°Ëϲµç×ÓÊé > ¿Æ»ÃÊÀ½çµç×ÓÊé > pale blue dot -carl sagan >

µÚ12²¿·Ö

pale blue dot -carl sagan-µÚ12²¿·Ö

С˵£º pale blue dot -carl sagan ×ÖÊý£º ÿҳ4000×Ö

°´¼üÅÌÉÏ·½Ïò¼ü ¡û »ò ¡ú ¿É¿ìËÙÉÏÏ·­Ò³£¬°´¼üÅÌÉ쵀 Enter ¼ü¿É»Øµ½±¾ÊéĿ¼ҳ£¬°´¼üÅÌÉÏ·½Ïò¼ü ¡ü ¿É»Øµ½±¾Ò³¶¥²¿£¡
¡ª¡ª¡ª¡ªÎ´ÔĶÁÍꣿ¼ÓÈëÊéÇ©ÒѱãÏ´μÌÐøÔĶÁ£¡



¡¡you¡¡make¡¡out¡¡a¡¡star¡¡or¡¡a¡¡patch¡¡of¡¡blue¡ªreminders¡¡of¡¡what¡¡was¡¡there¡¡long¡¡before¡¡humans¡¡came¡¡to¡¡be¡£¡¡But¡¡the¡¡bright¡¡lights¡¡of¡¡the¡¡big¡¡cities¡¡bleach¡¡out¡¡the¡¡stars£»¡¡and¡¡even¡¡that¡¡patch¡¡of¡¡blue¡¡is¡¡sometimes¡¡gone£»¡¡tinted¡¡brown¡¡by¡¡industrial¡¡technology¡£

It's¡¡not¡¡hard£»¡¡going¡¡to¡¡work¡¡every¡¡day¡¡in¡¡such¡¡a¡¡place£»¡¡to¡¡be¡¡impressed¡¡with¡¡ourselves¡£¡¡How¡¡we've¡¡transformed¡¡the¡¡Earth¡¡for¡¡our¡¡benefit¡¡and¡¡convenience£¡¡¡But¡¡a¡¡few¡¡hundred¡¡miles¡¡up¡¡or¡¡down¡¡there¡¡are¡¡no¡¡humans¡£¡¡Apart¡¡from¡¡a¡¡thin¡¡film¡¡of¡¡life¡¡at¡¡the¡¡very¡¡surface¡¡of¡¡the¡¡Earth£»¡¡an¡¡occasional¡¡intrepid¡¡spacecraft£»¡¡and¡¡some¡¡radio¡¡static£»¡¡our¡¡impact¡¡on¡¡the¡¡Universe¡¡is¡¡nil¡£¡¡It¡¡knows¡¡nothing¡¡of¡¡us¡£



YOU'RE¡¡AN¡¡ALIEN¡¡EXPLORER¡¡entering¡¡the¡¡Solar¡¡System¡¡after¡¡a¡¡long¡¡journey¡¡through¡¡the¡¡blackness¡¡of¡¡interstellar¡¡space¡£¡¡You¡¡examine¡¡the¡¡planets¡¡of¡¡this¡¡humdrum¡¡star¡¡from¡¡afar¡ªa¡¡pretty¡¡handful£»¡¡some¡¡gray£»¡¡some¡¡blue£»¡¡some¡¡red£»¡¡some¡¡yellow¡£¡¡You're¡¡interested¡¡in¡¡what¡¡kinds¡¡of¡¡worlds¡¡these¡¡are£»¡¡whether¡¡their¡¡environments¡¡are¡¡static¡¡or¡¡changing£»¡¡and¡¡especially¡¡whether¡¡there¡¡are¡¡life¡¡and¡¡intelligence¡£¡¡You¡¡have¡¡no¡¡prior¡¡knowledge¡¡of¡¡the¡¡Earth¡£¡¡You've¡¡just¡¡discovered¡¡its¡¡existence¡£

There's¡¡a¡¡galactic¡¡ethic£»¡¡let's¡¡imagine£º¡¡Look¡¡but¡¡don't¡¡touch¡£¡¡You¡¡can¡¡fly¡¡by¡¡these¡¡worlds£»¡¡you¡¡can¡¡orbit¡¡them£»¡¡but¡¡you¡¡are¡¡strictly¡¡forbidden¡¡to¡¡land¡£¡¡Under¡¡such¡¡constraints£»¡¡could¡¡you¡¡figure¡¡out¡¡what¡¡the¡¡Earth's¡¡environment¡¡is¡¡like¡¡and¡¡whether¡¡anyone¡¡lives¡¡there£¿

As¡¡you¡¡approach£»¡¡your¡¡first¡¡impression¡¡of¡¡the¡¡whole¡¡Earth¡¡is¡¡white¡¡clouds£»¡¡white¡¡polar¡¡caps£»¡¡brown¡¡continents£»¡¡and¡¡some¡¡bluish¡¡substance¡¡that¡¡covers¡¡two¡¡thirds¡¡of¡¡the¡¡surface¡£¡¡When¡¡you¡¡take¡¡the¡¡temperature¡¡of¡¡this¡¡world¡¡from¡¡the¡¡infrared¡¡radiation¡¡it¡¡emits£»¡¡you¡¡find¡¡that¡¡most¡¡latitudes¡¡are¡¡above¡¡the¡¡freezing¡¡point¡¡of¡¡water£»¡¡while¡¡the¡¡polar¡¡caps¡¡are¡¡below¡¡freezing¡£¡¡Water¡¡is¡¡a¡¡very¡¡abundant¡¡material¡¡in¡¡the¡¡Universe£»¡¡polar¡¡caps¡¡made¡¡of¡¡solid¡¡water¡¡would¡¡be¡¡a¡¡reasonable¡¡guess£»¡¡as¡¡well¡¡as¡¡clouds¡¡of¡¡solid¡¡and¡¡liquid¡¡water¡£

You¡¡might¡¡also¡¡he¡¡tempted¡¡by¡¡the¡¡idea¡¡that¡¡the¡¡blue¡¡stuff¡¡is¡¡enormous¡¡quantities¡ªkilometers¡¡deep¡ªof¡¡liquid¡¡water¡£¡¡The¡¡suggestion¡¡is¡¡bizarre£»¡¡though£»¡¡at¡¡least¡¡as¡¡far¡¡as¡¡this¡¡solar¡¡system¡¡is¡¡concerned£»¡¡because¡¡surface¡¡oceans¡¡of¡¡liquid¡¡water¡¡exist¡¡nowhere¡¡else¡£¡¡When¡¡you¡¡look¡¡in¡¡the¡¡visible¡¡and¡¡near¡­infrared¡¡spectrum¡¡for¡¡telltale¡¡signatures¡¡of¡¡chemical¡¡position£»¡¡sure¡¡enough¡¡you¡¡discover¡¡water¡¡ice¡¡in¡¡the¡¡polar¡¡caps£»¡¡and¡¡enough¡¡water¡¡vapor¡¡in¡¡the¡¡air¡¡to¡¡account¡¡for¡¡the¡¡clouds£»¡¡this¡¡is¡¡also¡¡just¡¡the¡¡right¡¡amount¡¡that¡¡must¡¡exist¡¡because¡¡of¡¡evaporation¡¡if¡¡the¡¡oceans¡¡are¡¡in¡¡fact¡¡made¡¡of¡¡liquid¡¡water¡£¡¡The¡¡bizarre¡¡hypothesis¡¡is¡¡confirmed¡£

The¡¡spectrometers¡¡further¡¡reveal¡¡that¡¡the¡¡air¡¡on¡¡this¡¡world¡¡is¡¡one¡¡fifth¡¡oxygen£»¡¡O2¡£¡¡No¡¡other¡¡planet¡¡in¡¡the¡¡Solar¡¡System¡¡has¡¡anything¡¡close¡¡to¡¡so¡¡much¡¡oxygen¡£¡¡Where¡¡does¡¡it¡¡all¡¡e¡¡from£¿¡¡The¡¡intense¡¡ultraviolet¡¡light¡¡from¡¡the¡¡Sun¡¡breaks¡¡water£»¡¡H2O£»¡¡down¡¡into¡¡oxygen¡¡and¡¡hydrogen£»¡¡and¡¡hydrogen£»¡¡the¡¡lightest¡¡gas£»¡¡quickly¡¡escapes¡¡to¡¡space¡£¡¡This¡¡is¡¡a¡¡source¡¡of¡¡O2£»¡¡certainly£»¡¡but¡¡it¡¡doesn't¡¡easily¡¡account¡¡for¡¡so¡¡much¡¡oxygen¡£

Another¡¡possibility¡¡is¡¡that¡¡ordinary¡¡visible¡¡light£»¡¡which¡¡the¡¡Sun¡¡pours¡¡out¡¡in¡¡vast¡¡amounts£»¡¡is¡¡used¡¡on¡¡Earth¡¡to¡¡break¡¡water¡¡apart¡ªexcept¡¡that¡¡there's¡¡no¡¡known¡¡way¡¡to¡¡do¡¡this¡¡without¡¡life¡£¡¡There¡¡would¡¡have¡¡to¡¡be¡¡plants£»¡¡life¡­forms¡¡colored¡¡by¡¡a¡¡pigment¡¡that¡¡strongly¡¡absorbs¡¡visible¡¡light£»¡¡that¡¡knows¡¡how¡¡to¡¡split¡¡a¡¡water¡¡molecule¡¡by¡¡saving¡¡up¡¡the¡¡energy¡¡of¡¡two¡¡photons¡¡of¡¡light£»¡¡that¡¡retains¡¡the¡¡H¡¡and¡¡excretes¡¡the¡¡O£»¡¡and¡¡that¡¡uses¡¡the¡¡hydrogen¡¡thus¡¡liberated¡¡to¡¡synthesize¡¡organic¡¡molecules¡£¡¡The¡¡plants¡¡would¡¡have¡¡to¡¡be¡¡spread¡¡over¡¡much¡¡of¡¡the¡¡planet¡£¡¡All¡¡this¡¡is¡¡asking¡¡a¡¡lot¡£¡¡If¡¡you're¡¡a¡¡good¡¡skeptical¡¡scientist£»¡¡so¡¡much¡¡O2¡¡would¡¡not¡¡be¡¡proof¡¡of¡¡life¡£¡¡But¡¡it¡¡certainly¡¡might¡¡be¡¡cause¡¡for¡¡suspicion¡£

With¡¡all¡¡that¡¡oxygen¡¡you're¡¡not¡¡surprised¡¡to¡¡discover¡¡ozone¡¡£¨O3£©¡¡in¡¡the¡¡atmosphere£»¡¡because¡¡ultraviolet¡¡light¡¡makes¡¡ozone¡¡out¡¡of¡¡molecular¡¡oxygen¡¡£¨O2£©¡£¡¡The¡¡ozone¡¡then¡¡absorbs¡¡dangerous¡¡ultraviolet¡¡radiation¡£¡¡So¡¡if¡¡the¡¡oxygen¡¡is¡¡due¡¡to¡¡life£»¡¡there's¡¡a¡¡curious¡¡sense¡¡in¡¡which¡¡the¡¡life¡¡is¡¡protecting¡¡itself¡£¡¡But¡¡this¡¡life¡¡¡¨night¡¡be¡¡mere¡¡photosynthetic¡¡plants¡£¡¡A¡¡high¡¡level¡¡of¡¡intelligence¡¡is¡¡not¡¡implied¡£

When¡¡you¡¡examine¡¡the¡¡continents¡¡more¡¡closely£»¡¡you¡¡find¡¡there¡¡are£»¡¡crudely¡¡speaking£»¡¡two¡¡kinds¡¡of¡¡regions¡£¡¡One¡¡shows¡¡the¡¡spectrum¡¡of¡¡ordinary¡¡rocks¡¡and¡¡minerals¡¡as¡¡found¡¡on¡¡many¡¡worlds¡£¡¡The¡¡other¡¡reveals¡¡something¡¡unusual£º¡¡a¡¡material£»¡¡covering¡¡vast¡¡areas£»¡¡that¡¡strongly¡¡absorbs¡¡red¡¡light¡£¡¡£¨The¡¡Sun£»¡¡of¡¡course£»¡¡shines¡¡in¡¡light¡¡of¡¡all¡¡colors£»¡¡with¡¡a¡¡peak¡¡in¡¡the¡¡yellow¡££©¡¡This¡¡pigment¡¡might¡¡be¡¡just¡¡the¡¡agent¡¡needed¡¡if¡¡ordinary¡¡visible¡¡light¡¡is¡¡being¡¡used¡¡to¡¡break¡¡water¡¡apart¡¡and¡¡account¡¡for¡¡the¡¡oxygen¡¡in¡¡the¡¡air¡£¡¡It's¡¡another¡¡hint£»¡¡this¡¡time¡¡a¡¡little¡¡stronger£»¡¡of¡¡life£»¡¡not¡¡a¡¡bug¡¡here¡¡and¡¡there£»¡¡but¡¡a¡¡planetary¡¡surface¡¡overflowing¡¡with¡¡life¡£¡¡The¡¡pigment¡¡is¡¡in¡¡fact¡¡chlorophyll£º¡¡It¡¡absorbs¡¡blue¡¡light¡¡as¡¡well¡¡as¡¡red£»¡¡and¡¡is¡¡responsible¡¡for¡¡the¡¡fact¡¡that¡¡plants¡¡are¡¡green¡£¡¡What¡¡you're¡¡seeing¡¡is¡¡a¡¡densely¡¡vegetated¡¡planet¡£

So¡¡the¡¡Earth¡¡is¡¡revealed¡¡to¡¡possess¡¡three¡¡properties¡¡unique¡¡at¡¡least¡¡in¡¡this¡¡solar¡¡system¡ªoceans£»¡¡oxygen£»¡¡life¡£¡¡It's¡¡hard¡¡not¡¡to¡¡think¡¡they're¡¡related£»¡¡the¡¡oceans¡¡being¡¡the¡¡sites¡¡of¡¡origin£»¡¡and¡¡the¡¡oxygen¡¡the¡¡product£»¡¡of¡¡abundant¡¡life¡£

When¡¡you¡¡look¡¡carefully¡¡at¡¡the¡¡infrared¡¡spectrum¡¡of¡¡the¡¡Earth£»¡¡you¡¡discover¡¡the¡¡minor¡¡constituents¡¡of¡¡the¡¡air¡£¡¡In¡¡addition¡¡to¡¡water¡¡vapor£»¡¡there's¡¡carbon¡¡dioxide¡¡£¨CO2£©£»¡¡methane¡¡£¨CH4£©£»¡¡and¡¡other¡¡gases¡¡that¡¡absorb¡¡the¡¡heat¡¡that¡¡the¡¡Earth¡¡tries¡¡to¡¡radiate¡¡away¡¡to¡¡space¡¡at¡¡night¡£¡¡These¡¡gases¡¡warm¡¡the¡¡planet¡£¡¡Without¡¡them£»¡¡the¡¡Earth¡¡would¡¡everywhere¡¡be¡¡below¡¡the¡¡freezing¡¡point¡¡of¡¡water¡£¡¡You've¡¡discovered¡¡this¡¡world's¡¡greenhouse¡¡effect¡£

Methane¡¡and¡¡oxygen¡¡together¡¡in¡¡the¡¡same¡¡atmosphere¡¡is¡¡peculiar¡£¡¡The¡¡laws¡¡of¡¡chemistry¡¡are¡¡very¡¡clear£º¡¡In¡¡an¡¡excess¡¡of¡¡O2£»¡¡CH4¡¡should¡¡be¡¡entirely¡¡converted¡¡into¡¡H2O¡¡and¡¡CO2£»¡¡The¡¡process¡¡is¡¡so¡¡efficient¡¡that¡¡not¡¡a¡¡single¡¡molecule¡¡in¡¡all¡¡the¡¡Earth's¡¡atmosphere¡¡should¡¡be¡¡methane¡£¡¡Instead£»¡¡you¡¡find¡¡that¡¡one¡¡out¡¡of¡¡every¡¡million¡¡molecules¡¡is¡¡methane£»¡¡ail¡¡immense¡¡discrepancy¡£¡¡What¡¡could¡¡it¡¡mean£¿

The¡¡only¡¡possible¡¡explanation¡¡is¡¡that¡¡methane¡¡is¡¡being¡¡injected¡¡into¡¡the¡¡Earth's¡¡atmosphere¡¡so¡¡quickly¡¡that¡¡its¡¡chemical¡¡reaction¡¡with¡¡Oz¡¡can't¡¡keep¡¡pace¡£¡¡Where¡¡does¡¡all¡¡this¡¡methane¡¡e¡¡from£¿¡¡Maybe¡¡it¡¡seeps¡¡out¡¡of¡¡the¡¡deep¡¡interior¡¡of¡¡the¡¡Earth¡ªbut¡¡quantitatively¡¡this¡¡doesn't¡¡seem¡¡to¡¡work£»¡¡and¡¡Mars¡¡and¡¡Venus¡¡don't¡¡have¡¡anything¡¡like¡¡this¡¡much¡¡methane¡£¡¡The¡¡only¡¡alternatives¡¡are¡¡biological£»¡¡a¡¡conclusion¡¡that¡¡makes¡¡no¡¡assumptions¡¡about¡¡the¡¡chemistry¡¡of¡¡life£»¡¡or¡¡what¡¡it¡¡looks¡¡like£»¡¡but¡¡follows¡¡merely¡¡from¡¡how¡¡unstable¡¡methane¡¡is¡¡in¡¡an¡¡oxygen¡¡atmosphere¡£¡¡In¡¡fact£»¡¡the¡¡methane¡¡arises¡¡from¡¡such¡¡sources¡¡as¡¡bacteria¡¡in¡¡bogs£»¡¡the¡¡cultivation¡¡of¡¡rice£»¡¡the¡¡burning¡¡of¡¡vegetation£»¡¡natural¡¡gas¡¡from¡¡oil¡¡wells£»¡¡and¡¡bovine¡¡flatulence¡£¡¡In¡¡an¡¡oxygen¡¡atmosphere£»¡¡methane¡¡is¡¡a¡¡sign¡¡of¡¡life¡£

That¡¡the¡¡intimate¡¡intestinal¡¡activities¡¡of¡¡cows¡¡should¡¡be¡¡detectable¡¡from¡¡interplanetary¡¡space¡¡is¡¡a¡¡little¡¡disconcerting£»¡¡especially¡¡when¡¡so¡¡much¡¡of¡¡what¡¡we¡¡hold¡¡dear¡¡is¡¡not¡£¡¡But¡¡an¡¡alien¡¡scientist¡¡flying¡¡by¡¡the¡¡Earth¡¡would£»¡¡at¡¡this¡¡point£»¡¡be¡¡unable¡¡to¡¡deduce¡¡bogs£»¡¡rice£»¡¡fire£»¡¡oil£»¡¡or¡¡cows¡£¡¡Just¡¡life¡£

All¡¡the¡¡signs¡¡of¡¡life¡¡that¡¡we've¡¡discussed¡¡so¡¡far¡¡are¡¡due¡¡to¡¡paratively¡¡simple¡¡forms¡¡£¨the¡¡methane¡¡in¡¡the¡¡rumens¡¡of¡¡cows¡¡is¡¡generated¡¡by¡¡bacteria¡¡that¡¡homestead¡¡there£©¡£¡¡Had¡¡your¡¡spacecraft¡¡flown¡¡by¡¡the¡¡Earth¡¡a¡¡hundred¡¡million¡¡years¡¡ago£»¡¡in¡¡the¡¡age¡¡of¡¡the¡¡dinosaurs¡¡when¡¡there¡¡were¡¡no¡¡humans¡¡and¡¡no¡¡technology£»¡¡you¡¡would¡¡still¡¡have¡¡seen¡¡oxygen¡¡and¡¡ozone£»¡¡they¡¡chlorophyll¡¡pigment£»¡¡and¡¡far¡¡too¡¡much¡¡methane¡£¡¡At¡¡present£»¡¡though£»¡¡your¡¡instruments¡¡are¡¡finding¡¡signs¡¡not¡¡just¡¡of¡¡life£»¡¡but¡¡of¡¡high¡¡technology¡ªsomething¡¡that¡¡couldn't¡¡possibly¡¡have¡¡been¡¡detected¡¡even¡¡a¡¡hundred¡¡years¡¡ago£º

You¡¡are¡¡detecting¡¡a¡¡particular¡¡kind¡¡of¡¡radio¡¡wave¡¡emanating¡¡from¡¡Earth¡£¡¡Radio¡¡waves¡¡don't¡¡necessarily¡¡signify¡¡life¡¡and¡¡intelligence¡¡Many¡¡natural¡¡processes¡¡generate¡¡them¡£¡¡You've¡¡already¡¡found¡¡radio¡¡emissions¡¡from¡¡other£»¡¡apparently¡¡uninhabited¡¡worlds¡ªgenerated¡¡by¡¡electrons¡¡trapped¡¡in¡¡the¡¡strong¡¡magnetic¡¡fields¡¡of¡¡planets£»¡¡by¡¡chaotic¡¡motions¡¡at¡¡the¡¡shock¡¡front¡¡that¡¡separates¡¡these¡¡magnetic¡¡fields¡¡from¡¡the¡¡interplanetary¡¡magnetic¡¡field£»¡¡and¡¡by¡¡lightning¡£¡¡£¨Radio¡¡¡¨whistlers¡¨¡¡usually¡¡sweep¡¡from¡¡high¡¡notes¡¡to¡¡low£»¡¡and¡¡then¡¡begin¡¡again¡££©¡¡Some¡¡of¡¡these¡¡radio¡¡emissions¡¡are¡¡continuous£»¡¡some¡¡e¡¡in¡¡repetitive¡¡bursts£»¡¡some¡¡last¡¡a¡¡few¡¡minutes¡¡and¡¡then¡¡disappear¡£

But¡¡this¡¡is¡¡different£º¡¡A¡¡portion¡¡of¡¡the¡¡radio¡¡transmission¡¡from¡¡Earth¡¡is¡¡at¡¡just¡¡the¡¡frequencies¡¡where¡¡radio¡¡waves¡¡begin¡¡to¡¡leak¡¡out¡¡of¡¡the¡¡planet's¡¡ionosphere£»¡¡the¡¡electrically¡¡charged¡¡region¡¡above¡¡the¡¡stratosphere¡¡that¡¡reflects¡¡and¡¡absorbs¡¡radio¡¡waves¡£¡¡There¡¡is¡¡a¡¡constant¡¡central¡¡frequency¡¡for¡¡each¡¡transmission£»¡¡added¡¡to¡¡which¡¡is¡¡a¡¡modulated¡¡signal¡¡£¨a¡¡plex¡¡sequence¡¡of¡¡ons¡¡and¡¡offs£©¡£¡¡No¡¡electrons¡¡in¡¡magnetic¡¡fields£»¡¡no¡¡shock¡¡waves£»¡¡no¡¡lightning¡¡discharges¡¡can¡¡generate¡¡something¡¡like¡¡this¡£¡¡Intelligent¡¡life¡¡seems¡¡to¡¡be¡¡the¡¡only¡¡possible¡¡explanation¡£¡¡Your¡¡conclusion¡¡that¡¡the¡¡radio¡¡transmission¡¡is¡¡due¡¡to¡¡technology¡¡on¡¡Earth¡¡holds¡¡no¡¡matter¡¡what¡¡the¡¡ons¡¡and¡¡offs¡¡mean£º¡¡You¡¡don't¡¡have¡¡to¡¡decode¡¡the¡¡message¡¡to¡¡be¡¡sure¡¡it¡¡is¡¡a¡¡message¡£¡¡£¨This¡¡signal¡¡is¡¡really£»¡¡let¡¡us¡¡suppose£»¡¡munications¡¡from¡¡the¡¡U¡£S¡£¡¡Navy¡¡to¡¡its¡¡distant¡¡nuclear¡­armed¡¡submarines¡££©

So£»¡¡as¡¡an¡¡alien¡¡explorer£»¡¡you¡¡would¡¡know¡¡that¡¡at¡¡least¡¡one¡¡species¡¡on¡¡Earth¡¡has¡¡achieved¡¡radio¡¡technology¡£¡¡Which¡¡one¡¡is¡¡it£¿¡¡The¡¡beings¡¡that¡¡make¡¡methane£¿¡¡Those¡¡that¡¡generate¡¡oxygen£¿¡¡The¡¡ones¡¡whose¡¡pigment¡¡colors¡¡the¡¡landscape¡¡green£¿¡¡Or¡¡somebody¡¡else£»¡¡somebody¡¡more¡¡subtle£»¡¡someone¡¡not¡¡otherwise¡¡detectable¡¡to¡¡a¡¡spacecraft¡¡plummeting¡¡by£¿¡¡To¡¡search¡¡for¡¡this¡¡technological¡¡species£»¡¡you¡¡might¡¡want¡¡to¡¡examine¡¡the¡¡Earth¡¡at¡¡finer¡¡and¡¡finer¡¡resolution¡ªseeking£»¡¡if¡¡not¡¡the¡¡beings¡¡themselves£»¡¡at¡¡least¡¡their¡¡artifacts¡£

You¡¡look¡¡first¡¡with¡¡a¡¡modest¡¡telescope£»¡¡so¡¡the¡¡finest¡¡detail¡¡you¡¡can¡¡resolve¡¡is¡¡one¡¡or¡¡two¡¡kilometers¡¡across¡£¡¡You¡¡can¡¡make¡¡out¡¡no¡¡monumental¡¡architecture£»¡¡no¡¡strange¡¡formations£»¡¡no¡¡unnatural¡¡reworking¡¡of¡¡the¡¡landscape£»¡¡no¡¡signs¡¡of¡¡life¡£¡¡You¡¡see¡¡a¡¡dense¡¡atmosphere¡¡in¡¡motion¡£¡¡The¡¡abundant¡¡water¡¡must¡¡evaporate¡¡and¡¡then¡¡rain¡¡back¡¡down¡£¡¡Ancient¡¡impact¡¡craters£»¡¡apparent¡¡on¡¡the¡¡Earth's¡¡nearby¡¡Moon£»¡¡are¡¡almost¡¡wholly¡¡absent¡£¡¡There¡¡must£»¡¡then£»¡¡be¡¡a¡¡set¡¡of¡¡processes¡¡whereby¡¡new¡¡land¡¡is¡¡created¡¡and¡¡then¡¡eroded¡¡away¡¡in¡¡much¡¡less¡¡time¡¡than¡¡the¡¡age¡¡of¡¡this¡¡world¡£¡¡Running¡¡water¡¡is¡¡implicated¡£¡¡As¡¡you¡¡look¡¡with¡¡finer¡¡and¡¡finer¡¡definition¡¡you¡¡find¡¡mountain¡¡r

·µ»ØĿ¼ ÉÏÒ»Ò³ ÏÂÒ»Ò³ »Øµ½¶¥²¿ ÔÞ£¨0£© ²È£¨0£©

Äã¿ÉÄÜϲ»¶µÄ