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sible identification of new effects of a s s in photoresistance in thin metal films from 1931 to 1937 between Ettore and tional tional Congress organised to celebrate the re, that this correspondence allows us to ally, ally, the article refutes the widespread and es es insight into the specifically experimental erned himself with physics. with erned himself rich exchange of scientific correspondence to Ettore, and moreover us toallows identify t t many theoretical parts of the most mature on Galvani that Quirino Majorana presented in NonCommercial - century author author of those publications and studies, thanks al - his uncle Quirino as a methodologically astute cri vis - à

- reative Commons Attribution Commons reative vis

[email protected] It is offered a preview of the lengthy, intense and Abstract (currently in press) which took place in Quirino Majorana. the This collection period of letters provid and theoretical aspects tied to exposed the to study of light change in suitable photoelectric conditions type. and It also the leads pos us to papers realise by Quirino Majorana are attributable in tha fact Ettore as being, in a certain sense, the co the constant role he played epistemological epistemological guide. It is pointed out, recognise Ettore as the true furthermo author of the Lecture Bologna in 1937, on the occasion of a great interna second centenary of the birth of Luigi Galvani. Fin belief after 1933that common Ettore no longer conc mail: 6 October, 2006 - - Copyright owned by the author(s) the of the C owned under terms by Copyright

Giorgio Dragoni University of Bologna Via Irnerio 46 Bologna 40126, Italy E Ettore Majorana as a guide in Quirino Majorana’s Majorana’s Quirino in guide a as Majorana Ettore anddocumentsonan letters Original experiments. collaboration andtheoretical experimental Ettore Majorana's legacy and the Physics of the XXI University of Catania, Italy 5 

PoS(EMC2006)005

the aching aching anyone, may may anyone, the possible the Physics Giorgio Dragoni e correspondence nd a postcard written ents of these letters, nce, and “sure leads” nce in thin films metal via via Toniolo Majorana, ys, ys, barring one or two research topic, 6 letters , Arnoldo Mondatori, Milan ical procedures contained me, it becomes of essentialof becomes it me, t should be said right away jorana family (to whom we ense collaboration between this point of view there have ter) written Quirinoby in his

t in these topics, and above all the Il Caso Majorana . The brief correspondence are we talking 1

em and the em BolognaPhysics, of Bologna Department in Ettore Majorana. Then a veil of obscurity fell

2 on E. Recami, also in view of later and current developments in the - joie de vivre

, where Quirino Majorana, as Director of in the te Institute of engaged Physics, ) 2

Introduction Correspondence The The specific contents of the letters in question are almost alwa But what does this correspondence consist in? It includes 34 letters a “I “I really hope to go to Naples”: thus ended the intense and constructiv Being one of theBeing last lettersinjustice doing writtenwithout Ettore,to by who, Indeed aboutonly published ten were letters Syst Museum the of Physics Museum University 1 2

exceptions, exquisitely scientific in nature. They testify to uncle an and int nephew on the subject of research undertaken existence of new photoelectric andphenomena the effects by of photoresista Quirino, regarding when the latter are illuminated by a suitable light. The interes manner in which they are addressed 1987 and editions. following University scientific research in question, as well as the careful methodolog

and experimental for activity thirty over years. therein high. – is very 1. between Ettore and Quirinoof contains Majorana.one 1937, 16 The letter,November, dated rare testifyingmoments to a great over Ettore’s life and work. But not silence. On the contrary, from been all too many interpretations concerning his mysterious disappeara identified various parties. by be consideredtihis one of of thephysicistgreatest greatest,the not if importance to acquaint scholars, and all those interested, scientificwhich are of great human, value. and methodological with the cont 1.1 by Ettore to his uncle Quirino and 2 letters (and an excerpt of a let own hand to his nephew. To this add, we asmay they relate to the same addressed to Quirino Majorana by the mathematician Dario Graffi. I that nearly the entirety of this material is unpublished about on this occasion is part of a much vaster archive that the Ma acknowledge our thanks), above all through the initiative Quirino’s of Mrs. daughter, Sil has chosen to Museum donate to the University of Bologna (for E. Majoranaas a guide PoS(EMC2006)005

or ratheror

o the pure nisperna in tore’s most xchange xchange of 1938) Ettore - 1925 and 1940 Giorgio Dragoni . However, this 3 films films of varying ttore and Quirino ically rich image of image rich ically s.” his subject, already a university chair in devoting himself to icular, the increase in ibed, with a distinctiona withibed, tion of light – to which nstein (1905), and whose epared. Then follows the as actually known from a ctually exists a new effect fied, or believed to have s own to explain all the of the collection of letters ight, ight, especially if periodically tion – the sophisticated,refinedthe – tion

s theory do not always coincide be added to the classic one earlier

in those years (1933 -

Rome June 11,Rome 1936

3

hundredth of anniversary Ettore’s birth.

- members members of Fermi’s Group at the Institute of Physics in Via Pa -

based interpretation Millikan experimentally was verified by (1916). - The experimental research of Quirino Majorana on metallic of Quirino on metallic Majorana research The experimental Historical relevance of the correspondence and whose opinion is shared by many historians - n actual fact, Ettore was not only still interested in but physics, followed, he also But here is what Quirino has to say: «The experimental studies on t I These were experimental studies conducted by Quirino Majorana between These letters thus bring to light an unexpected but humanly and scientifand humanly unexpectedbut an light toThese letters bring thus Our presentation aims to pay reverent, respectful and due homage to E Moreover, the historical value of what is contained in this close e E&QM Correspondence, E.of to Letter Q. from 3

previously previously reported, have now continued, being limited to the descrobtainedareresultsThe now glass. deposited thickness,on or fixed case of gold made according to the method by which the films themselves were pr presentation of a theory of the thermal observed effect. It phenomena, is pointed considered out, finally, as that the being results of due thi t with the experimental ones. This confirms the hypothesis that there a was butwas an isolated and, as it were, generic allusion. guided – as will become apparent from the reading of these letters presentathis in offer we excerptsthe from andpress, incurrently and difficult experiences of his uncle. Majorana, on the one 2. photoresistance (circa) on phenomena of photoresistance in thin metal films and, in part electrical resistance that metal films undergo when exposed to l interrupted. In these experiments Quirino observed that the thermal ac these effects are traditionally ascribed characteristics – of the does effects not in suffice question. identified, Quirino a new effect on or effects of a Majoranaphotoelectric type – to it identi discovered by Hertz (1886), studied and theoretically interpreted by Ei quantum famous correspondence grows in importance when one intimate friends, co considers that, according to Et Majorana practically no longer concerned himself with physics. It w letter of 1936, again addressed to his physics: “I uncle have Quirino, been working that for some he time was on quantum still electrodynamic the only Italian physicist who, at least up to now, succeeded in obtaining theoretical virtue of his by physics clear fame! 1.2 Rome E. Majoranaas a guide PoS(EMC2006)005

gure: Giorgio Dragoni it, which is thus of radiation and the ir or in or hydrogen), ture and thickness of , in “Il Nuovo Cimento”, the more general and circuit employed, the ch, I have noticed that ce of the film, fixed as trate itself by chemical, ting ting substrate (glass, quartz, , “Rendiconti Accademia dei , “Rendiconti Accademia her or lower speed; using the film i audion i lamine metalliche ompanied ompanied by the thermal common effect

4

4

5

and the principal and most refined experimental device devised 6

803 -

Ulteriori ricerche sull’azioneUlteriori ricerche della luce su sottil Su di un fenomeno fotoelettrico constatabile con gl

806; 802 - 593; 573 - Quirino’s research (1928) 801 7

«In «In the lengthy experimental period I have dedicated to this resear The research in question, to which reference is made here by citing The drawings in Fig. 1, Fig. 2 and Fig. 3 respectively represent the Q. Majorana, Q. Majorana, Ibidem, 573 4 6 5

(1938) 573 2.1 almost conclusive paper written by Quirino in 1938, has a long story behind described the Author: by the observed effects depend on numerous circumstances. They are: the na the metal constituting the film; the method of fixing it on an insula ebonite, etc.), using an adhesive substance; or generating it on the subs thermal, mechanical or cathodic precipitation; exposing the other surfa just described, to water or a gas made to flow over it at a hig without any substrate (just supporting it at either (a in a gas end) immersed a vacuum; and, finally, changing the nature and intensity offrequency of interruption of the latter.» the source 15 of light on metal films; this effect is almost always acc concealed it.» and completely at remains by times the photoelettric cell (audion) Quirino Majoranaby in the course of his experiments is illustrated in the following fi E. Majoranaas a guide Lincei” Lincei” PoS(EMC2006)005

. - I solid parts y y arrives on a Giorgio Dragoni , which bears a , and a pointer V quartz lamp with se trials so as to S - scribed by Quirino ompensation ompensation of the

the compensator layout screw . Special protections, not is a subsidiary adjustable B L΄ the rotating disc from acting upon is equal to that of the

7 keyed to the rotating shaft of the disc, supported by a bracket

NN΄

may be identified by taking readings on the . The relative angular position between the two thepositionbetween relativeTheangular . through the indented edge of the rotating disc KK΄,

Fig. 3 Fig. indentations B C 5 cell C

-

with a diameter of 50 cm, whose periphery whose with is a diameter provided of 50 cm,

, 576 (which can be an incandescent or mercury , it is possible in any case to control the value and constancy L T lampL΄ elektron

of interruption of the light ray equal to 600 or 1200 periods per n are borne by an arm and L΄ bearing the metal film (gold in (gold bearing the theseto film metal preparedaccording experiments),

(having its centre on the disc shaft) and ring M is a potassium photoelectric cell in a vacuum; plate M Ulteriori ricerche… C

HG –

is rotating disc of D D lamp L

Fig. 3 represents, specifically, the main apparatus which is thus de Q. Majorana, 7 . The apparatus is connected with the other accessories indicated in . The cell C and lamp graduated sector published previously. It thus achieves the formation, amplification and pulsing current which characterises the effect in question.» c which can be shifted angularly around this by means of a micrometric pointer sliding over a graduated horizontal ring ring horizontalgraduated a pointer over sliding illustrated in the figure, prevent the air currents generated by M systems systems intensity incandescent lamp which illuminates D of this frequency. sliding over the graduated scale power adjustable to up to around 900 and 300 watts, plate glass common respectively), periodicall one of the methods mentioned. The rotation speed of the disc is set in the With this, the light from a lamp generate, usually, a frequency second. By means of a centrifugal force device with 48 radial indentations. The width of the Majorana. « E. Majoranaas a guide PoS(EMC2006)005

r/r

ast evidence y y graphs (see h as about 5°. h as about Giorgio Dragoni thermal thermal ones. For - l the size of the effect. effects identified, or icient to explain all of rmal rmal origin. At this point (after compensation) which said effect if anything, must,

find no explanation in pure given given of the theoretical study

ence of a photoelectric fact of 8 thephase shift φbetween the tween the experimental ones of onesexperimental the tween alue of this magnitude gives the magnituder/risequal,aswas

Fig. 4 Fig. 6

10

described apparatus makes it possible to determine «the value of -

9 Experimental results These results confirm the influence of the nature of the radiation on The fundamental point of all this work is thus to assess whether the The lengthy experimental ofwork Quirinobe condensedmay in two summar «The experimental curves diverge considerably from the theoretica The above

The existence of a possible photoelectric new effect type is or confirmed, at le «In the case of glued films, these latter facts can naturally Ibidem, 583 Ibidem, 577 Ibidem, 581 8 9 10

believed to have been identified, are, or are not, of a typically the small thicknesses and for each frequency they lieintermediatebe they frequency eachfor and thicknesses small For as largethe thicknesses muc two lamps. lie by they deviating decidedly above, Further considerations will be made after an illustration has been of the pure thermal hypothesis, which here as well does not appear suff of thethe facts modes observed.» (maximum change in the electrical resistance of the film) and Quirino, with by a certain 4), which areFig. thus of degree satisfaction:commented 2.2 thermal theory. They give, once again, clear evidence of the exist nature.» a new E. Majoranaas a guide seen, to the ratio between the peaks of the two circulate electricin the currentsphotoelectric cell and in the metal film. The v measure of the effect. And as saidI earlier, it is to be admitted that nature:be of a mixed and thermal photoelectric of nature.» a new thereof shortly thereafter is given, the article are we citing. pulsationofthelightandthatoftheelectricalresistance.The PoS(EMC2006)005

ssed by ssed by 11 odically, by

cur according Giorgio Dragoni

ofile of the metal such a prediction on thereof.» ms. ve ve characteristics of ion of light does not ill occur to the degree th fall on the film in a termining, termining, accordingly, ons that will enable him lm lm progressively rises, in film film in the unit of time is m m of identifying the exact no Majorana realises that, tion, the size of the effect the increase in electrical

e, as a consequence of external i.e. easily observable if the light is ffect in question. It may thus be period and decreases during the -

ω.Thisresultmaybeachievedwithsufficient

7 which is transferred to the film in each unit of time w

of film per second. contrast,by If, said rays are delivered peri

3

The theory of the phenomena studied of phenomena The theory the Theoretical development Under the action of this thermal energy, the temperature of the fi where = W/2.A This relationship establishes the pulsation posse of energy thermal Here’s how Quirino Majorana presents the mathematical calculati Quirino intends to study «metallic photoresistance», His research has led him to the conclusion that: «the thermal act «Let «Let us now suppose, first of all, that light rays of any waveleng A A very reasonable hypothesis is advanced concerning the interpretati With said contrivance, the energy

Ibidem, 584 calories per cm 11

W

relation to the ambient temperature, until reaching a steady stat heat dissipation. It may thus be said that the energy absorbed by the expressed by: the film. Therefore, such energy increases during one half Quirino develops a detailed mathematical argumentation with the ai order of magnitude of the thermal effect in his experiments and of whether the origin of the recognised effects is otherde than thermal. 3. to determine the entity of the effect due to variations thermal in the fil metal resistance that a metal film undergoes when exposed to light. Quiri using the devices described earlier, such an effect will be more periodically interrupted. suffice on its own to explain all of the characteristics of the e interesting to establish, based on the classic theory of heat propaga predictable by such means, in order to see, thedeviates actually from shall facts. observed thus I proceed to an illustrati afterwards, whether and how E. Majoranaas a guide 3.1 studied.the phenomenon continuous manner. They will be partially absorbed. Let us thatsay this w of means ofmeans a disc with radial indentations, that can we admit the interruption will oc frequency angular toan a sinusoidalwith and law approximation by suitably configuring the indentations in the disc and the pr film. variablewill rather become than constant and can be indicated with the expression: PoS(EMC2006)005

δ, e

: , it is = t E may be ; x 2

s periodic h N, N, P, Q. Let it Giorgio Dragoni gated gated inside the , the analogous lass surface are e and sin ω around a certain

t ows that:ows m : φ.Forthepurposes cos ω is used to increase the ect contact with the film, ipation to the outside occur

:

andφ.

m

, moreover, be the thermal conductivity of the

k 8 ρε,thethermalcapacityofthefilmpercm ΄beingknown,thetemperatureatadept . Let c 0 3 T ΄,whichwillbequitedifferentduetothepoorthermal 0 = C

the specific heat of the metal and δ, c known procedure and isknown expressed by: -

being unknown constants. unknown being N ,

The variable be indicated part of the temperature as film may It is now a question of finding four equations enabling us to determine M, From this, given (2) and (3), and equating the coefficients of Since the phases of the thermal pulsations of the metal and of the g of amplitude the pulsation thermal by of the is film the given maximum M To obtain the other two, we must examine the way in which heat is propa The anterior surface of the glass, which is in more or less perf constants. two other being Q unknown P, Generally speaking: In In such conditions, the film temperature pulses with an amplitude T Now let ρ be the density, possible to deduce two of the four equations sought being glass. magnitudes magnitudes for the glass. Let us say the thermal capacity of the glass per cm different,thephaselagφwearelookingforcorrespondsto: be observed, first of all, that part temperature of thereof and part is transferred toward the air foll and the It glass. the heat absorbed by the film of a wellobtained means by other; this is so since the absorption and of said energy and its diss continuously in aperiodic andwith phases. opposing mode than higher temperature, the somewhat external temperature. ambient The phase of thi is in delayed, relationphenomenon to that of the light pulsation, an angle by of this discussion, it is of interest T to determine only glass. The latter’s surface temperature E. Majoranaas a guide likewise has a variable temperature, T ofconductivity the adhesive and the considerable propagation of heat in We glass. can say PoS(EMC2006)005

. Then to a graphic Q , P Giorgio Dragoni icationsbe will , ing ing as usual the N ,

M

12

» ne

is more interesting and e must now be equated with

φ,which,asmaybeseentherefrom,

9

and assuming: t

andsinω t 587 -

cosω

andφ,itwillsufficetouse(5)and(4). Experimental theoretical and comparison where: T

Thus concludes the main part of the mathematical discussion. Some simplif discussion.Some mathematical theThus ofpart concludes the main By By replacing the values with those expressed in (2), (3) and (7), equat obtainwe the other two equations sought: «To clarify the meaning of the previous formulas, one may construct In his 1938 article MajoranaIn Cimento” for “Nuovo continues: The quantity of heat transmitted by the film to the glass surfac The four equations (I), (II), (III), (IV) must enable us to determi The written equations are thus satisfied the following expressions: by Ibidem, 584 12

3.2 coefficients of illustrated below. representation, varying some of the parameters contained therein. simpler It to do this for (9); this formula gives the value of E. Majoranaas a guide that which penetrates this from surface toward the inside. follows that:It obtain PoS(EMC2006)005

- x are inear

deoflarge absorbed by A Giorgio Dragoni for the special k his we may derive value of h. This is from from current manuals. s fixed on glass. The el to the abscissas ( y y of heat nesses of gold film: 0.08 mmersed mmersed in air) posed a be so even for a l mentally, as was said, no vary between the extendedthe between vary presented on a linear scale, determined

tedearlier:ρ=19.2;δ=2.51;

Thus the graphs of figure 5 are constructed,are 5 Thus figure the of graphs

Fig. 5 Fig. 10 of film, per second, and per degree of thermal difference = 0.00018. Among these, the latter two (internal heat 2 h on the values of η expressed on a logarithmic scale, to better = 0.0017; k

p. calorie per cm = 0.21; ofordinate90°,forηtendingtozero(orinfiniteinsulation).Onthesi , being very small, has little importance and I drew its value

e h The curves are based

I I refer to the experimental case described previously: gold film = 0.030; coordinates) values of η they are still asymptotic (and they would always highlight highlight what occurs for small values; and on the arc degrees fromre 0° to 90°. They show asymptotic, a due minimum, which, to for the 0.08 logarithmic films, representation, is to around 10°. a They curve parall and as is largely confirmed by experience, is independent of the quantit the and thus film, also of the intensity of the that rays fall it. upon followingvaluesmaybechosenforthevariousparametersindica c greater degree of uncertainty. Therefore, using the direct method, I glass used; Two frequencies of light ray interruption were chosen: 600 and 1200; from t the two values of ω. In (9), φ and η thus remain variable. Experi limits: 50 and 0.005 point by point, for the aforesaid frequencies and for two different thick and 0.7 microns. In calculating the points of these curves, we ignored the perfectly within legitimate the limits of graphic approximation. conductivity conductivity of the glass, and external heat conductivity of the gold i between metal and the anterior surface of the glass. E. Majoranaas a guide predictioncanbemadeastothevalueofη.Iassumeherethatitmay PoS(EMC2006)005

he

Giorgio Dragoni ngtheformula ons of the film are compared with the mple mple space has been he years documented by fied,somuchsothatt elevant to point out this orana. In considerationorana. In of

gherthanthatvalue,forη

y – as may be inferred the from y – as may

14, 1935). Please, note equivalence the

11

between this writing and one the above printed. writing this between

13

589 - and because of the light it sheds on Ettore’s character. becomes becomes completely negligible. In such a case, the thermal pulsati - Ettore Majorana’s letter addressed to Quirino (May – h It may perhaps surprise some that in this brief presentation such a Assumingpermanentlyη=∞,theformulas(8)and(9)aresimpli

Two curves corresponding to the theoretical computation of φ,madeusi Ibidem, 587 13 Fig. 6Fig. value value of channelled into exclusively almost the Saidglass. become: formulas dedicated to this theory. The reason lies in the fact that the theor correspondence we are referring to – was written in full Ettore by Maj the exiguous quantity of published writings by Ettore, it is hardly irr aspect. Both for general reasons – his profound interest in physics in t the letters representationofη)toanordinateproximateto45°,butslightlyhi totending infinity (perfect as conductivity, for cathodic films). (11), have already been plotted in figure 4 of the paragraph above, and thus experimental results.» E. Majoranaas a guide PoS(EMC2006)005

his of his vis - - entarily à - act to be alculation if vis Azione della luce uly uly 17, 1932). Giorgio Dragoni to confirm or ch. “Dear uncle, ry ry often consider measures measures through difference; that is, more more authoritative se with the passing ts already obtained uirino February 20, scientists and their to its consequences” ys”(to Quirino April part of the energy is sicist, who develops you ascribe me credit mi mi suggests two more by by whoever you judge itude and phase can be weekend.” (to Quirino 14 ght: ght: “Intensity measures y y also warrants careful en the two demonstrates a the correspondence instead y the frequency.” (toy Quirino self important and significant. ion of Ettore in his uncle’s sor, perhaps in part disinterested, t Ettore acted as exclusively a almost albeit an affectionate, attentive one -

12 rca Scientifica”, National Council, Scientifica”, rca Research

(1935) 1 ,

(to Quirino 7, 1936). September

Experimantal suggestions The role of Ettore of Ettore The role

Scholars who have already had an opportunity to see these letters ve Besides what was already known, namely that Ettore helped his uncle The reference is probably Rice related to reference “La The known known uncle Quirino is in fact surprising, given the considerable age - 14 between between Quirino Majorana and Enrico Fermi. Quirino appeared in f

-

ould facilitate the interpretation. Perhaps the easier is to var mean to Quirino May 9, 1935). And furthermore: “As regards the experiments mom interrupted, my impression continues to be that discussing the cannot lead to any only conclusion.” and: “It is resul not indispensable that on p.8 for an elementary calculation that you can do and redo or have checked May May 4, 1935). Or when he raises doubts: “The fact you referred to, that absorbed directly by the glass examination, but I lack too many data rather to be able to express an than opinion as by the ( films, certainl 4.1 anxious to know what opinion the young, brilliant Fermi held about his resear only tonight I have been able to see Fermi, who had been off for some da 17, 1931). And again, more than a year after: comments (on “If the you subject), wold I will like ask Fermi, to whom I have hope to see next July 12, 1932). And the week after: “Beside the thermal hypothesis Fer ones, whose worth can be judged only by the experimentalist…” (to Quirino Then J the role of Ettore becomes calculations and defined works out formulas as for his uncle: that “However, the ampl of a theoreticalobtained almost simultaneously with both methods, and would I have used the old c phy it” had saved I Ettore’s role to have been limited to this behaviour, already in it That is, he is seen basically as a simple and occasional supervi of his uncle’s experimental research. A more complete analysis of reveals an active, interested, increasingly research. “You don’t involved describe me the participat device that you have used…” (to Q 1935). Or, like when, as an example, he suggests new types variation of of the luminous obtainable intensity or the frequency of the employed li c well Ettore acted as a guide, a referee, a scientific judge uncle’s This work. initial increasingly definite impression becomes and preci of time and thus the pages respective roles are better defined and clarified. of At the star the letters exchanged between go the two su sottili lamine metalliche 4. formulate some calculations, in actual fact the correspondence betwe much more profound and complex form of collaboration. The young Ettore’s role E. Majoranaas a guide PoS(EMC2006)005

of the essively essively Or Or when he

being two ethodological Giorgio Dragoni it would not be believed in his their exchange, l astuteness that yet again: “The s which in other fter the considerable l effect;”lQuirino (to It It is possible that the ome ome such objections it 19, 1936). ious ones to be sure, on ust 11, 1935). Or: “The inly inly will not be difficult heir interpretation, since l results. “But as it is now now is it as results.l“But uled out, it does not seem them when it is not only ith the varying of certain you you will want to do upon ul criticism of his uncle’s king, king, help may come from ter of immediate, tangible pts, has already reached the auses which is its intent. But earch: “I have nothing else nothing have toearch: “I exity of the facts observed, to earch. I do not think you will h theoretical assumptions. For cannot be denied by theories and r time, as when he presses his uncle

(to Quirino September 17, 1936). In reality,

Or Or else, as he seeks to placate and mitigate the

13

Methodological indications Another general function systematically performed by Ettore throughout

besides the one illustrated above, was to exert a cautious, enthusiasms. Like respectf when he expressly invites him to suspend judgment: “ observed phase lags indicate the existence of a new phenomenon, but perhaps therma simple superfluousa toitsbeing exerciseout caution ruling in some May 4, 1935) or when he encourages him, implying that his uncle has adopted m caution by his own initiative: “There is not much to say concerning t you deliberately refrain from advancing hypotheses” (to Quirino August pays deference to the typical role, experimental, of his uncle in res add as a “theoretician”, other than the hope that where theory is lac experience” (to Quirino February 20, 1935). experimental convictions, with a display of diplomacy and of methodologica still has resonance today: inverisimilitudes in conflict, one “I should definitively side with one do of not easy, but well extremely easy, to solve understand the dilemma with further why, res wish however, simply to reply to me there that a definitely ascertained fact above all by theoretical assumptions. It evidence but is rather of facts not, recognised with the aid in of hypotheses, obv reality, a mat the experimental conditions, but subjective to judgment, attribute greater which verisimilitude than to we suc may these not, reasons without it making appears to an be exc good method to examine other possibilitie Ettore’s role in the research increases systematically ove 4.2 annoyance expressed in the reply of his uncle, who felt he was not being best if you do not wish to take responsibility for it.” (to Quirino curves Aug you sent me do not actually correspond to the formula. It certa for you to discover the source of the error”(to Quirino January 23, 1937). Or possibility of an immediate comparison of the two curves being thus r that any definitive conclusions can yet be drawn” specificexperimenta more furtheraboutand requests,asking new with too late to take advantage, I must confine myself, given the compl questions.” more suppositions rather some venturing all….some you vague and above to asking (to Quirino July 25, 1935), or: “Naturally, in order to definitively overc would suffice to demonstrate the stability of the results obtained experimental w conditions” (to Quirino August 29, problem: “The main question is whether the technique of 1936). the experiment, a And, addressing the heart and effective improvements you have made since the first attem necessary perfection, such as to achieve the rigorous isolation of c perhaps there is no call to think so far in advance about everything returnyour (to to Bologna” 2, 1935). Quirino August E. Majoranaas a guide PoS(EMC2006)005

ourses in experiments. ities and the at the present Giorgio Dragoni etter regarding and other papers oblems oblems and if you uggests uggests techniques reassures him about fic competences and s occasion where we as he mentions the takes upon himself is y y are likely to be of rned, and for the news well, after all, that no causes that may perturb he method employed in ing ing in physics (Ettore’s agnitude, narrowing the n theory andn theory experiment: objections I have been d may fall in the face of ticise. But it was my duty ticise. duty But it my was der to depurate the main ly ly further tests (with an implicit) hypotheses made ves ves – Ettore stands out not shall mention two: …” (to I I have made a point of not practical purposes of life, no ts.” (to Quirino February 20, aim Ettore availed certainly est shadow of misunderstanding. improbable. I thus do not find the

a priori

14 quoted passage Ettore Majorana demonstrates a -

exists (indeed he says: “with an approximate value of ‘experimentum

Concluding remarks Concluding remarks In the case we have analysed – unlike those concerning other areas

nephew Fabionephew Majorana do quite on this agree and I point). 5. published by Ettore Majorana and investigated by other colleagues, on thi have reflected upon this extraordinary figure from various perspecti circumstances would be rightfully ignored because accusation of a lack of serenity to be justified;attributing on excessive, the and contrary certainly not decisive, obliged to importance raise. Naturally, if you allude to this aboutspeaking the to the one can expect you to continue experiments that may constantly pose new pr choose to leave this task to others shallI certainly not be the one to cri to point out to you precisely what, in my modest opinion, are the open problems time. I would be truly grieved if there remained even the slight Affectionately yours, Ettore” (to Quirino September 5, 1935). Or when he the importance of his lengthy and engineer Baldini, which arduous we immediately delivered research: to the “Thank person conce you for you give me about the the new phenomena l you have observed in the course of your Whatever may be their explanation, considerable given applicative their interest.” (to impressiveness, Quirino the March 9, possibility 1935). of Or else conducting further, decisive approximate value of ‘experimentum crucis’) verifications: are always possible. I “Natural Quirino May 16, 1935). methodological In foresight that the frankly surprises above us. experimentum He crucis knows very crucis’…”) but he leaves his uncle room for hope, emphasising his speci role as an experimenter, fundamental in the eternal comparison betwee “Therefore, the theoretical assumption against the result you obtaine experiments that quantitativelygive definite and reproducible resul 1935). To summarize, Ettore takes upon himself the task to single out the phenomenon, secondary effects, sources of parameters error, involved, the determination main physical of quant their respective research orders field of to better m isolate the phenomenon capable at of hand minimizing ... certain But effects he and also maximizing others, s in phenomenon of or all possible perturbing causes. A further task that Ettore that of checking – logically and methodologically – the explicit (or by his uncle while comparing the general physical collecting principles with and representing t graphically his data. To achieve this himself of and knowledges competences he had acquired following undergraduate c by engineering to near fulfillment of a bachelor degree before graduat E. Majoranaas a guide PoS(EMC2006)005

ds to isolate ade, and to t of a further Giorgio Dragoni With regards to the readers? Do attention to the

ps warranted. He the experimental it would not be to meet him next formulation of the ector connected to ’s name disappears beneath his dignity abilities: “I wanted he simplicity of the n turned to you for we we witness Ettore’s ty ty for it.” (to Quirino case, do you do it for ore refuses to accept e citations”(toe Quirino the Institute any more hy hy and truly surprising author – something that n do and redo or have e in this connection. On - iveness and brilliance of We witness a progressive

estly, to underscore their the correspondence we may his case, do you believe that ponding ponding with his uncle and in “It “It is not indispensable that on ating to Ettore’s behaviour as a

15 )” (to Ettore August 22, 1936). He fails to realise, reproachable 33 he repeatedly mentions Fermi’s name, almost as if to provide an -

Still later Ettore refuses to take credit, unless as co

Human aspects ith regard to the first aspect, as we read through the letters W However, However, rather than dwelling upon this point, we wish to draw readers’

so much for the extraordinary quality of his calculations or the invent his predictions and theoretical formulations, but rather for the notewort ability he showed in the procedures supervision carried and out methodological by verification his uncle. of Indubitably, photoelectric has been extended, phenomena broadened and considerably developed since those years the s importance of the aspects of general historiographic interest rel human being, to this through considerations be documented correspondence. that of may method the small historiographic discoveries that have been m 5.1 progressive withdrawal into himself. At the time he began corres the first letters dated 1931 friendship, familiar acquaintance and the esteem weekend…” (to Quirino heJuly 12, 1932). After enjoyed these initial mentions, Fermi “…I have for good from his dialogue with his uncle. From the end himself of from 1933, Ettore the procee Group of Via Panisperna; he “…send the letters to at me almost (tohome…” Quirino September 6, 1933). never goes to estrangement of Ettore from his friends. As we read further into perceive another worrying sign – knowing how things later credit went for a – calculation his Ett uncle would like to attribute to him p.8 you ascribe me credit for an checked elementary by whoever you judge best if you do not calculationwish to take responsibili that you ca August 11, 1935). absolute guarantee of scientificity and, at the same time, manif E. Majoranaas a guide would have been only right given his contribution to those studies – for the giv “There’storeason investigated. no phenomenon the of theory thermal August 23, 1936). His uncle is worried, but not as much as the situation perha thinks such behaviour is due to reasons of modesty on Ettore’s calculations part, performed by his or nephew, to t whom he attributes extraordinary to ask you something else. In the collaboration. Already last course year, you did not of want me to cite this your nam work of mine, the I other ofte hand, I think that inappropriate in to mention a some of the complete developments that account you favoured to of me. the this point, observed I ask you: Do facts you think this would be considered inappropriate by you insist in denying me the pleasure to mention your name? And, in this modesty or because these matters are too simple for you? But, in t your uncle could wrap himself in your doctrine without doing something (subsequently corrected in maybe maybe because he loves his nephew too much, that Ettore is in the mids PoS(EMC2006)005

surgical mmittee for for mmittee

Giorgio Dragoni didn’t easy look nce Ettore leaves links with the rest. cant finding of our e to be the lines you which in actualfactin which given on the occasionthe on given to him and society in d. In any case, if you ified by the following tural gifts that we may n words suitable to the much much too long trip from an entire chapter within Rome Rome within a week, and a fication of an entire lecture

n and formulated by Ettore: the

16 rer for theoretical physics and secretary of theof Co and theoreticalfor rer physics secretary

had informed me about the congress on Galvani. I would like to 15

Historiografical results

As As regards the second aspect, we notemay that through this corresponde

lectu Noce, Dalla at thatGiulio Cesare time 15

the Galvanian celebrationsthe Galvanian involutional process, becoming estranged even from the persons closest will lead which, as know, to we estrangement general. his An decision to disappear. 5.2

E. Majoranaas a guide participate, but shall very likely be obliged to renounce to avoid a us, as in all the other fields he concerned include himself among the with, results precious of cul our research. We were able to Quirino’sidentify article of 1938 which was in reality completely writte thermal theory of the phenomena investigated by Quirino. Another signifi research – one we have yet not talked about – relates to the identi traditionally attributedbut tosignature, Quirino,his and objectivelybearing written Ettore: completely was by Galvani, Quirino’s Luigi conferenceon of the second centenary (1937) of the quotation: birth “Dalla of Noce Galvani. As it is test Sicily. have animprovised I opening speech according to to m what seemed had in You mind. will probably think that to kept generalities,tooI much but it to me to tell much more without exceeding the limits you don’t had like indicateit, send it back to me with your comments. I shall be in few days later, I guess, in Sicily. occasion, are not an example Theof eloquence, but added I them for the possible opening and closing parts, i (to Quirino September 1, 1937). Evidently operation Quirino, a little before, time for had asked the aid of the nephew. that had been submitted to a PoS(EMC2006)005

. Giorgio Dragoni and theoretical Italy’s Italy’s monarchs in

historical and epistemological o the galvanian celebrations Bolognao in galvanian the (1937). E. Schrödinger (Nobel Prize), Q. Majorana. resent: L. deL. resent: Broglie, E. D. Adrian, K.M.G.

obel Prize), W. Heisenberg (Nobel Prize), Niels ome other ome participants obtained Nobelthe Awards ce of A. Einstein, perhaps ceEinstein, of A. due to political reasons

17 (Courtesy by “Sapere”, by October(Courtesy 31, 1937, p. 266)

Scientists and Nobel Scientists Prize Winners participating t –

A A conference of extraordinary importance because it was held before Attending the conferences other conferences the Nobel Attending Prizes p were Bohr (Nobel Prize), O.W. Richardson (Nobel Prize), From the left: A. Turpain, (NA. left: the Cotton, From A. C.V. Raman in the following decades. Full of meaning the absenthe decades. of meaning Full following the in Siegbahn, P.J.W.Siegbahn, F.W.Debye, and W.R. Aston Hess. S Fig. 7Fig. 1937 and above all because physicists it of that time. It was was a text abounding in notes attended of great by the value. leading experimental E. Majoranaas a guide PoS(EMC2006)005

ost - . A lot 16

heir awareness Giorgio Dragoni But, alas, despite experimental ability ability experimental - 17 ific traditions of the deceptive). Galvani inherent in our very - , which Ettore shows to Ettore shows which , rd the role exercised in ind.” is wanted to be seen and ing ing reality in an adequate not make one immune to eived eived also ‘Sapere’ oo, saw what wished to see r 31, 1937, p. 265) cked in making experiments and in making cked ailure to recognise this principle

ensitivity, based on their effective ty ty shown by Ettore Majorana (and modern “Occam’s Razor”. Almost such Almost “Occam’s modern Razor”. l experiments on frogs with mono and bi mono with on frogs l experiments

nnasio Palace lectured.nnasio Galvani Bologna, in where expression, in front of the expression,didacticof front the in (when thought is influenced by desire and hence 18

, ed. G. Barbensi, UTET ,Torino ed.Barbensi, 1967, G. UTET 262

Opere Scelte Opere Principle of Wishful Thinking shown by Q. Majorana.by “Sapere”, by Octobe (Courtesy shown Quirino Majorana’s historica replicas of Galvani’s – Ettore Majorana will comment therefore the event: “I have rec (October “Sapere” 31, 1937) Galvani, L. 16 17 Fig. 8Fig. metallic arcs in the anatomical Theater arcs anatomical the in of metallic Archigi Please note Niels Bohr’s interested and astonished E. Majoranaas a guide his wariness, he was unable to avoid its inexorable effects and he, t thisand casediscover. In as well, Ettore aligned himself with the best scient past. Both Galileo and Newton had been process perfectly of thinking and which lead us, aware almost inevitably, “to see what of the traps importance principletantamount epistemologicalof an is It found”. be to be well aware of, practically elevating it to the role of a as to be applicable to scientists in general and their cultural s comprehension and adhesion to this subtle principle, and hence on the basis of t with respect to the validity and applicability of this principle. F strongly limits, though it does not exclude, the possibility of interpret fashion. Naturally, even being aware of it is no guarantee, it does admired, admired, and from many, your speech.” (to Quirino November relevant aspects 16, in 1937). this regard Among is the the extraordinary m sensitivi which may have stemmed from his reading of Galvani’s work) science towa by the inevitably lacks objectiveness and himself had been perfectly cognizant of this: “it individualis to beeasy tri judgment becomes self to believe to have seen and to have found what we wish to see and to f PoS(EMC2006)005

most most e of Physics reality, in our greatest Italian Giorgio Dragoni have been able than those of his istant of Fermi, who who istantFermi, of what no other in the d, by now it is passed ana, with his genius, if genius, hiswith ana, s the body ofs Majorana the body mi mi some months after personage with whom to prof. Silvio Bergia,

and here I have clear the in the history of science e, inyou know, the world

reach discoveries of great o to prof. Carlo Bernardini then there are the geniuses, o find in the other men, the 115 - , Galileo, Galvani, Righi and many nd third rank, who make their best

, Bibliopolis, Napoli 1987, 134 19

, F.lli Fabbri editori, Milano 1974, 114

18 Dossier MajoranaDossier Lezioni all’Università di Napoli

19 A conclusiveA remark

We would like to conclude our considerations with two quotations we judge to be the be toWejudge to would like conclude quotationsconsiderations we our two with The first quotation is due to Giuseppe Cocconi, at the time a young ass young a time theat Cocconi, Giuseppe tofirstThe quotationdue is The second is due to Antonio Carrelli, the director of Naples Institut They seem so remote from each other in both meaning and motivation. In Castellani, L. E. Majorana, 19 18

falling prey to wishful thinking. Just as the cases of Aristotle others teach us. 5.3 E. Majoranaas a guide adequate and pertinent with respect to the figure of Ettore Majorana and his disappearance. They are both from Enrico Fermi, the Ettore greatest consciously exchanged views, deciding, perhaps, to follow other paths friend and mentor. remembers the opinion of his master about Ettore Majorana: ``Becaus there are several categories of scientists; people of second a but do not go very far ahead. There are also people of first rank, who level, of fundamental importance for the development of the science ( impression that in this category he wanted to include himself). But like Galileo and Newton. Well, Ettore was one of those. Majorana world owns; had unfortunately he lacked the thing that is instead easy t sense”. good simple wherewith Ettore collaborated at that time, Ettore’s disappearance, asked who, the following question: speaking “Yes, he’d be with dea Fer time some has already gone since we last heard i about come him…How thatMajor think you not“But answered found?”. Carrelli Fermi thisway: he had the problem to disappear and to hismake corpse to disappear, would not to resolve it?” opinion, these quotes both express the same admiring wonder of another of the physicists of that Enrico time: Fermi. Acknowledgements I would like to express my best thanks for Magda Giorgi, their Martina Lodi and Luca Verzelloni. help Special thanks als and suggestions actual Director of “Sapere”. PoS(EMC2006)005

Giorgio Dragoni , in “Il Nuovo ,“Il in , “Rendiconti Accademia Accademia , “Rendiconti

, “Sapere”, October 31, 1937,

i i audion

oderna

i i lamine metalliche “La Ricerca National Scientifica”, “La

, Bibliopolis, Napoli 1987 20 , F.lli Fabbri editori, Milano 1974

, Arnoldo Mondatori, 1987Milan

593 806 - - , ed. G. Barbensi, UTET Torino 1967 (1935) 1

Dossier Dossier Majorana Su di un fenomeno fotoelettrico constatabile con gl Agli albori dell’eletricità. Galvani e la scienza m Azione della luce su sottili lamine metalliche, Ulteriori ricerche sull’azione della luce su sottil Lezioni all’Università di Napoli (1938) 573 (1928) 801 Opere Scelte 7 Il Caso Majorana 15

265 - Q. Majorana, dei Lincei” dei Lincei” Cimento”, Q. Majorana, Q. Majorana, Research Council, 261 Q. Majorana, E. Majorana, L. Galvani, Galvani, L. L. Castellani, Castellani, L. E. Recami,

[1] [3] [2] [4] [5] [6] [7] [8] References E. Majoranaas a guide