYTHECOASTNORTHOFVANCOUVERHASSOMEOFTHEOLDESTANDMOSTBEAUTIFULFORESTSINTHEWORLDITISSOWETTHERETHATTHETREESAREEXTREMELYTALL,SOMEMEASURINGOVER90METRES”THATAFTERNOONABOARDTHETRAIN,THECOUSINSSETTLEDDOWNINTHEIRSEATSEARLIERTHATDAY,WHENTHEYCROSSEDTHEROCKYMOUNTAINS,THEYMANAGEDTOCATCHSIGHTOFSOMEMOUNTAINGOATSANDEVENAGRIZZLYBEARANDANEAGLETHEIRNEXTSTOPWASCALGARY,WHICHISFAMOUSFORTHECALGARYSTAMPEDECOWBOYSFROMALLOVERTHEWORLDCOMETOCOMPETEINTHESTAMPEDEMANYOFTHEMHAVEAGIFTFORRIDINGWILDHORSESANDCANWINTHOUSANDSOFDOLLARSINPRIZESAFTERTWODAYSTRAVEL,THEGIRLSBEGANTOREALIZETHATCANADAISQUITEEMPTYATSCHOOL,THEYHADLEARNEDTHATMOSTCANADIANSLIVEWITHINAFEWHUNDREDKILOMETRESOFTHEUSABORDER,ANDCANADASPOPULATIONISONLYSLIGHTLYOVERTHIRTYMILLION,BUTNOWTHEYWEREAMAZEDTOSEESUCHANEMPTYCOUNTRYTHEYWENTTHROUGHAWHEATGROWINGPROVINCEANDSAWFARMSTHATCOVEREDTHOUSANDSOFACRESAFRERDINNER,THEYWEREBACKINANURBANAREA,THEBUSYPORTCITYOFTHUNDERBAYATTHETOPOFTHEGREATLAKESBECAUSEOFTHEGREATLAKES,THEYLEARNED,CANADAHASMOREFRESHWATERTHANANYOTHERCOUNTRYINTHEWORLDINFACT,ITHASONETHIRDOFTHEWORLDSTOTALFRESHWATER,ANDMUCHOFITISINTHEGREATLAKESTHA