CHAPTER 13 THE GENERAL THEORY OF RELATIVITY

  Einstein's Special Theory of Relativity deals with the effects of the uniform motion on the relative space and time perceptions of moving and stationary observers. Discussion within the special theory of relativity was always limited to non-accelerated motion. As soon as accelerated motion was encountered, as in the twin paradox, we found ourselves beyond the scope of the special theory of relativity.

  It is in Einstein's General Theory of Relativity, published in 1916, that accelerated motion is taken into account. The general theory of relativity generalizes the results of the special theory and deals with the effect of accelerated motion on space and time perception. The general theory also deals with the effects of a gravitational field on space and time perception by showing the equivalence of accelerated motion and the existence of a gravitational field. This is accomplished by exploiting the fact that the inertial and gravitational masses of all particles are equal. Finally, the general theory of relativity provides a theory of gravity which replaces Newton's theory of gravity.

  We discovered that, within the framework of the special theory of relativity, it is impossible to determine the absolute motion of a frame of reference through space as long as that frame is not undergoing acceleration. Once a frame of reference undergoes acceleration, however, it is impossible to detect this motion because of the fictitious forces which arise as a consequence of the acceleration. These forces are fictitious because, in actuality, the acceleration of a body, with respect to the frame of reference that these fictitious forces seem to cause, it only apparent. In actuality, the body continues to move with constant velocity because of inertia but, relative to the accelerating frame, it appears to be accelerating. The fictitious force causes real motion with respect to the accelerating frame, however, and hence, is perceived as a gravitational force. Einstein exploited this fact and claimed that the effects of the accelerated motion are equivalent to those of a gravitational force. In order to make this assertion, he explained the fact that the gravitational and inertial masses are the same and hence, all particles accelerate at exactly the same rate in a gravitational field. This is also true of the apparent acceleration of the particles in an accelerating frame of the reference. They, too, accelerated at the same rate.

  In order to illustrate the equivalence of accelerated motion and the action of a gravitational field, let us consider the two elevator cars in Fig 13:1. One elevator car is sitting at rest on the surface of the earth. The other elevator car is situated in outer space completely removed from the effects of any gravitational field. The elevator car is being accelerated upwards with a constant acceleration, g, equal to the acceleration of the particle falling near the surface of the earth. We claim that an observer in one of these cars would not be able to determine in which car he was situated because his experiences in both cars would be identical. We would experience a gravitational pull towards the floor of the elevator in both cars. If he dropped two objects, let us say, an iron ball and a wooden ball, in the elevator car on earth, these two balls would fall at exactly the same rate because of the equality of their gravitational and inertial masses.

  If our observer were to drop the balls in the elevator car in outer space, he would experience the two balls accelerating towards the floor at exactly the same rate as they did in the elevator car on earth. The reason for this is as follows: As the observer, releases the two balls from his hand, the balls will no longer be accelerated upwards. They will remain at rest in an inertial frame of reference which was moving at the same speed as the elevator at precisely the time the balls were released. The elevator continues to be accelerated, however, and hence, the floor of the elevator will accelerate up at the rate, g, towards the balls, until the floor hits the balls. To an observer in the elevator, however, it appears as though the balls have fallen to the floor with the acceleration, g. to an observer in the accelerating elevator, masses behave exactly as they do in the elevator on earth. The acceleration of his elevator car acts exactly like a gravitational field.

  If the direction in which the elevator car was being accelerated changed direction so that the elevator was being pulled down with an acceleration, g, then there would be an effective gravitational field pulling things towards the ceiling of the elevator instead of towards the floor. If such an elevator was placed near the surface of the earth, then the effects of the gravitational field produced by its acceleration down would exactly cancel the gravitational field of the earth. This is exactly what happens in an aircraft which is experiencing free fall. The effective gravitational field created as a result of its being accelerated down by the earth, exactly cancels the gravitational field of the earth and hence, observers in the free falling craft experience no gravity. Objects will float around inside the aircraft just as they do when an astronaut travels to the moon and is no longer within the influence of the earth's gravitational field.

  Following Einstein, we have established that the laws of physics describing the motion of massive particles are the same in the elevator car sitting in the earth's gravitational field at rest and in the elevator car being constantly accelerated upwards with an acceleration, g. Einstein concluded that, on the basis of this demonstration, all the laws of physics would be identical in these two frames of reference. He expressed his hypothesis in terms of the equivalence principle which states the following: the phenomena in an accelerating frame of reference are identical with those in a gravitational field.

  The equivalence principle forms the heart of the general theory of relativity. Einstein exploited this principle to successfully predict that, a beam of light, i.e., a beam of photons, would be bent by a gravitational field. This is somewhat surprising in view of the fact that the rest mass of a photon is zero. Although the rest mass is zero, the photo still has energy, and since Einstein showed that mass and energy are equivalent, perhaps light can also be affected by gravity. To demonstrate this, we turn to the propogation of light in an accelerating elevator car.

  Let us consider a beam of light propogating perpendicular to the direction of the acceleration and entering the elevator from one wall and exiting the elevator on the opposite wall. The beam of light will appear bent to an observer inn the elevator, as shown in Fig. 13:3. The reason for this is that, by the time the light beam has propogated from one wall to the other, the elevator has moved upwards because of its acceleration. The beam of light, however, is unaffected by the elevator's acceleration ad hence, continues to propogate along the same straight line it was moving along before it entered the elevator as shown in Fig. 13:4A. Relative to the accelerating elevator, however it appears to exit at a point below the one it entered as shown in Fig. 13:4B. The beam of light will appear, to a observer in the accelerating elevator, to have been bet by the same gravitational field that causes the objects he drops to also fall to the floor. If, instead of a beam of photons, we had sent a beam of massive particles through the elevator, they would behave exactly like the beam of light. An observer in the accelerating frame will conclude that the paths of both the massive particles and the light were bent because both the massive particles and the light were attracted by the gravity. At this point, Einstein exploits the equivalence principle. He argues that, since the laws of physics are the same in the accelerating frame and the stationary frame sitting in a gravitational field, then, one can expect the beam of light to be bent by a bonafide gravitational field such as that generated by the sun.

  On the basis of this argument, he predicted that starlight passing close to the sun would be bent by its gravitational field and hence, during a solar eclipse, the position of a star close to the sun would be displaced from its normal position. In Fig. 13:5, we illustrate how the bending of the starlight by the sun makes it appear that the position of the star has changed position. The first opportunity to measure the effect of the gravitational pull of the sun on starlight came during the total solar eclipse of 1919. The expedition of British scientists who traveled to Africa to observe the eclipse, found that the position of stars near the sun had indeed changed, as Einstein had predicted. This measurement verified the validity of the equivalence principle.

  Einstein further exploited the equivalence principle to determine the effects of a gravitational field on the space and time perceptions of an observer. Let us consider from the point of view of a stationary observer in an inertial frame, a clock in an accelerating elevator car. By virtue of the fact that the clock develops a velocity with respect to the stationary observer, as a result of the elevator's acceleration, we expect the clock to slow down. Hence, the stationary observer will observe a time dilation in the accelerating frame of reference. By virtue of the principle of equivalence, we would also expect that a clock sitting in a gravitational field would also slow down.

  This gravitational time dilation has been experimentally verified in two separate experiments, both of which involve 'atomic clocks'. An atom is like a clock. The electrons orbit the nucleus of the atom with a fixed periodicity. The frequency of light that an atom emits is related to the periodicity of the electron's orbits. Since two identical atoms will radiate the same discreet frequencies or spectral lines if they are in the same inertial frame, a change in the frequency of the radiation of an atom can indicate a change of the time in the frame of reference in which it is situated. The first detection of gravitational time dilation was made by observing the slowing down of the 'atomic clocks' on the surface of the extremely dense white-dwarf stars. The expected shift of the spectral lines towards the red was observed. A more precise observation of the gravitational time dilations was made by Pound in a laboratory setting at Harvard University. Pound compared the spectral lines of two atomic clocks separated by a mere 70 feet in the earth's gravitational field. He found that, the 'atomic clock' sitting closer to the earth and hence, more strongly influenced by its gravitational field, slowed down more than its counterpart 70 feet above it.

  Einstein's General Theory of Relativity describes the effect on space and time measurements of an observer, either imbedded in a gravitational field or else undergoing non-uniform motion. The General Theory of Relativity also provides a theory of gravitation which competes with Newton's theory of gravity. In addition to providing relativistic corrections to Newton's theory, Einstein's theory attempts to explain how the gravitational interaction arises. Newton's principle of action at a distance is replaced by a field concept. According to Einstein, matter warps the space. The warped space, in turn, affects the motion of the matter contained in it. The sun, for example, warps the space in which the solar system is embedded, creating grooves in which the planets move. Determining the gravitational interaction of matter becomes a matter of geometry.

  Before turning to the details of Einstein's model of gravity, we must first discuss the four-dimensional space-time continuum of relativity which replaces Newton's concept of three-dimensional space and absolute time. In the special theory of relativity, we discover an intimate relationship between space and time. Time is no longer independent of the position or motion of an observer. Shortly after Einstein's special theory appeared in 1905, Minkowski proposed that three-dimensional continuum with time playing the role of the fourth dimension. In this space, every event is described by four co-ordinates or number. Three of these co-ordinates, x, y, and z, describing the spatial location of the event while the fourth component, t, describes the time when the event occurs. These co-ordinates are defined with respect to an inertial frame of reference. With respect to some other frame of reference moving with a constant velocity, v, with respect to the original frame, another set of co-ordinates x¢ , y¢ , z¢ , and t¢ are defined. Einstein showed that the co-ordinates x¢ , y¢ , z¢ , and t¢ are related to those of x, y, z, and t by the following formulae when the velocity, v is along the x-axis:  y = y¢ z = z¢

  The details of these equations are not important for the purposes of our discussion so don't let their apparent complication disturb you if you are not mathematically inclined. The important thing to notice about these equations, known as the Lorentz transformation, is that both the position, x, and the time, t, in the stationary frame, depends on both x¢ and t¢ in the unprimed frame. In Newtonian physics, the time in the moving frame would be identical to the time in the stationary frame.

  We see, in relativistic physics, that space and time are interwoven. The contraction of length and the dilation of time that the observer in the stationary frame observes occurring in the moving frame, may be described as rotations in the four-dimensional space-time continuum. From the Minkowski point of view, an interval of time may be regarded as a length in the four-dimensional space-time continuum lying in the t-direction. The time interval is multiplied by c so that it has the same dimension as a length. Let us reconsider the example of the lightning striking the two ends of a train that we discussed in the beginning of the last chapter. From the point of view of the observer at rest, the lightning strikes the front of the train v/c2 Lo seconds before it hits the end of the train, as can be verified from Fig. 12:. The spatial length of the train, on the other hand, is contracted and hence, appears to have the length . The separation of the two events, which to the moving observer were purely spatial, become both spatial and temporal to the stationary observer, demonstrating the equivalence of space and time. The observation of the stationary observer may be obtained from the moving observer's observations by rotating in the space-time continuum about an axis perpendicular to the x- and t- axes so that a length, which is purely spatial in the primed co-ordinates, becomes both spatial and temporal in the unprimed co-ordinates as is illustrated in Fig. 13:.

  Another example of this rotation in the space-time continuum was encountered when we considered the time dilation of a moving clock. In the frame moving with the clock, the two events of the clock reading 8:00 a.m. and 9:00 a.m., are separated by a purely temporal length. In the stationary frame, however, the two events are separated by both a spatial and temporal duration, since the clock moves with respect to the stationary observer. Einstein utilized the Minkowski four-dimensional space-time continuum to formulate his theory of gravity. He acknowledged his debt to Minkowksi referring to his contribution as follows:

"Without it, the general theory of relativity would perhaps get no farther than its long clothes".   Although the space-time continuum is four-dimensional in the special theory of relativity, its geometry is still basically Euclidean. Space is not warped or curved. The shortest distance between two points is a straight line, as is the trajectory of a light beam. In the general theory of relativity, however, the geometry of the space-time continuum is no longer Euclidean; space is curved. The curvature of space was demonstrated, theoretically, using the equivalence principle and, subsequently, verified experimentally, with the detection of the curvature of a beam of light passing close to the sun during a solar eclipse. The shortest distance between two points in the vicinity of the sun is not a straight line. The most basic axiom of Euclidean geometry, which Kant had elevated to an a priori truth, is ironically and empirically untrue. One must describe the four-dimensional space-time continuum in terms of non-Euclidean geometry which, fortunately for Einstein, had been worked out by Lobachevsky, Gauss and Riemann in the nineteenth century.

  In non-Euclidean geometry, the ratio of the circumference of a circle to its diameter is no longer equal to pi as it is in Euclidean geometry. We can show that the ratio of the circumference of the diameter of a circle in a rotating frame of reference is less than pi and hence, invoking the equivalence principle demonstrates the need to describe the space-time continuum embedded in a gravitational field in terms of non-Euclidean geometry. Let us consider a disc which is a perfect circle at rest with the circumference equal to p times its diameter (C = p D). Let us consider the same disc rotating such that its outer edge has the velocity v with respect to an observer sitting at rest at the centre of the disc. To this observer, a length on the edge of the disc will appear contracted by the Lorentz-Fitzgerald factor because of the motion of the outer edge. This observer will measure the circumference to be .

  The diameter of the circumference will not appear contracted, however, because it lies perpendicular to the motion of the disc. The ratio of the circumference to the diameter of a circle in this rotating frame of reference is not p but . The geometry in this frame of reference is non-Euclidean, and since a frame in non uniform motion is equivalent to a frame in which there is a gravitation field, we see that the geometry of the space-time continuum is also non-Euclidean. Space is curved in a gravitational field. The slowing down of a clock is also easily demonstrated in our rotating frame. A clock at the edge of the disc will appear to slow down to our observer at the centre by virtue of its velocity.

  The curvature of space is difficult to comprehend in three dimensions, let alone four dimensions, as required in relativity theory. Let us consider a two-dimensional example to give ourselves a felling for non-Euclidean geometry. We shall compare a flat, two-dimensional plane, described by Euclidean geometry, with the surface of a sphere. On the flat plane, the shortest distance between two points is a straight line and the ratio of the circumference to the diameter of a circle is p . The surface of a sphere is a curved, two-dimensional space, described by non-Euclidean geometry. The shortest distance between two points is not a straight line but a segment of a circle which includes the two points under consideration and whose centre is the centre of the sphere (See Fig. 13:8). This circle is called a great circle and the path between the two points is called the geodesic. Let us now consider a circle inscribed on the surface of the sphere (See Fig. 13:9). This circle is defined as the locus of all points equidistant from the centre of the circle. If we were to measure the circumference and the diameter of this circle, we would discover that the ratio of these quantities is less than p .

  In formulating the gravitational interaction between masses, Einstein does not use the concept of one mass exerting a force upon another. Instead, he calculates the curvature of the space-time continuum due to the presence of matter. He then assumes that a mass will travel along the shortest possible path in this non-Euclidean, four-dimensional space. The path, geodesic or world line, along which the particle travels, is determined by the curvature of the space and the initial position and velocity of the particle. The world line of the sun and the earth are illustrated in Fig. 13:10, in which we attempted to draw a four-dimensional picture on a two-dimensional surface. In this diagram, time is increasing as one moves from the bottom of the figure to the top. From Einstein's point of view, the earth remains on its world line, not because of the force exerted on it by the sun, but rather because this is the shortest possible path it can find in the curved space-time continuum surrounding the mass of sun. Einstein's model of the gravitational interaction is able to account for something which Newton's model could never explain. Mercury, the closest planet to the sun, orbits the sun every 88 days in an eliptical orbit. The entire orbit of Mercury rotates at an extremely slow rate about the sun. The distance of closest approach, perihelcon, of Mercury, advances 43 seconds or arc per century. Since there are 360( in a circle, 60 minutes in a degree and 60 seconds a minute, it would take a little more than 3,000,000 years for the perihelcon of Mercury to make one complete rotation about the sun. This extremely small effect, nevertheless, cannot be explained in terms of Newton's theory of gravity. Astronomers tried to explain this effect in terms of the interaction of the other planets on Mercury. In fact, the existence of a planet lying between Mercury and the sun, called Vulcan, was postulated to explain the advance of the perihalcon of Mercury. This planet was never discovered and the anomolous behaviour of Mercury remained a mystery until Einstein's general theory of relativity which was able to explain this effect in terms of the curvature of space. Decke has since shown that the advance for the perihalcon of Mercury could also be explained if the shape of the sun were not spherical. Since the shape of the sun is not known, this is also a possible explanation. The experimental evidence to support the general theory of relativity is not as conclusive as the evidence supporting the special theory of relativity. Experimental confirmation of Einstein's special theory occurs every day in a laboratory of the elementary particle physicists who explore the properties of particles using high energy accelerators. Experimental confirmation of general relativity has only been obtained in three instances:

1. the bending of light by the sun

2. the shift of spectra from the white-dwarf star and in the laboratory due to a gravitational field.

3. An explanation of the advance of the perihalcon of Mercury.

   Research in general relativity continues. Two areas of research that are being actively pursued in general relativity are the search for a unified field theory and the detection of gravity waves. After Einstein published his General Theory of Relativity, he pursued the problem of finding an underlying structure of the gravitational field and the electromagnetic field which would unite them. In the special theory of relativity, he was able to find the underlying structure which united the electric and magnetic fields. In the general theory of relativity, he showed that gravity may be regarded as a property of the space-time continuum. He tried to show that the electromagnetic field could also be explained as a property of the space-time continuum so he could unite the gravitational and the electromagnetic fields. He never succeeded during his lifetime to solve this problem.

  The idea of gravity waves was proposed in analogy to electromagnetic waves. If the electromagnetic field has waves in the form of light, it would seem that the gravitational waves should also exist. Electromagnetic waves are generated through the acceleration of charge, so, perhaps, the acceleration of matter would produce gravity waves. Theoreticians estimated that gravity waves will be very weak. The experimental detection of gravity waves has not been established. Experimental work in this area continues.

CHAPTER 14

Kuhn's Structure of Scientific Revolutions and the Impact of the Theory of Relativity

  Einstein's special and general theories of relativity caused a revolution in scientific thought which affected a number of other fields as well. We will study the nature of this revolution and its influence on the various aspects of human thought. Thomas Kuhn, in his book, The Structure of Scientific Revolutions, proposes a model to explain the nature of how a scientific revolution takes place. We shall review Kuhn's theory and examine the Einsteinian revolution in terms of it.

  Kuhn does not regard the history of science as the accumulation of "the facts, theories and methods collected in current texts". He believes this view of history arises from the tradition of teaching physics from textbooks in which the true historical processes are suppressed and science is presented as an accumulation of knowledge. Kuhn sees the history of science as a competition between different world views in which revolutions periodically occur whenever a world view fails to accommodate new observations or new ways of looking at older observations.

  He claims that:

"The early developmental stages of most sciences have been characterized by continual competition between a number of distinct views of nature, each partially derived from, and all roughly compatible with, the dictates of scientific observation and method." One body of beliefs wins out over the others because it provides a more satisfying picture. This usually occurs as a result of some success that the new theory achieves. This success becomes the model or paradigm for future scientific work which Kuhn labels as normal science. The paradigm becomes a conceptual box into which all of nature is forced to fit. The paradigm reduces the number of things the scientists must consider. He can take the foundation and assumption of his work for granted and can, therefore, exert his full effort in extending, articulating and generalizing his paradigm.

  Within the context of normal science, novelty is suppressed. No changes in scientific thinking takes place until new facts arise which can not be accommodated by the old paradigm. Out of the frustration of the failure to fit the new information into the old conceptual box, a new picture emerges. The new paradigm is usually proposed by someone new to the field who has not become set in his ways through frequent use of the old paradigm. With the proposal of a new paradigm a revolution in thinking takes place in which the old view and new view are in conflict and competition. Eventually, one of the theories triumphs and a return to normal science ensues in which the whole revolutionary process may repeat itself. Kuhn does not regard only the major upheavels in though such as those brought about by Copernicus, Newton or Einstein as the only scientific revolutions. He also regards the discovery of X-rays or Maxwell's formulation of electromagnetic theory as a scientific revolution as well. Each of them brought about a new way of thinking.

  Perhaps the most controversial aspect of Kuhn's view of science history is his rather startling claim that the resolution of the conflict between the two competing theories during the revolutionary period is not really rational. The two sides of the controversy make different assumptions, speak a different language and hence, really don't communicate with each other. Max Planck, the man whom the quantum revolution began, perhaps best expressed this idea:

 "A new scientific truth does not triumph by convinving its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it." An illustration of what Kuhn and Planck are saying is found in the response of William Magie to Einstein's theory of relativity. Magie felt that, although the formulae of Einstein described phenomena accurately from a mathematical point of view, they did not really explain the phenomena. Only an explanation which he could comprehend with his common sense, i.e., fit into his notion of normal science, was valid as far as he was concerned. His attitude is reflected in the following passage from his presidential address to the American Physical Society in 1911: "The elements of which the model is constructed must be of types which are immediately percieved by everybody as the ultimate data of consciousness. It is onlyout of such elements that an explanation, in distinction from a mere barren set of formulae, can be constructed. A description of phenomena, in terms of four dimensions in space, would be unsatisfactory to me as an explanation, because by no stretch of my imagination, can I make myself believe in the reality of a fourth dimension. The description of phenomena in terms of a time, which is a function of the velocity of the body on which I reside, will be, I fear, equally unsatisfactory to me, because, try I ever so hard, I can not make myself realize that such a time is conceivalbe."   In contrast to the response of Magie, the supporter of the old Newtonian paradigm, we have the euphoric response of Eddington. Eddington was a member of the 1919 solar eclipse expedition to Africa which detected the bending of starlight by the sun. He finds Einstein's new ideas exhilarting and liberating as this is, except from his early writings, reveals:  "To free our thought from the fetters of space and time is an aspiration of the poet and the mystic, viewed somewhat coldly by the scientist who has too good a reason to fear the confusion of loose ideas likely to ensue. If others have had a suspicion of the end to be desired, it has been left to Einstein to show the way to rid ourselves of those 'terrestrial adhesions to thought.' And in removing our fetters he leaves us, not (as might have been feared) vague generalities for the ecstatic contemplation of the mystic, but a precise scheme of world-structure to engage the mathematical physicist."   Kuhn maintains that a scientific revolution occurs when the existing forms can no longer accommodate new facts and offer no possibility of resolution. The only recourse is to a new system with a different set of values. It is obvious that Magie and Eddington have a different set of values and hence, can never convince each other who is correct. It can be argued that Newtonian physics is not really incompatible with Einsteinian physics since, as we saw earlier, that the relativistic effects disappear as the velocities involved become very small compared with the velocity of light. While it is true that the formulae become identical in the limit of small velocities, the interpretation of space and time still remains radically different for the Newtonian and the Einsteinian.

Because of the fact that the new theory always incorporates the valid results of the old theory, science continues to make progress by definition. Kuhn claims that the progress made by science arises from the fact that the range of phenomena explained is continually increasing, not because the Einsteinian point of view is superior to the Newtonian point of view. There are no absolute truths for Kuhn. In this sense, his ideas have been influenced by Einstein's theory of relativity. Kuhn points out that scientific revolutions are often fomented by those who are new to the field and/or those who do not belong to the scientific establishment. No one could provide a better example of this viewpoint than Einstein as the following brief sketch of his life reveals.

  Einstein was born in Bavaria in 1879 to a middle class Jewish family. He was a slow learner as a child. His parents feared that he was retarded because he was so late in learning how to speak. He was never a good student since he was given to daydreaming. At the age of fifteen, he dropped out of school and travelled in Italy. He finally settled down, applied for admission to university, and failed the entrance exam. He went back to secondary school for a year and passed the entrance exam to the Swiss Federal Polytechnical School in Zurich. He was not a model student in university, either. He passed his exams by cramming his friends' notes. He preferred reading on his own to attending lectures. He found the whole experience of higher education appalling as the following remarks penned some years later reflect:

 "... after I had passed the final examination, I found the consideration of any scientific problem distasteful to me for an entire year. It is little short of a miracle that modern methods of instruction have not already completely strangled the holy curiosity of inquiry, because what this delicate little plant needs most, apart from initial stimulation, is freedom; without that it is surely destroyed ... I believe that one could even deprive a healthy beast of prey of its voraciousness, if one could force it with a whip to eat continuously whether it were hungry or not ..."   He, nevertheless, completed his Ph.D. in physics. Afterwards, he earned money as a tutor until an influential friend found him an undemanding job in the Swiss Patent Office on Berne. He held this position for seven years (1902-1909), during which he published his most famous papers. In 1905, the year his papers on the Special Theory of Relativity appeared, he also published two other major works, which, in themselves, also represented revolutions in physics thinking. It was for his 1905 paper on the photoelectric effect, which established the existence of the photon, and not relativity that he received the Nobel Prize in 1921. In the same year, he published his paper describing Brownian motion which established the first direct detection of atoms.

  It was in 1909, after he had completed his most revolutionary work with the exception of the general theory of relativity, that Einstein began to receive academic acclaim. In the years following 1909, he accepted professional chairs from Prague, Zurich and Berlin. In 1932, as Hitler came to power in Germany, Einstein fled to the United States where he spent the remainder of his life. He was also a great humanist devoting much of his efforts to world peace. Einstein's theory of relativity caused as large a response in the non-scientific world as it did in the scientific world. The overwhelming response of the layman was bewilderment because the notions of relativity violated their notion of common sense very much as it had violated the common sense of the physicist, Magie. Relativity for them was strictly a mathematical model which they could not relate to intuitively.

  One aspect of Einstein's ideas, however, became very popular and that was the notion of relativity. If everything is relative in the physical world, it was argued then that the same must be true of things in the world of art, morals or ideas. Some people were appalled by this notion and were opposed to Einstein's ideas because they considered them downright immoral. Other thinkers found the aspect of Einstein's physical theories extremely liberating. For example, Jose Ortega y Gasset wrote in his book, The Modern Theme;

 "The theory of Einstein is a marvelous proof of the harmonious multiplicity of all possible points of view if the idea is extended to morals and aesthetics, we shall come to experience history and life in a new way. It is the same with nations. Instead of regarding non-European cultures as barbarous, we shall now begin to respect them, as methods of confronting the cosmos which are equivalent to our own. There is a Chinese perspective which is fully as justified as the Western."   Another thinker, Paul Squires, saw in Einsteinian relativity support for the notion of gestalt psychology. He likens traditional psychology to Newtonian Physics and Gestalt Psychology to Einsteinian physics. He writes:  "For the traditional psychology, particular experiences and bets of behaviour possess a more or less absolute character. For the Gestalt psychologist, any aspect of mentality has meaning only in its relation to the larger context, the whole, in which it exists."   The art critic, Thomas Craven, in an article written in 1921, claimed that Einstein's ideas support the position of the modern artists. He wrote:  "While the celebrated physicist has been evolving his shocking theories of the course of natural phenomena, the world of art has suffered an equivalent heterodoxy with respect to its expressive media. This revolt has sprung from concoction that the old art is not necessarily infallible, and that equally significant achievements may be reached by new processes and by fresh sources of inspiration."   Craven regards the rigidity of "the old art" as corresponding to the "immovable reference-body" of Newtonian physics. He claims just as Einstein's theory changed Newton's concepts of absolute space and time "similarly has the modern painter broken the classical tradition." Rather than clinging to the rigid laws of photographic vision, he claims that the artist injects his own "personal feeling". Instead of arriving at an absolute truth "which serves all purposes of illustration" but "reveals nothing psychologically", the artist achieves at to greater truth, a psychological truth, relative to himself.

 

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