Three scientists exemplified the cautious behavior that we might like all scientists to display: indeed, they were so critical of their own ideas that they risked losing credit for them. Nevertheless, they finally earned at least as much fame as they deserved, leaving historians to wonder about what they really believed. Maxwell initially rejected the kinetic theory of gases because two of its predictions disagreed with experiments; later he revived the theory, showed that one of those experiments had been misinterpreted, and eventually became known as one of the founders of the modern theory. Planck seems to have intended his 1900 quantum hypothesis as a mathematical device, not a physical discontinuity; later he limited it to the emission (not absorption) of radiation, thereby discovering “zero-point energy.” Eventually he accepted the physical quantum hypothesis and became known as its discoverer. Hubble (with Humason) established the distance–velocity law, which others used as a basis for the expanding universe theory; later he suggested that redshifts may not be due to motion and appeared to lean toward a static model in place of the expanding universe.

1.
F.
Reif
, “
The competitive world of the pure scientist
,”
Science
134
,
1957
1962
(
1961
).
Some of the evidence for Reif’s description of this world is disputed by
R. V.
Pound
, “
Weighing photons. II
,”
Phys. Perspective
3
,
4
51
(
2001
).
See also
S. G.
Brush
, “
Should the history of science be rated X?
Science
183
,
1164
1172
(
1974
);
Donald
Kennedy
, “
Good news, bad news
,”
Science
293
,
761
(
2001
),
and (for a specific recent example)
Charles
Seife
, “
Berkeley crew unbags element 118
,”
Science
293
,
777
778
(
2001
).
2.
“Experimental science has progressed thanks in great part to the work of men astoundingly mediocre, and even less than mediocre. That is to say, modern science, the root and symbol of our actual civilization, finds a place for the intellectually commonplace man and allows him to work therein with success. … In this way the majority of scientists help the general advance of science while shut up in the narrow cell of their laboratory, like the bee in the cell of its hive.” José Ortega y Gasset, Revolt of the Masses, translated from the Spanish edition of 1930 (Norton, New York, 1932), pp. 122–23. This thesis, now known by sociologists of science as the Ortega hypothesis, has been refuted (at least for modern physics) by
Jonathan R.
Cole
and
Stephen
Cole
, “
The Ortega hypothesis
,”
Science
178
,
368
75
(
1972
). The basic premise goes back to Francis Bacon; see his New Organon (1620), available in several modern editions. He argued that anyone of moderate intelligence could make significant contributions to science by diligently following the correct (that is, Baconian) method. While he used his method to provide inductive evidence that heat is atomic motion, Bacon is notorious for his refusal to accept Copernican astronomy and Gilbert’s geomagnetic theory.
3.
For general background, details, and references, see the book by Gerald Holton and Stephen G. Brush, Physics, The Human Adventure: From Copernicus to Einstein and Beyond (Rutgers U.P., New Brunswick, NJ, 2001) and its associated Web site bibliography, http://www.ipst.umd.edu/Faculty/brush/physicsbibliography.htm.
4.
This section and the following sections are based mostly on my book, The Kind of Motion We Call Heat: A History of the Kinetic Theory of Gases in the 19th Century (North-Holland/American Elsevier, Amsterdam, 1976).
For biographical information, see C. W. F. Everitt, James Clerk Maxwell: Physicist and Natural Philosopher (Scribner, New York, 1975);
Lewis Campbell and William Garnett, The Life of James Clerk Maxwell, with a New Preface and Appendix with Letters by Robert H. Kargon (Johnson Reprint Corp., New York, 1969).
A complete scholarly edition of his letters and papers is being published by P. M. Harman, The Scientific Letters and Papers of James Clerk Maxwell (Cambridge U.P., New York, 1990-).
A good philosophical discussion of Maxwell’s kinetic theory is given by Peter Achinstein, Particles and Waves: Historical Essays in the Philosophy of Science (Oxford U.P., New York, 1991).
5.
The Probabilistic Revolution, edited by Lorenz Krüger, Lorraine J. Daston, Michael Heidelberger, Gerd Gigerenzer, and Mary S. Morgan (MIT, Cambridge, MA, 1987).
6.
The Collected Papers of Albert Einstein, edited by John Stachel et al. (Princeton U.P., Princeton, 1987), Vol. 1, p. xxxix.
See also Bruce J. Hunt, The Maxwellians (Cornell U.P., Ithaca, NY, 1991);
Jed Z. Buchwald, From Maxwell to Microphysics: Aspects of Electromagnetic Theory in the Last Quarter of the Nineteenth Century (University of Chicago Press, Chicago, 1985).
7.
C. W. F. Everitt, “Maxwell’s scientific creativity,” in Springs of Scientific Creativity, edited by Rutherford Aris, H. Ted Davis, and Roger H. Stuewer (University of Minnesota Press, 1983), pp. 71–141, quote on p. 119.
8.
Reference 7, p. 129. According to Sir Ambrose Fleming, Maxwell once said that “Because we can imagine a mechanism which can achieve some result we find in Nature, it does not in the least follow that it is done in that way.”
A.
Fleming
, “
Physics and physicists of the eighteen seventies
,”
Nature (London)
143
,
99
102
(
1939
), quote on p. 102.
9.
J. C. Maxwell, “Address to the mathematical and physical sections of the British Association,” Report of the 40th Meeting of the British Association for the Advancement of Science, 1870, pp. 1–9; reprinted in Maxwell on Molecules and Gases, edited by E. Garber, S. G. Brush, and C. W. F. Everitt (MIT, Cambridge, MA, 1986), pp. 90–104, quotation from p. 103.
See also Maxwell’s A Treatise on Electricity and Magnetism (1891, Dover reprint 1954), 3rd ed., Vol. 1, pp. 380–381. For a detailed discussion of Maxwell’s views see Buchwald, Ref. 6, Chap. 3;
Daniel M. Siegel, Innovation in Maxwell’s Electromagnetic Theory: Molecular Vortices, Displacement Current, and Light (Cambridge U.P., New York, 1991);
essays by D. M. Siegel, P. M. Harman, and J. Z. Buchwald, in Wranglers and Physicists: Studies on Cambridge Physics in the Nineteenth Century, edited by P. M. Harman (Manchester U.P., Dover, NH, 1985).
Salvo
d’Agostino
, “
On the difficulties of the transition from Maxwell’s and Hertz’s pure-field theories to Lorentz’s electron
,”
Phys. Perspective
2
,
398
410
(
2000
).
10.
J. C. M
axwell
, “
A dynamical theory of the electromagnetic field
,”
Phil. Trans. Roy. Soc.
155
,
459
512
(
1965
),
reprinted in The Scientific Papers of James Clerk Maxwell, edited by W. D. Niven (reprinted by Dover Publications, New York, 1965), quotation from Vol. 1, p. 535.
11.
J. C.
Maxwell
, “
Illustrations of the dynamical theory of gases
,”
Philos. Mag.
(Ser. 4)
19
,
19
32
(
1860
);
J. C.
Maxwell
,
Philos. Mag.
21
,
21
37
(
1860
);
reprinted, with related documents and commentary, in Garber et al. Ref. 9; the quoted passage is on p. 300.
12.
Garber et al., Ref. 9, p. 318.
13.
J. C. Maxwell, “On the results of Bernoulli’s theory of gases as applied to their internal friction, their diffusion, and their conductivity for heat,” Report of the 30th Meeting of the British Association for the Advancement of Science, Oxford, June and July 1960, Notes and Abstracts, pp. 15–16;
reprinted Garber et al. (Ref. 9), pp. 320–321.
14.
Letter from J. C. Maxwell to H. R. Droop, 28 January 1862, reprinted in Garber et al. (Ref. 9), p. 336, note 8.
15.
Rayleigh (John William
Strutt
), “
Clerk-Maxwell’s papers
,”
Nature (London)
43
,
26
27
(
1890
),
reprinted in Rayleigh’s Scientific Papers, Vol. III (Cambridge, 1902, reprinted by Dover, New York, 1964), pp. 426–428, quotation from p. 427.
16.
J. C.
Maxwell
, “
Review of A Treatise on the Kinetic Theory of Gases by H. W. Watson
,”
Nature (London)
18
,
242
246
(
1877
),
reprinted in Maxwell on Heat and Statistical Mechanics, edited by Elizabeth Garber, Stephen G. Brush, and C. W. F. Everitt (Lehigh U.P., Bethlehem, PA, 1995), pp. 156–167; quotation is from pp. 164–165. This book also contains a comprehensive bibliography of primary and secondary sources for Maxwell’s work on kinetic theory (see pp. 495–525).
17.
J. L. Heilbron, The Dilemmas of an Upright Man: Max Planck as Spokesman for German Science (University of California Press, 1986), pp. 3, 62.
18.
Max Planck, Scientific Autobiography and other Papers, translated by Frank Gaynor (Philosophical Library, New York, 1950), pp. 33–34.
19.
D. L.
Hull
,
P.
Tessner
, and
A.
Diamond
, “
Planck’s principle
,”
Science
202
,
717
723
(
1978
);
see also Hull, Science as a Process (University of Chicago Press, 1988) and references therein.
20.
Martin J.
Klein
, “
Max Planck and the beginnings of the quantum theory
,”
Arch. Hist. Exact Sci.
1
,
461
479
(
1962
). This article is a good introduction to the subject, which helped to explode the myth of the ultraviolet catastrophe. Many scientists had assumed that Planck proposed his theory in order to remove the problem that when the equipartition theorem is applied to the ether model of blackbody radiation, the integral of the energy over frequency diverges at high frequencies.
The myth was so widely disseminated that it inspired a children’s book by Margaret Mahy, Ultra-Violet Catastrophe! Or the Unexpected Walk with Great-Uncle Magnus Pringle (Parents’ Magazine Press, New York, 1975). But Klein failed to note Planck’s reluctance to propose an explicit physical quantization in 1900 (see below).
See also Hans Kangro, Early History of Planck’s Radiation Law (Crane, Russak, New York, 1976) for a survey of research on blackbody radiation before Planck.
21.
M.
Planck
, “
Zur Theorie des Gesetzes der Energieverteilung im Normalspektrum
,”
Verh. Dtsch. Phys. Ges.
2
,
237
245
(
1900
); translation by D. Ter Haar, in Planck’s Original Papers in Quantum Physics, edtied by H. Kangro (Taylor & Francis, London, 1972), pp. 38–45; quotation from page 40. I thank Joshua Rosenbloom for calling the last sentence to my attention.
22.
O. Darrigol, From c-Numbers to q-Numbers: The Classical Analogy in the History of Quantum Theory (University of California Press, Berkeley, 1992), p. 73.
23.
T. S. Kuhn, Black-body Theory and the Quantum Discontinuity: 1894–1912 (Oxford U.P., New York, 1978).
24.
S. G.
Brush
, “
Thomas Kuhn as a historian of science
,”
Sci. & Educ.
9
,
39
58
(
2000
).
C.
Carson
, “
The origins of the quantum theory
,”
Beamline
30
(
2
),
6
19
(Summer/Fall
2000
).
Reference 22, pp. 67–73;
“Continuities and discontinuities in Planck’s Akt der Verzweiflung,” Ann. Phys. (Leipzig) [Ser. 8] 9, 851–960 (2000).
H.
Kragh
, “
Max Planck: The reluctant revolutionary
,”
Phys. World
13
(
12
),
31
35
(December
2000
).
25.
When I pointed out to Kuhn that he had not quoted this passage, which supported his thesis, he replied: “you are quite right that I did not use it, but I did call readers’ attention to a more general version of the point on pp. 126 and 131. All three of Planck’s autobiographical accounts of the origin of his theory fit my version of the story quite well.” Letter from T. S. Kuhn to S. G. Brush, 10 January 1978.
26.
M. Planck, Die Entstehung und bisherige Entwicklung der Quantentheorie [Nobel Prize Lecture] (Barth, Leipzig, 1920). Translation by R. Jones and D. H. Williams, in A Survey of Physical Theory (Dover, New York, 1960), pp. 102–114, quotation from p. 109.
27.
M.
Planck
, “
Ueber das Gesetz der Energieverteilung im Normalspectrum
,”
Ann. Phys. (Leipzig)
[Ser. 4]
4
,
553
63
(
1901
), see pp. 556–557.
28.
M.
Planck
, “
Zur Theorie der Wärmestrahlung
,”
Ann. Phys. (Leipzig)
[Ser. 4]
31
,
758
768
(
1910
).
29.
M.
Planck
, “
Eine neue Strahlungshypothese
,”
Verh. Dtsch. Phys. Ges.
13
,
138
148
(
1911
).
30.
N.
Hetherington
, “
Edwin Hubble: Legal eagle
,”
Nature (London)
319
,
189
190
(
1986
), quotation on p. 189.
31.
Letter from Hubble to N. Mayall, 23 February 1934, quoted by Hetherington, Ref. 30, note 12.
32.
E. P.
Hubble
, “
A relation between distance and radial velocity among extra-galactic nebulae
,”
Proc. Natl. Acad. Sci. U.S.A.
15
,
168
173
(
1929
).
33.
Hubble to de Sitter, 21 August 1930, quoted by N. S. Hetherington, “Philosophical values and observation in Edwin Hubble’s choice of a model of the universe,” Hist. Studies Phys. Sci. 13, 41–67 (1982), quotation on p. 48.
On de Sitter’s cosmology, see J. D. North, The Measure of the Universe: A History of Modern Cosmology (Dover, New York, 1990).
34.
M. L.
Humason
, “
Apparent velocity-shifts in the spectra of faint nebulae
,”
Astrophys. J.
74
,
35
42
(
1931
).
35.
Karl
Hufbauer
, “
Astronomers take up the stellar-energy problem, 1917–1920
,”
Hist. Studies Phys. Sci.
11
,
277
303
(
1981
).
36.
E. P.
Hubble
, “
The realm of the nebulae
,”
Sci. Mon.
39
,
193
202
(
1934
), quotation on p. 199.
37.
Reference 36, p. 202.
38.
S. G. Brush, “Is the Earth Too Old? The Impact of Geochronology on Cosmology, 1929–1952,” in The Age of the Earth: From 4004 BC to AD 2002, edited by C. L. E. Lewis and S. J Knell (Geological Society, London, 2001), pp. 157–175.
39.
F.
Zwicky
, “
On the Red Shift of Spectral Lines through Interstellar Space
,”
Proc. Natl. Acad. Sci. U.S.A.
15
,
773
779
(
1929
);
F.
Zwicky
, “
Remarks on the Redshift from Nebulae
,”
Phys. Rev.
48
,
802
806
(
1935
);
W. D.
MacMillan
, “
Velocities of the Spiral Nebulae
,”
Nature (London)
129
,
93
(
1932
).
40.
E. P.
Hubble
and
R. C.
Tolman
, “
Two Methods of Investigating the Nature of the Nebular Red-Shift
,”
Astrophys. J.
82
,
302
337
(
1935
).
41.
E. P.
Hubble
, “
Effects of Red Shifts on the Distribution of Nebulae
,”
Astrophys. J.
84
,
517
554
(
1936
), quotations from pp. 517, 554.
42.
E. P.
Hubble
, “
Effects of Red Shifts on the Distribution of Nebulae
,”
Proc. Natl. Acad. Sci. U.S.A.
22
,
621
627
(
1936
), quotations from pp. 624–626.
43.
S. G. Brush, Ref. 38.
44.
S. G.
Brush
, “
Prediction and Theory Evaluation: Cosmic Microwaves and the Revival of the Big Bang
,”
Perspect. Sci.
1
,
565
602
(
1993
).
45.
F. J. Sulloway, Born to Rebel: Birth Order, Family Dynamics, and Creative Lives (Pantheon, New York, 1966), p. 194. According to Sulloway’s theory, the temperament of scientists and their behavior in revolutions is strongly correlated with their birth order. He did not analyze Maxwell and Hubble from this viewpoint.
46.
At least this belief is predominant in the United States; in other countries the credit may be given to de Sitter, Lemaitre, or Friedmann, with Hubble seen as merely confirming their theories. R. W. Smith, The Expanding Universe (Cambridge U.P., New York, 1982);
A. Pannekoek, A History of Astronomy (Barnes and Noble, New York, 1962, translated from the Dutch edition of 1951), pp. 488-489;
E. A. Tropp, Y. Va. Frenkel, and A. D. Chernin, Alexandr A. Friedmann: The Man Who Made the Universe Expand (Cambridge U.P., New York, 1993), p. 218.
47.
G. W. Gray, The Advancing Front of Science (Whittlesey House–McGraw-Hill, New York, 1937), pp. 66–67.
48.
See the papers by Whitrow, Sandage, and Osterbrock, cited by S. G. Brush, Ref. 38;
also Helge Kragh, Cosmology and Controversy (Princeton U.P., Princeton, NJ, 1996), p. 21;
Mario Livio, The Accelerating Universe (Wiley, New York, 2000), p. 48;
R. W. Smith, “Galaxies,” in History of Astronomy: An Encyclopedia, edited by John Lankford (Garland, New York, 1997), pp. 221–225, on p. 224. Whitrow points out that Hubble’s work with Tolman (Ref. 40), which led him to reject the expanding universe model, was criticized by McVittie, Heckmann and others who disagreed with his “method of analyzing the observational results and disputed his conclusions…these criticisms of Hubble’s analysis came to be generally accepted.” G. J. Whitrow, The Structure and Evolution of the Universe (Harper, New York, 1959), p. 44.
49.
According to “Stigler’s Law of Eponymy,” no scientific discovery is named after its original discoverer; the law seems to be correct in a very large number of cases. Stephen M. Stigler, Statistics on the Table (Harvard U.P., Cambridge, 1999), Chap. 14.
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