According to research published in Physical Review D on July 16, 2026, Queen Mary University of London mathematician Professor Ginestra Bianconi has examined the thermodynamics of spacetime using the Gravity from Entropy (GfE) quantum gravity theory, revealing how total cosmic entropy increases while local entropy per unit volume declines as the universe expands.
Reconciling Thermodynamics With Cosmic Complexity
Galaxies, stars, planets, and life emerged as the Universe expanded and became more complex, yet the second law of thermodynamics states that the total entropy of an isolated system should rise over time. According to Albert Einstein, the second law occupies a unique position among the laws of nature as one of physics’ most fundamental and durable principles. Cosmology faces a persistent puzzle because the early Universe is generally thought to have begun in a low-entropy state before moving toward higher entropy, while matter assembled into increasingly elaborate structures during that same history.
Did you know? Albert Einstein famously stated that the second law of thermodynamics is among the most fundamental and durable principles of nature, creating a central paradox for how complex structures like stars and planets manage to form as the universe ages.
Deriving Gravity From Spacetime Information
To address this entropy puzzle, Professor Ginestra Bianconi investigated the Gravity from Entropy (GfE) theory in a paper published in Physical Review D. GfE is a quantum gravity framework that uses statistical mechanics to derive gravity from the microscopic degrees of freedom within spacetime geometry. The idea that gravity and thermodynamics are closely connected traces back to work by Jacob Bekenstein and Stephen Hawking in the 1970s, whose research established that black holes have entropy and release thermal radiation.
Gravity from Entropy describes gravity as emerging from an information-theoretic tension between the physical spacetime metric and another metric produced by matter fields and curvature. This relationship is measured by the Quantum Geometric Relative Entropy (QGRE) within the GfE Lagrangian. At low energies and weak curvature, these gravitational equations reduce to General Relativity, though they begin to differ under stronger conditions by generating a dynamical dark energy term that changes over time.
Expansion Separates Total and Local Entropy
Professor Bianconi explored the thermodynamics of GfE in Friedmann–Robertson–Walker cosmological spacetimes, which are mathematical models used to describe an expanding and broadly uniform Universe. The results indicate that local geometric degrees of freedom follow a first law of thermodynamics, where the dynamical dark-energy term acts as internal energy and the QGRE represents local entropy per unit volume. Effective forms of temperature and pressure also arise naturally within this framework.
As cosmic expansion increases the local volume element defined by the physical metric, the total entropy rises while the amount of QGRE within each unit of volume falls. This separation between total and local entropy provides a mechanism for how organized structures could develop locally even as overall entropy rises. According to Professor Bianconi, this work reveals how the theory tackles the challenge of reconciling cosmological irreversibility with the emergence of complex structures and life.
Frequently Asked Questions
What is the Gravity from Entropy theory?
Gravity from Entropy (GfE) is a quantum gravity framework that uses statistical mechanics to derive gravity from the microscopic degrees of freedom within spacetime geometry, suggesting that gravity and spacetime are fundamentally connected to thermodynamics and information.
How does the universe’s entropy change during expansion?
According to the research published in Physical Review D, the Universe’s total entropy increases with time while its entropy per unit volume declines due to cosmic expansion.
Who authored the recent Physical Review D study on spacetime thermodynamics?
The study was authored by Professor Ginestra Bianconi, a mathematician at the Queen Mary University of London.
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