Can someone tell Superman about E=mc^2 and that he's about to collapse into a black hole any second now?

Fun fact: The comic is obviously an exaggeration, but If you could somehow become massless and travel at the speed of light, the very concept of having a point of view would cease to make physical sense. Space and time wouldn't simply freeze for you; relativity wouldn't even define a valid frame of reference from which you could experience them.