Einstein Essay Example

Einstein Essay Example Einstein Essay Einstein Essay Essay Topic: Apocalypse Now Einsteinian concept of space time 1.0. Introduction Meditations on the nature of time began with the questions about its nature of existence. Though many problems are related to the concept of time, these problems will be more in the epistemological realm and less in the ontological level. Time is the basic category of existence,â„ ¢ wrote Heidegger, referring very definitely to time. Time is the immediate datum of consciousness,â„ ¢ said Bergson. Time, for Kant, is the formal a priori condition of all appearance whatsoever.â„ ¢ Aristotle defined time as the number of motion in respect of before and after.â„ ¢ St. Augustine, when asked about time, conferred: What, then, is time If no one asks me, I know; if I wish to explain to him who asks, I know not.â„ ¢ In his book A Sense of Time Vatsyayan explains beautifully, the different thoughts about time. Usually when somebody says to us you missed meeting him; he was waiting for you long time. Then I may ask, when did he goâ„ ¢ The answer can be: he came at 12 oâ„ ¢ clock and went just now; he must have reached the road junction. Here my question was about time, but the answer was related to space and distance i.e. 12 oâ„ ¢ clock is when the small and big metallic pointers in the clock meets at 12, which is a spatial representation and road junction (from the house)â„ ¢ is distance. Ordinary use of time is without much problem provided we have a watch or clock and we know how to say it. This experiential aspect gives rise to the philosophical aspects when we dive deep into the river of time. It is interesting to quote Kant here Time is ideal, but the concept of time is not derived from sense experience alone[further] Kant insists that all possible knowledge of objects mus t be tied to and constrained by sense experience.â„ ¢ 2.0. What is Time A question we generally ask and easily get the answer immediately is whatâ„ ¢s timeâ„ ¢ But if somebody stares at us when the question is asked he must be a philosopher. For many centuries people believed that time was essentially cyclic in nature, but later the idea of time replaced with the linear progression measured by the clock (though the time showed in the clock is circular) and calendar ( which seems to be linear). The problem of time has the two aspects: 1) As it is lived by man, whether linear or circular. 2) In its relation to its existence, whether it is eternal, infinite or relative. Whether we like it or not, we cannot escape from time. That may be the reason why the 3-dimensional experience of space was added with one more dimension of time to make it four-dimensional experiences. So what will we say Time flows in us or we flow in time Be it circular or linear, time is not at all static. If then, we are always caught up in the questions, if time is so much inter-related to oneâ„ ¢s life what it isâ„ ¢ What is the moment which always escapes from us What is the relation between the no-longer-past and present What is the relation between not-yet-future and present Because they confused the intelligible with eternal the early philosophers saw that in every exercise of the intelligence we detect an attempt to suspend and even to suppress time. This obliged them to look down individual feeling, moving, enduring element in human beings to nothingness and to conceive of eternal life as a logical life absorbed in the contemplation of unity. 2.1. Greek view of Time Greeks, though they believed in the cosmo-centric universe, had a good knowledge in astronomy. They had a cyclical view of time by which they believed nothing new can be introduced onto earth. For them, Plato would be born again and teach in the same school in Athens where he once taught. As a circle cannot have a beginning and an end, so as the cyclical time cannot have beforeâ„ ¢ and afterâ„ ¢. The time was infiniteâ„ ¢. For them, the concept of time and the cyclical movement of stars were linked. The universe was a reflection of the divine. The metaphysical necessaries goodness, truth and beauty are present in the universe. The cosmic order is the note of a universal symphony of harmonyâ„ ¢. Aristotle in his cosmological views considered that there are seven spheres in this universe and in the 8th sphere is the unmoved mover. This view was also a teleological one, for we came from him and ultimately moving to him. But the contradiction seen here is that how from this cyclical time † where events appear, disappear and reappear † do we go out 2.2. The Christian Concept of Time Christianity washed away the Greek concept of cyclical time. While for Greeks time was reversible and lacked the concept of teleology, the Christian concept of linear time was based on the firm belief in the Bible, and was irreversible. From the days of Jews of the Old Testament people were looking for the Messiah and after the Messiah had reached the Christians believe that they were freed from the bondages of sin. The history of incarnation of Christ is the centre of the redemptive history of the Christians. There was a time ran before the birth of Jesus. St. Augustine declared Christ died, once and for all, for our sins. There is a linear time running in the Bible from the first chapter of Genesis to the last chapter of the Apocalypse, which describes the salvation of humanity by the redemptive suffering, death and resurrection. The time runs in a linear process from the first fall of man. This is not a cyclical one, rather the gift of life given to him only once. Time as linear and irreversible always moves forward in one direction. It had a beginning, however remote, and an end, however distant. Now the time, as linear and irreversible has an orientation and meaning which it did not have in cyclical and reversible time. 3.0. Background of Einsteinâ„ ¢s Relativity Theory Every man is influenced by some or other external influences, no matter whatever field it may be. Scientists are not an exception for this. Einstein had a long way to go many centuries back. Let us see the different persons and concepts which acted as stepping stones for the success of the Einstein of today. 3.1. Geometry There shall be 101 questions about any theory. When these epistemological questions are answered by proving that the theory is evident or self-evident by reason, it is with satisfaction we accept that the theory has a rational description of the world. Such a kind of self-evident theory is geometry and mathematics. Even in geometry there are different geometries which have different explanation. 3.1.1. The Development of Euclidean Geometry It is interesting to note that before the beginning of great era of Greek philosophy there was a quite systematic knowledge of a wide range of Geometric truth. The Greek mathematicians have treated many problems like congruence of plane figures, division of angles into equal parts, and so on. The greatest bulk of their systematic knowledge was in the study of plane figures bounded by segments of straight lines. One of those ancient geometries was formed by Euclid (c. 300 B.C). These results like the sum of interior angels of a triangle is equal to a straight angleâ„ ¢ and that the square of the length of hypotenuse of a right triangle is equal to the sum of the squares of the lengths of its sidesâ„ ¢ are familiar to school children. The early Greeks thought that this universe was an unending plane. This may be the reason why Euclid must have built geometry of plane figures bounded by segments of straight lines. His geometry consisted of a system of theorems logically ded uced from five axioms and five postulates. Euclidean geometry specified the properties of Euclidean space and these properties were assumed to be logically certain. So, naturally what happened was that the philosophers who followed after Euclid took this geometry to be logically true. Thus was the concept of space and time created by the Greeks, medieval as well as classical physicists. The five axioms and five postulates are only assumptions which are not proved, but taken to be true. From them remaining truth of geometry are deduced. What relation does these postulates and axioms hold is not at all clear. The form (not the original form) of the axioms and postulates for our purpose is given below. AXIOMS 1. Things equal to the same thing are equal to each other. 2. Equals added to equals yield equals 3. Equals removed from equals yield equals 4. Coincident figures are equal to one another in all respects 5. A whole is greater than any of its parts. POSTULATES 1. Two points determine a straight line. 2. A straight line may be extended in a straight line in either direction. 3. About any point a circle at a specified radius exists. 4. All right angles are equal 5. If a straight line falling across two straight lines makes the sum of the interior angles on the same side less than two right angles then the two straight lines intersect, if sufficiently extended, on that side. A logical conclusion from the 5th postulate was that through a point outside a given line one and only one (parallel) line can be drawn which does not intersect the given line, no matter how far it is extended. 3.1.2. Non-Euclidean Geometries During the nineteenth century two mathematicians, George Friedrich Benhard Riemann (1826-1866) and Lobachevski suggested two different geometries for two theoretical spaces. The problem was lying in the fifth postulate. And both of them refuted and postulated another possible postulate. Riemann postulated that through a point outside a given line no parallel line can be drawn and the lines will intersect at some point. Lobachevski, on other hand, postulated that through a point outside a given line infinitude of intersecting lines may be drawn. These two different sets of axioms gave birth to two non-Euclidean geometries. Though during the time of formulation they were regarded as mathematical speculations of theoretical space, later Einstein made Riemannian geometry a stepping stone of his success. 3.2. Astronomy The world picture was systematized about 140 A.D. by Ptolemy of Alexandria in his famous work Almagest. It was Ptolemy who proposed that earth being the centre of the solar system. Though he was aware the earth was spherical in shape [because of his proof that Polar Star was higher in the north and lower in the south; also an eclipse of the moon was observed at different times thought the eclipse was single objective event and should be seen everywhere at same time] he was not admitting that it could move. Though he was a great astronomer, he also took the commonsensical opinion into consideration and concluded earth is at the centre. This principle had dominated the human minds for more than thousand years. Then came Nicholas Copernicus (1473-1543) to undermine the hitherto principle which governed the world. It is remarkable to applaud his scientific knowledge. Contemporary period to Copernicus was Tycho Brahe who was a builder of outstanding instruments. From him, later, h is student Johann Kepler continued the work with precise instruments. He was the one who determined that Mars was also elliptical in shape from the many individual observations of the course of the motion of Mars. Thus with these mere measurements he suggested the other laws of planetary motion, called after him The Keplers lawsâ„ ¢. Kepler used to dream, what we call the impossible. This may be the reason why he worked hard for factual accuracy. But he himself in his work Harmony of the world (1619) humbly wrote that he used to dream natural harmony present in the heavenly movements, but later he discovered that they were more perfect than the perfection of his imagination. His expressions in the following words are more impressive: Here I cast my dice and write a book to be read by my contemporaries or by the future generations. It may wait long centuries for its reader. But even God himself had to wait for six thousand years for those who contemplate his work. Astronomy got its realm a little closer to us by the observations of the universe made by Galileo Galilei (1564-1642) through the invention of the telescope. He constructed it after hearing about such instruments used by Kepler. He directed his telescope towards the moon, the Venus, Saturn and Jupiter and found the marvellous reality. By the invention of all these things and the discoveries made by this he was establishing slowly what Copernicus proposed was true. But poor Galileo had to pay with many years of imprisonment for his adherence to the Copernican theory. Galileo invited many noted philosophers from the University to take a view either at the moon or the telescope. But all closed their eyes to the light of truth. Galileo in his letter to Kepler thanked him for having taken interest in his investigations and giving full credence to his contentions. He was pouring out his heart in the letter saying to Kepler that those philosophers in the University compares the text a nd try to existence of the new planets by mere logical arguments. They (the philosophers) assert themselves comparing the text rather than through the study of the world or nature. He even shared the experience with a scientist who was when asked to take a look at the telescope refused to do so telling that he might be confused. Galileo was the first man to establish the basic laws of mechanics. He was the first man to investigate the laws of falling bodies. He had no watch to measure the time of the falling body from a distance. In spite of this difficulty he was able to determine the relationship between the distance and the time of fall, and also the law of acceleration. Finally, he formulated the basic law of motion that every body unaffected by external forces moves in a straight line at a uniform speed and that this motion can never stop by itself. We see that Galileo had discovered many laws which are merely bits of factual information. But Galileo might not even have thought the far reaching applicability of his findings which was destined to attain significance when the English physicist Isaac Newton (1642-1727) came onto the scene. Newtonâ„ ¢s achievement was that he combined all the individual discoveries of Copernicus, Kepler and Galileo into one magnificent system. His contribution to physics was this: He discovered that the power of attraction or gravitation proposed by Galileo concerning falling bodies had a far reaching region which transcends the earth. This power of attraction is a property of all mass, and that it determines the planetsâ„ ¢ behaviour across cosmic distances. Newton discovered that this power of attraction diminishes with distance. Newton even calculated the length of time required for the revolution of the moon around the earth and wanted to know whether this gravitational power was indeed responsible for the revolving of the moon in a particular way. But unfortunately Newton was not able to prove it. Later, astronomers gave a new measurement of earthâ„ ¢s radius and showed the blunder made by Newton in basing the calculation on incorrect radius of earth. New radius of earth proved Newton was right and thus the Copernican conception of the universe was, at last, scientifically established. Also as Kepler dreamt the universe was in perfect harmony in their cosmic motions. 3.3. Electro-Magnetic Field Einsteinâ„ ¢s doctrines are by no means an outgrowth of astronomical reflections alone, but also they are grounded in the facts of the theory of electricity and light as well. At this juncture of finishing the discussion on astronomy and mechanics let us proceed to the theory of electricity and light in order to make room for the discussion on Einsteinâ„ ¢s theory of Relativity. We might think that it would be easy to answer the problem of light too by explaining electrical and optical phenomena. But the studies show that the problem was solved the other way round i.e. by studying electrical and optical phenomena we solve the problem of astronomy and mechanics. Light is the electromagnetic radiation that can be detected by the human eye. In terms of wavelength, electromagnetic radiation occurs over an extremely wide range, from gamma rays with a wavelength of 3 ? 10-14 centimetre to long radio waves measured in millions of kilometres. In that spectrum the wavelengths visible to humans occupy a very narrow band, from about 7 ? 10-5 centimetre (red light) down to about 4 ? 10-5 centimetre (violet). The spectral regions adjacent to the visible band are often referred to as light also, infrared at the one end and ultraviolet at the other. The first step in understanding the phenomenon called lightâ„ ¢ was taken by a Danish astronomer Olaf Roemer during Newtonâ„ ¢s time. It was he who discovered the velocity of light in 1676 by his investigation the eclipses of Jupiterâ„ ¢s satellites. He noticed the appearance reappearance of these moons in their orbital motion when they passed the cone-shaped shadow of the planet. As a result, he found that the duration of such darkening of the moon were not always precisely the same but varied by seconds, according to the time of the year. Roemer observed these durations and inferred the velocity of light. The explanation he gives about the above figure is that: The path of the earth is here portrayed as an ellipse with the sun (s) occupying one of its foci. Jupiter (J), with the orbit of one of its moons, is found to the right. When the moon enters the conical shadow of Jupiter at point M, it sends the last beam of light reaching the earth several minutes later at point E1. After a few day the moon emerges from the conical shadow, turns slowly around Jupiter and reaches once more point M (in reality this is not the same point M, insofar as Jupiter with its moons will have moved forward; but this movement is very slow and can be disregarded in our explanation). At the moment of this second disappearance the moon sends again its last beam to the earth. The latter (the earth) has moved in the meantime to E2, however, so that the beam has now a longer trip to make. If the earth would have remained at E1 itself the astronomer could have seen the disappearance of the moon at definite intervals the time required the light to travel at ME1. But this is not the case because the earth is moving. So now the astronomer with his calculations of (i) duration of each revolution of moon (ii) the distances of ME1 and ME2, calculate the intervals of time required for propagation of light. Now, Newton who knew the discovery of Roemer explained the propagation of light as the emission of tiny particles thrown into space and capable of passing through air and gases because virtually they are small particles. Those who supported the view of Isaac Newton were Henry Lord Brougham and David Brewster. The historical background of this theory which proposes light as particles traces back to the first edition of Opticksâ„ ¢ by Isaac Newton in 1704. Book III of this edition contains 16 questions concerning nature of light. Later editions expanded this number to 31. Query 29 begins as follows: Are not the Rays of light very small Bodies emitted from shining substances For such Bodies will pass through uniform Mediums in right lines without bending into the shadow, which is the Nature of the Rays of light. They will also be capable of several properties, and be able to conserve their properties unchanged in passing through several Mediums, which is another condition of the Rays of light. But later Newton was proved wrong by the mathematician Christian Huyghens who recognised that the phenomenon of light-transmission was by means of wave-propagation. It was put like a cart before the horse. Only a few scientists accepted it, because in ordinary and easily observable facts of light-propagation Huyghens theory had extreme difficulty in offering explanations. It explained the phenomena of the bending and interference of light easily understood, but it was very difficult to explain the rectilinear propagation of light. This is why scientists cling to Newtonâ„ ¢s emission theory of light which explained the rectilinear propagation of light easily. An analogy is given to show that wave-theory, though complicated, is true comparing to Newtonâ„ ¢s emission theory. The analogy was this: when we look from a high mountain at the smooth surface of the sea we will not be inclined to think that, in reality, it has the character of a wave like curved surface; rather, we will visualize it on a large scale and consider it as a plane. Similarly, when we face nature in everyday experience, we see it only in a broad outline. It needs the sharp eyes of science to explain everything. The scientific discovery with great precision done by Roemer proves that naive beliefs will not withstand long. This is a clear evidence for those who attack science saying that science does not study anything from the nature, but only from the laboratory conditions which control the phenomena which do not exist in nature. The victory of wave theory of light was achieved in connection with the phenomenon of interference. The theory can be described in this way that the addition of two brightness results in darkness or to follow an equation: light +light= dark. This phenomenon cannot be observed in daily life, but by a special arrangement of light rays. But if it is for Newtonian theory the combination of two material particles can result in more material, not the negation of it. By another example this can be made clear. Let us imagine a wave produced by the swinging of a rope attached to a flag-pole. The arrival of a wave-crest at the top of the pole will result in a shaking of the pole, and a similar shaking in the opposite direction will be produced by the arrival of a wave-trough. If we produce, in such a way, that both wave-crest and wave-trough reach the top of the pole simultaneously, then the crest and trough will cancel each other and no tremor of the pole will occur. We can symbolically put this as: push +push =repose. This will be further made clear when we understand light is not light-particlesâ„ ¢ but light-waves.â„ ¢ This great merit of making the theory of light-waves reasonable and true belongs to the French Physicists Augustine Fresnel. There are two types of waves: longitudinal (linear waves) and transverse (waves across something). Water waves belong to transverse waves in which individual particles of water dance up and down and move transverse to the progressive direction of the wave. In longitudinal waves individual particles move back and forth, in which thickening and thinning take place and spread forward. Sound waves belong to longitudinal waves. Fresnel, from his study proved that the light was connected not to longitudinal waves but to transverse waves and the studies dealt primarily with the so-called polarization of light, a phenomenon characterised by the transverse quality of light. Then the question raised was that if light is not a substance but a wave, which also a phenomenon of motion in a medium, then what is that mediumâ„ ¢ The proponents of wave-theory of light of course believed that light can move only through a medium and designated this imaginary medium, ether. This designation wa s something interesting because water-waves are produced because of the material water particles dance up and down, but this movement of light wave presents an immaterial phenomenon on a material background. But we need such a background to explain the movement of light waves. But yet the question about the ether remains: if ether is present for light waves to move it should also exhibit itself in some other manner too, such as water can be experience in many ways other than the transverse-waves it produces. In what form did the ether exist Hence to know the presence of ether we need to have finest physical instruments. Similar to that of current arising in water, which is transverse waves, the assumption of current, other than light, in ether is questioned. But the results attained by experiments were that there was no ether. The results of the experiments of science were not in favour of light travelling in a medium. Then, we need to look into the nature of water itself. Water is not a uniform substance but material (atomic) particles. This realisation showers some positive light for our discussion. These so-called scientists denied the existence of ether only because it cannot be experienced anywhere else other than to support the propagation of light. This denial from the part of scientists was because they were experimenting only macroscopic relations. Now, thus, our discussion turns to the microscopic dimensions. This path in the microscopic dimension reaches in the progress made in another physical discipline, the theory of electricity. Here we come across with field of forces which are different from mechanics. We are going to lay down the following rule regarding the artificial field of force. There is always a muscular sensation felt when we start or stop a motion of matter. The measure of the force applied is scientifically calculated by the momentum in a given time. Force is not a mysterious agency, but a flow of motion of molecules which is moving to the body that is being acted upon which can be seen in a laboratory set up. But what is dealt in this section is a different kind of field of force, i.e. electromagnetic field of force. We have bridged between the waves of wireless and light rays. Waves of wireless are of higher frequency because of shorter waves. But the light rays are of longer waves which are not seen by the human eye. All these waves together are called a spectrum. There are electrical waves of different wavelength in a spectrum. By this knowledge of multitude of electrical waves scientists have succeeded in producing electrical waves which has the frequency greater than that of light. These waves of high penetrating capacity are the X-rays, discovered by Roentgen. When examined the radioactive substances we find that they send out even faster vibrating and more penetrating radiation namely the gamma-rays. In the spectrum of electric waves light is only a small narrow section, only for which the human eye is sensitive. The highest known frequency is gamma rays. The eye responds only to the frequency of light. To know the other frequencies we need complicated instruments. Though the sun emits rays of different realms, the eye is sensitive only of light rays. These rays are permeated on the earth permits for an action between human beings and things which we call seeingâ„ ¢. The biological set up of our eye is in such a way to receive only light rays. But we avail ourselves of other physical instruments to modify the action of the waves of higher and lower frequency than that of the light and enjoy the effects which our sense organs register as visual or auditory phenomena. At this juncture it is worth knowing the experimental investigations of Michael Faraday (1791-1867). He was the first to produce an electric current from a magnetic field, invented the first electric motor and dynamo, demonstrated the relation between electricity and chemical bonding, discovered the effect of magnetism on light, and discovered and named diamagnetism, the peculiar behaviour of certain substances in strong magnetic fields. He provided the experimental, and a good deal of the theoretical foundation upon which the English man James Clerk Maxwell erected classical electromagnetic field theory which shows that the electrical current flows not only in the wire, but also the electrical and magnetic fields found in the air or empty space contain power and energy. This existence of electric and magnetic fields permeate space and penetrate bodies. It is not a kind of substance or existence as air or water, but a different kind of microscopic existence. They have the qualit y which the material bodies do not have i.e. penetrability. They are present everywhere, but at the same time do not enclose space. While the material body can be placed alongside each otherâ„ ¢ the electric field can be placed within each other.â„ ¢ When they are placed within each other they both altogether form a new electrical field. But simultaneously when the third new field is created the other two fields can still be explained. Hence it will be good to retain the word fieldsâ„ ¢ opposed to substanceâ„ ¢. All material bodies contain electrons. These are negative charges circulating around heavier nuclei that are positively charged. When an electric field is applied to a material body, the average positions of the negative charges relative to the positions of the positive charges are changed. This creates an internal electric field. Similarly the action of a magnetic field on a material changes the movement of the electrons and sets up an internal magnetic field. This study of electricity taught us to conceive materiality in a new way i.e. not only as substanceâ„ ¢ but also as fields.â„ ¢ We can consider ether in this concept of matter of microscopic form. This binding-together of electric and magnetic conditions through the phenomena of induction (creating magnetic field by means of electric current, or vice versa) was done by Maxwell. Thus he reduced optics to phenomena of electricity. His mathematical conclusions made him to propose that electrical vibrations spreads through the space and they are identical with light which is nothing other than electrical phenomenon similar to the electric or magnetic fields arising in the area surrounded by electrical currents. The difference between electric fields and magnetic fields is that the electric fields have extraordinarily high rate of vibrations. Though these were established with mathematical precisions Maxwell was himself not able to give any experimental proof. But these were confirmed by other experiments in two lines. On the one side Starkâ„ ¢s and Zeemannâ„ ¢s effect proved that the electric and magnetic fields can have effect on light generating structures or radiant atoms and thus prove that the emission of light was essentially an electrical phenomenon. On the other hand Heinrich Hertz (1857-1894) a German physicist began his studies of the electromagnetic theory of James Clerk Maxwell. Between 1885 and 1889, while he was professor of physics at the Karlsruhe Polytechnic, he produced electromagnetic waves in the laboratory and measured their length and velocity. He showed that the nature of their vibration and their susceptibility to reflection and refraction were the same as those of light and heat waves. As a result he established beyond any doubt that light and heat are electromagnetic radiations. It i s interesting to see how a discovery made purely for theoretical reasons in search of understanding natural phenomena can yield unsuspected benefit, never thought even by Maxwell himself. These fields should not be regarded to be bound to a material medium. These electric waves are in which electricity is continually alternated between positive and negative. They are independent of material particles which have up and down, but move through space. Today we are able to say that light is a simply a train of electrical waves of high frequency. Now, as we conclude this discussion we introduce a new type of wave called electrical wave other than longitudinal waves and transverse waves. These electric waves pervades everywhere in all directions. Though earlier we proposed that light is connected to transverse waves we alter it because we need to presuppose a current in the ether as we see current in the water. The problem of presupposing a current in the ether is that current also presupposes light as a solid or material object or particle, because water is a material particle. But what we conclude here is that light is an electrical wave including electric process rather than a mechanical one. It is not related to water waves or sound waves, but more related to radio waves. But the presence of ether is not answered in negative yet. 3.4. Presence of Ether Proved Wrong The explanations in the previous sections made clear that light is not water wave or sound wave, rather electrical waves of the electrical spectrum, more akin to radio waves emitted into space from aerials and consisting in rapid changes of an electric and magnetic field. Yet, the question about the medium of light-travel is remaining. We had explained that ether is not a substance in the mechanical sense of the world. But, it is to be discovered yet whether there cannot be a particular fine substance underlying electrical fields so that we can answer the existence of the unknown ether in negative. The justification given to the presence of ether was that for our cruder senses only cruder material substances can be seen and ether being a fine matter cannot be seen to our senses.â„ ¢ Scientists cannot take this explanation for the presence of ether. That too for physics which dive deep into the nature of things should look for precision than supposition. The theory of Einste in gained important only because it explained itself with the experimental facts more than the structure of thought or the depth of its ideas. The position that the theory enjoys today is only because its relation to the experimental facts. Many contemporary scientists of Einsteinâ„ ¢s time want to determine the movement of this hypothetical (theoretical) light-ether. We concluded by saying that ether fills the universe for the light to travel, which means earth had to move through it. The aim of the scientists was to measure the movement of the earth with regard to the ether. But, as usual, result blinked negative. In our previous section we mentioned the light is of the quality penetrability and so, different from substance which is of impenetrability. But we should also take into consideration the second property which is the determination of state of motion.â„ ¢ For example, we shall take water itself into consideration. The waves of the water are in movement and the velocity is calculated both during the low tide and high tide. The velocity will be higher when it is at high tide e.g. waves moving from ship to island. Only with regard to the wave the speed of the wave is equal in all direction. This is what we understand from state of motion.â„ ¢ Only with respect to the water the water waves receives the natural value. Water and state of motion of water are distinctive. Now we shall take this reflection for the explanation of the astronomical relation of ether. Let us compare water and ether, water-waves and light-waves. As we know light travels the world-space and ether is filled as mass of water in which planets float like isles. Thus there should be a relation between the state of motion of ether and state of motion of planets. Consequently there will be variation in the velocity of light in ether and velocity of light on a planet, earth. Light has no property which says it is like water waves or air waves. As we have mentioned earlier light has the property of impenetrability, there is also the second property of light as an electric field which is the determination of state of motion. To explain the concept of state of motion let us now take the example of throwing a stone to a calm water surface. The velocities of the water wave when it is at rest and when it is in motion are different to that of water surface. Only with regard to the water surface the velocity of water is detected. That is what we understand by the determination of state of motion. Such reflections were entertained with that of the presence and movement of ether. The scientists were questioning the relation of ether to astronomical objects. As light traverses the worldâ„ ¢s space, ether must fill it like a great mass of water in which planets float like isles. In so far as planets move around the sun, they must be characterised by a different state of motion from that of ether. Thus one comes to the assumption that the velocity of light, as measured on planet like the earth, must vary with direction, simply because ether is understood as substratum of light waves and only with regard to it can the velocity of light receives its natural value. But all these astronomical relations were in assumptions till Michelson with his devised instrument proved that the presence of ether is impossible. Michelson began constructing an interferometer send the two parts of light beam along perpendicular paths, then bring them back together. If the light waves had, in the interim, fallen out of step, interference fringes of alternating light and dark bands would be obtained. From the width and number of those fringes delicate measurements could be made, comparing the velocity of light rays travelling at right angles to each other. The arrangement was like this: The apparatus consisted of two horizontal metal bars AB and AC. In A there is a source of light from which rays are sent to B and C where they are reflected in a mirror and meet again at A. The question is: if the rays leave A simultaneously, will they return to it simultaneously This would be the case were the apparatus and its metal bars to rest motionless in ether, for then the speed of light is equally great in both directions AB and AC. But the apparatus rests on the earth and hence participates in the motion of the earth through ether. It follows that the velocity of light must be different in the two directions. A simple calculation shows that, when the earth moves through ether in the direction AB, the ray A-B-A must return to the starting point a little later than A-C-A. Michelson felt sure at that time that it was possible to prove the tardy return of that ray; after all, his methods were exact enough, and he used the finest optical instruments. The belated arrival of the ray could be proved by means of interference, by the appearance of shadow-bands created by the coincidence of hills and the dales of the two current of waves. Yet the surprising result was that no shadow-bands appeared at all. It was Michelsons intention to use the interferometer to measure the earths velocity against the etherâ„ ¢ that was then thought to make up the basic substratum of the universe. If the earth were travelling through the light-conducting ether, then the speed of the light travelling in the same direction would be expected to be equal to the velocity of light plus the velocity of the earth, whereas the speed of light travelling at right angles to the earths path would be expected to travel only at the velocity of light. His earliest experiments in Berlin showed no interference fringes, however, which seemed to signify that there was no difference in the speed of the light rays and, therefore, no earth motion relative to the ether. In 1883 he accepted a position as professor of physics at the Case School of Applied Science in Cleveland and there concentrated his efforts on improving the delicacy of his interferometer experiment. By 1887, with the help of his colleague, American chemi st Edward Williams Morley, he was ready to announce the results of what has since come to be called the Michelson-Morley experiment. Those results were still negative; there were no interference fringes and apparently no motion of the earth relative to the ether. It was perhaps the most significant negative experiment in the history of science. In terms of classical Newtonian physics, the results were paradoxical. Evidently, the speed of light plus any other added velocity was still equal only to the speed of light. To explain the result of the Michelson-Morley experiment, physics had to be recast on a new and more refined foundation, something that resulted, eventually, in Albert Einsteins formulation of the theory of relativity in 1905. These many experiments were made but nothing could prove the existence of ether and it was better to stop believing in ether. In the opinion of Einstein there was no such thing called ether, in the sense of a carrying medium of light and there was no special frame of reference in which the velocity of light is equally great in all direction, but this is the case in every uniformly moving frame of reference. At last, since the existence of ether could not be determined Einstein concluded that there was no such thing called ether. In Michelsons experiment he showed the velocity of light, not measured in one single direction, but as the totality of time necessary for a light-ray to travel there and back to the same point. Einsteinâ„ ¢s contribution was that related to single direction which says that for every uniformly moving frame of reference the velocity of light is equal in all directions. Then a question is raised how do we know that the velocity is identical in both the directionsâ„ ¢ This takes us to the famous doctrine of Einstein, relativity of simultaneity.â„ ¢ 4.0. What Is Theory Of Relativity We see that the post-modern philosophy giving importance to individuals because every one is unique. Uniquenessâ„ ¢ is thought of only when there are minimum two. Why to go to such a difficult understanding when we have simple examples at hand Take for example, somebody asking which side of the road is your house, right or left I can answer it only being in a reference i.e. from the side of junction X it is on to the right side and from the side of junction Y it is on to the left side. Like this every assertion makes sense only being in a particular frame of reference. Likewise the answer to the question is it day or night nowâ„ ¢ depends on the location of which part of the world we are in. Once the people believed that earth was flat and assumed that everywhere on earth the vertical distance is same, but when it was discovered that the earth is spherical the distance upâ„ ¢ and downâ„ ¢ became relative. No one questioned the concept of space and time which was proposed by Newton who used Euclidean geometry. But there came the scientist Albert Einstein (1879-1955) whose new physics arose from his study of problems relating to the transmission of light and other electromagnetic vibrations. But to solve these problems Einstein had to postulate that the velocity of light was constant in all frames of reference. This basic assumption of Einstein brushed away the notion of simultaneity in classical physics which had the assumption that velocity of light changes according to the frames of reference. These are the concepts he takes up in his special theory of relativity which he proposed in 1905. One of the consequences of Special Theory of Relativity was that the space and time which was established as absolute by Newton was re-established as relative by Einstein. Newton: Newton, a God-fearing man, was a very humble scientist. He was humble enough to acknowledge his predecessors in saying: If I have gone further in my experiments it is only because I stood the shoulders of the giants. Newton proposed the concept of absolute time and time was independent from the frame of reference. Let us see in Newtonâ„ ¢s own words in which he described two understanding of time. He defines time as follow: Absolute, true, mathematical time, of itself, and from its own nature, true, flows equably without relation to anything external, and by another name is called duration: relative, apparent, and common time, is some sensible and external measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year. Newton was a scientist who based his laws observing the everyday world. The nature was an immediate picture by which a scientist can easily understand the events. Newtonâ„ ¢s first contribution to science was the laws of motion. The first law states that until and unless an external force is applied the object continues to be in the state of rest or in a state of uniform motion. But later Newtonâ„ ¢s law was replaced by saying that moving objects come to rest eventually because of friction â€Å" friction of air, friction of water, friction between substances and the like. For Newton, mathematical time was real time and not merely a conceptual construct or an abstraction from matter and motion. Newton conceives of true time as flowing in a single mathematical line, independently of all matter and motion. The ontological existence of time was in a particular manner. It was neither substance nor accident, but it was an emanent (coming out) of God. Time was real and it was imp ossible for God to exist without time. God was also with time and temporal existence was attributed to God by Newton. Since God necessarily exists He must exist at some time, namely always. Because Newton calls time as emanation; he denies the aspect of creation for time. God as a creator of everything in time He existed prior to time but with time. He based his metaphysical assumption on appeal to God. Absolute space and Absolute time were manifestations of God. For him, space was eternal and changeless. Newton conceived of space itself as having an absolute position, so that any portion of space (as opposed to any body in space) was fixed. As Newton perfected the absolutistic conceptions of space and time which were supported by Democritus, Euclid and other, Einstein perfected the relativistic conceptions of space time which were in the line of Parmenides, Aristotle and Leibniz. Einstein, the inventor of relativity theory, harmonized in this single theory the ideas of scientists like Mach, Lorentz and Maxwell. This is also called as revolutionary physical theory because it brushed away the notion of space and time of classical mechanics. The views of time and space, which I have to set forth, have their foundation in experimental physics. Therein is their strength. Their tendency is revolutionary. From henceforth space in itself and time in itself sink to mere shadows and only a kind of union of the two preserves an independent existence. (H. Minkowski) 4.1. The Special Theory Of Relativity Classical physics owes its definitive formulation to the British scientist Sir Isaac Newton. According to Newton, when one physical body influences another body, this influence results in a change of that bodys state of motion, its velocity; that is to say, the force exerted by one particle on another results in the latters changing the direction of its motion, the magnitude of its speed, or both. Conversely, in the absence of such external influences, a particle will continue to move in one unchanging direction and at a constant rate of speed. This statement, Newtons first law of motion, is known as the law of inertia. As motion of a particle can be described only in relation to some agreed frame of reference, Newtons law of inertia may also be stated as the assertion that there exist frames of reference (so-called inertial frames of reference) with respect to which particles, not subject to external forces, move at constant speed in an unvarying direction. Ordinarily, all laws of classical mechanics are understood to hold with respect to such inertial frames of reference. Each frame of reference may be thought of as realized by a grid of surveyors rods permitting the spatial fixation of any event, along with a clock describing the time of its occurrence. According to Newton, any two inertial frames of reference are related to each other in that the two respective grids of rods move relative to each other only linearly and uniformly (with constant direction and speed) and without rotation, whereas the respective clocks differ from each other at most by a constant amount (as do the clocks adjusted to two different time zones on earth) but go at the same rate. Except for the arbitrary choice of such a constant time difference, the time appropriate to various inertial frames of reference, then, is the same. If a certain physical process takes, say, one hour as determined in one inertial frame of reference, it will take precisely one hour with respect to any other inertial frame; and if two events are observed to take place simultaneously by an observer attached to one inertial frame, they will appear simultaneous to all other inertial observers. This universality of time and time determinations is usually referred to as the absolute cha racter of time. The idea that a universal time can be used indiscriminately by all, irrespective of their varying states of motion†that is, by a person at rest at his home, by the driver of an automobile, and by the passenger aboard an airplane†is so deeply ingrained in most people that they do not even conceive of alternatives. It was only at the turn of the 20th century that the absolute character of time was called into question as the result of a number of ingenious experiments described below. As long as the building blocks of the physical universe were thought to be particles and systems of particles that interacted with each other across empty space in accordance with the principles enunciated by Newton, there was no reason to doubt the validity of the space-time notions just sketched. This view of nature was first placed in doubt in the 19th century by the discoveries of a the English scientist Michael Faraday, and the theoretical work of the Scottish-born physicist James Clerk Maxwell, all concerned with electric and magnetic phenomena. Electrically charged bodies and magnets do not affect each other directly over large distances, but they do affect one another by way of the so-called electromagnetic field, a state of tension spreading throughout space at a high but finite rate, which amounts to a speed of propagation of approximately 186,000 miles (300,000 kilometres) per second. As this value is the same as the known speed of light in empty space, Maxwell hypothesiz ed that light itself was a species of electromagnetic disturbance; his guess has been confirmed experimentally, first by the production of light like waves by entirely electric and magnetic means in the laboratory by a German physicist, Heinrich Hertz, in the late 19th century which we had seen in the previous sections. Both Maxwell and Hertz were puzzled and profoundly disturbed by the question of what might be the carrier of the electric and magnetic fields in regions free of any known matter. Up to their time, the only fields and waves known to spread at a finite rate had been elastic waves, which appear to the senses as sound and which occur at low frequencies as the shocks of earthquakes, and surface waves, such as water waves on lakes and seas. Maxwell called the mysterious carrier of electromagnetic waves the ether, thereby reviving notions going back to antiquity. He attempted to endow his ether with properties that would account for the known properties of electromagnetic waves, but he was never entirely successful. The ether hypothesis, however, led two U.S. scientists, Albert Abraham Michelson and Edward Williams Morley, to conceive of an experiment (1887). Albert Abraham Michelson a German-born American physicist established the speed of light as a fundamental constant and pursued other spectroscopic and metrological investigations. In 1878 Michelson began work on what was to be the passion of his life, the accurate measurement of the speed of light. He determined the velocity of light to be 299,853 kilometres (186,329 miles) per second, a value that remained the best for a generation, until Michelson bettered it. 4.2. Relativity of Space and Time An Irish and a Dutch physicist, George Francis FitzGerald and Hendrik Antoon Lorentz respectively, independently showed that the negative outcome of Michelsons and Morleys experiment could be reconciled with the notion that the Earth is travelling through the ether, if one hypothesizes that any body travelling through the ether is foreshortened in the direction of travel. The travelling body would be flattened completely if its speed through the ether should ever reach that of light. Suppose, now, that the variations in the speed of light were to be determined not by interference but by means of an exceedingly accurate clock and assume further that in such a modified experiment the motion through the ether were still imperceptible, then, Lorentz showed, one would have to conclude that all clocks moving through the ether are slowed down compared to clocks at rest in the ether. Thus, all rods and all clocks would be modified systematically, regardless of materials and construction des ign, whenever they were moving relative to the ether. Accordingly, for theoretical analysis, one would have to distinguish between apparent and true space and time measurements, with the further condition that true dimensions and true times could never be determined by any experimental procedure. Conceptually, this was an unsatisfactory situation, which was resolved by Albert Einstein in 1905. Einstein realized that the key concept, on which all comparisons between differently moving observers and frames of reference depended, is the notion of universal, or absolute, simultaneity; that is to say, the proposition that two events that appear simultaneous to any one observer will also be judged to take place at the same time by all other observers. This appears to be a straightforward proposition, provided that knowledge of distant events can be obtained practically instantaneously. Actually, however, there is no known method of signalling faster than by means of light or radio waves or any other electromagnetic radiation, all of which travel at the same rate, c. Suppose, now, that someone on Earth observes two events, say two supernovae appearing in different parts of the sky. Nothing can be said about whether these two supernovae emerged simultaneously or not from merely noting their appearance in the sky; it is necessary to know also their respective distances from the observer, which typically may amount to several hundred or several thousand light-years. By the time one sees the eruption of a supernova, it has in actuality faded back into invisibility hundreds of years ago. Applying this simple idea to the observations and measurements made by different observers of the same events, Einstein demonstrated that if each observer applied the same method of analysis to his own data, then events that appeared simultaneous to one would appear to have taken place at different times to observers in different states of motion. Thus, it is necessary to speak of relativity of simultaneity. Once this theoretical deduction is accepted, the findings of FitzGerald and Lorentz lend themselves to a new interpretation. Whenever two observers are associated with two distinct inertial frames of inference in relative motion to each other, their determinations of time intervals and of distances between events will disagree systematically, without one being right and the other wrong. Nor can it be established that one of them is at rest relative to the ether, the other in motion. In fact, if they compare their respective clocks, each will find that his own clock will be faster than the other; if they compare their respective measuring rods (in the direction of mutual motion), each will find the others rod foreshortened. The speed of light will be found to equal the same value, c = 186,000 miles per second, relative to every inertial frame of reference and in all directions. The status of Maxwells ether is thereby cast in doubt, as its state of motion cannot be ascertained by any conceivable experiment. Consequently, the whole notion of an ether as the carrier of electromagnetic phenomena has been eliminated in contemporary physics. 4.3. Relativity of Simultaneity Einstein distinguishes between simultaneity at the same spot and simultaneity of events separated by distance. To explain this simultaneity we shall take astronomic dimensions into consideration. An astronomical observer is attached to his spatial place; yet he receives messages or signals from distant points. He is able to record immediately only the simultaneity of their arrival to his place. Although this place is by no means a mathematical point, nevertheless it may be considered as virtually dimensionless as compared to distances traversed by light in a few seconds and referred to by the theory of relativity. The arrival of a signal may be designated as a coincidence, as a point-event; that is to say, as phenomenon spatially and temporally dimensionless. The logical problem arising beyond the sensory perception is this: How does an observer arrive at the temporal order of events separated by space The answer is simple i.e. by means of physical instruments and mathematical calculations. The time for the signal to travel for a particular distance is calculated from dividing the spatial distance and the speed of the signal. If a beam of light from Sirius reaches the earth simultaneously with a beam from the sun, then it is possible to estimate at what time each of the beams was emitted by taking into consideration the respective distances of the stars and the velocity of light. 4.4. Velocity of Light From the previous section we understand that the measurement of velocity of light is a necessary element for the result of the calculation. Then, how can the velocity of light be measuredâ„ ¢ is our concern in this section. To determine the velocity for one single direction we need to place clocks at both the points A and B. But there too occur a difficulty in our measurement of the velocity of light. In order to estimate the differences in time at the points the clocks are arranged so that both show the same figures at the same time. The problem here is that we arrange the clocks for the measurements of velocity solely for the purpose of finding the simultaneity at points located remotely from each other. Now we are caught up in a vicious circle that in order to know the simultaneity at a distance we need to know a velocity, and in order to measure the velocity we must be capable of judging the simultaneity of events separated by distance. Einstein with his famous theory o f relativity of simultaneity has shown a way out from this circle. For Einstein: The simultaneity of distant events cannot be verified, it can only be defined. It is arbitrary; we can determine it in any manner without committing a mistake. When accordingly we make measurements, the results will contain the simultaneity which has been introduced by definition; this process can never lead to contradiction. Indirectly the theory contains the mind of Einstein concerning the non-existence of any special frame-of-reference with regard to the propagation of light. But there is a hidden contradiction in this theory. To study that contradiction let us go deep into the theory itself. The theory in its exact form is, the velocity of light is identical in all directions in a uniformly moving frame of reference, provided simultaneity is correspondingly defined. The last words makes Einsteins mind clearer. There is also an assumption for Einsteins theory which is nothing other than the assumption that no velocity greater than that of light can occur in nature. Let us check out the depth of this assumption. A light signal is sent out from A at 12 oâ„ ¢ clock; it is then reflected and returns to A at 10 minutes after 12 oâ„ ¢ clock. At what time did it reach B According to Einstein, this cannot be determined by experiments; we can only establish it by definition. We may, for instance, record it as having occurred at 12:05; but we can think of it also as occurring at 12:02 or 12:08. But we may not declare that the arrival at B takes place at 11:59; for then the light would have arrived at B earlier than it has started from A. We know that no physical occurrences can run backward as to time. This is the only limitation; any number within the stretch of time between 12:00 and 12:10 can be chosen. Let us therefore set the time for the arrival of the light beam at 12:02. Can this lead to no contradiction There would always be a possibility of contradiction were there signals faster than light in existence. Let us suppose that there is a signal requiring three minutes less than light to traverse the distance AB. Let this signal be sent from the point A simultaneously with the light-beam. As the light-beam arrives at B at 12:02, the other signal will arrive, according to our assumption, at 12:02 minus 3 minutes, that is, at 11:59. Now, both signals were sent out from A at 12 oâ„ ¢clock. It follows, absurdly enough, that the new signal arrives at B sooner than it starts from A. The determination of simultaneity has led us to a contradiction; but only because we have accepted the possibility of the existence of signals travelling faster than light. Though we question the contention that there are no other rays which travel faster than the velocity of light we need to admit that no one has found any other rays which has the velocity fastest than the light. This does not mean that there cannot be any, but we need to wait with science to unprove the most important contention of special theory of light. Einsteinâ„ ¢s point on this absoluteness of the velocity of light can be connected also to the energy of the moving bodies. Every body in motion carries within itself an amount of energy which increases with the velocity of the body. This energy is required to start the motion. According to Einstein the content of energy in a moving body grows with an increasing speed. In order to bring a body up to the velocity of light, an infinite amount of energy would be required. It is impossible for a body to move quicker than light; in fact no material body can reach the velocity of light. Also, as we have seen in the previous sections, the limitation of this velocity of light rests upon our knowledge that light is not a physical phenomenon, rather it represents an electrical phenomenon and that light waves are only a small section of the great spectrum of electrical waves. With these realms of knowledge can we be clear in the idea of simultaneity. An example will do to explain this notion of simultaneity. Let us say that I wish to visit a friend of mine in Southampton. I depart in a steamer from New York at 12 oâ„ ¢clock. Now it happens that my friend leaves Southampton for New York precisely at the same time. Neither of us knows about the otherâ„ ¢s departure. Only at the last moment do we send telegrams to each other. We shall now consider a small delay of the telegram due to its being written out and carried out, and we shall assume that the telegram arrives within a few minutes. Such a telegram is then the quickest practical signal, although the delay makes it a little slower than the velocity of light. If both the telegrams start out simultaneously, each will reach its destination slightly late, that is, after the shipâ„ ¢s departure. The fact that we both left simultaneously means an exclusion of causal connection. When two events P and Q take place simultaneously, there is no possible effect of P on Q or of Q on P. This makes clear the indeterminacy of simultaneity and also the limited character of the velocity of light. Though great the velocity of light there cannot be simultaneous events in a time interval of zero, but arbitrarily with a short time interval. With these different contentions one may further read Einsteins theory of space-time in the following way. The clocks we use have no magnitude independent for themselves, but adjust themselves to metric field of space; it is clear in the case of magnetic needle adjusting itself to the field of the magnetic forces. If a clock is moved from a place and returned to its original place it shows a time slower than a clock which remained motionless at the same spot. Theory of relativity goes to the extent to say that any running mechanism, regardless of any kind, would manifest a similar retardation. If this is to be fully understood, we must realise that all the processes of the