Once, I read that Einstein founded the special relativity theory by imagining how an observer moves at the speed of light.
How does this thought experiment work? How to reach from this imagination to the relativity of time?
John Norton at Pitt relates the story quite nicely.
In Einstein's own words:
In other words, assuming both
leads to an impossibility:
Since he judged (3) to be impossible, then either (1) or (2) or both must be wrong. His insight was that (2) is wrong, that the speed of light is not attainable.
http://www.ivorcatt.co.uk/x41w.pdf This idea is undermined by the pulse, or step, travelling unchanged down a transmission line (a circular loop of coaxial cable) at the speed of light. It happens in a USB cable, which Einstein did not know about. Ivor Catt
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