Fascinating correspondence on physical science between Professor Einstein and his colleague Dr. Gustav Mie after the latter decided not to be swept away by the dark antisemitic current of the times, but to proceed with pure scientific spirit specifically to deliberate, question and listen, in opposition to the majority of scientists of his generation.
The correspondence includes 13 letters between Einstein [8] and Mie [5] in which Einstein convinces his colleague about the correctness of the Theory General of Relativity.
The following correspondence between Albert Einstein and Gustav Mie (who at that time was full professor for experimental physics in Halle, Germany) offers its reader a unique chance to witness the dawn of General Relativity (GR) and the hurdles which this new theory had to overcome to gain acceptance among physics faculty. It illustrates Einstein’s efforts and struggles to convince and educate his fellow colleagues, some of whom remained highly skeptical of this groundbreaking discovery. But they also show us how Einstein navigated the path of correcting Gustav Mie’s misunderstandings without hurting his feelings or damaging their good relationship.
Before discussing the letters, we will review the circumstances under which they were written. Starting in the year 1917, this correspondence took place less than two years after Einstein unveiled his general theory of relativity. This theory revolutionized our understanding of gravity, inertia and mass.
The new concept of curved space-time required a high degree of abstraction from Einstein’s contemporaries. As a result, two groups of physicists emerged in Germany, roughly split among theoreticians and experimentalists.
While many colleagues, especially theoretical physicists, embraced Einstein’s new theory and started to contribute to its further development by e.g. searching for possible solutions to the basic Einstein equations, another group, consisting mainly of experimentalists, vehemently rejected GR. This second group was led by Philipp Lenard, a former Nobel prize winner who later became an active Hitler supporter and anti-Semite. The rejection of General Relativity paved the way to the creation of the so-called “Deutsche Physik” (German Physics) movement during the Nazi period, which disparagingly labeled the work of Einstein and other theoretical physicists of that time as “Jewish physics.”
What was Gustav Mie’s role in this debate? Mie was at the time of the correspondence a well-known experimentalist, who shared some of the skepticism of his colleagues. However, he actively sought out Einstein and tried to explain his difficulties and to understand Einstein’s viewpoints in these letters. This is the reason why Einstein’s responses are written in a very polite and cordial manner and why both scientists met personally to further discuss aspects of GR. We can presume that these written and oral discussions greatly influenced Mie and enabled him to publish a textbook about General Relativity later in 1921. Interestingly, during the Nazi period Gustav Mie became a member of a liberal university opposition group in Freiburg, Germany.
So what are the main topics of discussion between Einstein and Mie? One of the major initial disagreements between them lies in Mie’s preference for a preferred set of coordinates in which our universe should be described. From his point of view, an adequate theory of gravity should fix the structure of space-time to be flat asymptotically far away from any matter. However, these ideas contradict key axioms of GR, which are that the structure of space-time is determined exclusively by the matter content of the universe and that no preferred coordinate system exists. Einstein himself was keen to at least allow the equations of General Relativity to have a largely flat and static Universe as one of possible solutions. This is why he refers to the famous λ*gµν term in his letters, an addition to the original equations which he introduced in 1917.
This term counteracts the forces of the gravitational masses which, according to the understanding of that time, alone would force the contraction of our Universe on asymptotically long time scales. Thus, λ*gµν allows Mie’s favorite view of static global space-time to be at least mathematically feasible. Einstein himself later regretted introducing this term to his theory and even called it his “biggest blunder” after Edwin Hubble discovered the expansion of the Universe in 1931.
Here, the reader should make a step back from the correspondence and humbly realize that the questions of the nature and origin of the cosmological constant λ, which these two brilliant physicists touched already more than a century ago, remain one of the greatest unsolved mysteries of cosmology up to this day. In 1998, scientists discovered that our Universe is undergoing a phase of accelerating expansion through observations of distant supernovae. This new observation, which was honored by the Nobel prize in physics in 2011, can only be explained in terms of the λ parameter having a small positive value. Today cosmologists believe that a yet unknown substance, called “dark energy”, is responsible for this cosmological constant.
What would Einstein and Mie think of these recent findings? Would they congratulate each other for raising these questions long before any experiment could test their philosophical assumptions? We can only study their thoughts and feel connected to them through the years, not least because of preserved letters and correspondences like these.
For a historian, these letters also give hints about the broader, not physics-related circumstances in which they were written. The Great War was ravaging in Europe and even thinkers like Einstein could not close their eyes on its impacts. Einstein’s hope that he and Mie may finally meet during happier times when trains would again be used for private trips and not for troop transports show us how desperate people became at that time after years of suffering and war.
Gustav Mie and Albert Einstein survived the First World War unharmed, but one of their colleagues, a brilliant physicist and author of first exact solutions to Einstein’s equations whom Mie references in one of his responses, Karl Schwarzschild, died in 1916 due to an illness which he developed while in the trenches on the Russian front.
The collection before us came from Dr. Mie’s estate, so that the letters from him to Einstein are drafts he wrote for himself at first, and after he decided on a final version, he copied them onto blank sheets of paper and sent the letters to Einstein (except for letter 12).
1: From Gustav Mie 30.5.1917, [1] leaf paper, 30×23 cm, includes the envelope. Written on the blank side of an ad. Very fine condition.
2: From Albert Einstein 2.6.1917, [1] leaf paper, 21×27 cm. Folded with writing on three of the sides, fine-very fine condition, fold marks, stains and perforation marks.
3: From Albert Einstein 14.12.1917, postcard 9×14 cm, very fine condition.
4: From Albert Einstein 22.12.1917, postcard 9×14 cm, very fine condition.
5: From Albert Einstein 29.12.1917, postcard 9×14 cm, very fine condition.
6: From Gustav Mie 4.2.1918, [5] leaves, written on both sides, 21×16 cm, fine-very fine condition, many comments and erasures.
7: From Albert Einstein 8.2.1918 [1] leaf written on both sides, 33×21 cm, very fine condition, fold marks. Includes the envelope.
8: From Gustav Mie 17.2.1918, [3] leaves written on both sides, fine condition, fold marks, many comments and erasures.
9: From Albert Einstein 22.2.1918, [2] leaves, one of which is written on both sides. Very fine condition, fold marks, few erasures. Includes the envelope.
10. From Albert Einstein 24.3.1918, [1] leaf written on both sides, 14×22 cm. Fine-very fine condition, fold marks and some stains. Includes the envelope.
11. From Gustav Mie 5.5.1918, [3] leaves written on both sides. 21×33 cm. Fine condition, fold marks, many erasures and comments.
12. From Gustav Mie 27.4.1926, [1] leaf folded in two and written on three sides, 28×22 cm. Very fine condition, erasures and comments, fold marks.
13. From Albert Einstein 22.5.1926, [1] leaf, 28×22 cm. Fine condition, hole and stains in the upper left corner, fold marks.
Written with the guidance of Dr. Daniel Gelfand.
