“Let's return to Archytas's staff and to the expanding Universe. A javelin that is thrown straight upward will drop back down a long time before we can sensibly ask the question about the edge of the universe. The javelin cannot… — Henning Genz Copy Share Image
“In order to show that not even light can escape from the gravitational pull of a black hole, we have to hone the argument further. Light, as we know, always moves at the same velocity. When it rises against gravity,… — Henning Genz Copy Share Image
