NATIONAL ACADEMY OF SCIENCES Ch ARLES GREELEY Abb OT 1872—1973 A Biographical Memoir by D A V I D H . D EVORKIN Any opinions expressed in this memoir are those of the author(s) and do not necessarily reflect the views of the National Academy of Sciences. Biographical Memoir COPYRIGHT 1998 NATIONAL ACADEMIES PRESS WASHINGTON D.C. PhotographbyBachrach CHARLESGREELEYABBOT May31,1872–December17,1973 BYDAVIDH.DEVORKIN HARLESGREELEYABBOTwastheseconddirectorofthe C SmithsonianAstrophysicalObservatoryandthefifth SecretaryoftheSmithsonianInstitution.Hewasthesec- ondandlastpersontoholdbothpostssimultaneouslyand isrememberedtodayforhisskillasaninstrumentalistand hisunshakablebeliefthattheSunisavariablestarand thatitsvariationshadameasurableeffectontheEarth’s weather.HewaselectedtotheNationalAcademyofSci- encesin1915andservedasitshomesecretaryfrom1919 to1923underPresidentCharlesDoolittleWalcott,who wasAbbot’spredecessorasSmithsonianSecretary. AbbotwasborninMay1872inWilton,NewHamp- shire,thesonandgrandsonoffarmers.Theyoungestof fourchildrenofHarrisandCarolineAnn(Greeley)Abbot, CharlesGreeleyattendedpublicschools,butfinishedat PhillipsAndoverAcademy.HethenattendedMIT,where hegraduatedin1894withathesisinchemicalphysics.He expectedtoteach,butremainedatMIT,studyingosmotic pressureandearninganM.Sc.in1895.Skilledatlabora- torywork,hecametotheattentionofSamuelPierpont Langley,whowaslookingforanassistantattheSmithsonian’s AstrophysicalObservatory(APO).Abbotsoonwashired, thoughhelackedanyexperienceinastronomywhenhe 3 4 BIOGRAPHICALMEMOIRS arrivedinWashingtoninJune1895.Langley,however,was notatraditionalastronomerandAbbotwasjustthetype ofassistanthewantedtoaidhismappingoftheinfrared spectrumoftheSun,adaptingbolometersforphotographic recordinganddeterminingdispersionstandardsforrock- saltandfluoriteprismstomeasurefundamentalwavelengths intheinfraredregionofthesolarspectrum. UnderLangley,Abbotflourishedasacreativedesigner andbuilderofdelicatedevicesformeasuringsolarradia- tion.AsLangleyfocussedmoreandmoreonhisaeronau- ticalexperiments,Abbot,workingwithF.E.Fowle,be- cameresponsibleformaintainingtheobservatory’ssolar program,includinganexpeditiontoobservethe1900so- lareclipseinWadesboro,N.C.,whereAbbotapplieda vastlyimprovedbolometertotakereadingsoftheSun’s innercorona.HewasalsoaleadingmemberoftheAmeri- caneclipseexpeditiontoSumatrain1901.Heprovedto beareliableobserverandimpressedmanyastronomers whoencounteredhimattheseplaces. Abbotwasanaffablefellow,deferentialtohissuperiors whilemakingsignificantcontributionstothemissionof Langley’sinstitution.Thatmission,verymuchrepresenta- tiveofthetimes,wastodemonstratetheutilityofgovern- ment-supportedscience.Yearslater,inhisramblingauto- biographicalessayAdventuresintheWorldofScience,Abbot recalledLangley’swordsexplainingwhymeasurementof theheatoftheSunwasimportant: Iftheobservationoftheamountofheatthesunsendstheearthisamong themostimportantanddifficultinastronomicalphysics,itmayalsobe termedthefundamentalproblemofmeteorology,nearlyallwhosephe- nomenawouldbecomepredictable,ifweknewboththeoriginalquantity andkindofthisheat.1 CertainlytheideathatsolarradiationgovernedtheEarth’s fateasanabodeforlifewasnotoriginalwithLangley.The CHARLESGREELEYABBOT 5 keytoLangley’smission,however,wastomaketheamount andcharacterofthatradiation“predictable”andthereby usefulforplanningstrategiesforagriculturalmanagement andcontrol.Langleybelievedthatsolarradiationvaried inacyclicmanner.AsSmithsonianSecretary,however,Lan- gleyhadotherinterests,butwhatmayhavebeenpromo- tionalrhetoricforhimbecameapermanentandpassion- ateconvictionforhisable,dutifulassistant. WithinafewweeksofLangley’sdeathinFebruary1906, AbbotwasmadeactingdirectoroftheAPO,becomingits seconddirectorin1907underSecretaryCharlesWalcott. Astrophysicaloperationscontinuedunabated,withWalcott providingadviceandsupportthatallowedAbbottoex- tendLangley’smissionintwoways:first,bydeveloping refinedtechniquesforthespecificdeterminationofthe solarconstant;andsecond,byapplyingthesetechniques inastandardizedmannertobuildasynopticmonitoring programthatwouldsearchforsolarvariations.Asunder Langley,AbbotfoundWalcottwhollyattunedtothepro- gressivenotionofusefulscience.Beforehebecamethe Smithsonian’sfourthSecretary,WalcottwasheadoftheU.S. GeologicalSurvey,andcampaignedforpracticalresearch inpubliclysupportedagencies. WhenAbbotbecameAPOdirectorin1907,American astronomy’smostsignificantstrengthsandpotentiallayin vastcataloguingprojectscenteredatafewmajorobserva- tories,includingHarvard,Yerkes,andLick.Americanas- tronomywasinthethroesoforganizingitselfasaprofes- sion,anditsstandardsandmodesofconductwereinflux. Celestialmechanicsandmathematicalastronomywerestill thestrengthsofthediscipline,butnowthephotographic plateandthespectroscopewereavailableforassessingthe physicalnatureoftheSunandstars.Langleyhadprac- ticedthenewastronomy.Primarilyanengineer,hehad 6 BIOGRAPHICALMEMOIRS createdanastrophysicalprogramattheAlleghenyObserva- toryinPittsburgh,definingitbytheuseofnewtypesof instruments,thebolometerandspectrobolometer,and broughtboththeseinstrumentsandtheirpracticetothe Smithsoniantoestablishthefirstandonlyfederallyfunded astrophysicalobservatoryintheUnitedStates. WhenAbbotretiredasAPOdirectorandasSmithsonian Secretaryin1944,settingaprecedentasthefirstSmithsonian Secretarynottodieinoffice,mostbutnotallofthegreat cataloguingprojectsweregoneandthedisciplinewasun- dergoingprofoundchange.Problem-orientedresearch,in- formedbymodernphysicaltheory,dominatedthedisci- pline.YettheSmithsonian’sAstrophysicalObservatory pursueditssinglemissionallalong,elaboratingonits purposenotbyabroadeningofitsastronomicalbasebut byrefiningitsinstrumentationandtechnique,searching forevidencethatEarth’smeteorologyandbiologywere intimatelyconnectedtovariationsintheSun’soutputof energy.Althoughheeschewedphysicaltheory,Abbotwas thoroughlymoderninhisproblem-orientedapproachto research.Thus,hisfailuretobroadentheastrophysical scopeoftheAPOduringhislongtenurehastobeappre- ciatedasduetoacomplexsetoffactorscenteredonhis singularsenseofmission,whichtranscendeddisciplinary linesbetweenastronomy,geophysics,meteorology,andbi- ology. TheamountandcharacteroftheSun’sradiationare basicquantitiesforawiderangeofscientificandenviron- mentalconcerns.Determiningthesequantitiesinpractice, however,wasfarfromsimple.Astronomerslongknewthat theabsorptionofsolarenergybytheEarth’satmosphere wasbothselectiveandgeneral.Langley’smethodofdeter- miningthesolarconstantwastotakeobservationsofthe Sunasitroseinthesky,notingitsincreaseinradiating CHARLESGREELEYABBOT 7 powerandthenextrapolatingtothetopoftheatmosphere. Giventhevagariesoftheatmosphereandthelimitations oftechnology,thevalueofthesolarconstantcouldvaryas muchas50%.Langleyestablishedthevalue3.00cal/cm2/ minoutsidetheatmosphereastheSmithsonianstandard andheldtoittenaciouslytotheendofhislife.Butothers whomadedifferentassumptionsaboutatmosphericab- sorptioncoefficientsorothervariablescameupwithval- uesbetween1.5and4.0. AftersomesevenyearsworkingforLangley,Abbotknew thattheSmithsonianvalueforthesolarconstantwastoo high,buthecarefullyavoidedtheissueuntilhewasin charge.Then,hequicklyannouncedresultsfromobserva- tionsatMountWilson,California,thatreducedthesolar constantfirstto2.1andthento1.93,largelythroughthe introductionofimproved,standardizedmethodsandbet- terthermalisolationforhispyrheliometersandbolom- eters.2Abbotpaidcloseattentiontodetail. Abbot’srevision,however,drewcriticismfromvarious quarters,mainlyfromadisgruntledandgenerallycombat- iveLangleyprotege,butalsofromtwoEuropeanswho arguedthatthewayinwhichheaccountedforatmospheric absorptionwasincorrect.Abbotmetthiscriticismbyre- turningtothehighestmountainintheRockies,following Langley’sleadin1881.AbbotcooperatedwithW.W. CampbellattheLickObservatoryandwiththeSierraClub tobuildasturdyfieldstationonthesummitofMount Whitney.Abbotusedthesitesporadicallyin1909and 1910tomeasurethesolarconstantandaccompaniedthe LickastronomerstostudythespectrumofMars. Stillharriedbycritics,however,Abbotturnedto balloonsondestoreachgreaterheights.Collaboratingwith theWeatherBureauandSignalCorps,withAndersKnut Angstrom,whohadbeeninresidenceforseveralyears, 8 BIOGRAPHICALMEMOIRS andwiththehelpofhischiefassistantLoyalB.Aldrich, Abbotflewspecialpyrheliometersonballoons.Hecreated anewtypeofroboticpyrheliometeroutofpartsfrom standardWeatherBureaumeteorgraphsthatwasfullyau- tomaticandself-recording.Automatictechniquesforme- teorologicalobservationsfromballoonswerewelldevel- opedbythen.ButAbbotwasthefirsttousesuchautomata inAmericaforastronomicalmeasurements. Abbot’sinstruments,builtbyAndrewKramer,weremar- velsofsophisticationandplanning.Theywereflownby AldrichfromtheCaliforniacoastin1913and1914,and someoftheballoonsondesreachedover25kilometers;at leastoneofthemreturnedclearevidenceforthermomet- ricandbarometricvariationsthatconfirmedhisterres- trialextrapolationsandallowedhimtodeterminethevalue ofthesolarconstantatthetopoftheEarth’satmosphere. Thistechnicalfeat,requiringthecooperationoftheWeather BureauandtheSignalCorps,quietedcriticismofthe Smithsonianvalueforthesolarconstant.Ithelpedtoaf- firmAbbot’sreputationandestablishedthemodernrange forthesolarconstant. EvenbeforeheassumedthedirectorshipoftheAPO, Abbotwasamongtheastronomicalelite.Ina1903census bytheAAAShewaslistedamongthetopthirtyastrono- mersbyhispeers.Langleywasamongthefirstrank,and bothscoredevenhigheramongphysicistswhowerepolled. AbbotwontheprestigiousDraperGoldMedaloftheNa- tionalAcademyofSciencesin1910andtheRumfordMedal oftheAmericanAcademyofArtsandSciencesin1916. Withhissolar-constantcriticsvanquished,Abbotfocussed