* Astronomy

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RE: Entropy

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Maximum Causal Entropy

Blobrana · L

RE: Entropy

Blobrana · L

Australian researchers have measured the amount of entropy that exists now in the Universe. They found that the Universe has much less energy available that had been previously measured. Are they right? Is the Universe aging faster?
The authors of the research are Charles "Charley" H. Lineweaver, a professor from the Research School of Astronomy and Astrophysics at Australian National University (ANU), and Chas A. Egan, Ph.D. student at ANU.
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A Larger Estimate of the Entropy of the Universe

The end of the universe is not nigh, but it could be closer than originally thought.
Australian scientists have measured the amount of the universe's stored energy that has been lost - in a process known as entropy - since the Big Bang.
The result, as calculated by Dr Charley Lineweaver and PhD student Chas Egan, was about thirty times higher than other projections indicating there was less left in the universe's "gas tank".
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Mammoth black holes push universe to its doom

Egan and Lineweaver found that everything within the observable universe contains about 10^104 units of entropy (joules per Kelvin), a factor of 10 to 1000 times higher than previous estimates that did not include some of the biggest known black holes
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Title: A Larger Estimate of the Entropy of the Universe
Authors: Chas A. Egan, Charles H. Lineweaver

Using recent measurements of the supermassive black hole mass function we find that supermassive black holes are the largest contributor to the entropy of the observable Universe, contributing at least an order of magnitude more entropy than previously estimated. The total entropy of the observable Universe is correspondingly higher, and is S_{obs} = 3.1^{+3.0}_{-1.7}\xt{104} k. We calculate the entropy of the current cosmic event horizon to be S_{CEH} = 2.6 ±0.3 \xt{122} k, dwarfing the entropy of its interior, S_{CEH int} = 1.2^{+1.1}_{-0.7}\xt{103} k. We make the first tentative estimate of the entropy of dark matter within the observable Universe, S_{dm} = 10^{88 ±1} k. We highlight several caveats pertaining to these estimates and make recommendations for future work.

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Title: What is the entropy of the universe?
Authors: Paul Frampton, Stephen D.H. Hsu, Thomas W. Kephart, David Reeb

Standard calculations suggest that the entropy of the universe is dominated by black holes, although they comprise only a tiny fraction of its total energy. We give a physical interpretation of this result. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. The largest uncertainty in the present and future state of the universe is due to the (unknown) internal microstates of its black holes. We also discuss the qualitative gap between the entropies of black holes and ordinary matter.

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