I've been trying to track down one of the popular physics books, a title I read years ago and can't recall. The author referred to a hypothetical astronaut, travelling at or close to lightspeed. Looking out of his ship's rear window he observes the stars behind him gradually reddening and dimming and eventually disappearing altogether as wavelength becomes infinite. In the forward direction the universe is foreshortened to a point as all light is completely blue-shifted. The author suggested that the astronaut is effectively dragging along his own personal black hole behind him, as this would logically account for his inability to see any stars astern of him. I eventually saw in these observations the answer to something which had been puzzling my poor brain for years (ever since reading "Einsteins Universe" even earlier !!) I'm darned if I can remember the title or author of the book that I found this in. I've tried all the ones I can remember, not that there have been very many, I'm not much of a scientist and less of a mathematician. I havent looked around the site yet (newbie) and for all I know this is Mother's Milk to the regulars.