A Theory of Everything (That Matters): A Brief Guide to Einstein, Relativity, and His Surprising Thoughts on God by Alister McGrath- Part 4, Chapter 3- A Scientific Revolutionary: Einstein’s Four Papers of 1905
We are reviewing Alister McGrath’s new book, “A Theory of Everything (That Matters): A Brief Guide to Einstein, Relativity, and His Surprising Thoughts on God”. Chapter 3 is entitled- “A Scientific Revolutionary: Einstein’s Four Papers of 1905”. In 1905, Albert Einstein was working as a clerk in the Swiss patent office, the Federal Office for Intellectual Property in Bern. At that time, he held no academic position in any university or research institute. The accounts of his time there suggest he was diligent in his duties. But the job was intellectually undemanding, and he found he had time to work on projects that really mattered to him – solving the riddles of physics that remained unsolved at the beginning of the 20th century.
Einstein was born to nonobservant Jewish parents at Ulm, in the kingdom of Württemberg, on March 14, 1879. Württemberg had recently become part of a unified Germany after the Franco-Prussian War in 1871. He began his education in Munich, after his parents moved there. His goal was to settle in Switzerland and train as a teacher in physics and mathematics at the Swiss Federal Polytechnic School in Zurich, which he attended as a student. However, his grades were not outstanding, and it was clear to Einstein that there was little likelihood he would secure an academic position in Switzerland. He renounced his German citizenship in 1896 and in 1901 he acquired Swiss citizenship. In 1902 he found the relatively well-paid job as a technical assistant in the Swiss patent office. In January 1903 he married the Serbian mathematician Mileva Marić, who was a fellow student during his time at Zurich Polytechnic. The couple had two children: Hans Albert born in 1904, and Eduard, born in 1910.
Einstein was influenced at that time by German physicist Ludwig Boltzmann, who explained the observed properties of gases as “discreet particles of definite size which move according to certain conditions”. This “kinetic theory of gases”, developed by Boltzman, emphasized that atoms were not some kind of hypothetical theoretical construction but were real objects. This ran counter to the dominant view of that time, which was forcefully expressed in the writings of Ernst Mach. Einstein later criticized Mach and his followers for allowing their scientific ideas to be determined by their philosophical presuppositions, arguing their prejudices against atomic theory were due to “their positivistic philosophical views”. Positivism is a philosophical system deeply rooted in science and mathematics. It’s based on the view that whatever exists can be verified through experiments, observation, and mathematical/logical proof. Everything else is nonexistent. As we’ll see later in the book, although Einstein as a good scientist was an empiricist, he did not agree with the assertion that only statements verifiable through direct observation or logical proof are meaningful: he was a vibrant imaginative and valued intuition.
Boltzmann’s ideas stimulated Einstein to write his first published paper in 1901 on the implications of the well-known “capillary effect”, the ability of fluid to flow in confined spaces without the assistance of gravity, or even in opposition to gravity. A familiar example is water moving upward in concrete, or sap rising in trees. The paper was not particularly well written or argued. Einstein’s proposal for a correlation between the atomic weight of a liquid and the extent of its capillary action is no longer taken seriously. But having a published paper to his name, he was able to circulate it to academic institutions in hope of finding a position.
In recent years, increased attention has been paid to this early article on account of a suspicion that Einstein might have had some unacknowledged assistance from Mileva Marić. McGrath notes there was a 2003 documentary, titled Einstein’s Wife, that asserted that Marić was originally credited as a coauthor on several of these 1905 papers before her name was supposedly mysteriously removed from the final version of the texts. McGrath notes this fits an influential media narrative which notes that male artists and academics of this period were prone to incorporate the ideas of female students or collaborators into their own work without due acknowledgment, a point which no doubt was true and ubiquitous. However, this suggestion is no longer taken seriously. Mileva Marić did indeed support and encourage Einstein, but the core ideas were Einstein’s own, even if he was wise enough to consult others in his quest to present them most effectively.
Which brings us to March 1905 and the first of Einstein’s seminal papers in his annus mirabilis – wonderful year that established his reputation as one of the most significant scientific thinkers of his age. What is now known as the “photoelectric effect” was first observed in 1887 by German physicist Heinrich Hertz, and investigated more thoroughly by Hertz’s colleague Philipp Lenard in 1902. Under the right circumstances, it was found that if a beam of light was shone on certain metals, the beam was able to eject electrons from the surface of those metals.
As might be expected, Lenard’s 1902 experiments found that the rate of emission of electrons from the surface of the metal was directly proportional to the intensity of the light falling on it. The brighter the light the more electrons were dislodged from the metal surface. But the intensity of the light seemed to have no effect on the energy of the electrons emitted. The electrons emitted through exposure to a very bright light turned out to have the same energy as those emitted from exposure to a very dim light. That didn’t make sense. Furthermore, photoelectrons were emitted only if the frequency of the light (the number of light waves that pass a point per a certain time—typically one second) exceeded a threshold frequency, which varied from metal to metal. So why should the color of the light matter? Why did blue light seem more effective than red light?
In his first paper of 1905, Einstein proposed that according to the evidence, light seemed to be composed of particles (later named photons). Based on the work of Max Planck, energy may seem to be continuous, but on closer examination, it is made up of tiny packets (Planck called quanta) of energy. Einstein argued that the photoelectric effect was best understood in terms of a collision between incoming particle-like bundle of energy and an electron close to the surface of the metal. Einstein’s theory allowed two of Lenard’s otherwise puzzling observations to be explained:
- The critical factor that determines whether an electron is ejected is not the intensity of the light but its frequency (color).
- The observed features of the photoelectric effect can be accounted for by assuming that the collision between the incoming photon and the metallic electron obeys the principle of the conservation of energy. If the energy of the incoming photon is less than a certain quantity (the “work function” of the metal in question), no electrons will be emitted, no matter how intense the bombardment with photons. Above this threshold, the kinetic energy of the emitted electrons is directly proportional to the frequency of the radiation.
Einstein’s brilliant theoretical account for the photoelectric effect suggested that electromagnetic radiation had to be considered as behaving as particles under certain conditions. McGrath says it met with intense opposition, not least because it appeared to involve the abandonment of the prevailing classical understanding of the total exclusivity of waves and particles: something could be one or the other but not both. It wasn’t until 1915 that Einstein’s approach began to achieve acceptance, and he did not receive his Nobel Prize in physics until 1921. Einstein’s article was of critical importance in developing the field of quantum mechanics, yet Einstein later did not like the way in which quantum theory developed during the 1920s, especially as it came to place an emphasis on probability. Nevertheless, Einstein was instrumental in the development of what he called the “wave-particle duality of light”.