Chasing a Beam of Light: Einstein’s Most Famous Thought Experiment

John D. Norton in his Goodies at the University of Pittsburg:

Einstein recalled how, at the age of 16, he imagined chasing after a beam of light and that the thought experiment had played a memorable role in his development of special relativity. Famous as it is, it has proven difficult to understand just how the thought experiment delivers its results. It fails to generate serious problems for an ether based electrodynamics. I propose a new way to read it that fits it nicely into the stages of Einstein’s discovery of special relativity. It shows the untenability of an “emission” theory of light, an approach to electrodynamic theory that Einstein considered seriously and rejected prior to his breakthrough of 1905.

How could we be anything but charmed by the delightful story Einstein tells in his Autobiographical Notes of a striking thought he had at the age of 16?

More here.