On 30.01.2021 17:56, Pentcho Valev wrote:
Albert Einstein Institute: "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:

https://www.einstein-online.info/wp-...ein-Online.gif

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. In this particular animation, which has the receiver moving towards the source at one third the speed of the pulses themselves, four pulses are received in the time it takes the source to emit three pulses." http://www.einstein-online.info/spotlights/doppler.html

The speed of the light pulses as measured by the source is c = 3d/t, where d is the distance between the pulses and t is "the time it takes the source to emit three pulses".

The speed of the pulses as measured by the moving receiver is c' = 4d/t c, in violation of Einstein's relativity.

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Pentcho Valev



There is something very basic what you seemingly have not understood so
far. The Doppler effect is additional to relativistic effects. It is the
dominant effect at low speeds of course in case that the source is
approaching or leaving the target. Do not mismatch the effects. I
recommend to read a book about relativity and make the exercises. Then
read about Doppler effects and make the exercises. Then combine both
effects. Then talk and write about it.