Annus Mirabilis Papers
From Biocrawler, the free encyclopedia.
The Annus Mirabilis Papers (from Annus mirabilis, Latin for 'year of wonders') are the papers of Albert Einstein submitted to the "Annalen der Physik" journal. The four articles provided a foundation for modern physics. Einstein was a bureaucrat at the Patent Office in Bern, this provided him information on various effects and devices via inventors. Besides his work, family, and friends, Einstein was without much scientific literature to which he could refer elsewhere nor many scientific colleagues with whom he could discuss theories with. Mileva Marić, though, was both Einstein's wife and intellectual partner. The author of the papers of 1905 could rightly be ascribed to Einstein — Marić. Her influence on Einstein's work is highly controversial, though, and is a debated question.
| Contents |
Papers
Three of those papers (on Brownian motion, the photoelectric effect, and special relativity) deserved Nobel Prizes according to some physicists. Only the paper on the photoelectric effect would win one. What makes these papers remarkable is that, in each case, Einstein boldly took an idea from theoretical physics to its logical consequences and managed to explain experimental results that had baffled scientists for decades.
Photoelectric effect
The first paper, named "On a Heuristic Viewpoint Concerning the Production and Transformation of Light", ("Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt") proposed the idea of "energy quanta" and showed how it could be used to explain such phenomena as the photoelectric effect. The idea of energy quanta was motivated by Max Planck's earlier derivation of the law of black-body radiation by assuming that luminous energy could only be absorbed or emitted in discrete amounts, called quanta. Einstein showed that, by assuming that light actually consisted of discrete packets, he could explain the mysterious photoelectric effect.
The idea of light quanta contradicted the wave theory of light that followed naturally from James Clerk Maxwell's equations for electromagnetic behavior and, more generally, the assumption of infinite divisibility of energy in physical systems. Even after experiments showed that Einstein's equations for the photoelectric effect were accurate, his explanation was not universally accepted. However, by 1921, when he was awarded the Nobel Prize and his work on photoelectricity was mentioned by name in the award citation, most physicists thought that the equation (hf = Φ + Ek) was correct and light quanta were possible.
The theory of light quanta was a strong indication of wave-particle duality, the concept, used as a fundamental principle by the creators of quantum mechanics, that physical systems can display both wave-like and particle-like properties. A complete picture of the photoelectric effect was only obtained after the maturity of quantum mechanics.
Brownian motion
His second article in 1905, named "On the Motion — Required by the Molecular Kinetic Theory of Heat — of Small Particles Suspended in a Stationary Liquid", ("Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen") delineated a stochastic model of Brownian motion. Brownian motion generates expressions for the root mean square displacement of particles. Using the then-controversial kinetic theory of fluids, it established that the phenomenon, which still lacked a satisfactory explanation decades after it was first observed, provided empirical evidence for the reality of atoms. It also lent credence to statistical mechanics, which was also controversial at the time.
Before this paper, atoms were recognized as a useful concept, but physicists and chemists hotly debated whether atoms were real entities. Einstein's statistical discussion of atomic behavior gave experimentalists a way to count atoms by looking through an ordinary microscope. Wilhelm Ostwald, one of the leaders of the anti-atom school, later told Arnold Sommerfeld that he had been converted to a belief in atoms by Einstein's complete explanation of Brownian motion.
Special relativity
Einstein's third paper that year was called "On the Electrodynamics of Moving Bodies" ("Zur Elektrodynamik bewegter Körper", published on June 30, 1905). The content of the paper is highly self-contained work, hardly making reference to other works which may have lead to it's development. While developing this paper, Einstein wrote to Mileva about "our work on relative motion", and this has led some to ask whether Mileva played a part in its development (as well as the other papers). This paper introduced a theory of time, distance, mass and energy which was consistent with electromagnetism, but omitted the force of gravity.
Special relativity avoided the problem in science that was present since the Michelson-Morley experiment, which had did not detected a medium of conductance for light waves unlike other known waves which require a medium (such as water or air). Einstein stated,
- ... the unsuccessful attempts to discover any motion of the earth relatively to the "light medium," suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest.
The speed of light was thus fixed, and not relative to the movement of the observer. This was impossible under Newtonian classical mechanics. Einstein stated,
- ... the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good. We will raise this conjecture (the purport of which will hereafter be called the "Principle of Relativity") to the status of a postulate, and also introduce another postulate, which is only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body. These two postulates suffice for the attainment of a simple and consistent theory of the electrodynamics of moving bodies based on Maxwell's theory for stationary bodies. The introduction of a "luminiferous ether" will prove to be superfluous inasmuch as the view here to be developed will not require an "absolutely stationary space" provided with special properties, nor assign a velocity-vector to a point of the empty space in which electromagnetic processes take place.
- The theory [...] is based - like all electrodynamics - on the kinematics of the rigid body, since the assertions of any such theory have to do with the relationships between rigid bodies (systems of co-ordinates), clocks, and electromagnetic processes. Insufficient consideration of this circumstance lies at the root of the difficulties which the electrodynamics of moving bodies at present encounters.
It had already been conjectured by George Fitzgerald in 1894 that the Michelson-Morley result could be accounted for if moving bodies were squashed in the direction of their motion. Indeed, some of the paper's core equations, the Lorentz transforms, had been introduced in 1903 by Dutch physicist Hendrik Lorentz, giving mathematical form to Fitzgerald's conjecture. But Einstein revealed the underlying reasons for this geometrical oddity.
His explanation arose from two axioms. First was Galileo's old idea that the laws of nature should be the same for all observers that move with constant speed relative to each other. Einstein stated,
- The laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two systems of co-ordinates in uniform translatory motion.
The second was the rule that the speed of light is the same for every observer. Einstein stated,
- Any ray of light moves in the "stationary" system of co-ordinates with the determined velocity c, whether the ray be emitted by a stationary or by a moving body.
Special relativity has several striking consequences, because the absolute concepts of time and distance are rejected. The theory came to be called the "special theory of relativity" to distinguish it from his later theory of general relativity, which considers all observers to be equivalent. The theory abounded with paradoxes, and appeared to make little sense, landing Einstein substantial ridicule, but he eventually managed to work out the apparent contradictions and solve the problems.
Energy equivalence
A fourth paper, "Does the Inertia of a Body Depend Upon Its Energy Content?", ("Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?") was published late in 1905. Einstein considered the equivalency equation to be of paramount importance because it showed that a massive particle possesses an energy, the "rest energy", distinct from its classical kinetic and potential energies. Nevertheless, most scientists simply regarded the finding as a curiosity until the 1930s.
The paper was based on James Clerk Maxwell's and Heinrich Rudolf Hertz's investigations and, in addition, the axioms of relativity, as Einstein stated,
- The results of the previous investigation lead to a very interesting conclusion, which is here to be deduced.
- [The previous investigation was based] on the Maxwell-Hertz equations for empty space, together with the Maxwellian expression for the electromagnetic energy of space ...
- The laws by which the states of physical systems alter are independent of the alternative, to which of two systems of coordinates, in uniform motion of parallel translation relatively to each other, these alterations of state are referred (principle of relativity).
The equation set forth was that energy of a body at rest (E) equals its mass (m) times the speed of light (c) squared or E = mc². Einstein stated,
- If a body gives off the energy L in the form of radiation, its mass diminishes by L/c². The fact that the energy withdrawn from the body becomes energy of radiation evidently makes no difference, so that we are led to the more general conclusion that
- The mass of a body is a measure of its energy-content; if the energy changes by L, the mass changes in the same sense by L/9 × 1020, the energy being measured in ergs, and the mass in grammes.
- [...]
- If the theory corresponds to the facts, radiation conveys inertia between the emitting and absorbing bodies.
The mass-energy relation can be used to predict how much energy will be released or consumed by chemical and nuclear reactions; one simply measures the mass of all constituents and products and multiplies the difference by c2. The result shows how much energy will be released or consumed, usually in the form of light or heat. If applied to certain nuclear reactions, the equation shows that an extraordinarily large amount of energy will be released, much larger than in the combustion of chemical explosives, where the mass difference is hardly measurable at all. This explains why nuclear weapons produce such phenomenal amounts of energy.
According to Umberto Bartocci (University of Perugia historian of mathematics), the famous equation was first published two years earlier by Olinto De Pretto, an industrialist from Vicenza, Italy, though this is not generally regarded as true or important by mainstream historians. Even if De Pretto introduced the formula, it was Einstein who connected it with the theory of relativity.
Commemoration
The International Union of Pure and Applied Physics (IUPAP) plans to commemorate the 100th year of the publication of Einstein's extensive work in 1905 as the 'World Year of Physics 2005'.
Futher reading
- Stachel, John, et. al., "Einstein's Miraculous Year". Princeton University Press, 1998. ISBN 0691059381
References
- "On a heuristic viewpoint concerning the production and transformation of light". Annalen der Physik, 17(1905), pp. 132-148.
- "On the motion of small particles suspended in liquids at rest required by the molecular-kinetic theory of heat". Annalen der Physik, 17 (1905) pp. 549-560.
- "On the Electrodynamics of Moving Bodies (http://www.fourmilab.ch/etexts/einstein/specrel/www/)". Annalen der Physik, 17 (1905), pp. 891-921.
- "Does the Inertia of a Body Depend Upon Its Energy Content? (http://www.fourmilab.ch/etexts/einstein/E_mc2/www/)". Annalen der Physik, 18 (1905), pp. 639-641.
