Black holes have been the subject of controversy over a long period of time dating back to history. Black holes have been a part of Physics and the first person who predicted them was Laplace. It was he who said that it may be possible that the biggest luminous object in the universe is invisible.
Black holes are luminous stars that have the same weight as the earth having the size of 250 times bigger than the sun. Theoriticians have been trying to use mathematics of Black Holes to formulate solutions to a lot of mysteries on earth which remain a question until now such as the beginning of earth existence and the end of the universe, travel in time, etc.
What causes Black Holes to form? The pressure created inside a star because its hydrogen fusion balances its gravitational attraction to its core, forms a star. The amazing feature of a star is that it has its own system to exist and control all its powers and properties. Since the hydrogen fusion and the gravitational pull balance each other, the star is able to maintain its size while hydrogen is active.
However, when the hydrogen has been transformed to helium, the existing pressure inside the star will lose its ability to balance with the gravitational attraction resulting to the decrease in its size. This decrease in the size of the star causes its temperature to rise which results to the existence of the Fusion of Helium and the development of too much pressure.
In this case, the pressure becomes more than the gravitational attraction and this causes the star to expand. This stage when the star has expanded is known as Red Giant stage. This stage is followed by the depletion in the amount of helium that causes the star to contract. Thus, it becomes a cycle.
There are 2 theories that may be involved in this cycle. First, if the mass of the star is not enough to make another fusion, the star appears to be a white tiny star that radiates to release its internal energy. Second, if the mass of the star dominates the whole body, then, the star turns into a contracted star.
In this process, a very powerful gravitational field is created that can control everything inside the star including its reflection of light outside its body. This is the reason why its light cannot be fully seen on earth. The process that the star impedes the ability of the light to travel outside is called Schwarzschild radius where kinetic energy of light is equal to gravitational potential energy of the contracted star.
Therefore above the radius, the gravitational field of the contracted star occurs and below the radius, light cannot escape the star. This process where the light cannot go out from the interior of the star due to its strong gravity makes it invisible outside. This is why we cannot fully see the lights of the stars, and this is the reason why they are called Black Holes.