But problems arise if one considers light as waves traveling through an aether, which are resolved by applying the relativity of simultaneity. It is entirely possible, therefore, that Einstein arrived at special relativity through a different path than that commonly assumed, through Einstein's examination of fizeau's experiment and stellar aberration. 15 we therefore do not know just how important clock synchronization and the train and embankment thought experiment were to einstein's development of the concept of the relativity of simultaneity. We do know, however, that the train and embankment thought experiment was the preferred means whereby he chose to teach this concept to the general public. P 5 :2931 General relativity edit falling painters and accelerating elevators edit see also: Equivalence principle In his unpublished 1920 review, einstein related the genesis of his thoughts on the equivalence principle: When I was busy (in 1907) writing a summary of my work. While attempts in this direction showed the practicability of this enterprise, they did not satisfy me because they would have had to be based upon unfounded physical hypotheses. At that moment I got the happiest thought of my life in the following form: In an example worth considering, the gravitational field has a relative existence only in a manner similar to the electric field generated by magneto-electric induction.
Albert, einstein - facts summary
P 5 :2931 note 3 A routine supposition among historians of science is that, in accordance with the analysis given in his 1905 special relativity paper and in his popular writings, einstein discovered the relativity of simultaneity by thinking about how clocks could be synchronized. 15 The einstein synchronization convention was originally developed by telegraphers in the middle 19th century. The dissemination of precise time was an increasingly important topic need during this period. Trains needed accurate time to schedule use of track, cartographers needed accurate time to determine longitude, while astronomers and surveyors dared to consider the worldwide dissemination of time to accuracies of thousandths of a second. 16 :132144;183187 Following this line of argument, einstein's position in the patent office, where he specialized in evaluating electromagnetic and electromechanical patents, would have exposed him to the latest developments in time technology, which would have guided him in his thoughts towards understanding the relativity. 16 :243263 However, all of the above is supposition. In later recollections, when Einstein was asked about what inspired him to develop special relativity, he would mention his riding a light beam and his magnet and conductor thought experiments. He would also mention the importance of the fizeau experiment and the observation of stellar aberration. "They were enough he said. 17 he never mentioned thought experiments about clocks and their synchronization. 15 The routine analyses of the fizeau experiment and of stellar aberration, that treat light as Newtonian corpuscles, do not require relativity.
Documentary evidence concerning the development of the ideas that went into it consist of, quite literally, only two sentences in a handful of preserved early letters, and various later historical remarks by einstein himself, some of them known only second-hand and at times contradictory. 8 Train and embankment thought experiment In regards to the relativity of simultaneity, einstein's 1905 paper develops the concept vividly by carefully considering the basics of how time may be disseminated through the exchange of signals between clocks. 15 In his popular work, relativity: The Special and General Theory, einstein translates the formal presentation of his paper into a thought experiment using a train, a railway embankment, and lightning flashes. The essence of the thought experiment is as follows: Observer M stands on an embankment, while observer m' rides on a rapidly traveling train. At the precise moment that m and m' coincide in their positions, lightning strikes points a and b equidistant from m and m'. Light from these two flashes reach m at the same time, from which M concludes that the bolts were synchronous. The combination of Einstein's first and second postulates implies that, despite the rapid motion of the train relative to the embankment, m' measures exactly the same speed of light as does. Since m' was equidistant from a and B when lightning struck, the fact that m' receives light from B before light from A means that to m', the bolts were not synchronous. Instead, the bolt at B struck first.
P 1 :49 That decision ultimately led to his development of special relativity as a theory founded on two postulates of which he could be sure. 10 Expressed in contemporary physics vocabulary, his postulates were as follows: note. The laws of physics take the same form in all inertial frames. In any given inertial frame, the velocity of light c is the same whether the light be emitted by a body at rest or by a body in uniform motion. Emphasis added by editor 12 :140141 Einstein's wording of the second postulate was one with which nearly all theorists of his day could agree. His wording is a far more intuitive form of the second postulate than the stronger version frequently encountered in popular writings and college textbooks. 13 note 2 Trains, embankments, and lightning flashes edit see essay also: Relativity of simultaneity The topic of how Einstein arrived at special relativity has been a fascinating one to many scholars, and it is not hard to understand why: A lowly, twenty-six year old patent. 8 Einstein's paper, On the Electrodynamics of moving Bodies, is a polished work that bears few traces of its gestation.
review on the fundamental Ideas and Methods of the Theory of Relativity (unpublished einstein related how disturbing he found this asymmetry: The idea that these two cases should essentially be different was unbearable. According to my conviction, the difference between the two could only lie in the choice of the point of view, but not in a real difference in the reality of nature. P 4 :20 Einstein needed to extend the relativity of motion that he perceived between magnet and conductor in the above thought experiment to a full theory. For years, however, he did not know how this might be done. The exact path that Einstein took to resolve this issue is unknown. We do know, however, that Einstein spent several years pursuing an emission theory of light, encountering difficulties that eventually led him to give up the attempt. 10 Gradually i despaired of the possibility of discovering the true laws by means of constructive efforts based on known facts. The longer and more desperately i tried, the more i came to the conviction that only the discovery of a universal formal principle could lead us to assured results.
Albert, einstein : His, musical, life - cmuse
7 8 9 Magnet and conductor edit see also: moving magnet and conductor problem In the essay very first paragraph of Einstein's seminal 1905 work introducing special relativity, he writes: It is known that the application of Maxwell's electrodynamics, as ordinarily conceived at the present time. Let us, for example, think of the mutual action between a magnet and a conductor. The observed phenomenon in this case depends only on the relative motion of the conductor and the magnet, while according to the usual conception, a strict distinction must be made between the cases where the one or the other of the bodies is in motion. If, for example, the magnet moves and the conductor is at rest, then an electric field of certain energy-value is produced in the neighbourhood of the magnet, which excites a current in those parts of the field where a conductor exists. But if spill the magnet be at rest and the conductor be set in motion, no electric field is produced in the neighbourhood of the magnet, but an electromotive force is produced in the conductor which corresponds to no energy per se; however, this causes equality. P 2 Magnet and conductor thought experiment This opening paragraph recounts well-known experimental results obtained by michael Faraday in 1831. The experiments describe what appeared to be two different phenomena: the motional emf generated when a wire moves through a magnetic field (see lorentz force and the transformer emf generated by a changing magnetic field (due to the maxwellFaraday equation ).
9 10 11 :135157 James Clerk maxwell himself drew attention to this fact in his 1861 paper On Physical Lines of Force. In the latter half of Part ii of that paper, maxwell gave a separate physical explanation for each of the two phenomena. P 3 Although Einstein calls the asymmetry "well-known there is no evidence that any of Einstein's contemporaries considered the distinction between motional emf and transformer emf to be in any way odd or pointing to a lack of understanding of the underlying physics. Maxwell, for instance, had repeatedly discussed Faraday's laws of induction, stressing that the magnitude and direction of the induced current was a function only of the relative motion of the magnet and the conductor, without being bothered by the clear distinction between conductor-in-motion and magnet-in-motion. 11 :135138 Yet Einstein's reflection on this experiment represented the decisive moment in his long and tortuous path to special relativity. Although the equations describing the two scenarios are entirely different, there is no measurement that can distinguish whether the magnet is moving, the conductor is moving, or both.
The second issue is that a 19th century aether theorist would have had no difficulties with the thought experiment. Einstein's statement, ".there seems to be no such thing. On the basis of experience would not have counted as an objection, but would have represented a mere statement of fact, since no one had ever traveled at such speeds. An aether theorist would have regarded ".nor according to maxwell's equations" as simply representing a misunderstanding on Einstein's part. Unfettered by any notion that the speed of light represents a cosmic limit, the aether theorist would simply have set velocity equal to c, noted that yes indeed, the light would appear to be frozen, and then thought no more. 7 Rather than the thought experiment being at all incompatible with aether theories (which it is not the youthful Einstein appears to have reacted to the scenario out of an intuitive sense of wrongness.
He felt that the laws of optics should obey the principle of relativity. As he grew older, his early thought experiment acquired deeper levels of significance: Einstein felt that Maxwell's equations should be the same for all observers in inertial motion. From Maxwell's equations, one can deduce a single speed of light, and there is nothing in this computation that depends on an observer's speed. Einstein sensed a conflict between Newtonian mechanics and the constant speed of light determined by maxwell's equations. 6 :114115 Regardless of the historical and scientific issues described above, einstein's early thought experiment was part of the repertoire of test cases that he used to check on the viability of physical theories. Norton suggests that the real importance of the thought experiment was that it provided a powerful objection to emission theories of light, which Einstein had worked on for several years prior to 1905.
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For how should the first observer know or be able to determine, that he is in a state of fast uniform motion? One sees in this paradox the germ of the special relativity theory is already contained. P 1 :5253 Einstein's thought experiment as a 16 year old student Einstein's recollections of his youthful musings are widely cited because of the hints they provide of his later great discovery. However, norton has noted essay that Einstein's reminiscences were probably colored by a half-century of hindsight. Norton lists several problems with Einstein's recounting, both historical with and scientific:. At 16 years old and a student at the gymnasium in Aarau, einstein would have had the thought experiment in late 1895 to early 1896. But various sources note that Einstein did not learn Maxwell's theory until 1898, in university.
Discorsi trip e dimostrazioni matematiche (1638). 5, einstein had a highly visual understanding of physics. His work in the patent office "stimulated him to see the physical ramifications of theoretical concepts." These aspects of his thinking style inspired him to fill his papers with vivid practical detail making them quite different from, say, the papers of Lorentz or Maxwell. This included his use of thought experiments. 6 :2627;121127 Special relativity edit pursuing a beam of light edit see also: Einstein's views on the aether Late in life, einstein recalled. A paradox upon which I had already hit at the age of sixteen: If I pursue a beam of light with the velocity c (velocity of light in a vacuum i should observe such a beam of light as an electromagnetic field at rest though. There seems to be no such thing, however, neither on the basis of experience nor according to maxwell's equations. From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest.
thought experiment is a good argument; a bad thought experiment is a bad argument." 3, when effectively used, the irrelevant particulars that convert a straightforward argument into a thought experiment can act as "intuition. Thought experiments have a long history. Perhaps the best known in the history of modern science. Galileo 's demonstration that falling objects must fall at the same rate regardless of their masses. This has sometimes been taken to be an actual physical demonstration, involving his climbing up the. Leaning Tower of Pisa and dropping two heavy weights off. In fact, it was a logical demonstration described by galileo.
In a profound contribution to the literature on quantum mechanics, einstein considered two particles briefly interacting and then flying apart so that their states are correlated, anticipating the phenomenon known as quantum entanglement. Contents, introduction edit, see also: Thought experiment, a thought experiment is a logical argument or mental model cast within the context of an imaginary (hypothetical or even counterfactual) scenario. A scientific thought experiment, in particular, may examine the implications of a theory, law, or set of principles with the aid of fictive and/or natural particulars (demons sorting molecules, cats whose lives hinge upon a radioactive estate disintegration, men in enclosed elevators) in an idealized environment. They describe experiments that, except for some specific and necessary idealizations, could conceivably be performed in the real world. 2, as opposed to physical experiments, thought experiments do not report new empirical data. They can only provide conclusions based on deductive or inductive reasoning from their starting assumptions. Thought experiments invoke particulars that are irrelevant to the generality of their conclusions.
50 Interesting Facts About, albert, einstein - the fact File
A hallmark of, albert Einstein 's career was his use of visualized thought experiments german : Gedankenexperiment 1 ) as a fundamental tool for understanding physical issues and for elucidating his concepts to others. Einstein's thought experiments took diverse forms. In his youth, he mentally chased beams of light. For special relativity, he employed moving trains and flashes of lightning to explain his most penetrating insights. For general relativity, he considered a person falling off a roof, accelerating elevators, blind beetles crawling on curved surfaces and the like. In his debates with. Niels Bohr book on the nature of reality, he proposed imaginary devices intended to show, at least in concept, how the. Heisenberg uncertainty principle might be evaded.