Updated: Jan 27, 2022
[Photo Credit: ESO, ESA/Hubble, M. Kornmesser/N. Bartmann]
Our space-time is defined using coordinates that we consider events in our universe to be connected through. We have four dimensions, which we use for co-ordinations; these dimensions are 3-spatial¹+ 1-time dimensions. Thus, we are making cosmological events with each coordinated change. A tick in the clock starts one event and ends another―these are the dynamics of space-time.
We study relativity, which was investigated by physicist Albert Einstein, to understand these dynamics. Relativity tells us how an event occurs in space-time and theorizes the critical relation between frames at the speed of light. Relativity provides us with a set of equations, one of which is the Einstein Equation, and its solutions. Our space-time is a Minkowski’s metric, and because of the energy-momentum tensor, we get a curvature. Intuitively, when stretched uniformly by all ends, a bed sheet is used to put a ball, then the area surrounding the ball creates said curvature. Our space-time is a bedsheet, and the mass on it is the ball, and so a curvature exists. According to relativity, this curvature can attract another mass, roll a little ball around the big ball, and it will intend to go to a big ball―this is gravity. Reflecting on relativity equations, every solution to each equation describes a unique space-time―one that we do not require to be real. The black hole is also a solution to these equations, which Karl Schwarzschild first founded.
A black hole is a singularity in space-time that possesses a great mass. By singularity, we mean it to be not visible in structure. A supermassive black hole, which is the black hole situated at the center of every galaxy, can be up to 1 million solar masses. An ordinary black hole is also much heavier than existing stars. When these masses act on space-time, they dig an ever-lasting curvature at that singular point. As our curvature defines gravity, this black hole must have a tremendous yet clandestine gravitational power, and the black hole is remembered for its enormous gravity. This gravitational field, a field created by gravitational force around the origin, is so strong that even light with its super speed of 3 × 108 ms−1 can’t escape once it has fallen into this black hole.
Black holes are born out of stars. Every star has a lifetime, which is determined by the quantity of hydrogen it has. There is some thermonuclear process going inside the core of a star, and when such stars get near to their end, this core becomes unstable and collapses gravitationally, and produces singularity with much dense curvature over there. Black holes are surrounded by an area called ”Event Horizon.” If it passes this event horizon, any object will dwell inside the black hole and would feel relativistic effects, one of them is a time shift. Yet, they are still important areas of research with insufficient knowledge. We hope for additional shreds of evidence supporting the facts of “What’s Inside?".
 Curiel, Erik. ”What Is a Black Hole?.” (2018).
 Luminet, Jean-Pierre. ”Black holes: A general introduction.” Black holes:
Theory and observation. Springer, Berlin, Heidelberg, 1998. 3-34.
 Hawking, Stephen. The theory of everything. Jaico Publishing House, 2006.
¹Spatial means space, hence our three dimensions are usual space dimensions that we observe and use every day.