Black HolesMost scientists agree that black holes exist but are nearly impossible to locate.A black hole in the universe is not a solid object,like a planet,but it is shaped like a sphere (球体).Astronomers(天文学家)think that at the center of a black hole there is a single point in space with infinite(无限的)density(稠密).This single point is called a singularity (奇点).If the singularity theory is correct,it means that when a massive star collapses,all the material in it disappears into the singularity
