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Old July 6th 12, 01:42 PM posted to sci.astro
Pentcho Valev
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Textbooks correctly show that, if the observer starts moving towards the light source with speed v and if v is low enough, the frequency as measured by the observer shifts from f to f'=f(1+v/c). The derivation is impossible without assuming, explicitly or implicitly, that, relative to the observer, the speed of light shifts from c to c'=c+v. Of course the assumption is the most dreadful thing Einsteinians can imagine so prudent authors always make it as implicit as possible. Here are some examples of careless authors who don't see the danger and draw the reader's attention to c'=c+v:

Fang-Yuh Lo, Department of Physics, National Taiwan Normal University: "Observer moves toward source: frequency becomes higher. Observer moves away from source: frequency becomes lower. How much higher (lower)? Wavelength does not change. Change in velocity: Vnew=Vwave±Vobs."

"L'effet Doppler est le décalage de fréquence d'une onde acoustique ou électromagnétique entre la mesure à l'émission et la mesure à la réception lorsque la distance entre l'émetteur et le récepteur varie au cours du temps. (...) Pour comprendre ce phénomène, il s'agit de penser à une onde à une fréquence donnée qui est émise vers un observateur en mouvement, ou vis-versa. LA LONGUEUR D'ONDE DU SIGNAL EST CONSTANTE mais si l'observateur se rapproche de la source, il se déplace vers les fronts d'ondes successifs et perçoit donc plus d'ondes par seconde que s'il était resté stationnaire, donc une augmentation de la fréquence. De la même manière, s'il s'éloigne de la source, les fronts d'onde l'atteindront avec un retard qui dépend de sa vitesse d'éloignement, donc une diminution de la fréquence."

"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."

Albert Einstein Institute: "The frequency of a wave-like signal - such as sound or light - depends on the movement of the sender and of the receiver. This is known as the Doppler effect. (...) In the above paragraphs, we have only considered moving sources. In fact, a closer look at cases where it is the receiver that is in motion will show that this kind of motion leads to a very similar kind of Doppler effect. Here is an animation of the receiver moving towards the source: (...) By observing the two indicator lights, you can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. THIS TIME, THE DISTANCES BETWEEN SUBSEQUENT PULSES ARE NOT AFFECTED, but still there is a frequency shift: As the receiver moves towards each pulse, the time until pulse and receiver meet up is shortened."

"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 !"

Carl Mungan: "Consider the case where the observer moves toward the source. In this case, the observer is rushing head-long into the wavefronts... (....) In fact, the wave speed is simply increased by the observer speed, as we can see by jumping into the observer's frame of reference."

Professor Sidney Redner: "We will focus on sound waves in describing the Doppler effect, but it works for other waves too. (...) Let's say you, the observer, now move toward the source with velocity vO. You encounter more waves per unit time than you did before. Relative to you, the waves travel at a higher speed: v'=v+vO. The frequency of the waves you detect is higher, and is given by: f'=v'/(lambda)=(v+vO)/(lambda)."

Roger Barlow, Professor of Particle Physics: "Moving Observer. Now suppose the source is fixed but the observer is moving towards the source, with speed v. In time t, ct/(lambda) waves pass a fixed point. A moving point adds another vt/(lambda). So f'=(c+v)/(lambda)."

Tony Harker, University College London: "If the observer moves with a speed Vo away from the source (...), then in a time t the number of waves which reach the observer are those in a distance (c-Vo)t, so the number of waves observed is (c-Vo)t/lambda, giving an observed frequency f'=f((c-Vo)/c) when the observer is moving away from the source at a speed Vo."

Pentcho Valev

Old July 7th 12, 05:23 AM posted to sci.astro
Pentcho Valev
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Posts: 7,625

Let f', c' and L' be the frequency, speed of light and wavelength the observer moving with speed v towards the light source measures: f'=c'/L'. Textbook authors often derive the Doppler formula f'=(c+v)/L but then stop short, as though by instinct, at the threshold of a dangerous thought:

George Orwell: "Crimestop means the faculty of stopping short, as though by instinct, at the threshold of any dangerous thought. It includes the power of not grasping analogies, of failing to perceive logical errors, of misunderstanding the simplest arguments if they are inimical to Ingsoc, and of being bored or repelled by any train of thought which is capable of leading in a heretical direction. Crimestop, in short, means protective stupidity."

Where does the danger come from? Combining the formulas f'=c'/L' and f'=(c+v)/L gives either:

A) c'=c+v ; L'=L


B) c'=c ; L'=cL/(c+v)

A is obviously correct - and it is correct for all other waves. But it is fatal for Divine Albert's Divine Theory. B is obviously absurd - it would be too dangerous to teach that, due to the motion of the observer, the wavelength somehow shifts from L to L'=cL/(c+v). So textbook authors take refuge in crimestop.

Pentcho Valev

Old July 8th 12, 02:04 PM posted to sci.astro
Pentcho Valev
external usenet poster
Posts: 7,625

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. (...) 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."


If the waves overtake you at a much slower rate, you measure their speed relative to you to be lower don't you? Is that true for light waves? Einsteinians ready to answer:


Pentcho Valev


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