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A Larger Estimate of the Entropy of the Universe

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arxiv 0909.3983 v3 pith:CWRBM2GN submitted 2009-09-22 astro-ph.CO

Chas A. Egan , Charles H. Lineweaver This is my paper · ORCID
classification astro-ph.CO
keywords entropyuniverseobservableestimatemakeblackcalculatecaveats
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Using recent measurements of the supermassive black hole (SMBH) mass function, we find that SMBHs 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+3.0-1.7x10^104 k. We calculate the entropy of the current cosmic event horizon to be S_CEH = 2.6+-0.3x10^122 k, dwarfing the entropy of its interior, S_CEHint = 1.2+1.1-0.7x10^103 k. We make the first tentative estimate of the entropy of weakly interacting massive particle dark matter within the observable universe, S_dm = 10^87-10^89 k. We highlight several caveats pertaining to these estimates and make recommendations for future work.

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Cited by 4 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. How greedy is the Universe? An entropy ledger and a causal envelope for early black hole growth

    gr-qc 2026-07 conditional novelty 6.0 of 10

    Horizon entropy dominates the cosmic ledger by ~16 orders of magnitude, but the realized entropy production rate is only 10^-5±1.5 of the causal-hydrodynamic envelope at z=4–12.

  2. Gibbons-Hawking Entropy and BMN Strings

    hep-th 2025-11 conditional novelty 6.0 of 10

    A proposed universal finite entropy bound for quantum gravity is introduced and linked to the Gibbons-Hawking entropy of our universe, with BMN strings suggested as an unresolved test.

  3. Phantom-Divide Crossing in Barrow-Tsallis Holographic Dark Energy with a Scale-Dependent Barrow Exponent

    gr-qc 2026-07 conditional novelty 5.0 of 10

    For generalized-entropy holographic dark energy with a future-event-horizon cutoff, the phantom-divide crossing on the kinematic branch is unique, quintessence-to-phantom, and fixes the local entropy-scaling dimension...

  4. Elementary considerations on possible entropy-driven cosmological evolutions

    gr-qc 2025-01 conditional novelty 5.0 of 10

    In the entropy-modified Friedmann framework, sustained growth of the entropy source (ḟ/f > 0) makes the universe converge to an effective de Sitter state with density (ḟ/f)²/K², and current data bound the required sou...

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