What's at the Bottom of a Black Hole ?

      Black holes are already among most  mysterious  objects  in  the the  universe, even before we begin to  contemplate "bottom" of  what might be at the  one.  The concept of a tiny star whose gravitational field is so strong that neither light nor matter  can escape was so foreign to those  who first theorized their existence  that even Albert Einstein himself,  whose math confirmed   their possibility, dismissed the likelihood of their existence. As to the question of what's at the bottom, the answer- depending on the physicist-may be just about anything, or nothing, or even another universe. 
  
         At the outer edge of a black hole is the  event horizon, the boundary where velocity  required to escape its gravity exceeds the  speed of light. Past this point, all energy and matter that enter the black hole will proceed infinitely toward the singularity, a point of infinite density that, according to Einstein's theory of general relativity, represents a bottomless pit of space-time. Jf the hole is truly infinite and nothing can escape past the event horizon, then the  bottom of a black hole could theoretically  hold an infinite amount of matter and energy.   
     
       However, while that interpretation may square with general relativity, the laws of thermodynamics maintain that a system cannot infinitely increase its mass while maintaining a similar temperature and level of disorder. Other theories that account for black hole thermodynamics suggest that anything falling toward the event horizon never  really  reaches  the  singularity, eventually evaporating back into space. According  to  astrophysicist  Stephen Hawking, this is because black holes aren't truly black: They emit a minute amount of radiation, far less than the background radiation  of  space,  but  enough  to eventually return the mass of the black hole back to the rest of the universe.  

       

    Other more exotic theories posit that at the bottom of a black hole lies an entire universe.  How  can  this  be?  The combination  of the insanely high temperatures,  densities,  and  rotational velocity at the center of a black hole is so powerful that it could produce a massive expansion in space-time that might give rise to a new universe-a process not unlike that of the Big Bang that gave rise to our own universe. The logical extension of this theory implies that even our universe may lie at the bottom of a black hole.   
    
      The mystery has only deepened of late as prominent astrophysicists (including Hawking) change their minds on whether black holes even exist. According to Hawking and others, the laws of quantum mechanics may prevent a neutron star from collapsing beyond a small enough radius to fit within its event horizon. This would mean that no black hole is ever small enough for its escape velocity to exceed the speed of light, and thus there is no black hole.