Simulation A black hole is a star that has collapsed into a tiny point known as a singularity. It is so dense that it sucks in everything near it, including light. Black holes can be seen via the death throes of the matter being sucked in. Although it becomes invisible past a certain point, an accretion disk, which is visible, develops as the matter swirls toward the black hole. The collapsed star is so dense that nothing can escape its gravitational pull, not even light.A black hole is a star that has collapsed into a tiny point known as a singularity. It is so dense that it sucks in everything near it, including light. Black holes can be seen via the death throes of the matter being sucked in. Although it becomes invisible past a certain point, an accretion disk, which is visible, develops as the matter swirls toward the black hole. The collapsed star is so dense that nothing can escape its gravitational pull, not even light.A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior. The gravitational field is so strong that the escape velocity near it exceeds the speed of light. This implies that nothing, not even light, can escape its gravity, hence the word "black." The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return. Theoretically, black holes can have any size, from microscopic to near the size of the observable universe.A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior. The gravitational field is so strong that the escape velocity near it exceeds the speed of light. This implies that nothing, not even light, can escape its gravity, hence the word "black." The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return. Theoretically, black holes can have any size, from microscopic to near the size of the observable universe.Black holes are predicted by general relativity. According to classical general relativity, neither matter nor information can flow from the interior of a black hole to an outside observer. For example, one cannot bring out any of its mass, or receive a reflection back by shining a light source such as a flashlight, or retrieve any information about the material that has entered the black hole. Quantum mechanical effects may allow matter and energy to radiate from black holes; however, it is thought that the nature of the radiation does not depend on what has fallen into the black hole in the past.