mc.prey-第22部分

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t　couldn't　be　shot　down　because　a　bullet　would　just　pass　through　the　cloud。　Furthermore；　you　could　disperse　the　cloud；　the　way　a　flock　of　birds　disperses　with　a　gunshot。　Then　the　camera　would　be　invisible　until　it　re…formed　again。　So　it　seemed　an　ideal　solution。　The　Pentagon　gave　us　three　years　of　DARPA　funding。〃
　〃And？〃
　〃We　set　out　to　make　the　camera。　It　was　of　course　immediately　obvious　that　we　had　a　problem　with　distributed　intelligence。〃
　I　was　familiar　with　the　problem。　The　nanoparticles　in　the　cloud　had　to　be　endowed　with　a　rudimentary　intelligence；　so　that　they　could　interact　with　each　other　to　form　a　flock　that　wheeled　in　the　air。　Such　coordinated　activity　might　look　pretty　intelligent；　but　it　occurred　even　when　the　individuals　making　up　the　flock　were　rather　stupid。　After　all；　birds　and　fish　could　do　it；　and　they　weren't　the　brightest　creatures　on　the　planet。
　Most　people　watching　a　flock　of　birds　or　a　school　of　fish　assumed　there　was　a　leader；　and　that　all　the　other　animals　followed　the　leader。　That　was　because　human　beings；　like　most　social　mammals；　had　group　leaders。
　But　birds　and　fish　had　no　leaders。　Their　groups　weren't　organized　that　way。　Careful　study　of　flocking　behavior…frame…by…frame　video　analysis…showed　that；　in　fact；　there　was　no　leader。　Birds　and　fish　responded　to　a　few　simple　stimuli　among　themselves；　and　the　result　was　coordinated　behavior。　But　nobody　was　controlling　it。　Nobody　was　leading　it。　Nobody　was　directing　it。
　Nor　were　individual　birds　genetically　programmed　for　flocking　behavior。　Flocking　was　not　hard…wired。　There　was　nothing　in　the　bird　brain　that　said；　〃When　thus…and…such　happens；　start　flocking。〃　On　the　contrary；　flocking　simply　emerged　within　the　group　as　a　result　of　much　simpler；　low…level　rules。　Rules　like；　〃Stay　close　to　the　birds　nearest　you；　but　don't　bump　into　them。〃　From　those　rules；　the　entire　group　flocked　in　smooth　coordination。　Because　flocking　arose　from　low…level　rules；　it　was　called　emergent　behavior。　The　technical　definition　of　emergent　behavior　was　behavior　that　occurred　in　a　group　but　was　not　programmed　into　any　member　of　the　group。　Emergent　behavior　could　occur　in　any　population；　including　a　puter　population。　Or　a　robot　population。　Or　a　nanoswarm。
　I　said　to　Ricky；　〃Your　problem　was　emergent　behavior　in　the　swarm？〃
　〃Exactly。〃
　〃It　was　unpredictable？〃
　〃To　put　it　mildly。〃
　In　recent　decades；　this　notion　of　emergent　group　behavior　had　caused　a　minor　revolution　in　puter　science。　What　that　meant　for　programmers　was　that　you　could　lay　down　rules　of　behavior　for　individual　agents；　but　not　for　the　agents　acting　together。　Individual　agents…whether　programming　modules；　or　processors；　or　as　in　this　case；　actual　micro…robots…could　be　programmed　to　cooperate　under　certain　circumstances；　and　to　pete　under　other　circumstances。　They　could　be　given　goals。　They　could　be　instructed　to　pursue　their　goals　with　single…minded　intensity；　or　to　be　available　to　help　other　agents。　But　the　result　of　these　interactions　could　not　be　programmed。　It　just　emerged；　with　often　surprising　outes。
　In　a　way　this　was　very　exciting。　For　the　first　time；　a　program　could　produce　results　that　absolutely　could　not　be　predicted　by　the　programmer。　These　programs　behaved　more　like　living　organisms　than　man…made　automatons。　That　excited　programmers…but　it　frustrated　them；　too。　Because　the　program's　emergent　behavior　was　erratic。　Sometimes　peting　agents　fought　to　a　standstill；　and　the　program　failed　to　acplish　anything。　Sometimes　agents　were　so　influenced　by　one　another　that　they　lost　track　of　their　goal；　and　did　something　else　instead。　In　that　sense　the　program　was　very　childlike…unpredictable　and　easily　distracted。　As　one　programmer　put　it；　〃Trying　to　program　distributed　intelligence　is　like　telling　a　five…year…old　kid　to　go　to　his　room　and　change　his　clothes。　He　may　do　that；　but　he　is　equally　likely　to　do　something　else　and　never　return。〃
　Because　these　programs　behaved　in　a　lifelike　way；　programmers　began　to　draw　analogies　to　the　behavior　of　real　organisms　in　the　real　world。　In　fact；　they　began　to　model　the　behavior　of　actual　organisms　as　a　way　to　get　some　control　over　program　outes。　So　you　had　programmers　studying　ant　swarming；　or　termite　mounding；　or　bee　dancing；　in　order　to　write　programs　to　control　airplane　landing　schedules；　or　package　routing；　or　language　translation。　These　programs　often　worked　beautifully；　but　they　could　still　go　awry；　particularly　if　circumstances　changed　drastically。　Then　they　would　lose　their　goals。　That　was　why　I　began；　five　years　ago；　to　model　predator…prey　relationships　as　a　way　to　keep　goals　fixed。　Because　hungry　predators　weren't　distracted。　Circumstances　might　force　them　to　improvise　their　methods；　and　they　might　try　many　times　before　they　succeeded…but　they　didn't　lose　track　of　their　goal。
　So　I　became　an　expert　in　predator…prey　relationships。　I　knew　about　packs　of　hyenas；　African　hunting　dogs；　stalking　lionesses；　and　attacking　columns　of　army　ants。　My　team　had　studied　the　literature　from　the　field　biologists；　and　we　had　generalized　those　findings　into　a　program　module　called　PREDPREY；　which　could　be　used　to　control　any　system　of　agents　and　make　its　behavior　purposeful。　To　make　the　program　seek　a　goal。
　Looking　at　Ricky's　screen；　the　coordinated　units　moving　smoothly　as　they　turned　through　the　air；　I　said；　〃You　used　PREDPREY　to　program　your　individual　units？〃
　〃Right。　We　used　those　rules。〃
　〃Well；　the　behavior　looks　pretty　good　to　me；〃　I　said；　watching　the　screen。　〃Why　is　there　a　problem？〃
　〃We're　not　sure。〃
　〃What　does　that　mean？〃
　〃It　means　we　know　there's　a　problem；　but　we're　not　sure　what's　causing　it。　Whether　the　problem　is　programming…or　something　else。〃
　〃Something　else？　Like　what？〃　I　frowned。　〃I　don't　get　it；　Ricky。　This　is　just　a　cluster　of　microbots。　You　can　make　it　do　what　you　want。　If　the　programming's　not　right；　you　adjust　it。　What　don't　I　understand？〃
　Ricky　looked　at　me　uneasily。　He　pushed　his　chair　away　from　the　table　and　stood。　〃Let　me　show　you　how　we　manufacture　these　agents；〃　he　said。　〃Then　you'll　understand　the　situation　better。〃　Having　watched　Julia's　demo　tape；　I　was　immensely　curious　to　see　what　he　showed　me　next。　Because　many　people　I　respected　thought　molecular　manufacturing　was　impossible。　One　of　the　major　theoretical　objections　was　the　time　it　would　take　to　build　a　working　molecule。　To　work　at　all；　the　nanoassembly　line　would　have　to　be　far　more　efficient　than　anything　previously　known　in　human　manufacturing。　Basically；　all　man…made　assembly　lines　ran　at　roughly　the　same　speed：　they　could　add　one　part　per　second。　An　automobile；　for　example；　had　a　few　thousand　parts。　You　could　build　a　car　in　a　matter　of　hours。　A　mercial　aircraft　had　six　million　parts；　and　took　several　months　to　build。
　But　a　typical　manufactured　molecule　consisted　of　1025　parts。　That　was　10；000；000；000；000；000；000；000；000　parts。　As　a　practical　matter；　this　number　was　unimaginably　large。　The　human　brain　couldn't　prehend　it。　But　calculations　showed　that　even　if　you　could　assemble　at　the　rate　of　a　million　parts　per　second；　the　time　to　plete　one　molecule　would　still　be　3；000　trillion　years…longer　than　the　known　age　of　the　universe。　And　that　was　a　problem。　It　was　known　as　the　build…time　problem。
　I　said　to　Ricky；　〃If　you're　doing　industrial　manufacturing　。。。〃
　〃We　are。〃
　〃Then　you　must　have　solved　the　build…time　problem。〃
　〃We　have。〃
　〃How？〃
　〃Just　wait。〃
　Most　scientists　assumed　this　problem　would　be　solved　by　building　from　larger　subunits；　molecular　fragments　consisting　of　billions　of　atoms。　That　would　cut　the　assembly　time　down　to　a　couple　of　years。　Then；　with　partial　self…assembly；　you　might　get　the　time　down　to　several　hours；　perhaps　even　one　hour。　But　even　with　further　refinements；　it　remained　a　theoretical　challenge　to　produce　mercial　quantities　of　product。　Because　the　goal　was　not　to　manufacture　a　single　molecule　in　an　hour。　The　goal　was　to　manufacture　several　pounds　of　molecules　in　an　hour。　No　one　had　ever　figured　out　how　to　do　that。
　We　passed　a　couple　of　laboratories；　including　one　that　looked　like　a　standard　microbiology　lab；　or　a　genetics　lab。　I　saw　Mae　standing　in　that　lab；　puttering　around。　I　started　to　ask　Ricky　why　he　had　a　microbiology　lab　here；　but　he　brushed　my　question　aside。　He　was　impatient　now；　in　a　hurry。　I　saw　him　glance　at　his　watch。　Directly　ahead　was　a　final　glass　airlock。　Stenciled　on　the　glass　door　was　MicroFabrication。　Ricky　waved　me　in。　〃One　at　a　time；〃　he　said。　〃That's　all　the　system　allows。〃
　I　stepped　in。　The　doors　hissed　shut　behind　me；　the　pressure　pads　again　thunking　shut。　Another　blast　of　air：　from　below；　from　the　sides；　from　above。　By　now　I　was　getting　used　to　it。　The　second　door　opened；　and　I　walked　forward　down　another　short　corridor；　opening　into　a　large　room　beyond。　I　saw　bright；　shining　white　light…so　bright　it　hurt　my　eyes。　Ricky　came　after　me；　talking　as　we　walked；　but　I　don't　remember　what　he　said。　I　couldn't　focus　on　his　words。　I　just　stared。　Because　by　now　I　was　inside　the　main　fab　building…a　huge　windowless　space；　like　a　giant　hangar　three　stories　high。　And　within　this　hangar　stood　a　structure　of　immense　plexity　that　seemed　to　hang　in　midair；　glowing　like　a　jewel。
　　
　DAY　6　
　9：12　A。M。
　At　first；　it　was　hard　to　understand　what　I　was　seeing…it　looked　like　an　enormous　glowing　octopus　rising　above　me；　with　glinting；　faceted　arms　extending　outward　in　all　directions；　throwing　plex　reflections　and　bands　of　color　onto　the　outer　walls。　Except　this　octopus　had　multiple　layers　of　arms。　One　layer　was　low；　just　a　foot　above　the　floor。　A　second　was　at　chest…level；　the　third　and　fourth　layers　were　higher；　above　my　head。　And　they　all　glowed；　sparkled　brilliantly。
　I　blinked；　dazzled。　I　began　to　make　out　the　details。　The　octopus　was　contained　within　an　irregular　three…story　framework　built　entirely　of　modular　glass　cubes。　Floors；　walls；　ceilings；　staircases…everything　was　cubes。　But　the　arrangement　was　haphazard；　as　if　someone　had　dumped　a　mound　of　giant　transparent　sugar　cubes　in　the　center　of　the　room。　Within　this　cluster　of　cubes　the　arms　of　the　octopus　snaked　off　in　all　directions。　The　whole　thing　was　held　up　by　a　web　of　black　anodized　struts　and　connectors；　but　they　were　obscured　by　the　reflec