Annus Mirabilis Papers
From The UCSC Wikipedia Trust Project
The Annus Mirabilis Papers (from Latin, Annus mirabilis, for 'extraordinary year') are the papers of Albert Einstein published in the "Annalen der Physik" Scientific journal in 1905. These four articles contributed substantially to the foundation of modern physics and changed views on space, time, and matter. The Annus Mirabilis is often called the "Miracle Year" in English, in German, the "Wunderjahr".[1]
Contents |
Background
At the time the papers were written, Einstein lacked substantial scientific reference materials. Additionally, scientific colleagues available to discuss his theories were few.Template:Fact He worked as an examiner at the Patent Office in Bern, Switzerland. In addition to work, his wife, Mileva Marić, may have had some influence on Einstein's work but how much is unclear. It is speculated that, at the very least, she proofread many of his articles.[2][3] Through these papers, Einstein tackles some of the era's most important physics questions and problems. In 1900, a lecture titled Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light, by Lord Kelvin, suggested that physics was unsatisfactory in the explanations of two phenomena: the Michelson-Morley experiment and black body radiation. As introduced, Special relativity provided an account for the results of the Michelson-Morley experiments. Einstein's theories for the photoelectric effect demonstrate some quantum mechanics, which also explain black body radiation.
Papers
There is no doubt that Einstein's published works on Brownian motion, and special relativity deserved Nobel Prizes, but it was his work on the photoelectric effect which won him his Nobel Prize in 1921: "For services to theoretical physics and especially for the discovery of the law of the photoelectric effect." The Nobel committee had waited patiently for experimental confirmation of special relativity; however none was forthcoming until the 1941 time dilation experiments of Rossi and Hall.[4]
Photoelectric effect
The paper, "On a Heuristic Viewpoint Concerning the Production and Transformation of Light",[5] proposed the idea of energy quanta. This idea, motivated by Max Planck's earlier derivation of the law of black-body radiation, assumes that luminous energy can be absorbed or emitted only in discrete amounts, called quanta. Einstein states,
:Energy, during the propagation of a ray of light, is not continuously distributed over steadily increasing spaces, but it consists of a finite number of energy quanta localised at points in space, moving without dividing and capable of being absorbed or generated only as entities.
In explaining the photoelectric effect, the hypothesis that energy consists of discrete packets, as Einstein illustrates, can be directly applied to black bodies, as well.
The idea of light quanta contradicts the wave theory of light that follows naturally from James Clerk Maxwell's equations for electromagnetic behavior and, more generally, the assumption of infinite divisibility of energy in physical systems.
: A profound formal difference exists between the theoretical concepts that physicists have formed about gases and other ponderable bodies, and Maxwell's theory of electromagnetic processes in so-called empty space. While we consider the state of a body to be completely determined by the positions and velocities of an indeed very large yet finite number of atoms and electrons, we make use of continuous spatial functions to determine the electromagnetic state of a volume of space, so that a finite number of quantities cannot be considered as sufficient for the complete determination of the electromagnetic state of space.
: [... this] leads to contradictions when applied to the phenomena of emission and transformation of light.
: According to the view that the incident light consists of energy quanta [...], the production of cathode rays by light can be conceived in the following way. The body's surface layer is penetrated by energy quanta whose energy is converted at least partially into kinetic energy of the electrons. The simplest conception is that a light quantum transfers its entire energy to a single electron [...]
Even after experiments confirmed that Einstein's equations for the photoelectric effect were accurate, his explanation was not universally accepted. Niels Bohr, in his 1922 Nobel address, stated, "The hypothesis of light-quanta is not able to throw light on the nature of radiation."
By 1921, when Einstein was awarded the Nobel Prize and his work on photoelectricity was mentioned by name in the award citation, some physicists accepted that the equation (hf = Φ + Ek) was correct and light quanta were possible. In 1923, Arthur Compton's X-ray scattering experiment helped more of the scientific community to accept this formula. The theory of light quanta was a strong indicator of wave-particle duality, a fundamental principle of quantum mechanics.[6] A complete picture of the theory of photoelectricity was realized after the maturity of quantum mechanics.
Brownian motion
Template:MergefromThe article "On the Motion Required by the Molecular Kinetic Theory of Heat of Small Particles Suspended in a Stationary Liquid"[7] delineated a stochastic model of Brownian motion.
: In this paper it will be shown that, according to the molecular kinetic theory of heat, bodies of a microscopically visible size suspended in liquids must, as a result of thermal molecular motions, perform motions of such magnitudes that they can be easily observed with a microscope. It is possible that the motions to be discussed here are identical with so-called Brownian molecular motion; however, the data available to me on the latter are so imprecise that I could not form a judgment on the question ...
Brownian motion generates expressions for the root mean square displacement of particles. Using the kinetic theory of fluids, which at the time was controversial, the article establishes the phenomenon, which was lacking a satisfactory explanation even decades after the first observation provided empirical evidence for the reality of the atom. It also lends credence to statistical mechanics, which had been controversial at that time, as well. Before this paper, atoms were recognized as a useful concept, but physicists and chemists 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 convinced of the existence of atoms by Einstein's complete explanation of Brownian motion.Template:Fact
Special relativity
Einstein's third paper that year, "On the Electrodynamics of Moving Bodies"[8] reconciles Maxwell's equations for electricity and magnetism with the laws of mechanics, by introducing major changes to mechanics close to the speed of light. This later became known as Einstein's Special theory of relativity.
The paper makes no reference to any works that may have led to its development, and mentions the name of only one other scientist, Hendrik Lorentz.[9] While developing this paper, Einstein had written to his wife 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 her involvement on other papers). This paper introduces a theory of time, distance, mass, and energy that was consistent with electromagnetism, but omitted the force of gravity.
At the time, it was known that Maxwell's equations, when applied to moving bodies, led to asymmetries, and that it had not been possible to discover any motion of the Earth relative to the 'light medium'. Einstein puts forward two postulates to explain these observations. First, he applies the classic principle of relativity, which states that the laws of physics remain the same for any non-accelerating frame of reference (called an inertial reference frame), to the laws of electrodynamics and optics as well as mechanics. In the second postulate, Einstein proposes that the speed of light remains constant in all inertial frames of reference, independent of the state of motion of the emitting body.
Special relativity avoids an ever-present problem since the Michelson-Morley experiment, which had not detected a medium of conductance (or aether) for light waves unlike other known waves that require a medium (such as water or air). Einstein states, :... 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 is fixed, and thus not relative to the movement of the observer. This was impossible under Newtonian classical mechanics. Einstein argues,
: ... 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 previously been conjectured, by George Fitzgerald in 1894 and by Lorentz 1895, independent of each other, that the Michelson-Morley result could be accounted for if moving bodies were contracted in the direction of their motion. Some of the paper's core equations, the Lorentz transforms, had been published by Joseph Larmor (1897, 1900), Hendrik Lorentz (1899, 1903, 1904) and Henri Poincaré (1905), in a development of Lorentz's 1904 paper. Einstein reveals the underlying causes for this geometrical oddity, which differs from the explanations given by FitzGerald, Larmor, and Lorentz, but similar in many respects to the reasons given by Poincaré (1905).
His explanation arises from two axioms. First, Galileo's idea that the laws of nature should be the same for all observers that move with constant speed relative to each other. Einstein writes, : 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 is the rule that the speed of light is the same for every observer. : 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.
The theory, now called the "special theory of relativity" distinguishes it from his later general theory of relativity, which considers all observers to be equivalent. Special relativity at first met with disdain and even ridicule from some quarters since it abounds with apparent paradoxes, and violates "common sense". However, the self-consistency of special relativity, proven in 1908 by Hermann Minkowski, has been supported by an ever-increasing body of confirmatory experimental evidence. As a result, special relativity has come to be largely taken for granted in the scientific community.
Matter and energy equivalence
A fourth paper, "Does the Inertia of a Body Depend Upon Its Energy Content?",[10] was published on September 27 in Annalen der Physik, containing one of the most famous equations in the field of Physics: E=mc². 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 is based on James Clerk Maxwell's and Heinrich Rudolf Hertz's investigations and, in addition, the axioms of relativity, as Einstein states,
: 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 sets forth that energy of a body at rest (E) equals its mass (m) times the speed of light (c) squared, or E = mc².
: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. When 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, as they release binding energy during nuclear fission and nuclear fusion.
Commemoration
The International Union of Pure and Applied Physics (IUPAP) resolved to commemorate the 100th year of the publication of Einstein's extensive work in 1905 as the 'World Year of Physics 2005'. This was subsequently endorsed by both the United Nations and the United States Congress.
Further reading
- Stachel, John, et. al., "Einstein's Miraculous Year". Princeton University Press, 1998. ISBN 0-691-05938-1
- Renn, Jürgen, and Dieter Hoffmann, "1905 — a miraculous year". 2005 J. Phys. B: At. Mol. Opt. Phys. 38 S437-S448 (Max Planck Institute for the History of Science) [Issue 9 (14 May 2005)]
External links
References
Einstein's work
- "On a heuristic viewpoint concerning the production and transformation of light". Translation from the German article, "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt", Annalen der Physik, 17:132-148 (1905)
- "On the motion of small particles suspended in liquids at rest required by the molecular-kinetic theory of heat". Translation from the German article, "Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen", Annalen der Physik, 17:549-560. (1905)
The following two papers appear in The Principle of Relativity, London: Methuen and Company, Ltd. (1923) in English translations by W. Perrett and G.B. Jeffery from the German Das Relativatsprinzip, Tuebner, 4th ed., (1922).
- "On the Electrodynamics of Moving Bodies". (fourmilab.ch web site): Translation from the German article: "Zur Elektrodynamik bewegter Körper", Annalen der Physik. 17:891-921. (June 30, 1905)
- "Does the Inertia of a Body Depend Upon Its Energy Content?". (fourmilab.ch web site): Translation from the German article: "Ist die Trägheit eines Körpers von seinem Energiegehalt abhängig?", Annalen der Physik, 18:639-641. (September 27, 1905)
Other citations
- ↑ "Annalen der Physik - Factbites" (2005), Factbites.com, web: Factbites-Annalen: about annus mirabilis as "miraculous year" in English, or German "Wunderjahr".
- ↑ "Einstein's Wife : The Mileva Question". Oregon Public Broadcasting, 2003 Summary: There is at least one credible source, Abram Joffe, who indicates that Mileva collaborated with Albert on at least some of the 1905 papers. Joffe stated that he saw the names of two authors on the 1905 papers. The letters Mileva exchanged with Albert and other friends lends support to this assertion, also. The editors of The Collected Papers of Albert Einstein noted, though, that they simply do not know for certain if Mileva assisted Albert.
- ↑ Calaprice, Alice, "The Einstein almanac". Johns Hopkins University Press, Baltimore, Md. 2005.
- ↑ Template:Cite journal
- ↑ "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt"
- ↑ Physical systems can display both wave-like and particle-like properties
- ↑ "Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen"
- ↑ "Zur Elektrodynamik bewegter Körper", published on June 30, 1905
- ↑ Regarding the reference to Hendrik Lorentz in Special Theory of Relativity; This upset Henri Poincaré so much that he never mentioned Einstein in any of his papers, and Einstein retaliated, mentioning Poincaré only once; see relativity priority dispute
- ↑ "Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?"
