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What’s at the Bottom of a Black Hole ?

   

 Black holes are already among the most mysterious objects in the universe, even before we begin to contemplate what might be at the “bottom” of 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. If 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 latea s 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.

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