Einstein and the Quantum (19 page)

We have already heard that Einstein regarded Lorentz as the most powerful thinker he had ever encountered, but his admiration ran deeper than this because of Lorentz's elegant, generous, and kindly spirit. Late in his life Einstein wrote: “
Everything which emanated
from his supremely great mind was as clear and beautiful as a good work of art…. For me personally he meant more than all of the others I have met in my life's journey. Just as he mastered physics and mathematical structures, so he mastered also himself—with ease and perfect serenity.” Einstein's attitude toward Lorentz was, by 1908, shared by much of the European physics and mathematics community. His encyclopedic knowledge of many subdisciplines made his opinion the final word for many. “
Whatever was accepted by Lorentz
was accepted; and whatever was rejected by him was rejected or at best labeled controversial.” He, alone among all theorists, had preceded Einstein in noting Planck's essential use of the “energy element” in his derivation of the radiation law as early as 1903, and had “
wrestled continuously
with this problem [of heat radiation]” in the years leading up to 1908.

Lorentz, with his unmatched mastery of both electromagnetic theory and the dynamics of electrons, set out to
deduce
the Planck radiation law rigorously, directly from the motion of charged electrons, which radiate and absorb radiation, without introducing fictitious molecules or “resonators” as Planck had done. But no matter how hard he tried, he succeeded only in rediscovering the low-frequency, approximate law of Rayleigh-Jeans (and Einstein), which led to absurd consequences (infinite energy) at high frequencies. In April of 1908 he announced his findings at the International Congress of Mathematicians in Rome.

The theory of Planck is the only one
that would provide us with a formula in accord with experimental results; but we could accept it only with the stipulation that we completely rework our basic conception of electromagnetic phenomena…. However I must address myself to the question of how the Jeans theory, which involves no constants other than … [Boltzmann's constant]
k
, can take into account the peak of the radiation curve which has been demonstrated by experiments [the absence of high-frequency thermal radiation predicted by Jeans]. The explanation given by Jeans—which is really the only one that can be given—is that the maximum is illusory; its existence is simply an indication that it has not been possible to realize a body that is black to short wavelengths….
Fortunately, we can hope that new experimental determinations of the radiation function will permit a choice between the two theories.

Lorentz, the most respected theoretical physicist of his generation, was leaning in favor of the Jeans “slow catastrophe” theory!

The German physics community was initially stunned, and then apoplectic. Two outstanding experimenters, Lummer and Pringsheim (whom Angström had favored for the 1908 Nobel Prize) wrote scathingly, “
If we examine the Jeans-Lorentz formula
, we see at first glance that it leads to completely impossible consequences which are in crass conflict not only with the results of all observations of radiation, but with everyday experience.” They continued with more than a hint of sarcasm: “We might therefore dismiss this formula without further examination were it not for the eminence and authority of the two theoretical physicists who defend it.” Wilhelm Wien expressed the outrage felt by many when he stated, “
I was extremely disappointed
by the lecture which Lorentz presented in Rome…. he came up with nothing more than the old theory of Jeans without adding any new viewpoint…. [That theory] is not worthy of discussion in the experimental field…. What purpose is served by submitting these questions to mathematicians, since they can provide no judgment in this matter? …
In this instance Lorentz has not shown himself to be a leader of science
” (italics added).

Subjected to this torrent of criticism, even the serene Lorentz must have had second thoughts. By June 1908, only two months later, he wrote a long letter to Wien, which contained an apology in the form of an embarrassing thought experiment. In the Rayleigh-Jeans theory (which Lorentz had rederived), the energy emitted as heat radiation at a given frequency is proportional to the temperature. A metal such as silver heated to 1200°K (roughly 900°C) will glow with blinding white light. When the temperature is reduced to room temperature (roughly 300°K), it should still be emitting one-quarter as much white light, according this theory. Hence, Lorentz continued, if the theory were right an unheated silver mirror would glow visibly in the dark! He concluded, “
thus we should really dismiss
the Jeans theory … and we are
left with only the theory of Planck. Do not think that I do not respect it, quite the contrary, I admire it greatly for its boldness and success.”

Lorentz's speedy retraction and his professed admiration for Planck's theory, expressed privately, did not get as much publicity as his public criticism of it in Rome. A mathematician with substantial influence in the Swedish Academy, Gosta Mittag-Leffler, had gotten wind of Lorentz's critique and used it to his advantage. He wished to ingratiate himself with the French clique, led by the great mathematician Poincaré, and to divert the physics prize to the second-choice candidate, the French pioneer of color photography Gabriel Lippmann. In this scheme he was aided by the original nominator of Planck and Wien, the mathematician Ivar Fredholm, who was unhappy with the elimination of Wien from the award. Fredholm wrote to Mittag-Leffler before the full academy vote was taken, criticizing the Physics Committee decision and stating specifically that Planck had based the derivation of his radiation law on “
a completely new hypothesis
, which can hardly be considered plausible, namely the hypothesis of the elementary quanta of energy.”

With the sudden realization that Planck's law was radical and controversial, his nomination was soundly defeated in the general academy vote, and the prize was instead awarded to Lippmann. Mittag-Lefler sent a gleeful letter taking credit to a French mathematician: “
It is I, along with Phragmen
, who got the prize awarded to Lippmann. Arrhenius wanted to give it to Planck in Berlin, but his report, which he had somehow gotten accepted unanimously by the Committee, was so stupid that I was able to crush it easily.” The physics world was only beginning to grapple with the inevitability of the quantum revolution, proclaimed by the Valiant Swabian in his great works of 1905–7. Planck, Lorentz, and the other great scientists of Europe would have to look to this fearless interloper to lead them forward in the quest for a new microscopic mechanics. More than a decade would pass, and much would happen, before the Nobel committee would again be willing to consider giving the prize for an atomic theory.

 

¹
There is some irony here in comparison with Einstein, who sixteen years later would write to the very same man asking for a job, leading to a famous letter from his father to Ostwald (behind Einstein's back) essentially pleading with Ostwald to assent. No known answer was received, but in 1910 Ostwald became the first scientist to nominate Einstein for the Nobel Prize.

²
Rutherford, who had spent many years proving that elements transmuted during radioactive decay, later joked that “
he had seen many transmutations
in his time but none as quick as his own transmutation into a chemist.”

³
Arrhenius did have another reason to be interested in thermal radiation. He was the first scientist to recognize the role of CO
₂
in trapping heat radiation and warming the planet, and even suggested the possibility that human-generated industrial CO
₂
emissions would enhance this effect. He published this idea in that same year, 1908, arguing that it was a good thing and might forestall future ice ages.

⁴
It was initially called by many “Planck's constant,” leading to no end of confusion until the conventions settled down, assigning
h
to Planck and
k
to Boltzmann.

CHAPTER 15

JOINING THE UNION

“
So, now I too am an official
member of the guild of whores.” Thus Einstein announced to a friend, Jakob Laub, his long-overdue acceptance into the Swiss professoriate. Einstein had been appointed extraordinary professor of theoretical physics at the University of Zurich on May 7, 1909, and was writing shortly thereafter to describe the last phase of his “hazing” before admission to the fraternity. This same Laub, a young Austrian physicist who had studied with Wien, had written Einstein fourteen months earlier, saying, “
I must tell you quite frankly
that I was surprised to read that you must sit in an office for eight hours a day. History is full of bad jokes.” Laub was reflecting the general amazement in German physics at the mysterious oracle who had emerged in Switzerland with no fanfare, the protégé of no great man, and appeared to be rewriting physical theory as a hobby between reviewing patents. (There may be some truth to the latter in that Einstein admitted to hiding his physics calculations in his desk at the patent office for occasional perusal.)

What Einstein had done during his first five years while working six days a week at the patent office was beyond astonishing. From 1902 to 1904 he produced his fundamental studies in statistical mechanics, which were underappreciated but laid the foundations for many of his later breakthroughs. In 1905, the miracle year: light quanta, Brownian motion, special relativity, and
E
=
mc
²
, all eternal contributions to the physics canon. In 1906: the quantum theory of specific heats and the announcement that a quantum mechanics was needed for any correct atomic theory. In 1907: a masterful review article on relativity theory, which contained for the first time the “happiest thought” of Einstein's
life, the thought that a uniform acceleration was indistinguishable from the presence of a uniform gravitational field. This idea became known as the equivalence principle and provided the germ of the general theory of relativity, Einstein's magnum opus. Imagine what the guy could have done if he had actually had some time to focus on physics.

Having made these modest contributions to science, Einstein understandably began to think that he might now find employment in a university setting, where research would actually be part of the job description. But the Swiss physics establishment was not easily diverted from its traditional habits. The University of Bern had a stodgy, backward department, run by “
a few old fogies
”; Einstein had dismissed it as a “
pigsty
” soon after moving to Bern. To become a teacher at a university in the Germanic countries, one had to submit a so-called habilitation thesis, a more extensive and original work beyond the doctoral thesis. Einstein submitted a group of seventeen of his research papers for habilitation at the University of Bern in June of 1907, but the application was rejected, ostensibly because he had not integrated them into a single handwritten thesis, but there were other factors at work as well. The professor for experimental physics, Aimé Forster, saw no real value in adding a theorist to their faculty, and allegedly returned Einstein's paper on special relativity with the comment, “
I can't understand a word
of what you have written here.” Finally, in February 1908, he provided a more acceptable thesis, not a compilation of his papers but a specific work on the blackbody law and the constitution of radiation,
¹
and on this basis Einstein was granted the status of
Privatdozent
(private instructor) in physics at the university. This effort entitled him to provide additional lessons for the physics students, with no salary, on top of his full-time work at the patent office. However it was a necessary step toward obtaining a professor's position.

A few months later the pressure began to mount to end the embarrassment to Swiss science and award Einstein an actual academic position in theoretical physics. Lorentz and Minkowski spoke glowingly
of him at the infamous Rome Congress, at which Lorentz unwittingly undermined Planck's Nobel nomination; and Planck's great respect for Einstein's work was widely known. It so happened that an appropriate position
was
being created at the University of Zurich,
Professor Extraordinarius
, to lighten the load of his nominal thesis adviser, Alfred Kleiner, the
Professor Ordinarius
. Despite its impressive sound in translation, an extraordinary professor was actually a large notch below the “ordinary professor”; essentially he was a subordinate of Kleiner, with lower salary and fewer perks. Nonetheless, it was a real portal into an academic career for Einstein, and an opportunity for Swiss physics to improve its standing on the continent.

But parochialism would not die easily; Kleiner favored a local scholar from a well-known family, Friedrich Adler, for the position. After some back-and-forth, Adler, who was not an outstanding physicist and really was more interested in philosophy, withdrew his name from consideration, writing to his father, “
[Einstein] will most likely
get the professorship—a man who on principle … should certainly get it rather than myself … and if he gets it I will … be very pleased…. [He] was a student at the same time as I, … the people involved … have a bad conscience about the way they treated him in the past, and … it is felt to be a scandal, not only here but also in Germany, that a man like that should sit in the Patent Office…. Objectively … it is a fine thing that this man has asserted himself despite all difficulties.”

Even
with
Adler's withdrawal, Einstein was not immediately offered the job, as Kleiner deemed his teaching ability inadequate. Einstein had to ask Kleiner for a second teaching evaluation, through an arranged lecture at the Zurich Physics Society, and this time was successful, as he explained to Laub: “
I was really lucky
. Totally against my usual habit I lectured well.” In a final indignity Einstein was offered a considerably smaller salary than he was already earning at the patent office, but when he refused to take the position under those circumstances, it was agreed his patent salary would be matched. The formalities were then executed successfully, and Einstein was inducted into the guild. It is no wonder that Einstein was not feeling too grateful for his new position when it finally materialized in May of 1909.