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gine　that　everything　is　mediocre。　There　is　something　special　about　our　time—not　just　the　temporal　chauvinism　that　those　who　reside　in　any　epoch　doubtless　feel；　but　something；　as　outlined　above；　clearly　unique　and　strictly　relevant　to　our　species'　future　chances：　This　is　the　first　time　that　（a）　our　exponentiating　technology　has　reached　the　precipice　of　self…destruction；　but　also　the　first　time　that　（b）　we　can　postpone　or　avoid　destruction　by　going　somewhere　else；　somewhere　off　the　Earth。

These　two　clusters　of　capabilities；　（a）　and　（b）；　make　our　time　extraordinary　in　directly　contradictory　ways—which　both　（a）　strengthen　and　（b）　weaken　Gott's　argument。　I　don't　know　how　to　predict　whether　the　new　destructive　technologies　will　hasten；　more　than　the　new　spaceflight　technologies　will　delay；　human　extinction。　But　since　never　before　have　we　contrived　the　means　of　annihilating　ourselves；　and　never　before　have　w　e　developed　the　technology　for　settling　other　worlds；　I　think　a　pelling　case　can　be　made　that　our　time　is　extraordinary　precisely　in　the　context　of　Gott's　argument。　If　this　is　true；　it　significantly　increases　the　margin　of　error　in　such　estimates　of　future　longevity。　The　worst　is　worse；　and　the　best　better：　Our　short…term　prospects　are　even　bleaker　and—if　we　can　survive　the　short…term—our　long…term　chances　even　brighter　than　Gott　calculates。

But　the　former　is　no　more　cause　for　despair　than　the　latter　is　for　placency。　Nothing　forces　us　to　be　passive　observers；　clucking　in　dismay　as　our　destiny　inexorably　works　itself　out。　If　we　cannot　quite　seize　fate　by　the　neck；　perhaps　we　can　misdirect　it；　or　mollify　it；　or　escape　it。

Of　course　we　must　keep　our　planet　habitable—not　on　a　leisurely　timescale　of　centuries　or　millennia；　but　urgently；　on　a　timescale　of　decades　or　even　years。　This　will　involve　changes　in　government；　in　industry；　in　ethics；　in　economics；　and　in　religion。　We've　never　done　such　a　thing　before；　certainly　not　on　a　global　scale。　It　may　be　too　difficult　for　us。　Dangerous　technologies　may　be　too　widespread。　Corruption　may　be　too　pervasive。　Too　many　leaders　may　be　focused　on　the　short　term　rather　than　the　long。　There　may　be　too　many　quarreling　ethnic　groups；　nation…states；　and　ideologies　for　the　right　kind　of　global　change　to　be　instituted。　We　may　be　too　foolish　to　perceive　even　what　the　real　dangers　are；　or　that　much　of　what　we　hear　about　them　is　determined　by　those　with　a　vested　interest　in　minimizing　fundamental　change。

However；　we　humans　also　have　a　history　of　making　long…lasting　social　change　that　nearly　everyone　thought　impossible。　Since　our　earliest　days；　we've　worked　not　just　for　our　own　advantage　but　for　our　children　and　our　grandchildren。　My　grandparents　and　parents　did　so　for　me。　We　have　often；　despite　our　diversity；　despite　endemic　hatreds；　pulled　together　to　face　a　mon　enemy。　We　seem；　these　days；　much　more　willing　to　recognize　the　dangers　before　us　than　we　were　even　a　decade　ago。　The　newly　recognized　dangers　threaten　all　of　us　equally。　No　one　can　say　how　it　will　turn　out　down　here。



THE　MOON　WAS　WHERE　the　tree　of　immortality　grew　in　ancient　Chinese　myth。　The　tree　of　longevity　if　not　of　immortality；　it　seems；　indeed　grows　on　other　worlds。　If　we　were　up　there　among　the　planets；　if　there　were　self…sufficient　human　munities　oil　many　worlds；　our　species　would　be　insulated　from　catastrophe。　The　depletion　of　the　ultraviolet…absorbing　shield　on　one　world　would；　if　anything；　be　a　warning　to　take　special　care　of　the　shield　on　another。　A　cataclysmic　impact　on　one　world　would　likely　leave　all　the　others　untouched。　The　more　of　us　beyond　the　Earth；　the　greater　the　diversity　of　worlds　we　inhabit；　the　more　varied　the　planetary　engineering；　the　greater　the　range　of　societal　standards　and　values—then　the　safer　the　human　species　will　be。

If　you　grow　up　living　underground　in　a　world　with　a　hundredth　of　an　Earth　gravity　and　black　skies　through　the　portals；　you　have　a　very　different　set　of　perceptions；　interests；　prejudices；　and　predispositions　than　someone　who　lives　on　the　surface　of　the　home　planet。　Likewise　if　you　live　on　the　surface　of　Mars　in　the　throes　of　terraforming；　or　Venus；　or　Titan。　This　strategy—breaking　up　into　many　smaller　self…propagating　groups；　each　with　somewhat　different　strengths　and　concerns；　but　all　marked　by　local　pride—has　been　widely　employed　in　the　evolution　of　life　on　Earth；　and　by　our　own　ancestors　in　particular。　It　may；　in　fact；　be　key　to　understanding　why　we　humans　are　the　way　we　are。*　This　is　the　second　of　the　missing　justifications　for　a　permanent　human　presence　in　space：　to　improve　our　chances　of　surviving；　not　just　the　catastrophes　we　can　foresee；　but　also　the　ones　we　cannot。　Gott　also　argues　that　establishing　human　munities　on　other　worlds　may　offer　us　our　best　chance　of　beating　the　odds。

*　Cf。　Shadows　of　Forgotten　Ancestors：　A　Search　for　Who　We　Are；　by　Carl　Sagan　and　Ann　Druyan　（New　York：　Random　House；　1992）。

To　take　out　this　insurance　policy　is　not　very　expensive；　not　on　the　scale　on　which　we　do　things　on　Earth。　It　would　not　even　require　doubling　the　space　budgets　of　the　present　spacefaring　nations　（which；　in　all　cases；　are　only　a　small　fraction　of　the　military　budgets　and　many　other　voluntary　expenditures　that　might　be　considered　marginal　or　even　frivolous）。　We　could　soon　be　setting　humans　down　on　near…Earth　asteroids　and　establishing　bases　on　Mars。　We　know　how　to　do　it；　even　with　present　technology；　in　less　than　a　human　lifetime。　And　the　technologies　will　quickly　improve。　We　will　get　better　at　going　into　space。

A　serious　effort　to　send　humans　to　other　worlds　is　relatively　so　inexpensive　on　a　per　annum　basis　that　it　cannot　seriously　pete　with　urgent　social　agendas　on　Earth。　If　we　take　this　path；　streams　of　images　from　other　worlds　will　be　pouring　down　on　Earth　at　the　speed　of　light。　Virtual　reality　will　make　the　adventure　accessible　to　millions　of　stay…on…Earths。　Vicarious　participation　will　be　much　more　real　than　at　any　earlier　age　of　exploration　and　discovery。　And　the　more　cultures　and　people　it　inspires　and　excites；　the　more　likely　it　will　happen。

But　by　what　right；　we　might　ask　ourselves；　do　we　inhabit；　alter；　and　conquer　other　worlds？　If　anyone　else　were　living　in　the　Solar　System；　this　would　be　an　important　question。　If；　though；　there's　no　one　else　in　this　system　but　us；　don't　we　have　a　right　to　settle　it？

Of　course；　our　exploration　and　homesteading　should　be　enlightened　by　a　respect　for　planetary　environments　and　the　scientific　knowledge　they　hold。　This　is　simple　prudence。　Of　course；　exploration　and　settlement　ought　to　be　done　equitably　and　transnationally；　by　representatives　of　the　entire　human　species。　Our　past　colonial　history　is　not　encouraging　in　these　regards；　but　this　time　we　are　not　motivated　by　gold　or　spices　or　slaves　or　a　zeal　to　convert　the　heathen　to　the　One　True　Faith；　as　were　the　European　explorers　of　the　fifteenth　and　sixteenth　centuries。　Indeed；　this　is　one　of　the　chief　reasons　we're　experiencing　such　intermittent　progress；　so　many　fits　and　starts　in　the　manned　space　programs　of　all　nations。

Despite　all　the　provincialisms　I　plained　about　early　in　this　book；　here　I　find　myself　an　unapologetic　human　chauvinist。　If　there　were　other　life　in　this　solar　system；　it　would　be　in　imminent　danger　because　the　humans　are　ing。　In　such　a　case；　I　might　even　be　persuaded　that　safeguarding　our　species　by　settling　certain　other　worlds　is　offset；　in　part　at　least；　by　the　danger　we　would　pose　to　everybody　else。　But　as　nearly　as　we　can　tell；　so　far　at　least；　there　is　no　other　life　in　this　system；　not　one　microbe。　There's　only　Earthlife。

In　that　case；　on　behalf　of　Earthlife；　I　urge　that；　with　full　knowledge　of　our　limitations；　we　vastly　increase　our　knowledge　of　the　Solar　System　and　then　begin　to　settle　other　worlds。

These　are　the　missing　practical　arguments：　safeguarding　'the　Earth　from　otherwise　inevitable　catastrophic　impacts　and　hedging　our　bets　on　the　many　other　threats；　known　and　unknown；　to　the　environment　that　sustains　us。　Without　these　arguments；　a　pelling　case　for　sending　humans　to　Mars　and　elsewhere　might　be　lacking。　But　with　them—and　the　buttressing　arguments　involving　science；　education；　perspective；　and　hope—I　think　a　strong　case　can　be　made。　If　our　long…term　survival　is　at　stake；　we　have　a　basic　responsibility　to　our　species　venture　to　other　worlds。

Sailors　on　a　becalmed　sea；　we　sense　the　stirring　of　a　breeze。




CHAPTER　22　　　TIPTOEING　THROUGH　THE　MILKY　WAY

　

　

I　swear　by　the　shelters　of　the　stars　（a　mighty　oath；　if　you　but　knew　it）　。　。　。

—THE　QUR'AN；　SURA　56　（7TH　CENTURY）

The　prospect　of　scaling　heaven；　of　ascending　to　the　sky；　of　altering　other　worlds　to　suit　our　purposes—no　matter　how　well　intentioned　we　may　be—sets　the　warning　flags　flying：　We　remember　the　human　inclination　toward　overweening　pride；　we　recall　our　fallibility　and　misjudgments　when　presented　with　powerful　new　technologies。　We　recollect　the　story　of　the　Tower　of　Babel；　a　building　〃whose　top　may　reach　unto　heaven；〃　and　God's　fear　。shout　our　species；　that　now　〃nothing　will　be　restrained　from　them　which　they　have　imagined　to　do。〃

We　e　upon　Psalm　15；　which　stakes　a　divine　claim　to　other　worlds：　〃＇T＇he　heavens　are　the　Lord's；　but　the　Earth　lath　he　given　to　the　children　of　men。〃　Or　Plato's　retelling　of　the　Greek　analogue　of　Babel—the　tale　of　Otys　and　Ephialtes。　They　were　mortals　who　〃dared　to　scale　heaven。〃　The　gods　were　faced　with　a　choice。　Should　they　kill　the　upstart　humans　〃and　annihilate　＇their＇　race　with　thunderbolts〃？　On　the　one　Band；　〃this　would　be　the　end　of　the　sacrifices　and　worship　which　mien　offered〃　the　gods　and　which　gods　craved。　〃But；　on　the　other　hand；　the　gods　could　not　suffer　＇such＇　insolence　to　be　unrestrained。''

If；　in　the　long　term；　though；　we　have　no　alternative；　if　our　choice　really　is　many　worlds　or　none；　we　are　in　need　of　other　sorts　of　myths　of　encouragement。　They　exist。　Many　religions；　from　Hinduism　to　Gnostic　Christianity　to　Mormon　doctrine；　teach　that—as　impious　as　it　may　sound—it　is　the　goal　of　humans　to　bee　gods。　Or　consider　a　story　in　the　Jewish　Talmud　left　out　of　the　Book　of　Genesis。　（It　is　in　doubtful　accord　with　the　account　of　the　apple；　the　Tree　of　Knowledge；　the　Fall；　and　the　expulsion　from　Eden。）　In　the　G