Once in Bern, he earned his living by teaching private lessons in physics and mathematics to pupils and students which he advertised in a local newspaper. In early June, Einstein was finally employed at the Patent Office as a technical expert 3rd class. In September of that year his first paper on the foundations of the molecular (kinetic) theory of heat was published in the Annals of Physics.
On October 10, Einstein’s father passed away in Milan. Shortly before his death, he had given permission to his son to marry his study colleague and girl friend Mileva Marić.
On and after the Easter holidays 1903, Einstein met with his friends Maurice Solovine and Conrad Habicht for regular intellectual exchanges and discussions on a variety of scientific and philosophical topics. The group, named Akademie Olympia, lasted until 1905, and was warmly remembered by Einstein until the end of his life. On May 2nd, Einstein joined the Society for Natural Sciences Bern (SNSB) as a member.
At the end of October, Mileva and Albert rented an apartment in the old-town region of Bern at Kramgasse 49. In early December, Einstein contributed to the programme of the SNSB by delivering his first talk entitled ‘The theory of electromagnetic waves’.
In June the third paper of Einstein, dedicated to The Theory of Heat with an application to black-body radiation and confirming the already known displacement law of Willi Wien, appeared in the Annals. In mid-September, Einstein obtained a permanent employment at the Patent Office, combined with a significant enhancement of the salary.
Apart from an academic environment (universities) he, all alone, succeeded in a rather short time to shake up the then current fundamental understanding of physics and to open up far reaching scientific perspectives. In view of his 48 hour per week work load at the Office, this feat is really astounding. There is to add that during that same time period, Einstein and his family travelled abroad to Zagreb and Novi Sad to visit Mileva’s family.
In the first of these papers, addressing „Energetic Properties of Light“, he argued that there must be a fundamental difference between the description of the propagation of light and of its interaction with matter, respectively. He emphasized the discrepancy between the well established propagation of light as a travelling electromagnetic wave and, as he concluded from considering the thermodynamic properties of radiation, the obtruding description of light emission and -absorption in the form of quantized energy transfers between radiation and matter. Of course, he recognized the emerging fundamental problem which bothered him continuously, but he could not find a satisfactory solution for many years to come. It was, however, this work which finally earned him the Nobel prize in 1921.
In the second publication Einstein attempted to determine the size of molecules or atoms, respectively, by analyzing diffusion phenomena in dilute solutions and their relation to internal friction. He submitted this essay, directly proving the molecular structure of materials, as his doctoral dissertation to the University of Zürich and dedicated it to his friend Marcel Grossmann.
With the third publication, Einstein succeeded in offering an understanding of the long and well known but yet unexplained Brownian motion, i.e., the thermally induced motion of suspended particles in liquids at rest. From his discussion, involving the theory of heat, it follows that with an optical microscope it is possible to experimentally determine Avogadro’s number, i.e., the number of atoms contained in a unit volume. A really surprising result.
Most attention on short terms generated the fourth paper on „Electrodynamics of moving bodies“ which he later, after the advent of the General Theory of Relativity 1915, renamed as the „Special Theory of Relativity“. The insight that the state of absolute rest cannot be verified by experiment led Einstein to formulate the so-called „principle of relativity“ and postulated it to be universally valid. With the additional assumption that the speed of light in vacuum is fixed, i.e., the speed of light is independent of the velocity of a moving light source, he, by applying kinematics, succeeded in finding new relations between space- and time coordinates which are, to a large extent, counterintuitive.
In the last of the five mentioned publications of that short period of time, Einstein described a consequence of his Theory of Relativity and showed that energy and mass are equivalent as formally is captured in the famous equation E = mc2. To be precise, here E denotes the ‘rest energy E0’. Note that the mass of a body is independent of its motion.
During March and April of that year, H.A. Lorentz, Nobel laureate for physics in 1902, delivered a series of lectures as a guest professor at Columbia University in New York. On that occasion he discussed the content and the consequences of Einsteins new Theory of Relativity, a sure sign that Einstein’s work had already stirred the interest of then leading scientists. Other prompt written reactions on the theory were due to Max von Laue, then assistant of Max Planck, and to Wilhelm Röntgen, the first ever recipient of the Nobelprize in Physics in 1901. Both von Laue (1914) as well as Planck (1918) earned the Nobel prize a few years later.
In one of the various follow-up publications of the series of works completed in 1905, Einstein presented an alternative way to show that the inertia of a body depends on its energy content. Towards the end of the year, Einstein applied his insight of the previous year regarding the discrete or quantized energy transfer related to the emission or absorption of radiation (light), on the description of the energy balance of solid matter. He showed that this approach led to the understanding of the previously measured but puzzling temperature dependence of the specific heat of solids at very low temperatures. In this way he, on hindsight, can also be considered as the founder of modern condensed matter physics, no doubt yet another pioneering step.
In June, Einstein applied for the permission to teach courses at the University of Bern. Because of Einstein’s reluctance to follow the usual procedure, it was not granted. In August, Einstein and his family spent 10 days of vacation in Lenk, a village in the Bernese Oberland.
Later in the fall, on a request of Johannes Stark (Nobel laureate for physics in 1919) Einstein wrote a review on ‘The principle of relativity and its consequences’. Included in this work was a chapter ‘The Principle of Relativity and Gravitation’. In this, Einstein made the first step towards the general theory of relativity. The mathematically correct formal theory which also provided numerical agreement with a then established experimental result (perihelion rotation of Mercury) had to wait for another 8 years. It was completed by Einstein in November 1915 in Berlin.
In February, Einstein described a method to measure small amounts of electrical charge in the journal Physikalische Zeitschrift. It must be added that neither the method nor the practical layout of the apparatus which Einstein termed ‘the Maschinchen’ were really new. Under his supervision, the instrument was developed by the the brothers Conrad and Paul Habicht. The latter described the apparatus and its functioning in an article which appeared during 1910 again in the Physikalische Zeitschrift.
Starting in April Einstein taught a course on ‘The molecular Theory of Heat’ at the University. After the end of the summer term the family spent 2 weeks of vacation in the Bernese Oberland; this time in Mürren and Isenfluh, for one week each. Scientifically Einstein was involved in both theoretical and experimental activities. The first was a collaboration with Jakob Laub who, as a guest of Einstein, spent 3 weeks in Bern. The second, in the laboratory of Albert Gockel at the University of Fribourg, was dedicated to experiments to optimize the performance of the above mentioned Maschinchen.
His lecture course in the subsequent winter term ‘The theory of radiation’ was poorly attended, most likely due to the rather advanced level on which the topic was presented.
In May Einstein received an offer of the University of Zürich for an extraordinary professorship for Theoretical Physics. The principal promotor of the offer was Professor Alfred Kleiner, who earlier had recommended to accept Einstein’s submitted thesis and to grant him the doctoral degree in 1906.
In July the University of Geneva chose to honour Einstein, at the age of only 30, with a honorary doctoral degree for his outstanding achievements in the physical sciences.
In September Einstein accepted an invitation to participate at the annual meeting of the ‘Gesellschaft Deutscher Naturforscher und Aerzte’ in Salzburg (Austria), his first international appearance. In his presentation he spoke on ‘The development of our views on the nature and constitution of radiation’. He realized that he didn’t really reach the audience nor its understanding of what he was trying to convey.
At the beginning of October, he was, for the first time, nominated to receive the Nobel prize. In the middle of the same month he left Bern to take up his duties as a professor at the University of Zürich.
Thus, during his time in Bern Einstein, in a few years, rose from a scientific nobody to one the most influential scientists of his time.