Brachistochrone
Light is one of the most amazing phenomena in the Universe. It is pure energy and has zero mass. If you could experience a moment as a photon, you would experience eternity in that moment, for light experiences no time of its own (technically you’d experience nothing as psychological experience is time dependent, but lets keep the poetic tone). It is one of the primordial constituents of the Universe and is considered sacred in all religions, ditto physics. Among other things, a path of light is Brachistochrone....