Stationary light source; moving receiver: http://www.einstein-online.info/imag...ector_blue.gif

(Website: http://www.einstein-online.info/spotlights/doppler.html)

The speed of the light pulses relative to the source is

c = df

where d is the distance between the pulses and f is the frequency measured by the source. The speed of the pulses relative to the receiver is

c'= df' c

where f' f is the frequency measured by the receiver.

Einstein knew that the constancy of the speed of light was nonsense but found it profitable to introduce it. Space and time were vandalized accordingly (to fit the nonsensical constancy) and the post-truth (post-sanity) era in science began:

John Stachel: "But this seems to be nonsense. How can it happen that the speed of light relative to an observer cannot be increased or decreased if that observer moves towards or away from a light beam? Einstein states that he wrestled with this problem over a lengthy period of time, to the point of despair." http://www.aip.org/history/exhibits/...relativity.htm

Pentcho Valev