Why does a black hole not let light escape? how is this possible?
It's explained by Einstein's theory of relativity--which shows that time, mass, and energy are all related. In this system, gravity is not defined as the attraction between large bodies, it si defined as the curvature of space. And a black hole is so massive the space curves so tightly that all matter and energy is trapped and cannot escape.
There are lots of examples of phenomena in space that support this theory...showing that light does indeed curve when its path takes it past a large mass object. And if that object is large enough and massive enough, the light curves so tightly that it becomes part of the massive object, and does not leave.
Does that help?
I hope so. This stuff isn't simple!