2017-02-16 23:00:47 UTC
Consider a light source emitting a series of pulses equally distanced from one another. A stationary observer (receiver) measures the frequency of the pulses:
The observer starts moving with constant speed towards the light source - the measured frequency increases:
The following quotation is relevant:
Albert Einstein Institute: "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."
Since "four pulses are received in the time it takes the source to emit three pulses", the speed of the pulses relative to the receiver (observer) is greater than their speed relative to the source, in violation of Einstein's relativity.