are monster black holes on an entropy frenzy?

At the end of the universe, black holes will be the only things left and they will define what happens in the cosmos for countless eons.

pondering the universe

Over the last few decades, cosmologists discovered what the future of the universe holds. That concludes the part of the post where we entertain a single shred of optimism since it seems our future is bleak. On the grandest time scales, stars burn down to dark embers, life in all corners of space is extinct, galaxies fly apart, and black holes will inherit a dark, cold universe until they too evaporate into nothing. In short, and without mincing words, we’re all screwed to the fullest possible extent of, well, everything. Nothing personal, it’s just a function of entropy that an open universe is going to expand in all directions until the energy it contains spreads so thinly across such a vast distance, that everything chills to the same temperature and the processes we are used to today become impossible in this icy, static realm many trillions of years from now.

It seems that studying areas of cosmology which focus on exactly how everything we know will ultimately end is a bit like being the undertaker in a old Western movie, sizing up the hero of a story for a casket as soon as he strolls into town. And this role was embraced by astrophysicists Chas Egan and Charles Lineweaver, who wanted to find out whether supermassive black holes in the center of every galaxy were actually adding to the entropy of the universe, and if they will have a final role to play as the cosmos slowly cools into nothingness. By trying to measure the total amount of energy the cosmos can use, or the entropy budget of the universe, they found that monstrous black holes actually increase entropy since they effectively lock up both matter and energy in their mysterious innards.

Even if black holes evaporate due to Hawking radiation, it would still take 10102 years for all that energy to be hurled back into the cosmos, and at that point, it would only serve to increase the overall entropy even more. Considering how they form and how bizarrely they behave, it’s not a big surprise that black holes are often thought to be cosmic entropy machines by physicists. As the trapped matter and energy inside them are configured in weird and unexpected ways, that constant churning in their interiors creates utter chaos, especially in the singularity, an infinitely small entity theoretically deduced to be ruled by utter quantum anarchy. Since the energy is not usable and does no meaningful work, other than being savagely tossed around, it merely adds to the overall entropy of the system, and even after being freed by an evaporated black hole, it would simply cool and dissipate into the inert darkness.

See: C. Egan, & C. Lineweaver (2009). A Larger Estimate of the Entropy of the Universe, arXiv: 0909.3983v1

# space // astrophysics / black holes / cosmology / entropy

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