French astronomer-mathematician Pierre Laplace reasoned that some bodies might be dense enough to have escape velocities faster than the speed of light . Laplace thus assumed that light could never escape from such bodies and that they would be permanently black and opaque. Although this basic idea is nearly correct, we know that the situation is more complex because of Einstein's theories of relativity. Einstein's special theory of relativity starts with the observation that nothing travels faster than the speed of light. In addition, it is observed that the measured speed of light is a universal constant.
Any object can become a black hole if compressed enough.
If the Earth were compressed to the size of a marble, it would be a black hole. We can understand the nature of a black hole in terms of the idea of escape velocity. But as we get much closer to the black hole, the escape velocity increases. Larger speeds are needed to escape the stronger and stronger gravity. At a distance of 3 km, the speed needed to escape would be the speed of light.