In 1924, Walther Bothe and Hans Geiger applied a coincidence method to the study of Compton scattering with Geiger needle counters. Their experiment confirmed the existence of radiation quanta and established the validity of conservation principles in elementary processes. At the end of the 1920s, Bothe and Werner Kolhörster coupled the coincidence technique with the new Geiger–Müller counter to study cosmic rays, marking the start of cosmic-ray research as a branch of physics. The coincidence method was further refined by Bruno Rossi, who developed a vacuum-tube device capable of registering the simultaneous occurrence of electrical pulses from any number of counters with a tenfold improvement in time resolution. The electronic coincidence circuit bearing Rossi’s name was instrumental in his research on the corpuscular nature and the properties of cosmic radiation during the early 1930s, a period characterized by a lively debate between Millikan and followers of the corpuscular interpretation. The Rossi coincidence circuit was also at the core of the counter-controlled cloud chamber developed by Patrick Blackett and Giuseppe Occhialini, and became one of the important ingredients of particle and nuclear physics. During the late 1930s and 1940s, coincidences, anti-coincidences and delayed coincidences played a crucial role in a series of experiments on the decay of the muon, which inaugurated the current era of particle physics.
REFERENCES
1.
W.
Bothe
and H.
Geiger
, “Ein Weg zur experimentellen Nachprüfung der Theorie von Bohr, Kramers und Slater,”
Z. Phys.
26
, 44
(1924
).2.
R. Millikan, “Einstein’s Photoelectric Equation and Contact Electromotive Force,” Phys. Rev. 7, 18–32 (1916).10.1103/PhysRev.7.18 For a fascinating history of the development of physics in the 20th century see Abraham Pais,
Inward Bound of Matter and Forces in the Physical World
(Clarendon
, Oxford
, 1986
).3.
For a comprehensive study on the Compton effect, see
R. H.
Stuewer
, The Compton Effect: Turning Point in Physics
(Science History Publications
, New York
, 1975
).4.
N.
Bohr
, “The structure of the atom
,” Nobel Lecture, 11 December 1922
, <nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-lecture.pdf>, p. 14
.5.
C. T. R.
Wilson
, “Investigation on X-rays and β-rays by the cloud method. Part I: X-rays,”
C. T. R.
Wilson
, Proc. R. Soc. London, Ser. A
104
, 1
–24
(1923
); “C. T. R.
Wilson
, Investigation on X-Rays and β-Rays by the cloud method. Part II: β-rays
,” ibid.
104
, 192
–212
(1923
).6.
Quoted in Wilson’s biography, <nobelprize.org/nobel_prizes/physics/laureates/1927/wilson.html?print=1>.
7.
Reference 5, Part I, p. 2; Compton is quoted on p. 15.
8.
For an in-depth discussion on Bothe’s contributions on these topics, see
D.
Fick
and H.
Kant
, “Walther Bothe’s contributions to the understanding of the wave-particle duality of light,”
Stud. Hist. Philos. Mod. Phys.
40
, 395
–405
(2009
).9.
N.
Bohr
, H.
Kramers
, and J. C.
Slater
, “Über die Quantentheorie der Strahlung
,” Z. Phys.
24
, 69
–87
(1924
).10.
W.
Bothe
, “The coincidence method
,” Nobel Lecture
, December 1954
, <nobelprize.org/nobel_prizes/physics/laureates/1954/bothe-lecture.html>.11.
Counting methods date from the discovery by Julius Elster and Hans Geitel in
1903
[
J.
Elster
and H.
Geitel
, “Über die durch radioaktive Emanation erregte szintillierende Phosphoreszenz der Sidot-Blende
,” Phys. Unserer Zeit
4
, 439
–440
(1903
)] simultaneously with William Crookes[
W.
Crookes
, “Certain properties of the emanations of radium
,” Chem. News
87
, 241
–241
(1903
)] that when α-particles strike a zinc compound (ZnS) flashes of light are produced. This effect provided a simple optical means for detecting and counting α-particles and was used by Geiger and Ernest Marsden to measure the large angle scattering of α-particles in matter[
H.
Geiger
and E.
Marsden
, “On a diffuse reflection of the α-particles
,” Proc. R. Soc. London, Ser.
A 82
, 495
–500
(1909
)]. The latter experiment later led to the Rutherford-Bohr model of the atom[
E.
Rutherford
, “The scattering ofα andβ particles by matter and the structure of the atom
,” Philos. Mag.
21
, 669
–698
(1911
);N.
Bohr
, “On the constitution of atoms and molecules, Part I
,” Philos. Mag.
26
, 1
–24
(1913
);N.
Bohr
, Part II. Systems containing only a single nucleus
, ibid.
, 476
–502
;Part III. Systems containing several nuclei
, ibid
., 857
–875
]. Being well aware of the limitations of the scintillation method, Geiger and Rutherford developed in 1908 an electrical counting method where the ionization pulse produced by a single α-particle in a gaseous medium could be recorded due to the amplification effect induced by an electric field[
E.
Rutherford
and H.
Geiger
, “An electrical method of counting the number of α-particles from radio-active substances
,” Proc. R. Soc. London, Ser.
A 81
, 141
–161
(1908
)]. Geiger and Rutherford used the electric method to study the chemical nature of α-particles [
E.
Rutherford
and H.
Geiger
, “The charge and nature of the α-particle
,” Proc. R. Soc. London, Ser.
A 81
, 162
–173
(1908
)]. Once back in Germany Geiger developed the needle counter (Spitzenzähler) which responded as well to β-particles, and therefore also to radiation quanta of sufficiently high energy capable of releasing electrons within the counter [
H.
Geiger
, “Über eine einfache Methode zur Zählung von α und β-Strahlen
,” Verh. Dtsch. Phys. Ges.
15
, 534
–539
(1913
)].12.
Bothe recalled that “Film consumption however was so enormous that our laboratory with the film strips strung up for drying sometimes resembled an industrial laundry.”10
13.
Well aware that some coincidences could result from uncorrelated signals (chance coincidences), Bothe and Geiger also devised a simple method to evaluate their number. The evaluation was based on the number of events in which the two signals were at a time distance larger than 1 ms, for example, between 5 and 6 ms.
14.
Experimentelles zur Theorie von Bohr, Kramers und Slater
,” Die Naturwiss.
13
, 440
–441
(1925
);“
Über das Wesen des Comptoneffekts; ein experimenteller Beitrag zur Theorie der Strahlung
,” Z. Phys.
32
, 639
–663
(1925
), quotation on p. 663.15.
A. H.
Compton
and A. W.
Simon
, “Measurements ofβ-rays associated with scattered X-rays
,” Phys. Rev.
25
, 306
–313
(1925
);A. H.
Compton
and A. W.
Simon
, “Directed quanta of scattered X-Rays
,” ibid
. 26
, 289
–299
(1925
).16.
The name “photons” for light quanta was coined by Gilbert Lewis only in the 18 December 1926 issue of Nature:
G. N.
Lewis
, “The conservation of photons
,” Nature (London)
118
(2981
), 874
–875
(1926
).17.
W.
Bothe
, “Über die Kopplung zwischen elementaren Strahlungsvorgängen
,” Z. Phys.
37
, 547
–567
(1926
).18.
C.
Davisson
and L. H.
Germer
, “The Scattering of electrons by a single crystal of nickel,”
Nature (London)
119
(2998
), 558
–560
(1927
).19.
The Nobel Prize in Physics 1927 was divided equally between
A. H.
Compton
and C. T. R.
Wilson
, <nobelprize.org/nobel_prizes/physics/laureates/1927/>.20.
The Nobel Prize in Physics, 10 December
1927
,K. M. G.
Siegbahn
, Presentation speech, <nobelprize.org/nobel_prizes/physics/laureates/1927/press.html>.21.
V.
Hess
, “Durchdringende Strahlung bei sieben Freiballonfahrten
,” Phys. Z.
13
, 1084
–1091
(1912
), p. 1090. On 7 August 1912, Hess’ free balloon reached an altitude of 5300 m with Hess and three Wulf electrometers on board to measure the rate of ion production inside a hermetically sealed container. The Wulf bifilar electrometer had been specifically constructed by the Jesuit priest, father Theodor Wulf of Aachen to answer the question of how the intensity of the recognized strongly penetrating radiation changes as a function of altitude. This early version of the bifilar electrometer was later improved by Wulf and by Hess, and especially by Werner Kolhörster. It was easily transportable and could be sealed to be air-tight and withstand high and low pressures. It was thus very suitable for measurements aboard balloons and aircraft.22.
D.
Pacini
, “La radiazione penetrante alla superficie ed in seno alle acque
,” Nuovo Cimento
3
, 93
–100
(1912
), p. 100. This article, translated and commented by A. De Angelis, is available at <arxiv.org/abs/1002.1810>. A collection of Pacini’s articles can be found at <deangeli.web.cern.ch/deangeli/domenicopacini.html>.23.
For a discussion on Pacini’s forgotten contributions see A. De Angelis
, “Domenico Pacini, uncredited pioneer of the discovery of cosmic rays
,” Riv. Nuovo Cimento
33
, 713
–756
(2010
);P.
Carlson
and A.
De Angelis
, “Nationalism and internationalism in science: The case of the discovery of cosmic rays
,” Eur. Phys. J.
35H
(4
), 309
–329
(2010
).24.
M.
De Maria
, M. G.
Ianniello
, and A.
Russo
, “The discovery of cosmic rays: Rivalries and controversies between Europe and the United States,”
Riv. St. Scienza
2
, 237
–286
(1985
). See alsoQ.
Xu
and L. M.
Brown
, “The early history of cosmic ray research
,” Am. J. Phys.
55
, 23
–33
(1987
).25.
A most important advance in the ionization chamber technique as applied to cosmic-ray research occurred in the 1920s with the development of self-recording instruments, by Millikan and by Erich Regener. To carry out high-altitude observations, scientists, such as Hess and Kolhörster, previously had to personally “accompany” their ionization chamber in balloon flight. Now the measurements could be carried out with unmanned balloons, which could reach much greater altitudes, thus eliminating risks and high costs. For the first time it also became possible to perform measurements down to great depths under water.
26.
R. A.
Millikan
, “High frequency rays of cosmic origin
,” Proc. Natl. Acad. Sci. U.S.A.
12
, 48
–55
(1926
), p. 52. His lecture had such an immediate and incredible official echo that an article entitled “Dr. Millikan discovers strange new rays, 10 miles above the Earth, coming from the void” appeared in the 11 November 1925 issue of The New York Times, p. 25: “Scientists attending the National Academy of Sciences here are seeking a name for the powerful new rays discovered by Dr. R. A. Millikan […]. It is probable that the rays […] will become known as Millikan rays, in honor of the man who first found authentic evidence of their existence.” Available at <www.nytimes.com/ref/membercenter/nytarchive.html>. In the U.S. Millikan was considered the discoverer of the new rays. As a result European scientists in the field felt excluded from the priority of their pioneering discoveries (see Ref. 24).27.
For an accurate reconstruction of Millikan’s strategy for measuring cosmic ray energy, and his theories on the origin of cosmic rays see P. Galison, “
The discovery of the muon and the failed revolution against quantum electrodynamics,”
Centaurus 26
, 262–316 (1983). See also A. Russo, Le reti dei fisici. Forme dell’esperimento e modalità della scoperta nella fisica del Novecento (La Goliardica Pavese, Pavia, 2000
), Chaps. II and III.28.
R. A.
Millikan
and G. H.
Cameron
, “Evidence for the continuous creation of the common elements out of positive and negative electrons,”
Proc. Natl. Acad. Sci. U.S.A.
14
(6
), 445
–450
(1928
).29.
R. A.
Millikan
and G. H.
Cameron
, “The origin of the cosmic rays,”
Phys. Rev.
32
, 533
–557
(1928
), p. 533.30.
J. H.
Jeans
, Problems of Cosmogony and Stellar Dynamics (U.P., Cambridge, 1919
), p. 286
;J. H.
Jeans
, “Highly-penetrating Radiation and Cosmical Physics
,” Nature (London)
116
, 861
(1925
);A. S.
Eddington
, The Internal Constitution of the Stars
(Cambridge U.P.
, Cambridge
, 1926
), Chap. XI.31.
R. A.
Millikan
and G. H.
Cameron
, “Evidence that the cosmic rays originate in interstellar space,”
Proc. Natl. Acad. Sci. U.S.A.
14
(8
), 637
–641
(1928
); “
[PubMed]
R. A.
Millikan
and G. H.
Cameron
, New precision in cosmic ray measurements; yielding extension of spectrum and indications of bands
,” Phys. Rev.
31
, 921
–930
(1928
).32.
R. A.
Millikan
and G. H.
Cameron
, abstract of Ref. 29; see also discussion in p. 551. Such a terminal condition described by the German word Wärmetod, heat-death, was used by Rudolf Clausius in 1865
. After introducing the concept of entropy, Clausius argued that there would come a time when the entire universe would be a state of maximum entropy. See33.
Reference 27, p.
267
.34.
Reference 20.
35.
P.
Galison
, How Experiments End
(The University of Chicago
, Chicago London
, 1987
), pp. 86
–89
.36.
H.
Geiger
and W.
Müller
, “Elektronenzählrohr zur Messung schwächster Aktivitäten
,” Die Naturwiss.
31
, 617
–618
(1928
).37.
For the origin of the Geiger-Müller counter, see
T. J.
Trenn
, “The Geiger–Müller counter of 1928
,” Ann. Sci.
43
, 111
–135
(1986
).38.
Reference 11 and <www.answers.com/topic/geiger-johannes-wilhelm>.
39.
Reference 37, p.
134
.40.
D. V.
Skobeltzyn
, “The Early Stage of Cosmic Ray Particle Research,”
in Early History of Cosmic Ray Studies: Personal Reminiscences With old Photographs
, 1st. ed., edited by Y.
Sekido
and H.
Elliot
(Reidel
, Dordrecht
, 1985
), pp. 47
–52
, p. 48.41.
W.
Kolhörster
, “Eine neue Methode zur Richtungsbestimmung von Gamma-Strahlen,”
Die Naturwiss.
16
, 1044
–1045
(1928
).42.
W.
Bothe
and W.
Kolhörster
, “Eine neue Methode für Absorptionsmessungen an sekundären β-Strahlen,”
Die Naturwiss.
16
, 1045
(1928
).43.
O.
Klein
and T.
Nishina
, “Eine neue Methode für Absorptionsmessungen an sekundären β-Strahlen,”
Z. Phys.
52
, 853
–868
(1929
).44.
D. V.
Skobeltzyn
, “Über eine neue Art sehr schneller β-Strahlen
,” Z. Phys.
54
, 686
–702
(1929
).45.
W.
Bothe
and W.
Kolhörster
, “Die Natur der Höhenstrahlung
,” Die Naturwiss.
17
, 271
–273
(1929
), p. 272.46.
W.
Bothe
and W.
Kolhörster
, “Das Wesen der Höhenstrahlung
,” Z. Phys.
56
, 751
–777
(1929
), p. 751.47.
Bothe and Kolhörster remarked that the double Compton collision involving the same photon, is a rare phenomenon, so that the rate of double coincidences could not be ascribed to this occurrence (see Ref. 46, pp.
764
–765
).48.
This conclusion is not surprising, considering that in the 1920s electrons and ionized hydrogen were the only known elementary particles to serve as building blocks for atoms.
49.
50.
51.
Reference 50,
p
–7
.52.
B.
Rossi
, “Early days in cosmic rays
,” Phys. Today
34
(10
), 35
–43
(1981
), p. 35.53.
Reference 49,
p
–41
.54.
Reference 52,
p
–35
.55.
56.
B.
Rossi
, “Development of the cosmic ray techniques
,” in International Colloquium on the History of Particle Physics
(21–23 July, 1982, Paris), J. Phys. (Paris)
, Colloques 43
(C8
), 69
–88
(1982
), p. 72.57.
Reference 50, p. 10.
58.
M.
De Maria
and A.
Russo
, “The discovery of the positron,”
Riv. Stor. Sci.
2
, 237
–286
(1985
), p. 253.59.
For a review on the early impact of the introduction of the tube counter in Italy, see
M.
Leone
, A.
Mastroianni
, and N.
Robotti
, “Bruno Rossi and the introduction of the Geiger-Müller counter in Italian Physics: 1929–1934
,” Physis
42
, 453
–480
(2005
).60.
W.
Bothe
, “Zur Vereinfachung von Koinzidenzzählungen
,” Z. Phys.
59
, 1
–5
(1930
).61.
J.
Kunz
, “Amplification of the photoelectric current by the Audion
,” in Minutes of the Washington Meeting, Phys. Rev.
10
, 72
–100
(1917
).62.
H.
Greinacher
, “Über die akustische Beobachtung und galvanometrische Registrierung von Elementarstrahlen und Einzelionen
,” Z. Phys.
23
, 361
–378
(1924
);H.
Greinacher
, “Eine neue Methode zur Messung der Elementarstrahlen
,” Z. Phys.
36
, 364
–373
(1926
).H.
Greinacher
, Greinacher showed it was possible to amplify the current due to an α-particle sufficiently to register it as a click in a headphone: “Über die Registrierung von α- und H-Strahlen nach der neuen elektrischen Zählmethode
,” Z. Phys.
. 44
, 319
–325
(1927
);H.
Greinacher
, “Eine neue elektrische Zählmethode für α-und H-Strahlen
,” Die Naturwiss.
16
, 1102
–1102
(1928
).Greinacher’s method of “purely electronic amplification” spread all over Europe: in Wien and in England, where particularly appreciated by Rutherford and his collaborators in France and was adopted in Maurice de Broglie’s laboratory, thanks to the young Louis Leprince-Ringuet.
63.
B.
Rossi
, “Method of registering multiple simultaneous impulses of several Geiger counters,”
Nature
125
(3156
), 636
(1930
).64.
H.
Becker
and W.
Bothe
, “Die in Bor und Beryllium erregtenγ-Strahlen,”
Z. Phys.
78
, 421
–438
(1930
);H. J. v.
Baeyer
, “Anwendung der Koinzindenzmethode auf die Untersuchung von Kernprozessen
,” ibid
. 95
, 417
–439
(1935
);W.
Bothe
and H.
Maier-Leibnitz
, “Koinzidenzmessungen and den β- und γ-Strahlen des RaC
,” ibid
. 104
, 604
–612
(1937
).65.
W.
Bothe
and R.
Hilgert
, “Zur Struktur der kosmischen Ultrastrahlung
,” Z. Phys.
99
, 353
–362
(1936
).66.
The Nobel Prize in Physics 1954 was divided equally between Max Born and Walther Bothe <nobelprize.org/nobel_prizes/physics/laureates/1954/>.
67.
B.
Rossi
, “Magnetic experiments on the cosmic rays,”
Nature
128
(3225
), 300
–301
(1931
);the “Puccianti magnetic lenses” later became part of the heritage left by Rossi to the Italian physicists working in cosmic rays, and after about 15 years would be applied in the study of positive and negative mesons, playing a central role in the historical experiment performed in Rome by Marcello Conversi, Ettore Pancini, and Oreste Piccioni during World War II:
M.
Conversi
, E.
Pancini
, and O.
Piccioni
, “Sull’assorbimento e sulla disintegrazione dei mesoni alla fine del loro percorso,” Nuovo Cimento
3
, 372
–390
(1946
);B.
Rossi
, “On the disintegration of negative mesons
,” Phys. Rev.
71
, 209
–210
(1947
).68.
J.
Clay
, “Penetrating radiation
,” Proc. R. Acad. Sci. Amsterdam
30
, 1115
–1127
(1927
), http://www.dwc.knaw.nl/DL/publications/PU00011919.pdf;J.
Clay
, “Penetrating radiation, II
,” Proc. R. Acad. Sci. Amsterdam
. 31
, 1091
–1097
(1928
), http://www.dwc.knaw.nl/DL/publications/PU00015672.pdf;J.
Clay
, “Ultra radiation (penetrating radiation), III. Annual variation and variation with the geographical latitude
,” Proc. R. Acad. Sci. Amsterdam
. 33
, 711
–718
(1930
), http://www.dwc.knaw.nl/DL/publications/PU00015940.pdf.69.
W.
Bothe
and W.
Kolhörster
, “Vergleichende Höhenstrahlungsmessungen auf nördlichen Meeren
,” Sitzber. Preuss. Akad.
26
, 450
–456
(1930
).70.
R.
Millikan
and G.
Cameron
, “High altitude tests on the geographical, directional, and spectral distribution of cosmic rays
,” Phys. Rev.
31
, 163
–173
(1928
);R.
Millikan
and G.
Cameron
, “New results on cosmic rays
,” Nature
121
(3036
), 19
–26
(1928
).71.
B.
Rossi
, “On the magnetic deflection of cosmic rays
,” Phys. Rev.
36
, 606
–606
(1930
).72.
E.
Fermi
and B.
Rossi
, “Azione del campo magnetico terrestre sulla radiazione penetrante
,” Atti Acc. Naz. Lincei Rend.
17
, 346
–350
(1933
);see also Rossi’s introduction to the article reprinted in Enrico Fermi
, Collected Papers (Note e Memorie)
, Italy 1921–1938, Vol. 1
, edited by E.
Amaldi
et al (The University of Chicago and Accademia Nazionale dei Lincei
, Chicago and Rome
, 1962
), p
–509
.73.
L.
Alvarez
and A. H.
Compton
, “A positively charged component of cosmic rays,”
Phys. Rev.
33
, 835
–836
(1933
).74.
T. H.
Johnson
, “The azimuthal asymmetry of the cosmic Radiation
,” Phys. Rev.
43
, 834
–835
(1933
).75.
B.
Rossi
, “I risultati della missione scientifica in Eritrea per lo studio dei raggi cosmici
,” La Ric. Sc.
4
, 365
–368
(1933
)B.
Rossi
, and “Directional measurement on the cosmic rays near the geomagnetic equator
,” Phys. Rev.
45
, 212
–214
(1934
).At the beginning of 1930s Geiger, too, noted that counters placed in separate rooms periodically registered simultaneous bursts of radiation, T. J. Trenn, “Geiger, Hans (Johannes) Wilhelm
,” in Dictionary of Scientific Biography
, edited by C. C.
Gillispie
(Charles Scribner’s Sons
, New York
, 1981
) Vol. 5
, pp. 330
–333
, on p. 332.76.
B.
Rossi
, “I risultati della Missione scientifica in Eritrea per lo studio della radiazione penetrante (Raggi cosmici). Misure sulla distribuzione angolare di intensità della radiazione penetrante all’Asmara
,” La Ric. Sc. Supplemento
1
(9–10
), 579
–589
(1934
), pp. 588–589.77.
P.
Auger
, “Les grandes gerbes cosmiques de l’atmosphère
,” C. R. Acad. Sci.
207
, 228
–230
(1938
);P.
Auger
, P.
Ehrenfest
, R.
Maze
, J.
Daudin
, and R.
Fréon
, “Extensive cosmic-ray showers
,” Rev. Mod. Phys.
11
, 288
–291
(1939
).78.
Reference 50, pp.
35
–36
.79.
W. F. G.
Swann
, “Cosmic rays
,” Rep. Prog. Phys.
10
, 1
–51
(1944
), p. 6.80.
Toward the end of 1932, when Compton presented the results of the world survey supporting the existence of the latitude effect, an acrimonious debate with Millikan was played out in several tense scientific meetings and in the press. See
M.
De Maria
and A.
Russo
, “Cosmic ray romancing: the discovery of the latitude effect and the Compton–Millikan controversy
,” Hist. Stud. Phys. Biol.
19
, 211
–266
(1989
).81.
B.
Rossi
, “Absorptionsmessungen der durchdringenden Korpuskularstrahlung in einem Meter Blei,”
Die Naturwiss.
20
, 65
–65
(1932
). The original drawing of the experimental setup can be found in one of Rossi’s notebooks filed at Institute Archives & Special Collections, Massachusetts Institute of Technology Libraries, Cambridge MA, MC 166, box 1, folder 8.82.
B.
Rossi
, “Nachweis einer Sekundärstrahlung der durchdringenden Korpuskularstrahlung,
” Phys. Z.
33
, 304
–305
(1932
).83.
B.
Rossi
, “Über die Eigenschaften der durchdringenden Korpuskularstrahlung in Meeresniveau
,” Z. Phys.
82
, 151
–178
(1933
).For an undergraduate project on the reproduction of Rossi’s experiment see
D. P.
Jackson
and M. T.
Welker
, “Measuring and modeling cosmic ray showers with an MBL system: An undergraduate project,” Am. J. Phys.
69
, 896
–900
(2001
).84.
B.
Rossi
, “Sugli effetti secondari della radiazione corpuscolare penetrante
,” Atti Acc. Naz. Lincei Rend.
15
, 734
–741
(1932
), p. 739.85.
B.
Rossi
, “Measurements on the absorption of the penetrating corpuscular rays coming from inclined directions
,” Nature
128
(3227
), 408 (1931
).For a pedagogical example of this type of measurement see
C. R.
Gould
and R. L.
Ives
, “Integrated circuit counter for cosmic ray experiments,” Am. J. Phys.
43
, 918
–920
(1975
).86.
R. A.
Millikan
, “New techniques in the cosmic-ray field and some of the results obtained with them
,” Phys. Rev.
43
, 661
–669
(1933
), p. 663.87.
Fermi invited Rossi to give an introductory talk on the problems of cosmic rays. In discussing the most popular issue of the day, the problem of the origin and nature of the penetrating radiation, Rossi gave a detailed and cogent report on why he thought that Millikan’s assumption could not be correct. Rossi, who at the time was only 26 years old, later commented that “such a brash behavior on the part of a mere youngster […] clearly did not please Millikan who, for a number of years thereafter, chose to ignore my work altogether.” His talk stimulated Compton who, some time later, told him that it “had provided the initial motivation for his research program in cosmic rays.” See Ref. 52, p. 39.
88.
P. M. S.
Blackett
and G. P. S.
Occhialini
, “Photography of penetrating corpuscular radiation
,” Nature
130
(3279
), 363
(1932
).For a description of the apparatus and its development within the historical and scientific framework of 1930s physics, see
M.
Leone
and N.
Robotti
, “P. M. S. Blackett, G. Occhialini and the invention of the counter-controlled cloud chamber (1931–32),” Eur. J. Phys.
29
, 177
–189
(2008
);M.
Leone
, “Particles that take photographs of themselves: The emergence of the triggered cloud chamber technique in early 1930s cosmic-ray physics,” Am. J. Phys.
79
, 454
–459
(2011
).89.
P. M. S.
Blackett
and G. P. S.
Occhialini
, “Some photographs of the tracks of penetrating radiation
,” Proc. R. Soc. London, Ser.
A 139
, 699
–726
(1933
), p. 705.90.
P.
Blackett
, “Cloud chamber researches in nuclear physics and cosmic radiation
,” Nobel Lecture
, 13
December 1948
, <nobelprize.org/nobel_prizes/physics/laureates/1948/blackett-lecture.pdf>, p. 108
.91.
Reference 89, p.
702
.92.
An in-depth discussion of Rossi’s as well as Blackett and Occhialini’s experiments appeared in
H.
Bhabha
, “Zur Absorption der Höhenstrahlung
,” Z. Phys.
86
, 120
–130
(1933
).93.
C. D.
Anderson
, “The apparent existence of easily deflectable positives,”
Science
76
, 238
–239
(1932
), p. 239. The well known photograph of Anderson’s positron was published in his second article:
[PubMed]
C.
Anderson
, “The positive electron
,” Phys. Rev.
43
, 491
–494
(1933
).94.
C.
Anderson
, “Early work on the positron and muon
,” Am. J. Phys.
29
, 825
–830
(1961
).95.
Reference 89, p.
714
.96.
J. F.
Carlson
and J. R.
Oppenheimer
, “On multiplicative showers
,” Phys. Rev.
51
, 220
–231
(1937
).97.
H. J.
Bhabha
and W.
Heitler
, “The passage of fast electrons and the theory of cosmic showers
,” Proc. R. Soc. London, Ser.
A 159
, 432
–458
(1937
).98.
L.
Jánossy
and B.
Rossi
, “On the photon component of cosmic radiation and its absorption coefficient
,” Proc. R. Soc. London, Ser.
A 175
, 88
–100
(1940
).99.
B.
Rossi
and K.
Greisen
, “Cosmic-ray theory
,” Rev. Mod. Phys.
13
, 240
–309
(1941
).100.
P.
Auger
et al, Ref. 77.101.
Reference 96,
p
–220
.102.
S. H.
Neddermeyer
and C. D.
Anderson
, “Note on the nature of cosmic-ray particles,”
Phys. Rev.
51
, 884
–886
(1937
), p. 886.103.
J. C.
Street
and E. C.
Stevenson
, “New evidence for the existence of a particle of mass intermediate between the proton and electron,”
Phys. Rev.
52
, 1003
–1004
(1937
).104.
Reference 27, pp.
301
–302
.105.
K.
Nakamura
et al (Particle Data Group)
, J. Phys. G: Nucl. Part. Phys.
37
, 075021
, 1
–1422
(2010
).106.
H.
Yukawa
, “On the interaction of elementary particles. I
,” Proc. Phys.
(1935);107.
H. J.
Bhabha
, “Nuclear forces, heavy electrons and theβ-decay
,” Nature
141
(7278
), 117
–118
(1938
);reprinted in
Prog. Theor. Phys. Suppl.
1, 24–45 (1955); http://ptp.ipap.jp/link?PTPS/1/24/.108.
In 1932 Rossi left Florence and moved to a chair of experimental physics in Padua University. In 1938, when the anti-semitic laws passed in Italy, Rossi was dismissed, and had to emigrate from his country. See
L.
Bonolis
, “Bruno Rossi and the racial laws of fascist Italy
,” Phys. Perspect
. 13
(1
), 58
–90
(2011
).109.
B.
Rossi
, “The disintegration of mesotrons
,” Rev. Mod. Phys.
11
, 296
–303
(1939
).110.
B.
Rossi
, N.
Hilberry
, and J. B.
Hoag
, “The variation of the hard component of cosmic rays with height and the disintegration of mesotrons
,” Phys. Rev.
57
, 461
–469
(1940
).111.
B.
Rossi
and D. B.
Hall
, “Variation of the rate of decay of mesotrons with momentum
,” Phys. Rev.
59
, 223
–228
(1941
).112.
B.
Rossi
, K.
Greisen
, J. C.
Stearns
, D. K.
Froman
, and P. G.
Koontz
, “Further measurements of the Mesotron lifetime
,” Phys. Rev.
61
, 675
–679
(1942
).113.
B.
Rossi
, “The decay of ‘mesotrons’ (1939–1943). Experimental particle physics in the age of innocence
,” in The Birth of Particle Physics
, edited by L. M.
Brown
and L.
Hoddeson
(Cambridge U.P
., New York
, 1983
), pp. 183
–205
, p. 200.114.
E. J.
William
and G. E.
Roberts
, “Evidence for transformation of mesotrons into electrons
,” Nature
145
(3664
), 102
–103
(1940
).115.
F.
Rasetti
, “Disintegration of slow mesotrons
,” Phys. Rev.
60
, 198
–204
(1941
).For a detailed discussion of research related to mesotron decay, see D. Monaldi, “Life ofμ: The observation of the spontaneous decay of mesotrons and its consequences, 1938–1947,”
Ann. Sci.
62
(4
), 419
–455
(2005
); “The indirect observation of the decay of mesotrons: Italian experiments on cosmic radiation, 1937-1943,
” Hist. Stud. Nat. Sci.
38
, 353
–404
(2008
).For a discussion of undergraduate student experiments related to these problems see N. Easwar and D. A. MacIntire, “Study of the effect of relativistic time dilation on cosmic ray muon flux An undergraduate modern physics experiment
,” Am. J. Phys.
59
, 589
–592
(1991
);T.
Coan
, T.
Liu
, and J.
Ye
, “A compact apparatus for muon lifetime measurement and time dilation demonstration in the undergraduate laboratory
,” ibid
. 74
, 161
–164
(2006
).116.
B.
Rossi
and N.
Nereson
, “Experimental determination of the disintegration curve of mesotrons,”
Phys. Rev.
62
, 417
–422
(1942
).A detailed description of the time circuit was given in an article, which was received on January 6, 1943, but, due to secrecy concerns, was published only after the war:
B.
Rossi
and N.
Nereson
, “Experimental arrangement for the measurement of small time intervals between the discharges of Geiger-Müller counters,” Rev. Sci. Instrum.
17
, 65
–71
(1946
).
[PubMed]
117.
118.
L. W.
Alvarez
, “Recent developments in particle physics
,” Nobel Lecture
, 11
December 1968, <nobelprize.org/nobel_prizes/physics/laureates/1968/alvarez-lecture.html>, p. 241
.119.
C. M. G.
Lattes
, G. P. S.
Occhialini
, and C. F.
Powell
, “Observation of the tracks of slow mesons in photographic emulsions,”
Nature
160
(4066
), 453
–456
(1947
).120.
M.
Schein
, W. P.
Jesse
, and E. O.
Wollan
, “The nature of the primary cosmic radiation and the origin of the mesotron,”
Phys. Rev.
59
, 615
(1941
).121.
H. L.
Bradt
, P.
Freier
, E. J.
Lofgren
, E. P.
Ney
, F.
Oppenheimer
, and B.
Peters
, “Evidence for heavy nuclei in the primary cosmic radiation,”
Phys. Rev.
74
, 213
–217
(1948
);H. L.
Bradt
and B.
Peters
, “Investigation of the primary cosmic radiation with nuclear photographic emulsions
,” ibid
. 74
, 1828
–1837
(1948
).122.
Reference 113, p.
4
.123.
P.
Galison
, Image and Logic. A Material Culture of Microphysics
(University of Chicago
, Chicago
, 1997
).124.
L. M.
Brown
and H.
Rechenberg
, “Quantum field theories, nuclear forces, and the cosmic rays
(1934–1938),” Am. J. Phys.
59
, 595
–605
(1991
).125.
Reference 113, p.
204
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