Black holes are real phenomena in our universe according to black-holes. Black holes are so strong that not even light can escape them. Before Einstein, physicists believed that gravity is a strong force that pulls objects through space to a bigger object such as earth.gravity was thought to work with an external force; like wind. Einstein supposed that gravity is not forced nor forces other objects towards each other but instead bends time and space bringing things together. Bending time and space means that gravity imparts a sort of velocity to an open and empty space and matter kinda just goes along with it. The difference between dark stars and black holes is that the actual mass of a black hole has no size at all. The gravity for a black hole is so strong that it gets crushed into something called a singularity. The most common way people find black holes is to see the stars orbiting around it. We are unable to see black holes because they are invisible so the easiest way to see them is dark stars. Meaning two stars that orbit around each other. So when astronomers see a star orbiting with an invisible companion that could mean that it is a black hole.