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JIM AL-KHALILI, HIS BOXER SHORTS AND THE SPEED OF LIGHT
http://www.guardian.co.uk/commentisf...?newsfeed=true
Jim Al-Khalili: "I'd love it if neutrinos really have exceeded the speed of light. But I'm not eating my shorts just yet. (...) According to our understanding of the laws of physics, nothing can exceed the speed of light, an impressive billion kilometres an hour. And in my experience, there is nothing that annoys people more about Einstein's theory of relativity (for that is where this notion originates) than its claim to this cosmic limit. Since Einstein's work in 1905, thousands of experiments have only confirmed it – and indeed much of the beautiful edifice of modern physics rests on it being correct. The crucial point is not that light is so special but rather that this speed limit is written into the fabric of space and time." Jim Al-Khalili, Neutrinos may or may not have exceeded the speed of light and yet I am afraid you will have to eat your boxer shorts some day. Two experiments - that of Michelson-Morley and that of Pound-Rebka - show that the speed of light varies with v, the speed of the emitter relative to the observer, in accordance with the equation c'=c+v given by Newton's emission theory of light: http://www.pitt.edu/~jdnorton/papers/companion.doc John Norton: "These efforts were long misled by an exaggeration of the importance of one experiment, the Michelson-Morley experiment, even though Einstein later had trouble recalling if he even knew of the experiment prior to his 1905 paper. This one experiment, in isolation, has little force. Its null result happened to be fully compatible with Newton's own emission theory of light. Located in the context of late 19th century electrodynamics when ether-based, wave theories of light predominated, however, it presented a serious problem that exercised the greatest theoretician of the day." http://philsci-archive.pitt.edu/1743/2/Norton.pdf John Norton: "In addition to his work as editor of the Einstein papers in finding source material, Stachel assembled the many small clues that reveal Einstein's serious consideration of an emission theory of light; and he gave us the crucial insight that Einstein regarded the Michelson-Morley experiment as evidence for the principle of relativity, whereas later writers almost universally use it as support for the light postulate of special relativity. Even today, this point needs emphasis. The Michelson-Morley experiment is fully compatible with an emission theory of light that CONTRADICTS THE LIGHT POSTULATE." http://groups.google.com/group/sci.p...abc7dbb30db6c2 John Norton: "THE MICHELSON-MORLEY EXPERIMENT IS FULLY COMPATIBLE WITH AN EMISSION THEORY OF LIGHT THAT CONTRADICTS THE LIGHT POSTULATE." Tom Roberts: "Sure. The fact that this one experiment is compatible with other theories does not refute relativity in any way. The full experimental record refutes most if not all emission theories, but not relativity." Pentcho Valev: "THE POUND-REBKA EXPERIMENT IS FULLY COMPATIBLE WITH AN EMISSION THEORY OF LIGHT THAT CONTRADICTS THE LIGHT POSTULATE." Tom Roberts: "Sure. But this experiment, too, does not refute relativity. The full experimental record refutes most if not all emission theories, but not relativity." Of course, the epoch-making statement "But this experiment, too, does not refute relativity" needs a lot of discussion that for the moment is impossible in mainstream science. Still let me call your attention to the concept of "protective belt" advanced by Imre Lakatos: http://bertie.ccsu.edu/naturesci/PhilSci/Lakatos.html "Lakatos distinguished between two parts of a scientific theory: its "hard core" which contains its basic assumptions (or axioms, when set out formally and explicitly), and its "protective belt", a surrounding defensive set of "ad hoc" (produced for the occasion) hypotheses. (...) In Lakatos' model, we have to explicitly take into account the "ad hoc hypotheses" which serve as the protective belt. The protective belt serves to deflect "refuting" propositions from the core assumptions..." The protective belt ("contracting lengths, local time, or Lorentz transformations") referred to by Banesh Hoffmann: http://www.amazon.com/Relativity-Its.../dp/0486406768 "Relativity and Its Roots" By Banesh Hoffmann: "Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether." Pentcho Valev |
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JIM AL-KHALILI, HIS BOXER SHORTS AND THE SPEED OF LIGHT
http://personal.ph.surrey.ac.uk/~phs...tes11Nov08.pdf
Jim Al-Khalili (lecture notes): "Technically, M&M experiment showed not that the speed of light is constant in all inertial frames but rather that it was constant in all directions within the same frame. It was not until 1932 when another famous experiment was carried out (by Kennedy and Thorndike) that Einstein's second postulate was properly proven: that speed of light is constant in all inertial reference frames." http://en.wikipedia.org/wiki/Kennedy...ike_experiment Wikipedia: "While the Michelson-Morley experiment showed, that the speed of light is independent of the orientation of the apparatus, the Kennedy-Thorndike experiment showed that it is also independent of the velocity of the apparatus in different inertial frames." Jim Al-Khalili, Obviously your lectures are based on Wikipedia but that is not very good for your students. Are you sure that, while the Michelson-Morley experiment confirms the variable speed of light c'=c+v predicted by Newton's emission theory of light, the Kennedy-Thorndike experiment refutes it? http://personal.ph.surrey.ac.uk/~phs...tes11Nov08.pdf Jim Al-Khalili: "Einstein's second postulate states that the speed of light is the same in all inertial reference frames (or: speed of light has the same value as measured by all observers no matter what their relative velocity with respect to each other is)." Do the following observers continue to measure the same speed of the waves as they start moving towards the source? http://a-levelphysicstutor.com/wav-doppler.php "vO is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + vO. (...) The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time." http://www.expo-db.be/ExposPrecedent...%20Doppler.pdf "La variation de la fréquence observée lorsqu'il y a mouvement relatif entre la source et l'observateur est appelée effet Doppler. (...) 6. Source immobile - Observateur en mouvement: La distance entre les crêtes, la longueur d'onde lambda ne change pas. Mais la vitesse des crêtes par rapport à l'observateur change !" http://www.phys.uconn.edu/~gibson/No...6_3/Sec6_3.htm Professor George N. Gibson, University of Connecticut: "However, if either the source or the observer is moving, things change. This is called the Doppler effect. (...) To understand the moving observer, imagine you are in a motorboat on the ocean. If you are not moving, the boat will bob up and down with a certain frequency determined by the ocean waves coming in. However, imagine that you are moving into the waves fairly quickly. You will find that you bob up and down more rapidly, because you hit the crests of the waves sooner than if you were not moving. So, the frequency of the waves appears to be higher to you than if you were not moving. Notice, THE WAVES THEMSELVES HAVE NOT CHANGED, only your experience of them. Nevertheless, you would say that the frequency has increased. Now imagine that you are returning to shore, and so you are traveling in the same direction as the waves. In this case, the waves may still overtake you, but AT A MUCH SLOWER RATE - you will bob up and down more slowly. In fact, if you travel with exactly the same speed as the waves, you will not bob up and down at all. The same thing is true for sound waves, or ANY OTHER WAVES." Pentcho Valev |
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JIM AL-KHALILI, HIS BOXER SHORTS AND THE SPEED OF LIGHT
Jim Al-Khalili irreversibly mutilates young minds:
http://www.facebook.com/note.php?not...22654397787009 Ask the Expert - answers from Prof Jim Al-Khalili Question: "If the speed of light is constant, why is light affected by the Doppler shift?" Jim Al-Khalili: "In the Doppler shift, the speed of light (or sound) is not what is affected; it is the wavelength that changes, and the frequency. There is a formula for this: speed=wavelength x frequency. So if a light source is travelling towards us, the waves of light coming from it are getting squashed and so wavelength is smaller, but they are arriving more rapidly, so frequency gets higher. The product of smaller wavelength and higher frequency gives the same speed of light always." Jim Al-Khalili, As the observer starts moving towards the source of SOUND, the speed of sound waves relative to him increases while the wavelength remains unchanged (the wavelength simply cannot depend on the movements of the observer). The same happens in the case of LIGHT (see quotations below). Pentcho Valev wrote: http://personal.ph.surrey.ac.uk/~phs...tes11Nov08.pdf Jim Al-Khalili: "Einstein's second postulate states that the speed of light is the same in all inertial reference frames (or: speed of light has the same value as measured by all observers no matter what their relative velocity with respect to each other is)." Do the following observers continue to measure the same speed of the waves as they start moving towards the source? http://a-levelphysicstutor.com/wav-doppler.php "vO is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + vO. (...) The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time." http://www.expo-db.be/ExposPrecedent...%20Doppler.pdf "La variation de la fréquence observée lorsqu'il y a mouvement relatif entre la source et l'observateur est appelée effet Doppler. (...) 6. Source immobile - Observateur en mouvement: La distance entre les crêtes, la longueur d'onde lambda ne change pas. Mais la vitesse des crêtes par rapport à l'observateur change !" http://www.phys.uconn.edu/~gibson/No...6_3/Sec6_3.htm Professor George N. Gibson, University of Connecticut: "However, if either the source or the observer is moving, things change. This is called the Doppler effect. (...) To understand the moving observer, imagine you are in a motorboat on the ocean. If you are not moving, the boat will bob up and down with a certain frequency determined by the ocean waves coming in. However, imagine that you are moving into the waves fairly quickly. You will find that you bob up and down more rapidly, because you hit the crests of the waves sooner than if you were not moving. So, the frequency of the waves appears to be higher to you than if you were not moving. Notice, THE WAVES THEMSELVES HAVE NOT CHANGED, only your experience of them. Nevertheless, you would say that the frequency has increased. Now imagine that you are returning to shore, and so you are traveling in the same direction as the waves. In this case, the waves may still overtake you, but AT A MUCH SLOWER RATE - you will bob up and down more slowly. In fact, if you travel with exactly the same speed as the waves, you will not bob up and down at all. The same thing is true for sound waves, or ANY OTHER WAVES." Pentcho Valev |
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JIM AL-KHALILI, HIS BOXER SHORTS AND THE SPEED OF LIGHT
Jim Al-Khalili fiercely teaches Divine Albert's Divine Theory at the
University of Surrey: http://personal.ph.surrey.ac.uk/~phs...TR-Lec3,4n.pdf Jim Al-Khalili: "The speed of light has the same value (c) measured by all observers no matter how fast they are moving relative to each other. (e.g. the speed of light coming from the sun is the same whether measured on Earth or on a rocket speeding away from the Solar System at half the speed of light!)" Jim Al-Khalili, Is the wavelength of the light reaching the Earth equal to the wavelength of the light reaching the rocket speeding away from the Solar System at half the speed of light? If not, who or what has caused the difference? That is, who or what stretches the wavelength of the light reaching the rocket so that the speed of the light measured on the rocket can gloriously be equal to the speed of the light measured on Earth? Do your students sing "Yes we all believe in relativity, relativity, relativity", like Max Tegmark's students? http://www.youtube.com/watch?v=5PkLLXhONvQ We all believe in relativity, relativity, relativity. Yes we all believe in relativity, relativity, relativity. Einstein's postulates imply That planes are shorter when they fly. Their clocks are slowed by time dilation And look warped from aberration. We all believe in relativity, relativity, relativity. Yes we all believe in relativity, relativity, relativity. Pentcho Valev |
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