UNCLASSIFIED Communication_withExtraterrestrialIntelligence' BYLAMBROSD.cALi:.IMAHOS U~ified.. Wearenotaloneintheuniverse.A fewyearsago,thisnotion- seemed farfetched; today, the.existenceofnttaterrestrialintelligence is taken for grantedby mostscientists.SirBernardLovell, one of theworld's leading radioastronomers,hascalculatedthat,even al- lowing for a margin of error of 5000%,theremustbe in our owngalaxy 100 millionstarswhichhaveplanetsoftheright.chemistry, dimensions, andtemperature tosupportorganicevolution.Ifwe thatour owngalaXy,theMilkyWay,isbutone ofatleasta billion other galaxiessimilar to oursintheobservableuniverse, the numberofstars thatcouldsupportsome form of life is, toreachfor a word, astronomical.Astoadvanced(bymiserableearthstandards> formsof life, Dr.FrankD.Drakeof theNationalRadioAstronomy Observatoryat Green Bank, WestVirginia,has statedthat,putting all our knowledge together, thenumberofcivilizationswhich could havearisen by nowisaboutone billion.Thenextquestionis,"Where iseverybody?" Thenearest neighbor to our solarsystemis AlphaCentauri,only 4.3 lightyears away;but,according to Dr.Su-ShuHuangoftheNational - Aeronautics andSpaceAdministration,itsplanetarysystemis probablytoo young for the emergence of life. Twootherheavenly friends, Epsilon Eridani and TauCeti,about11lightyearsaway,are strongercontendersforharboringlife. vertheless,ifsuperior civilizationsareabundant,thenearestwouldprobablybeatleast100 light years away; therefore, it wouldtake200yearsfor a reply to be forthcoming, asmallmatterof sevengenerations.Thisshould, how- ever, makelittle differenceto us, in view oftheenonnouspotentialgain from ourcontact witha superiorcivilization.'Unless we'reterribly conceited (a very unscientificdemeanor),we mustassumethatthe "others"are far moreadvanced thanweare:Evena.50-yeargap betremendous; a500=yeargap.staggerstheimagination,andas _ IThesubstanceoCthisarticlewasp~ntedatapaneldiscussionofthesametide duringthe1205IEEEConferenceon~h1itaryElectronics held inWashington,D. C., on 23~te::lber1965.:&!sidesthe~uthorascryptologist,theothermemb!rsof thepanel wereDr.PaulGarvin,linlUist;Dr.John C. Lilly.delpbinolocWt;Dr.WilaamO.na..-is: .ph)"Sic:ist;aDdFr.FrancisJ.Heyden,S. J.,astronomer,..Themo9t:rat9r...-asDr. Harold Wooster.DirectorofInformationServicesoftheAirForceOffic:eofScientificResearch. . between;whenthesesignals are a', . .' ..~,!ould wa circle,thePythagor: design.Theseattention-getting~- . "language lessons,"interspersedwi . :k~pbringus uptothelevelofour s Itmay be assumedthatthesr possessed byallhigher forms ofIi jcouldthusbegreatlysimplified1 -representationsuch asthatof ate~ heldatGreenBankin 1961 todisci. withotherplanets,oneofthepan upahypotheticalmessage on ti consistingof 1271binarydigits 1271 hasbuttwo primefactors,3: towriteoutthe message inraster 31lines of41bitseach;thelatte nessinthepatternsdisclosed,in dimensions.InFig. 2isthewrit binaryl'shavebeen replacedbya Now for its interpretation. TherearedotsatthefourCOl points,markingtheoutlines of th representationof the sun;.directl; representing 8planets,identified} theirleft,precededby a legged beingsillustratedareobvk handofthemalefigurepointsto parentlyreside.Atthetopoftho tionsofhydrogen,carbon,and structureof life ontheir thirdplanetthereemerges a wavy therepresentationof a fish: iPdthe~(o.rehavespacetravel. to a six(precededby theusualb %Inthiseenaeetien,Professor1000fShklo\'sky,Russiascratestradioastronomerthere'afesix fingers on eachhar bastheioIlov.'ingto sayintheSeptember1965issueofSornetLiic"theirnumbersystemisprobably! "Profo~ndcriseslieinwait(or adevelopin:chilizationaadCIIleoCthemmaywellprovefemale figuremaybeseena bracke ral3l.Wearea1reaciyfamiJiarwithseveralsuchcritical(situatiaas):.binaryform(precededby abinar- (a) -destNctiol1"an~toCathennoDuclearcatastropbeor_od.rdiscxn'el1 ..wruchIDa}'haveUDpredictahlemduncontrollable~are11unitshigh.Areasonable (d.>Restri.cted.capacityoCtheindivi4\la1'sbrainwhichcaDladtoee-i ar';'"""'., .I '..Btishth'. on.WIcomequentdaDc.asofdepneration... .' _.(e)AcrisisprecipitatedbythecreationofartificialintellipDtbeinp.;.addressbeforetheBritishInterplr orFirstStepsinCelestialSyntax. UNCL~SSJFIED..EXTRATERRESTRIALINTELLIGENCE''.. behmdus,forgetit!).:Itisquitepossiblethat'.'others'.'havesatellite''. .'prC??esinspace,retransmi~to ..theIn'~;,anythingthatsoundsnon-'~:.. :randomtotheprobe.'Buttheyhaveprobably'calledusseveral~. thou~dyearsago,andarewaitingforananswer;or worseyet.they. havegivenup; or, moreprobably,theyhavereached such impressive technologicaladvances thattheyhavedestroyedthemseives.! ~ridaniandTauCetiwerethetargetsODwhichDr.Drake focussed. hIS attentionin~qesp'ririg _of'1960inProjectOimaan attempttodetectpossibleintelligentsignals from outerspace,:a. frequencyselectedforlisteningwas1420.405752megacycles second,or awavelengthof~lem.This particularfrequency, pas- tul~ted.indep~dentlybytwoprofessorson thefacultyof Cornell Um.ve:S1ty,GIuseppe Cocconi andPhilipMorrison, happens tobethe ~adlatlonfrequencyofatomicor freehydrogenwhichpermeatesspace Ingreatclouds;moreover,thisfrequencyiswithintheraneeof radiofrequenciesable topassthroughtheearth'satmosphere ~uma?ly,the.significanceofthisfrequencywould be known toother l ellige~tbeingsinth~universewhounderstandradio theory.We're s~111.talking~bo~tradiowavesasthecommunication medium;other possiblemedia mightbemasers;lasers, or theasyetundiscoveredand unnamed"rasers,"A.technologysuperiorto ours might evenhave lea~edhow tomodulatea beamofneutrinos(weightless,uncharged pa~lesthatphysicistsonearthfinditdifficult even todetect)if so "they"mayhavetowaita centuryor two before we learn how~build a neutrinoreceiver. Ifanothercivilizationweretl)ingtoestablishcommunicationwith us, it would firstembarkonattention-gettingsignalsof such anature thatwe coulddistinguishthemfromrandomcosmic noise' once we receive arecognizablesignal, wehavea good chance ofund~tanding themessage.Forexample,theycouldstartwithtrainsofsimals ccrrespondingtothenaturalnumbersI,2, 3,,followedperhaps b.yprunenumbers.Theymightcontinuewith equal-lengthextended . - - -signalsconsistingofstartand~op'i:mpulses,"Withoccasional pulses in.... UNCLASSIFIED IALINTELLIGENCE.'..... L. D.CALLIMAHOS..UNCLASSIFIED J,iftheyareasmuchas 50years siblethat"others"havesatellite anythingthatsoundsnon- .aveprobablycalledusseveral ananswer;orworseyet,they. eyhave-reachedsuchimpressive-.: ~destroyedthemselves,".'::.,.::::..:-...': ..thetargetSonwhiChDr.'Drak~.-. ~of-1960inProjectOZma,an- .' fromouterspace.The 1S1420.405752megacyclesper Thisparticularfrequency,pos- ssorsonthefacultyof Cornell .ilipMorrison, happensto bethe hydrogenwhichpermeatesspace quencyiswithintherangeof htheearth'satmosphere.Pre- uencywouldbeknowntoother .mderstandradiotheory.We're ~communicationmedium;other "ortheasyetundiscoveredand periortooursmightevenhave ieutrinos(weightless,uncharged itdifficulteventodetect);ifso, :wobeforewe learnhow tobuild o establish communicationwith -gettingsignalsofsuchanature randomcosmicnoise;once we a goodchance ofunderstanding ildstartwithtrainsofsignals I,2, 3,..., followedperhaps inuewithequal-lengthextended withoccasionalpulsesin ky,Russia's:;reatestradioastronomer, ".XeofSouidLife: ::li::ationandone ofthemmaywenprove critical[situation.'l}:. ---- eareatastrepbeor someotherdi!co\"ely :ol1abi~conseQuences.. :lwhich~leadtoucessh"especia!j~ icialintelligentbeings." be~ween;whenthesesignals arealignedBushoveroneanother,they _.~.. would show a circle, thePythagoreanTheorem,'orsimilargeometric design. : Theseattention-gettingsignals..wouldbefollowedbyearly "languagelessons,"interspersedwith.it.emSoftechnicalinformationto. .,..helpbringus uptothelevelofoursuperiorS,"them.n.,o_..'.- .-:;.:,It.maybeassumedthatthesenseofsight~-otan-equivalent,is .~._.~..possessedbyanhigherformsof life;theproblemsofcommunication begreatlySimplifiedthroughthemediumofa"raster" representationsuchasthatof atelevisjonJS..een.Aftera conference atGreenBankin 1961 todiscussthepossibilityofcommunication withotherplanets,one of thep~cipants,BernardM.Oliver,made upahypotheticalmessage ontherasterprinciple.Themessage, consisting of 12'11binary. digits or"bits,HisshowninFig.1.Since.. 1271 has but. twoprime factOlS,31and41,wewouldnaturallybeled towriteout themessageinrasterform,in41linesof31bitseach,or in 31lineSof41bitseach;thelattercaserevealsagreaternonrandom- ness in thepatternsdisclosed,indicatingthatthesearethecorrect dimensions. InFig. 2 is thewrite-outof themessage,inwhichthe binary1'shavebeen replaced by adotandtheO'sleftasblankspaces. Now for itsinterpretation. There are dots atthe fourcomersofthepictogramasreference points, marking theoutlines oftherectangle,Attheupperleftis a representationof. thesun;directlyunderneathin acolumnaredots representing8 planets.identifiedbytheappropriatebinarycodingto theirleft,precededbyabinarypointas amarkere--Theerect,two- beingsillustratedarecbviously..bisexualandmammalian;one handofthe male figure points tothefourthplanetwheretheyap- parenilyreside..Atthetop ofthepictogrammaybeseenrepresenta- hydrogen.carbon, and oxygenatoms,indicatingthatthe chemicalstructureof life ontheirplanetis similar toours.Fromthe thirdplanetthere emerges a wavy line,showingthatitiscoveredwith water;therepresentationof afishshowsthattheymusthavevisitedus and therefore have space travel.One handofthefemalefigurepoints to a~(preceded bytheusualbinarypoint),perhapsimplyingthat therearesixfingerson eachhand;we couldthereforeassumethat theirnumbersystemis probablytothebase12.Attherightofthe female figure may be seen abracket,inthemiddle ofwhichis eleven in binaryform (precededby abinarypoint}:thisimpliesthatthe"beings. ._ are11unitshigh. A reasonableinterpretationisthattheunitis 21 em. thewavelengthof thetransmission.makingthemabout7~-:!feet whichshould be all right foraverageMartians. In1952theBritishmathematicianLancelotHogbendeliveredan addressbefore theBritishInterplanetarySocietyentitled"Astraglossa, F~StepsinCelestialSynt8:t.'~Hogbenpointedoutthatnumber UNCLASSIFIED'. UNCLASSIFIEDEXTRATERRESTRIALINTELLIGENCE.. OOOOOOOOOOOOOOOOOO~OOOOOOOOOOOOOOOOOOOOO istoe-mostuniversalconceptfor - intelligentbeings;therefore, stepsinematerrestrialcommuni ::::.e~uldtransmitpulsesrepresentin "radiog)'Prepreseng latercarried outthebasicidea: shapestorepresentelementary differentapproachwasdevelope Mathematics attheUniversityI bookentitled"Linens:Design of "Lincos,"anacronymof"lingu; municationof ideasthroughsyro ofthosewhohavetaken is too difficult.Afterall,theo' across toanother party,whose differentfrom our own.Inothe an"inversecryptography,"or designed,not tohidemeaning,l' prebend.Clevern~on~hepar: factornotrelianceonmgenu crypt;grapher-somehow,thistl makehismeaningcleartothe r possess a cosmicequivalentofthe Asanillustrationof howmuch minimumof material,and as an letusconsider amessageIhavecit expect of aninitialco ical shown a series oftransmissronsv inhabitedplanet,manylighty~ arerepresentationsforthe32dil ordistinctivepulse shapes)heard --.Thepunctuationmarksarenotp' differenttimelapses:adjacents; unit)betweenthem;a space (2units);commas.semicolons, an . 16unitsrespectively. referencepurposes) .there15atim Thefirsttr~ion,(I),is symbols.whichwillbet mission(2)isthe"clearimplicatil aTheRosettaStoneisapieceorblac . oCtheNile.beanDgabilin:ualWc:ription andGreek)withwhichJeanFran~isC~ Egyptianhieroglyphs. e eeft.e.e.O' UNCLASSIFIED82 UALINTELLIGENCE L~D. CALLIMAHOS .UNCLASSIFIED isthemostuniversalconceptforestablishizigcommunicationbetween . intelligentbeings;therefore,mathematicsformsthebasisforthefirst.",' , stepsinextraterrestrialcommunicatimL:..Hethenillustratedhowhe ...-.' couldtransmitpulsesrepresentingintegci.'anddistinCtive.signelsor. " . ._- "radioglyphs"representing .later:carriedoutthebasicidea'a littlefurther~--usmgdifferentpulse"'".. shapestorepresentelementarY'mathematicalsYmbols~'"Anentirely. differentapproach wasdevelopedbyHans'Freudenthal,Professorof. MathematicsattheUniversityofUtrechtt-whoin 1960publisheda bookentitled"Lincos:Design ofa LanguageforCosmicIntercourse." "Lineos," anacronymof"linguacosmica,"triestoestablishacom- omunicationofideasthroughsymboliclogic,butthegeneralconsensus ofthosewhohavetakenthetroubleto studyhisbookisthathis:plan-- difficult.Afterall,theobjectoftheexerciseisgettingideas across toanotherparty,whose thinkingprocessesmaybeentirely differentfromourown.Inotherwords,whatweneedtodevelopis an"inversecryptography,"orcommunicationsymbolismspecially designed,notto hide meaning,buttobe aseasyaspossibletocom- prehend.Cleverness on thepartofthesenderisthentheimportant factor.notrelianceoningenuityoftherecipient.Theinverse c:ryptographer-somebow,thistermdoesn'tsoundquiteright-must makehismeaningcleartotherecipient,evenifthelatterdoesnot possess a cosmicequivalentoftheRosettaStone.:J anillustrationofhow.muchinfonnationcouldbeconveyedwitha material,and as anexampleof facileinversecryptography, letus consider a message I havedevisedto betypicalofwhatwemight espectofaninitialcommunicationfromouterspace.InFig. 3 is shown a series of ~..nsmissionswhichcouldhavecome fromanother inhabitedplanet,manylightyearsaway.The32arbitrarysymbols arerepresentationsfor the~2differentsignals(combinationsofbeeps, ordistinctivepulse shapes)heardon afrequencyof 1420.4megacycles. Thepunctuationmarksarenotpartofthemessage,buthererepresent differenttime lapses:adjacentsymbolsaresentwithashortpause(1 unit)betweenthem;a spacebetweensymbolsmeansa longerpause (2units);comma.s,semicolons,andperiodsindicatepausesof4,8,and 16units,respectively.BetweentTa:Dsmissions(numberedherefor ref~re.!1cep~)thereis atimelapseof 32units. Thefusttransmi$sion,(1), isobviouslyanenumerationofthe32 differentsymbols which will be used in thecommunications;in mission (2) istheclearimplicationthatArepresentstheintegerI,B , TheRosettaStoneispieceofblackbasaltfOUDd.in1799DartheRosettamouth " oftheNile.beariucabiJincualinicriptioD(inECYJ)tiaD.hieqlypbics,EgypEiaD.demotic:, Greek)widlwhich.leaDF~Clwnpollioowasabletosolvethemysteryof the Egyptianhieroglyphs. ~ooo~oooooo~ooooo~oo )OOO~OOOO~OOOOOO~OO JOOO OOOOOOOOOOOOOO UNCLASSIFIED L.D.CALLIMAHOS UNCLASSIFIED UNCLASSIFIED.EXTRATERRF. Thesolutionmt)befoundonp.1 whathehaSlearneduO.tr readerronnula~thesetwoquestions_d. compactCorm;thesolutionsappearon cl8ssicuasolvedproblemsinmathemati valuesof%,Y.andzcanbefound isanintepTPuterthaD2;Goldbach's othermathematiciansWledtomaket; number:raterthan2canbeexprased theinteger2,,Jtheinteger theie~areintroducedsymbolsfQr inteaching.ustheirmathemat addition,subtraction,multiplier .~andtheconceptof zero;lnequa roots; and definitions of new tothe31symbolsrecoveree mostbeautifulconcepts if theycanteach us'such a-com- be staggered bywhattheywill transmission.Beginningwith clusterconceptsareintroduce. transmission (30), we now areui pure Venerean.Furthermore, the code they are using on thousandsuponthousandsof this is easilyappreciatedby an. the meaning of all 30 transmissii Evenrightafterthis firstmeso withthatplanet,we shallhave( LastTheorem,Golc unsolved problems inmathem: not be difficult for "them"to d nologicalsuperiority(first of,. able to callus!).If"they"b- structureconstant,"theyare five for sure,suspectthesixth, ratio, amongothers,of the electron; it maytakea century afterwe resolve ourpre." appropriateto.makediscreet harmonyand peacewithour fe' otherwiseingested fortune tocontactus. 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