Current Ck3mrnerits”EUGENE GARFIELD

INSTITUTE FOR SCIENTIFIC INFORMATION(33501 MARKETST PHILADELPHIA PA 19104

The Most-Cited Physical-Sciences Publicationsin the 1945-1954 Science Cita~”on Index.

Part 3. Forty-Two Citation Classics inAstronomy and the Earth Sciences

Number 43 October 22, 1990

Last week, Stephen G. Brush, Departmentof History and Institute for Physical Scienceand Technology, University of Maryland,College Park, commented on 20 mathe-matics articles that were most cited in the1945-1954 cumulation of the Science Cita-tion [nde.r’.’ This continued his discussionof the most-cited physical-sciences publica-tions during this period, the fht part ofwhich appeared in Current Contents m (CC’)last May and presented 52 Citation Classi(s @in physics and chemistry.2

In the essay that follows, Brush concludeshis analysis with a discussion of highly citedarticles in astronomy (22 papers) and theearth sciences (20). As in Parts 1 and 2, hecompares these high impact articles withother Iists of publications deemed “influen-tial” by historians of science. By doing so,he illustrates how historians and scientistsinterested in the contemporary developmentof their fields can use quantitative citationdata to augment subjective impressionsabout major trends in contemporary re-search.

Among these trends in astronomy, Brushdiscusses the importance of quantum me-chanics and research bearing cm the originof the universe as well as chemical elementsin the crucial postwar decade. With respectto the earth sciences, under which he in-cludes research on the upper atmosphereand solar-terrestrial interactions, Brush fo-cuses on various topics: “Rossby waves”that influence global weather conditions,seeding clouds for artificial rainmaking, andplate tectonics and continental drift.

Plate tectonics and continental drift are aninteresting example of a resisted or “prema-

ture” discovery.s In the early 1900s, a Ger-man meteorologist, Alfred L. Wegener, pro-posed that the continents once formed a sin-gle land mass, which he called “Pangaea.”This land mass broke into continents mil-lions of years ago of which some driftedthousands of miles apart under “pole-flee-ing” and lunar-solar tidal forces.4 In 1915 hedescribed his theory in detail in a book, DieEntstehutrg der Krmtinente umi Oceans(The Origin of Continents and Oceans),which has been published in several lan-guages and was reprinted in 1968.s

His theory contradicted the scientificdogrnd of his time that the continents werefixed. Most geologists resisted Wegener’sconcept. But the South African geologist Al-exander L. Du Toit was one of the moreprominent champions of the controversialtheory.h He presented his own explication ofthe theory in a 1937 book, Our WanderingCmtinenIs.7

As Brush points out in the followingessay, the theory of continental drift was notwidely accepted until the 1960s, during theso-called “revolution in the earth sciences.”Figure 1 presents a graph of the annual dis-tribution of citations, 1945-1989, to thebooks by Wegener (387 to all editions) andDu Toit (213). While neither was cited morethan six times pa year through 1964, cita-tions in 1965 and thereafter increased.

CC readers interested in the earth and geo-sciences should refer to our earlier citationstudies of the most-cited articles and jour-nals in these fie]ds.x-] 1 Bmsh’s insights into

astronomy and astrophysics can be aug-mented by previous CC essays discussingthese fields. 12-’4

387

F- 1:Annual distributionnfcitations,1945-1989,to key bxh on continenrd drift by Alfred L,Wegener=cI Alexander L. Du Toit. (% references 5 and 7. respectively. )

I28- — %oemr, all ediibrm-- —___

27OuTok1937

26-

25-

24-

23-

22-

21-

20-

19-

16-

17-

16-

12-

11-

1O-I

9-

8-

L!!k!l6-

5- ?

4,11

3-

/

!!

2IIl\

1.’/’,l!,

Ilfll , I

,, ,* ~,,,,, ,?T

/!

l\II\

/

\“ !

1’ki

JLJU u

1945 1950 1955 1960 1965 1970 1975 1980 1985 1989

YEARS

I

2.

3.

4,

5.

6.

7.

REFERENCES

Brush S G. The mm-cited physical-sciences publications in the 1945-1954 Science CIIa/Ion /nde.t.Part 2. Mathematics. Currenf Confenfs (42):X-13, 15 October 1990.

-------- The most-cited physical-sciences publication in the 1945-1954 S<!cncc C[!ai(on Inder.Part 1. Current Comenrs (20):7- 17, 14 May 1990.

Garfield E. Premature discovery or delayed recognition—why? Essa.vs of an tnformatton ~cwnr!.\r.

Phdadelphm 1S1 Press, 19!I1. Vol. 4. p. 488-93.Bullen K E. Wegener, Alfred Lothar. Di[/wtwry ofs[ler?lifiti biograph,v. New York: %ribner’s, 1980

vol. 14. p, 214-7.Wegener A. The ori,gin of [ont(nents and oceans, London: Methuen, 1968.248 p.Wilson J T. Du Toit, Alexander Logic. Dw[lonury r~~(IemIfic biography. New York: Scr!bner’s, 1980.

Vol. 4. p. 261-3.DU Toil AL. CIU, wmdcr!ng continents: an hypo!hests of cwnlinen!alJrifling.Edinburgh, UK: Oliver &

Boy(t, 1937.366 p.

388

8. Garfield E. Journal citation studies. 10, Geology tmd geophysics. Op. cil., 1977. Vol. 2. p. 102-6,9. -------- Journal citation studies. 11. Journal of Geophysical Research. [bid. p. 114-7,

10. -------- Journal citation studies, 38. Earth sciences journals: what they ci[e and whaLcites them./hid., [983. Vol. 5. p. 791-800.

11. -------- The 1981 geosciences articles most cited from 1981 through 1983, /btd., 1985. Vol. 7,

p. 251-63.12. -------- Journal citation studies. 12. Astrophyslral Journal and its Supplements, Ibid., 1977,

Vol. 2, p, 120.4,

13. -------- Journal citation studies, 43. Astrosciences journals—what they cite and what cites them.Ibid., 1985. Vol. 7. p. 1S2-63.

14, -------- Training our cites on the stars: Helmut Abt’s observations on astrosociology, Parts I & 2Currerrf Cmrrenr$ (39):S-11, 24 September 1990: (40):5-II, I October 1990.

The Most-Cited Physical-Sciences Publications in tbe 1945-1954Science Ci~”on Index. Part 3. Astronomy and Earth Sciences

Stephen G, BrushDepartment of History andInstitute for Physical Science and TechnologyUniversity of MarylandCollege Park, MD 20742

This essay concludes an examination of the physical-sciences publications most cited in the 1945-1954Science Cirarion [nakx@by presenting 42 highly cited papers in astronomy and the earth sciences. InPart 2, the 20 most-cited papers in mathematics were examined, and Part 1 presented 52 chemistry andphysics publications. 1.1These papers are compared with other publications (including some highly citedbooks) considered impmtant by scientists artd historians of science, The essay discusses some of themajor trends, achievements, and researchers in these fields in the period includingWorld War 11.

Intreduction

In Part 1 of this essay, the 52 most-citedphysical-sciences publications in the 1945-1954 Science Citation index m (SCI’) werepresented and discussed. 1 The list of booksand articles was composed almost entirelyof publications in chemistry (25) and phys-ics (25 ). There were only two in mathemat-ics, and none in the earth sciences or astron-omy.

Rather than omit these fields, ISI” hascompiled lists of the articles in mathematics,astronomy, and the earth sciences most citedin the 1945-1954 SCI. This compilation al-lows us to take a look back at a historicperiod in science and see what papers wereCitation Classics @ during this time. Lastweek, the most-cited mathematics paperswere exarnined.2

In this essay, I dkcuss highly cited articlesin astronomy and the earth sciences. Ofcourse, as noted previously in Parts 1 and 2,

one should not simply rely on citationcounts as a measure of the importance orquafity of a publication. Thus, the lists ofmost-cited publications are compared withindependent judgments of the scientificcommunity (as indicated by prestigiousawards, such as the Nobel Prize or FieldsMedal, for example) or of historians of sci-ence.

Citation Data vs. Independent ExpertJudgment

Unfortunately, it is not so easy to obtainsuch judgments for astronomy and the earthsciences as it is for physics, chemis~, andmathematics, since there were no major in-ternational prizes that covered these fields inthe 1930s and 1940s. While there is noNobel Prize specifically designated for as-tronomy, two scientists won the Nobel Prizefor physics for a..trophysical research done

Table 1: Major publimlions in astronomy (including astrophysics) during the period 1935-1949. Basedon L&ng K R & Gmgerich 0 and Srruve O & Zeherg\ V (See references 3 and 4. ) Only items reprln[mi orrnt’ntimwit In [hew wwrce~ tire included. An aster!!k ( w) InclIcxtc\ that Ihe paper I> included [m the I]\t ofu,trn nom) p:Ipers highly cIIed In the 1945- 1954 sC/’~ Il:Ihle 3 ) A= 1945-1954 cltarmns

A

1X~

41

5115

14

~

I

1

21

I

11623

17

4

I()43

36

2!829

3

16

lx

0

Bibliographic Data

Alpher R A, Bethe H & Gamow G. The ongm of chem!cal elemenls. Phys. f?m 73:S03-4, 1948Am bartsumian V A. Expanding stellar associations. Asfro?, Zh. SSSft 26:1-9. 1949.

*Baade W. The resolution of Messier 32, NGC 20S, and {he central reg]on of the Andromeda nebula.A.,m,p}]y.s J, 100:137-50. 1944.

ttethe HA. Energy production in stars. Phy.!. Rc;t 55:434-56, 1939.ttolton J G, Stanley G J & Slee O B. Pmitions of three discrete sources of gtdachc rmh,]-frequency

mdiati on. ~dlitre 16$: (()(-2, (949.

Bondi H & Gold T. The sIeady -state theory of”the expanding universe, Mon No/it R,)y,A.,fro,i. so,. 108:252-70, I 948.

Cbandrasekhar S. The highly colltipwd configurations of a stellar ma~j. (Second paper )$l<m No(I( Roy Asrr<m S(I< 95:207-25, 1935.

Chandrasekbar S. Stellar con f]guratton, w ltb degenerate core,. M(MI N(III< RoyAs[mn SOC. 95226-60, 1935,

Cbandrasekhar S. Stellar configuratlom wlrh degenerate cores. (Second paper. ) Mon INOIII R(Iy.,A$[r,)?t .7,)< 95:676-93, 193S.

Chandrasekhar S & Henricb L R. An atlempt 10 mterprel Ihe rcltil!ve abundmwes of the element~tind their Iwtope>. A.>[rophv$.J 95:2X8-9X. 1942.

Edlin Lt. An flttempt 10 ]dcntif’y the emission lines in the spectrum of the $olar coron~.Ark. M<,{. .AS!V,III Fx.\ 28B: I-4, 1941.

Gamow G. Nuclear reacti[ms In +Iellar e,olution. IVu/[/re 144:575-7, [939.Hall J S. obwrvaticm, of’ the polarized Ilght from stars. SI icm e 109:166-7, 1949.Hey J S, Parson S J & Phillips J W. Fluctuation. in cosmic radiation at rad]o frequencies.

N,,(uIc 15X234, 1946.Hiltner W A. Pnlwl~ittmn of light from d[s[fln! ~tars by the imer~tellar med]um.

S({[>flcf, 109:165, 1949.JOY AH. Rotation effect>, inter~tellar absorption, and certain dynamical constants ot the gdtixy

determined from Cepheid Var!ables. Av[n,phy.$ J 89:356-76. 1939.Joy A H. T T.UII \ariahle Wm. A s(r(,phys J 102:168-95, 1945.

*Reber (;. Co\mtc static. Arfr[)ph?.$ J. 100:~79-U7. 1944.Seyfert C. %uclear emission m spiral nebulae. A.tfr(,pll?.$ J 97:28-40, 1943Spitzer L. The dlssip~tion of planetary filaments. Asrrophjs. J 90:675-88, 1939.

*Stromgren B. The ph}sical state of interstellar hydrogen. Aslrophy.\ J. 89:526-47. 1939.*Unsold A. Qutintltati\e Antil}se des BO-Sterne\ T ScorpII. 11 (The quantitative analysis of the

B()-\tar ~ Scnrp!l, part 11). Z ,A.\[wp/IyT 21:22-84, 1942!~an de Hulst H C. Radm w ave$ from \pace: ong]n of ritdiowaves. ,NtvJ 7i@chr ivarIiI(rM

11:210-21. 1945.van de Hulst H C. The wild panicles of interstellar space. Rcc h. A>tI-on (lb.\ L’[ret hr Pr 2

111-50.1949$on Weizsicker C F. Uber Elemcntu mwand lungen im lnnern der Sterne. 11(Element trwt~formation

Insldc ,ktr. 11), Phjs. Z 39:633-46. 1938.von Weizsacfcer c F. Zur E“t\te hung dej Planetensy stems (The origin of [he wlar syitem).

IVuturm.!.%ens[/la//en 33.8-14, 1946.

before 195S: Hans A. Bethe, Cornell Uni-versity, Ithaca, New York, and Sub-rahmanyan Chandrasekhar, University ofChicago, Illinois. William A. Fowler, Cali-fornia Institute of Technology (Caltech),Pasadena, who shared the prize withChandrasekhar, published most of the workfor which he was honored too late to becited in the period 1945-1954. Martin Ryleand Antony Hewish, University of Cam-bridge, UK, are coauthors of a highly cited —

1950 paper but won the prize primarily forwork done later.

To get an idea of the most important pub-lications in astronomy, 1 used A Source

Book inAstronomy and Astrophysics, 1900-

/97.5, compiled by Kenneth R. Lang, TuftsUniversity, Boston, Massachusetts, andOwen Gingerich, Harvard University, Cam-bridge, Massachusetts, together with thebeok by Otto Struve and Velta Zebergs, Na-tional Radio Observatory, Green Bank,—

390

Table 2: Chronologic distribution of publication

dates for lhe astronomy and astrophysics papersmost cited in the 1945-1954 SC/ @cumulation.

Publication Number of

Year Papers

1935-1939 3

1940-1944 10

1945-1949 7

1950- I 954 2

West Virginia, Astronomy in the 20th Cen-~111T,3,4Gingerich tells me that he and Lang

rev”iewed a list of the 10 most-cited ar-ticIesin the Astrophysical Journal and decidedthat most of them were not importantenough to be reprinted.5 On the other hand,they wanted to include some ofChandrasekhar’s papers but were refusedpermission to do S0.6

Table 1 lists 26 publications that origi-nally appeared in the Period 1935-1949,were reprinted or extracted by Lang andGingerich or mentioned in their section in-troductions, and were also mentioned byStrove and Zcbergs. The reason for select-ing the period 1935-1949 is that most of thehighly cited astronomy papers were pub-lished then, as can be seen in Table 2.

For the earth sciences, in which I includethe study of the upper atmosphere and solar-terrestrial interactions, there are no generalhistories or source books that cover the en-

tire field for the mid-twentieth century. So itis difficult to judge whether the most-citedpublications are the most important ones.Only one scientist, Hannes Alfw%, Univer-sity of California, San Diego, won theNobel Prize for earth-science research donein the period 1935-1949. Most of his papersin that period appeared in Swedish joumaisnot included in the SC] list of source publi-cations. Moreover, the scientific communityignored or rejected most of his work eventhough many of his ideas were eventuallyconfkmed and have become part of main-stream theories.’ So it is not surprising thatnone of his publications were highly citedbefore 1955. Another Nobel laureate, IrvingLarrgmuir, General Electric Company, Sche-nectady, New York, is the author of a highlycited ~amr in meteorolosw, but he had al-

ready received the prize before writing thatpaper.

Twenty-Two Citation Ckmsics inAstronomy: Quantum Mechanics

In Part I of this essay, I pointed out theimportance of quantum mechanics in sev-eral of the Cifafion Classics in chemistsy, 1Quantum mechanics also played an impor-tant role in the interpretation of astrophysi-cal observations, as can be seen in the list of22 astronomy papers most cited in the 1945-1954 SC1, which are shown in Table 3.

The spectrum of radiation coming from astar, planet, or interstellar matter can pro-v ide information about the physical andchemical state of the atoms emitting and ab-sorbing that radiation—provided one has anadequate theory to explain the emission andabsorption of radiation by atoms. Quantummechanics, together with statistical mechan-ics, is that theory, as was shown in the1920s by Cecilia H. Payne, Harvard Univer-sity, and Henry Norns Russell, PrincetonUniversity, New Jersey.8’9

The highly cited papers in Table 3 by Wal-ter S. Adams, Mount Wilson Observatory,Carnegie Institution of Washington, Pasa-dena (1949); Joel Stebbins, Mount WilsonObservatory, and colleagues (1940, 1945);and Gerard P. Kuiper, Yerkes Observatory,University of Chicago, Williams Bay, Wis-consin (1938), provided data. The some-what less frequently cited papers by HoraceW. Babcock, Mount Wilson Observatory(1947); Chandrasekhar (1945); Chandra-sekhar and Frances H. Breen, Yerkes Obser-vatory (1946); Bengt E&%, University ofUppsala, Sweden (1943); Donald H.Menzel, Harvard University, and Chaim L.Pekens, Massachusetts Institute of Technol-ogy (MIT), Cambridge (1936); SimonPastemack, Caltech (1940); BengtStromgren, Copenhagen Observatory, Den-mark (1939); and Albrecht Unsold, Univer-sity of Kiel, Germany ( 1942, 1948), pro-vided theoretical interpretations.

Missing from this list of highly cited as-tronomy papers, however, are the papers byCharrdrasekhar identified as the ones for

391

Table 3: The 22 most-cited papers from astronomy and astrophysics journals covered in the 1945-1954

SCl ‘@ cumulation. Papers are listed in alphabetic order by first author. A=total number of [945- 1954cltatlons.

A

26

25

41

33

29

27

35

25

?5

26

.$7

~~

26

43

30

49

39

43

28

29

28

29

Bibliographic Data

Adams W S. Observations of interstellar H and K. molecular line$. and radial velocities in thespectra of 3000 and B stars. AsIr(,phY~. J, 109:354-79, 1949,

Adel A. The grating infrared solar spectrum. V]. The map from 14P to 7K .4$/rophy.$ ./94:451-67, 1941.

Baade W. The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula.Astr,,pfiys, J. 100:137-50, 1944.

Babcock H W. Zeeman effect in stellar spectra. A.s/mphYf. J 105:105-19.1947.Chandrasekhar S. On the continuous absorption coefficient of the negative hydrogen ion.

As/roph~s. J, 102:223-31. 1945.

Chandrasekhar S & Breen F H. On the contmutms absorption coefficient of the negativehydrogen ion. 111. Asrroplys. J, 104:430-45, 1946.

Edlin B. DIe Deutung der Emissmmhmen Im Spektrum der .%nnenkorona (The interpretation of

emission line~ in the \pectrum of the ~un’s corona). Z. Asfmph?.y 22:30-64, 1943.Henyey L G & Keenan P C. Interstellar radiation from free elecwon> and hydrogen atom$.

A.moph},. J, 91:625-30. 1940.

Herzberg G. Laboratory production of the 14050 group occurring in cometary spectra; turtherevidence for the presence of CHZ molecules in comet>. Astrophys. J. 96:3 14-S. 1942.

.ttthnson H L & Morgan W W. Fundamental stellar photometry for standards of \pectrfll type on therevised system of the Yerkes $pectral A1/a$ A.wophys J. I ]7:31 3-55, ]953.

Kuiper G P. The magnitude of the sun, the stellar temperature \cale. and bolometric corrections.Astr(,phJs J, 88:429-71, 1938.

Menzel D H & Pekeris C L. Absorption coefficients and hydrogen line inten$,ties.Mon. NOII<. R(>Y. Astmn SOC. 96:77-111, 1936.

Pasternack S. Transition probabdities of forbidden lines. A$tmphy~ J. 92:129-55.1940.Reber (;. Co\mic 5[ot1c. ,4~rrophys. J 100:279-87, 1944.

Ryle M & Hewish A. The effects of the terrestrial mnoiphere on !he radio waves from di~cretesources ]n the galaxy. kfon IVo//[ R{)y As/rmI SOc. 110:38 I -94, 1950.

Stebbins J, Huffer C M & Whitford A E. The colors of 1332 B stars. Asfroph>! J91:20.50, 1940.

Stebbins J & Whitford A K. Six-color photometry of stars. Ill. The colors of 238 \tars of differentspectral types. A.!fmphy.! J 102318-46, 1945.

Stramgren B. On rhe density distribution and chem]cal compo~ition of the interstellar gas.Astr<,ph~s. J 108:242-75, 1948.

Strbmgren B. The physical state of interstellar hydrogen. A~f wph~s J 89:526-47, 1939.Uns6dd A. Quantitative Analyse des BO-Stemes T Scorpii. 11 (The quantitative analys!s of the

BO-star r Scorpii, part D). Z. Asfrophy.r. 2 I :22-84. 1942.Unsdld A. Qttmti[ative Spektralamdyse der Sonnenatmosphire (Quatttittative spectral

analysis of the sun’s atmosphere), Z. Aslmphs~. 24:306-29, 1948.von Weizsacker C F. ~ber die Entstehttng des PIanetensys~ ems (On the tmg!n of the solar system).

Z A.strophvs 22:319-55, 1943.

which he received [he Nobel Prize. 10Thesepapers presented perhaps the most brilliantapplication of quantum mechanics to astro-physics: the treatment of the degenerateelectron gas taking account of relativistic ef-fects, leading to a theory of the stability ofwhite dwarf stars and the prediction of alimiting mass for such stars. The instabilityof stars more massive than Chandrasekhar’slimit may lead to a su~mova explosion.

Most of these papers appeared in the jour-nals selected for the preparation of Table 3.But none received more than 24 citationsduring the 1945-1954 period. The impor-tance of Chandrasekhm’s work was not rec- .

ognized until the 1970s, when it becamefully integrated into the modern theory ofstellar evolution and was found to providean essential key to the processes leading topulsars (neutron stars) and black holes.

The Origin of the Universe andChemical Elements

Another major research area in astronomyis the origin of the universe and of thechemical elements, represented here by sixpapers listed in Table 1. Carl F. vonWeizsacker, Kaiser WiIhelm Institute, Ber-lin, Germany ( 1938), suggested how light

.

elements might be formed from hydrogen instars, and Bethe (1939) worked out the the-ory in more detail. George Gamow, GeorgeWashington University, Washington, DC(1939), also contributed to the theory.

The ongin of the elements is related to theorigin of the universe through the “BigBang” concept in cosmology. The standardinterpretation of the Hubble velocity-dis-tance relation is that the universe is expartd-ing as galaxies move away from each other,having originally been concentrated in asmall region of space. According to Gamowand his colleagues, the expansion startedwith a state of extremely high density andtemperature, in which all matter was in theform of protons, neutrons. and electrons. Asit cools, the heavier elements are formed byfusion reactions, perhaps along the linessuggested by von Weizsacker and Bethe.

The authors of the fundamental paper onthe synthesis of chemical elements follow-ing the Big Bang were listed as Ralph A.Alpher, Johns Hopkins University, Balti-more, Maryland; Beth~ and Gamow (1948)so they could call it the “et ~ ~’ theory.Bethe agreed to be listed as coauthor in ab-sentia for the sake of the pun.

The use of Hubble’s relation led to a basicdifficulty: the “age” of the universe (timeelapsed since the Big Bang) came out to beonly two billion years, less than the age ofthe earth as determined by radiometric dat-ing. This difficulty gave an opportunity forHermann Bondi and Thomas Gold, Univer-sity of Cambridge (1948). to propose theiralternative “steady-state” theory, in whichnew matter is contimraiiy created rather thanbeing created all at once. But the difficultywas resolved in a less sensational waythanks to research by Walter Baade, MountWilson Observatory (1944), reported in theonly one of these six papers that appears onthe most-cited list in Table 3.

Baade’s resolution of individual stars inthe galaxy Messier 32 led eventually to arevision of the astronomical distance andtime scales. By 1952 it appeared that thegalaxies were at least twice as far away ashad previously been believed, and the uni-

verse must therefore be twice as old. Subse-quent revisions of the distance and timescales extended the age of the universe tomore than 10 billion years, while estimatesof the age of the earth stabilized at about 4.5billion years after 1953.4,11

The Most-Cited vs. the Most-InfluentialAstronomy Publications

Comparing Tables 1 and 3 shows thatonly four of the items considered “influen-tial” by Lang-Gingerich and Struve-Zebergsalso appear on the list of most-cited publica-tions in astronomy journals. Note, however,that the list of most-cited paprs does notinclude general science journals such as Na-ture, Science, and Naturwissenscha ften, orphysics journals such as Physical I?et’ien,.

Thus, 10 of the 26 Table 1 papers could nothave appeared in Table 3 because they werenot published in “astronomy” journals. Onthe other hand, von Weizsacker’s paper inTable 3 was a longer version of the 1946paper that appears in Table 1 and shouldtherefore be counted as a most-cited paperjudged to be important by Lang andGingerich.

The result of this analysis is that 25 per-cent (4 out of 16) of the papers published inastronomy journals judged to be importantboth by Lang-Gingerich and Struve-Zebergsappear on the list of the 22 most-cited pa-pers in those journals. Another seven papersare by authors who published other papersthat are on the most-cited list. Conversely,of the 22 most-cited papers, 4 (18 percent)are on the Lang-Gingerich and Struve-Zebergs list, and another 7 are by authors ofthe papers on that list.

Even the most highly cited papers in as-tronomy average no more than five or sixcitations per year, The careful reader ofTable 3 will notice that one paper-’’Funda-mental stellar photometry for standards ofspectral type on the revised system of theYerkes spectral Atlas” by Harold L. John-son, Yerkes Observatory, and William W.Morgan, McDonald Observatory, Univer-sity of Texas at Austin, Fort Davis—was

393

cited at a much higher rate since it was pub-lished in 1953. This paper is the only astron-omy publication included among the 250most-cited Ci[a/im C/uf.~ic,.s for the follow-ing decade, 1955-1964, when it received342 citations. 12

Twenty Citation Ckzssics in the EarthSciences: Meteorology and Geology

Table 4 lists the 20 papers from earth-sci-ences journals that were most cited in the1945-1954 SC1. The highest impact paper,with 49 citations, was an analysis of mo-tions intheatmosphere bythe Swedish me-teorologist Carl-Gustaf” A. Rossby (b. 1898–d. 1957) andhiscollalmratorsat MIT. Thisis one case in which the most frequentlycited paper in a field is one of the mostimportant original research contributions(in part a rediscovery and interpretation ofwork by S.S. Hough, University of Cam-bridge, in 1897) inthatperiod.131 iAccord-ing to meteorology historian Gisela Kutz-bath. University of Wisconsin, Madison:

Rossby was instrumental in bringing

American mekomlogy to a pmition ofworld kmdership. ... In connection w,ithaproject on long-range forecwting startedin 1935, he began to investigate thecir-cumpo]ar system of long waves. nowcalled Rossby waves, in the westerlywinds of the middle and upper tropc-sphere. These wavei exert a controllinginfluence on weather conditions in thelower troposphere Rmsby developeddynamic theory of these longwaves.,. and derived a simple formula,now called the Rossby equation, fortheir propagation speed. This formulabecame perhaps the most celebmted amalytic solution of a dynamic equation inmeteorological literature. Rossby ’s the-oretical anatysis profoundly influencedboth applied and theoretical meteorol-ogy irnd oceawgmphy during subst.quent decades.

Rossby’s theory has become a standardtechnique for studying global patterns offluid motion, in the ocean as well as in theatmosphere. l~l~It hasalso been app]iedto

develop hypotheses about hydromagneticoscillations in the earth’s core in order to

explain the westward drift of the geomag-netic field. z’)z]

The other highly cited meteorology paperin Table 4 has quite a different character.The American scientist Langrmrir (b. 1881–d. 1957), winner of the1932Nobel Pnzeforhis work in surface chemistry, had a lifelonginterest in weather. During World Warllhewas involved in projects to generate smokescreens (for concealment from enemy air-craft) and to deice airplane wings.22

After the war his colleague at GeneralElecrnc, Vincent Schaefer, discovered thatthe condensation of supercooled watervapwcould betriggeredby ’’dry ice’’ (solidcarbon dioxide). One of Langmuir’s assis-

tants at General Electric, Bernard Vonnegut.

subsequently found that crystals of silver io-dide were more convenient for this purpose.Langmuir enthusiastically pursued the theo-retical analysis and experimental testing ofschemes for artificial rainmaking, Hishighly cited 1948 paper presents the resultsof this resewch with numerous suggestionsfor further work. Langmuir”s researchhelped to transform weather modificationfrom a dubious art to a progressive science,though not as yet a very exact one,23-26

Langmuir stressed the importance of whathe called “divergent phenomena” in na-ture—very large effects can be triggered byvery small causes,20 For this reason hewarned. at the end of his 1948 paper, that itmay never be possible to forecast theweather with great accuracy. This is nowknown, thanks to “chaos theory.” as the“ButterOy Effect’’-”a butterfly s[irnng theair today in Peking can transform storm sys-tems next month in New York.”27

For some critics the hazards of divergentphenomena were illustrated by one ofLangmuir’s own experiments. On October13, 1947. a hurricane moving northeastwardin the Atlantic Ocean was seeded with dryice. Shortly afterwards it changed courseand headed west, striking the coast of SouthCarolina and Georgia, doing considerabledamage to Savannah, h is not known forcertain whether the seeding caused thechange of coursq a detailed analysis 10years later concluded that the shift was the—

394

Table 4: The 20 most-cited papers from earth-sciences journals covered in the 1945-1954 SCI’$ cumulation.

Papers are listed in alphabetic order by first author, A=mtal number of 1945-1954 citations.

A

28

313829~~

35

374530

44

37

28

2834

28

31

49

27

27

27

Bibliographic Data

ftarsbad 1. Vermiculite and its relation to biotite as revealed by base exchange reactionj, x-rayanalyses, differential thermal curves, and water content. Amer. Mim’ral. 33:65 S-78, 1948.

Bowen N L & Scbairer J F. The system, FeO-SiO:. Amer ,/. Sci, 24:[77.213, 1932Bowen N L & Scbairer J F. The system, MgO-FeO-SiOl. .4rncr. ./ .SII. 29:15 I-217, 1935,Bowen N L & Tuttle O F. The system MgO-SiOz-H20. Cd Sm. Amer. Bu//. 60:439-60, 1949.Bowen N L & Tuttle O F. The system NaAISi~Ox-KAISi jOwH*O, J. Cd S8:489-5 I I, 1950Flint R F & Deevey E S. Radiwarbon dating of late -Plclsmcene events, Amer J. .${,.

249:257-300, 1951,Greig J W. Immiscibility in silicate melts. Amer. J. Sci. 13: I -44.1927.

Grim R E. Modern concepts of clay materials. J, Gd 50:225-75, 1942.

Grim R E, Bray R H & Bradley W F. The mica in argillaceous sediments. Amer. M~m’ra/,12:813-29, 1937,

Grim R E & Rowland R A. Differential thermal analysis of clay minerals and other hydrous materials.Part 1, Amer. Miners/. 27:746-61, 1942.

Grim R E & Rowland R A. Differential thermal analysis of clay minerals and other hydroui materials,Part 2. Amer. Mineral. 27:801-18, 1942,

Hendricks S B & Jefferson M E. Polymorphism of the micas with optical measurements.Amer. Mineral. 24:729-71, 1939,

Kerr P F & Kulp J L. Multiple dlfferemial thermal analysis. Amer. Mineru/. 33:387-419, 1948.Langmuir I. The production of rain by a chmn reaction in cumulus clouds at temperatures above

freezing. J. kfereorol 5:175-92, 1948.

Penndorf R. The vertical distribution of atom]c oxygen ]n the upper atmosphere.J. Geophys. Res. 54:7-38, 1949,

Ramsdell L S. Studies on silicon carbide. ,Amer. Mineru/. 32:6+82, 1947.Rossby C-G & collaborators. Relation between variations in the intensity of the zonal circulation

of the atmosphere and tbe displacements of the semipermanent centers of actmn. J. Mar. Res2:38-55, 1939,

Taber S. Perennially frozen ground in Alaska: its origin and history. Gt’o/ Soc Amer Bu//,54:1433-548, 1943,

Tuttle O F & Bowen N L. High-temperature alb]te and contiguous feld$pars. J. Gco/58:572-83, 1950.

Winsor C P & Clarke G L. A statistical studv of variation in the ca(ch of nlankton nets.J. Mar. Res. 3:1-34, 1940.

re~u]t of natural causes.28 But the incident

forced Langmuir to be much more cautiousin carrying out his ambitious schemes forweather modification.

Geology Before the Revolution

If asked to identify the most importantpublications in geology and geophysics be-fore 1950, earth scientists and historians ofscience would probably mention those thatplayed an important role in the “revolutionin the earth sciences” leading to the estab-lishment of plate tectonics in the 1960s.29’30A list compiled from this postrevolutionatyviewpoint might look something like Table5. But none of those works appear on the listof publications in earth-sciences journalsmost frequently cited in the decade 1945-1954 in Table 4.

One could regard this as evidence that thelatter were of no permanent value to sci-ence. But some are still cited in the geologi-cal literature of the 1980s, so this is not afair judgment. Instead, we might suspectthat, as a result of the revolution itself,scientists’ judgments about what researchfindings are most significant have changed;they see the world inadifferenfway.31

Judging the past in terms of presentknowledge is a well-known feature of theway scientists look at history. Historians callit the “Whig interpretation” of the histo~ ofscience. Here is where citation data can helpthe historian who wants to avoid whiggish-ness, by pointing fo research that was highlycited in its own day but now likely to beoverlooked because of changed paradigms.

Although a few geologists such as ArthurHolmes, University of Edinburgh, UK, andSouth African Alexander L. Du Toit ac-

395

Table 5: Major publications in earth science (geology/geophysics) during the period 1935-1949, accOrd -

ing 10 w n[ers on the “revo]utiun in the ear!h w’ience<.” 13aw!d on Glen W, LeGmnd H E. and Marvin U.(See reference\ 29, 30. and 33. ) Only works prominently mentioned !n IWO or mom of these source\ are]ncluded. A=1945-1954 clt~tmns.

Bibliographic Data

Bullard E C. The magnetic tield wlthm the earth. Fro{. Roy. S,X London Ser A 197:433-53, 1949.Du Toit A L. Om wundcring cont[nen(s on hypofhe.ri~ of c[m(inen!ui drf[in,q Edinburgh, UK:

Oliver & Boyd, 1937, 366p,F%asser W M. Induction effecti m terrestrial ma.gne[]sm. 1. Theory. Ph,vs Rev. 69:106-16.1946Elsasser W M. Induction effects In termmal magnetism. 11. The secular varlaticm. Phjs RC’I

70:202-12, 1946.Elsasser W M. Induction effects in terrestrial magnetism. Ill. Electric mOde~. Phy., Re~.

72:872-33, [947.Graham J W. The stabll!ty and significance of magnettsm In sedimentary rock~. J. Ge,lphy.~ Re.\.

54:131-67, 1949.Gutenberg B. Structure of the earth’s crust and the spreading of the continents.

Gal S~,[ Arm’r 6’1(//. 47:1587-610, 1936.

Hess H H. Drowned ancient islands of the Pacific basin. Amer. J SCI 244:772-91.1946.

Holmes A. Pnm ,ple.s qfph> $(w1 ,qt’,df>,q~ London: Nelson, 1944.531 p.N4el L E F. Th&me du tramtige magnitique des ferromagn+tique$ au gram fins a~ec applications

aux terres cuites (Theory of the magnetic drag of fine grain ferromagnetism with irpplicatmns tobaked earth I. Ann Gcwphys 5:99-136.1949.

Vening Meinesz F A. Gruvr[y ?tpf’d(t!orz.s UI .seu. ~’olume 1 Delft, The Netherlands: W’altman. 1932.Vening Meinesz F A, Llmbgrote J H & Kuenen P H. Gra\tt? rrpcdtrl<m.$ UI Mzu ki,iume 2. Delt’1,

The ?4etheriand\: Waltman, 1934.Vening Meinesz F A. Graw/y e.~pedirfom a( sea. Vb/I/nte 3, Del ft. The Netherlands: Waltman, 1941.Vening Meinesz F A. Gru\{m e~ped[flons at seu. Itdurrie 4 Delft, The Netherlands: Waltman, 194s.Willis B. Continental drift: on %t~rchen. Am<,r J. SCI. 242: S09-1.3. 1944.

cepted the German geophysicist Alfred L.Wegener’s theory of continental drift, themajority view during the 1930s- 1950s wasthat the continents are fixed in position,aside from relatively small up-and-downmotions. The gravity measurements of FelixA. Vening Meinesz, University of Delft,The Netherlands, revealed anomalies thatwere eventually explained with the help ofplate tectonics. Research in paleomagnetismsuggested that the earth’s magnetic field hadcompletely reversed itself several times inthe past several million years. This evidencewas not taken seriously until Louis E.F.N6el, Fdculty of Science, Grenoble, France,showed that it could not be interpreted asspontaneous self-reversal within the rock,and a possible mechanism for reversal wassuggested by the dynamo model for terres-trial magnetism by Walter M. Elsasser, Co-lumbia University, New York, and E.C.Btdlard, Toronto University, Ontario, Cart-ada.

The most-cited geology paper, “Modemconcepts of clay materials” by Ralph Early

Grim, then with the Illinois State GeologicalSurvey, is also the only one reprinted in thesource book by Kirtley F. Mather, HarvardUniversity, a collection compiled before theimportance of Wegener’s theory of conti-nental drift became obvious to everyone.32Grim (b, 1902) was later research professorof geology at the University of Illinois, Ur-bana. Mather says “his research has shedmuch light on many problems of sedimenta-tion and stratigraphy.”sz (p. 327)

Five other highly cited papers in geology,by Norman L. Bowen and colleagues at theCarnegie Institution of Washington’s Geo-physical Laboratory, reported experimentalstudies of the behavior at high temperaturesand pressures of substances present in theearth’s crust and mantle. These studies dem-onstrated the value of using quantitativephysiochemical techniques to study geo-logical problems. For example, there was along-standing controversy about the originof granite. Is it formed by fractional crystal-lization from the molten basaftic magma inthe earth’s mantle and subsequently ex-

396

truded through the crust to the surface? Or isgranite a secondary rock formed on the sur-face by the melting of sediments? Bowenlater argued that his experiments favored thefirst akemative.33-35

[n retrospect one might suppose that byraising a new question— What is the pro-cess that brings granite from the mantle tothe surface?-Bowen’s work challenged thedominant “fixed continents” theory. Pre-sumably, plate tectonics, with its postulatesof mantle convection and upwelling of mol-ten magma through mid-ocean ridges, couldprovide a better explanation for the upwardtransport of granitic material. But such anexplanation has not yet been developed tothe extent needed to satisfy experts in pe-trology, and in any case we cannot infer anycausal connection between Bowen’s papersand the revolution in tbe earth sciences. In-stead, his papers were highly cited becausethey provided exceptionally clear and per-suasive explanations of an important newmethod.sb

Conclusions

In a recent study, bet Leydesdorff andOlga Amsterdamska, University of Amster-dam, The Netherlands, selected four highlycited bioenergetics papers and sent a ques-tionnaire to all the authors who cited thosepapers, asking why they gave the citations.From the responses, they concluded:

Any interpretation of simple citationcounts as indlcatom of impact, quality,or importance must be considered prob-lematic,.., The impact of a cited paper

on the conduct of research or on the in-terpretation of results is often slight .... Itdiffers from case to case .... Citations arenot a valid indicator of the quality ofcited papers at the moment they arepublished.37

[t can hardly be disputed that the numberof citations is not a direct measure of thequality or importance of a publication. Ihave mentioned a number of authors andpublications that have been considered veryimportant by the scientific community butwere infrequently cited, even compared toother papers published in the same journalsin the same time period.

Nevertheless, the fact that a publication ishighly cited indicates something, and thehistorian of science should try to find outwhat that is. Some papers, such as those byRichard Feynman, Cakech; Julian Schwing-er, Harvard University; Niels Bohr, Institutefor Theoretical Physics, Copenhagen, andJohn Wheeler, Princeton University; andRobert MuUiken, University of Chicago,were original contributions of fundamentalimportance by any measure. 1 In physics andchemistry, a substantial number of thehighly cited publications were authored orcoauthored by Nobel laureates, even thoughthey may have received the prize for otherwork. In mathematics, as also in physics andchemistry, some books and review articlesbecome Citation Classics because they areconvenient sources for techniques and data.

But to me, the real value of a list of highlycited publications is that it focuses attentionon papers like those of Rossby and NathanJacobson, Yale University, New Haven,Connecticut, that are highly valued by spe-cialists and clearly have played an importantrole in tbe development of smaller fields buthave not been adequately recognized ingeneral surveys.

*****

My thanks to Eric Thurschwell for collect-ing the information used in preparing thisessay and to Owen Gingerich and H.S.Yoder for \-aluable suggestions. .,~ ,,,

REFERENCES

1, Brush S G. The most-cited physical-sciences publications in the 194 S-1 954 Science Citation Index.Part 1. Current Cortferrfs (20):7-1 7.14 May 1990.

2. -------- The most-cited ph ysical-scierrcei publications in the 1945-1954 Scirtrcf’ Cirarion /rrde.r.Part 2. Mathematics, Currenf Cowenfs (42): S- 13.15 October 1990.

3. Lang K R & Gingerich O, eds, A source hook in aswnnnty and u.s!rophysirs, 1900-1975.

Cambridge, MA: Harvard University Press, 1979.922 p.4, Struve t) & Zebergs V. Asfrormmy in [he 20fh cerIIury. New York: Macmillan, 1962. 544 p.

397

5. Gingerich O. Per>onal communicatwn, 29 January 1990.6. -------- Personal cummunicauon. 8 February 1990.7. Brush S G. Predlclion and theory evaluation: Alf’><n on space plasma phenomena.

Eos 71(2):19-33, 1990.8. Payne C H. .Sle/lar almrmpheres. Cambridge, MA: Harvard Observatory. 1925.2 I S p.

9. Russell H N. On tbe composition of the sun’, atmosphere. A~/rophw. J. 70:11-82, 1929.10, Chandrasekhar S. Subrahmanyirn Chandrasekhar. (Odelberg W, cd. ) L.es PrI.t NcdM’/ /983.

Stwkholm, Sweden: Almqvlst & Wi@ll, 1984. p. 55-7.11. Brtrsb S G, The age oftbe earth in the twentieth century, Earth Sci Hisr. 8:170-82, 1989,12 Garfield E. The 250 most-c] ted C/f(~fion C/us.vc.! from the essential decade 1955- 19@l. E.r.ra].} elan

!njormuflon .s<ic>!lll.~l,ghosturilinh~ Ond other e.s.%uss. PbiJadelphia: ISI Press, 1986. Vol 8, p. 37-49.13. Neis B. Forrschrlr[e it?der Merrc]r[>l[,xr.~lhe/lF’or.whun,q SeII /900 (Progress in meteorological research

~mce 1900), Frankfurt, FRG: Akademlsche Verkrgsgesell schaft, 1956.238 p,14. Hendershott M C. Long waves and ocean tides. (Warren B A & Wunsch C. eds, 1 EwdMton of

ph~.~i, a/ ocec~m),q)-up/ly. Cambridge, MA: MIT Pre\s, 1981. p. 292-341.15, Kutzbach G. Rossby, Car-G ustaf Awid, D!{tionury of M !cnftJic b{ographv, New York: Scr]bner’s,

1981. vol. Il. p. 557-Y.

16. Bolin B, ed. [he u[mosphere und the SC3UIn motion: .s[ient!frc contributions 10 the Rm\sb.v rnemor!ulIo/umt’. New York: Rockefeller In\litute Press, 1959.509 p,

17. Byers H R. Genrra/ merwwo/,~,f\. New Yrrrk: McGraw-Hill. 1959.540 p.18. Fofonoff N P. Dynamics of ocean currents. (Hill M N, cd. ) The sea. ~oIume 1. ph?.>l<a) O(eaw?ruph!.

New York: [mersclence, [962. p, 323-95

19. Pedlosky J. GeophysIca/f/IfId dynaml~~. New York: Springer-Verlag, 1987.710 p.20. Hide R. Free hydrtrmwgne ticoscillations of the Earth’s core mrd the theory of the geomagnetic secular

var]at ion. Ph{/ Trun.~ Roy Sm London A 259:615-47, 1966.

21. Brush S G & Banerjee S K. Geomagnetic vecular variation and {heorms of tbe Earth’s interior.(Schroder W, ed. ) Pu&I,pre.\enr urrdfitture trrnds I(I ,Veophy.slcol research. Bremen-Roennebeck,FRG lnterdi,i>ional Commission on Hi\tory of IAGA, 1988. p. 65-97.

ZZ, Rose”feld A. The ql<tn[,..$.$en<e CIJIr]{r]g Lun,qmuv. Neu York: Pergamon Pres\. 1961 369 p.

23. Suits C G, ed. The (ollecred works oflrv!ng LoncnIu Iv. New York.: Pergamon Press. 1961- 19tJ?Vols. lo& 11,

24. Byers H R. Htstory of weather mod] f]cat ion. (He\\ W N. ed. ) Weuther and cl{mule modifica~lon

New York: WIlty, 1974. p, 3-44.?5. Ha\ens B S, Jiusto J E & Vrmnegut B. Ea)-/y h{.}lory of[ /em/ .seedi~t~. Socorro. Nh!: New ,Mextco

lnstlrute of Mlmng and Technology. 1978.75 p.

26. Townsend J. Mukin,q vuln 111Anwr(c a u h[.~[or]. Lubbock. TX: Texas Tech Umverwt>, 1975.93 p.27. G[eick J. <’hu[>xma~!ny u new s<Ierwe New York: Penguin, 1987. p. 8.

28. Mook C P, Hoover F. W & Hoover R A. An analysis of [be movement of a hurric.ine oft’ [he East Co[lsrof the L’nl!ed Stute\, October 12-14. 1947. ,Mcmrh/j Weu/her Rtw 85:243-50. 1957.

>9. Glen W. J’}w r<>udI(I Jurumt{l<~. cI III(UI VC>UI.\oj lb<,ww]lut!on oJ”eur[h sc’tem e. Stanford. CA:Stanford fJnl\er\ity Pres\, 1982.459 p.

30, LeGrand H E. Driftin,i! [on/Inenu and .~h~flin,qtheor~e.s New York: Cambridge University Pre\s,1988.313p.

31. Kuhn T S. The >trti<[{(w of \<wttrrj;< rc\ O1[,ll,lll.%,Chicago. IL: Unlverhi[y of Chicago Pre\\,

1970210 p32. Malher K F, cd ‘i<n{r~ehook In ,qcw/+y /900-/950 Ctimb ridge, MA: Har\ard Uni\er\il) Press.

1967, 435 p,33. ,Marvin U. Corltrnt’n(ul drift the e~o[u!!or! <Iiu concept. Washington. DC Smithwmlan ln~titution

Pre\s. 1973.239 p.34. Yoder H S, ed. The evolution of the t~neo!<.\ r<><L\ jtfi[rrh anntvt’r~ur~ pcr\pec ttlc,.~. Prmcetnn, NJ.

Princeton Lniversi[} Press, 1979.588 p35. Yoder H S. Scientific higbl!gbts of tbe Geopbyslcal Laboratory, 1905-1989. Annual wp,wt of rhe

d!rector. Geophy.%t<ul Laboru(ory, 1988-1989. Wa,bington. DC; Carnegie [nsritution ofWashington, 1989. p, 143-97.

36. -------- Personal communlcat]on. 1990.37, Leydesdorff L & Amslerdamska 0. Dimensions of citat]on anal y\i5. .$c/ Te{hri{d. Jff{m \ U/

15(3):305-35, 1990,

398