Physicists have coaxed a black hole's most famous glow out of a strand of optical fiber and, for the first time, watched that light react back on the simulated black hole that produced it. The result gives researchers a rare, hands-on look at Hawking radiation — the faint thermal emission that Stephen Hawking predicted should leak out of black holes — and offers a first clue about the tiny push that could, in principle, make a real black hol…