"...and he showed that the speed of light within a vacuum is the same no matter the speed at which an observer travels." https://space.com/17661-theory-general-relativity.html

Before "showing" this obvious nonsense, Einstein wrestled with his conscience "over a lengthy period of time, to the point of despair":

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

"Seems to be nonsense" is a red herring. Einstein's constant speed of light is OBVIOUS NONSENSE. Frequency and speed of light pulses vary proportionally for the moving observer https://youtube.com/watch?v=bg7O4rtlwEE, in accordance with the formula

(frequency) = (speed of pulses)/(distance between pulses)

See more he https://twitter.com/pentcho_valev

Pentcho Valev