SPACE/COSMOS
The Gravity from Entropy theory offers new clues for reconciling gravity with the second law of thermodynamics
Queen Mary University mathematician Professor Ginestra Bianconi explores how gravity can be reconciled with thermodynamics within the Gravity from Entropy theory
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Professor Ginestra Bianconi from Queen Mary University of London
view moreCredit: Queen Mary University of London
A new study by Queen Mary University of London mathematician Professor Ginestra Bianconi proposes a new perspective on one of the deepest questions in modern physics: how can the Universe become increasingly structured and complex while still obeying the second law of thermodynamics?
Einstein famously stated that “The second law of thermodynamics occupies a unique position among the laws of Nature,” reflecting his conviction that it is among the most fundamental principles of physics and unlikely to be overthrown. The second law states that the total entropy of an isolated system tends to increase over time, a principle often associated with the growth of disorder.
This presents a long-standing puzzle in cosmology. The early Universe is generally believed to have existed in a low-entropy state and to evolve toward states of higher entropy. Yet over cosmic history, the Universe has also given rise to increasingly complex structures, including galaxies, stars, planets, and ultimately life itself. Reconciling the emergence of such ordered structures with the relentless increase of entropy remains an open challenge.
In a recent paper published in Physical Review D, Professor Bianconi investigates this question within the framework of the Gravity from Entropy (GfE) theory, a quantum gravity approach that derives gravity from the microscopic degrees of freedom of spacetime geometry using principles of statistical mechanics.
In this study, by exploring the thermodynamic properties of the Gravity from Entropy theory, she shows that while the total entropy of the Universe increases in time, the entropy per unit volume decreases in time, leaving open new interpretations for the emergence of local structures.
The connection between gravity and thermodynamics has been known since the pioneering work of Jacob Bekenstein and Stephen Hawking in the 1970s, which established that black holes possess entropy and emit thermal radiation. These discoveries suggested a deep relationship between spacetime, information, and thermodynamics.
Gravity from Entropy (GfE) proposes that gravity emerges from the information-theoretic tension between the true spacetime metric and the metric induced by matter fields and curvature. This new physical interpretation of gravity is reflected in the GfE Lagrangian, which is given by the Quantum Geometric Relative Entropy (QGRE) between these two metrics. The GfE gravity equations reduce to General Relativity for low energies and small curvature, but beyond the weak limit, they deviate from it. Interestingly, beyond the weak limit, the GfE equations include the emergence of a dynamical dark energy term that could lead to testable predictions of the theory.
This study explores the thermodynamic properties of the GfE theory in Friedmann–Robertson–Walker cosmological spacetimes. The results show that the local geometric degrees of freedom satisfy a first law of thermodynamics, in which the emergent dynamical dark-energy contribution can be interpreted as an internal energy, while the Quantum Geometric Relative Entropy (QGRE) can be identified as the local entropy per unit volume. Within this framework, effective temperature and pressure quantities also emerge naturally. Together, these findings suggest that the quantum state underlying the GfE theory may possess an intrinsic thermal nature.
The study also highlights the fundamental role of the local volume element defined by the measure induced by the physical metric. As the Universe expands, this volume grows over time. Within the framework of the GfE theory, this expansion leads to an increase in the total entropy, while the local QGRE per unit volume decreases with time. This result reveals a distinctive thermodynamic behaviour of the GfE theory.
Overall, this work proposes that gravity and spacetime may have an intrinsic thermodynamic and informational nature. This opens new possibilities for understanding the deep connections between gravity, quantum theory, and the emergence of complexity in the Universe.
While still at an early theoretical stage, the authors say the work could help bridge long-standing gaps between general relativity, thermodynamics, quantum mechanics, and cosmology. Hence, “This work reveals how the Gravity from Entropy theory can tackle the challenging question to reconcile the second principle of thermodynamics with the emergence of complexity in our Universe. These results may open new avenues for investigating the long-standing problem of reconciling the foundations of cosmological irreversibility, the emergence of complex structures, and ultimately life, with fundamental gravitational dynamics” says Professor Bianconi.
Journal
Physical Review
Article Title
Thermodynamics of the gravity from entropy theory
Lehigh University joins international consortium to advance commercial space research and innovation
Partnership with Ohio State University, Starlab, and global universities will develop future low-Earth orbit aerospace technology and microgravity science applications
Check out the Fall 2026 issue of Resolve magazine for more on Lehigh's heritage of innovation in aerospace and space systems.
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Lehigh's new Master's program in Aerospace and Space Systems Engineering is led by Lehigh alumnus Dr. Terry Hart, former fighter pilot, NASA astronaut, and satellite industry executive.
view moreCredit: Lehigh University
Seeking to expand the boundaries of microgravity science and accelerate the global space economy, Lehigh University has joined a newly formed international research consortium spearheaded by The Ohio State University.
The consortium, which recently hosted its inaugural meeting in Columbus, Ohio, unites an elite network of global academic and research institutions. The coalition is designed to spark collaborative research, facilitate faculty and student exchanges, and develop foundational technologies for future commercial low-Earth orbit (LEO) platforms, including the planned Starlab space station and its terrestrial counterpart, the VISTA science park.
Driving an institutional vision for space systems and science
Lehigh's entry into the consortium follows a formal framework agreement signed by Anand Jagota, Lehigh's vice provost for research, aligning the university with other premier research institutions across the globe. For Lehigh, the partnership serves as an accelerator for a broader, long-term commitment to space exploration and engineering innovation.
Central to this effort is a vision to position Lehigh students and researchers at the forefront of the aerospace sector, a priority highlighted by Nathan Urban, provost and senior vice president for academic affairs.
"This consortium reflects Lehigh's commitment to preparing students for careers at the leading edge of science and engineering," Urban says. "Space is no longer the domain of a handful of national agencies. It is quickly becoming a commercial sector with its own supply chains, infrastructure needs, and workforce demands. By joining this network, we're positioning Lehigh faculty and students to help define that future rather than simply react to it."
"Our engagement in this consortium is a direct extension of the strategic investments we've been making in aerospace and space systems engineering across the Rossin College," says Stephen DeWeerth, the Lew and Sherry Hay Dean of the P.C. Rossin College of Engineering and Applied Science. "From new faculty, to thriving student clubs, to our recently-launched interdisciplinary Master's in aerospace and space systems engineering, we've built the foundation. A partnership like this helps to turn that foundation into real opportunity for our students and researchers."
A growing space research ecosystem
Lehigh's role in the consortium anchors a rapidly growing aerospace and space-research footprint across campus, particularly within the Rossin College. Key initiatives driving this expansion include:
- New faculty expertise: The Department of Mechanical Engineering and Mechanics (MEM) recently expanded its core research capabilities with the addition of new faculty member Yao Yao, whose work focuses on multifunctional deployable structures and the on-orbit assembly of large-scale space structures.
- Specialized academic pathways: The university continues to develop advanced educational initiatives, including the Master of Science in Aerospace and Space Systems Engineering program, tailored to equip the next generation of engineers with the skills required by a rapidly evolving aerospace industry.
- A legacy of industry connection: Lehigh's expanding space initiatives build upon a strong foundation of alumni and faculty leadership. This includes long-standing expertise on campus, such as former NASA astronaut and current mechanical engineering professor Terry Hart, as well as ties to industry leadership through distinguished alumni like Scott Willoughby '89, vice president of performance excellence for Northrop Grumman's Space Systems sector.
Supporting the transition to commercial LEO platforms
The launch of the consortium arrives during a broader transition in global space exploration. As public and private entities plan the transition from the International Space Station to commercial platforms, sustained progress depends heavily on structured university research and technical pipelines.
The consortium will focus directly on generating the scientific research and talent pipeline necessary to support platforms like Starlab, a continuously crewed, free-flying commercial space station, and VISTA (the George Washington Carver Science Park) based at Ohio State, a U.S. science park dedicated to in-space research, manufacturing, and services.
By contributing to a highly unified network across global academia and industry, Lehigh is helping build the collaborative research foundation and talent pipeline necessary to sustain long-term operations and scientific discovery in low-Earth orbit.
Chang’e-6 samples reveal how Earth slows solar wind striking Moon’s near side
Chinese Academy of Sciences Headquarters
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Schematic illustration of the contrasting solar wind environments experienced by the lunar nearside and farside under the influence of Earth's magnetosphere.
view moreCredit: Image by ZHANG Xuhang
The Moon has been bathed in solar wind for billions of years, but the two hemispheres are struck by solar wind of different speeds and energies.
Now, research based on China’s Chang’e-6 samples reveals that Earth’s magnetosphere has shaped this difference. The study was published in Nature Geoscience.
The solar wind, a continuous stream of high-speed charged particles from the Sun, bombards the Moon’s surface directly. The lunar regolith has preserved a record of this bombardment, serving as a natural archive of solar-wind-derived volatiles, including the noble gases (He, Ne, Ar, Kr, Xe). These chemically inert elements are highly reliable tracers of solar-wind implantation and provide valuable clues to this process.
Before this study, the lack of far-side samples prevented direct experiments on systematic differences in solar-wind implantation between the two hemispheres.
However, China’s Chang’e-6 mission returned 1.935 grams of regolith from the South Pole-Aitken basin on the lunar far side, offering the first opportunity to directly compare solar-wind implantation processes on the near side and far side.
Based on the lunar samples, a research team led by the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences (CAS) conducted a noble-gas isotopic investigation on the Chang’e-6 regolith and determined the concentrations and isotopic compositions of He, Ne, Ar, Kr, and Xe.
The work was carried out by ZHANG Xuhang, a postdoctoral researcher at IGG under the supervision of Professor HE Huaiyu, together with collaborators from the University of Science and Technology of China and the Chang’e-7 volatile payload team.
In the analysis, the researchers first noticed that the Ne isotopic composition of the Chang’e-6 regolith is highly distinctive. The average 20Ne/22Ne ratio is 11.34 ± 0.22, substantially lower than what is reported for all previously analyzed nearside lunar samples yet close to the theoretical isotope composition expected after strong solar-wind fractionation. This implies that the lunar far side underwent stronger isotopic fractionation, resulting in preferential enrichment of the heavier isotope.
As for Kr and Xe, their release behavior also differs from that of near-side samples. In the stepwise-heating experiments, solar-wind-derived Xe in the Chang’e-6 regolith was released predominantly at high temperatures, producing a single high-temperature release peak. In contrast, Chang’e-5 samples exhibited a distinct double-peaked release pattern, with significant Xe release at both low and high temperatures. This indicates that solar-wind ions penetrated significantly deeper into the far-side regolith than into the near side—meaning the far side was exposed to higher-energy particles.
But why do the Moon’s two hemispheres receive solar wind of different energies?
The research team attributes this difference to the “speed-governing” effect of Earth’s magnetosphere. As the Moon orbits Earth, it periodically passes through the magnetosheath—a buffer zone around the magnetosphere—where the ambient solar wind is slowed from its typical velocity of 400 km/s to about 200 km/s.
This slower solar wind primarily reaches the lunar near side, resulting in shallower implantation depths within the near-side regolith. In contrast, the far side, which permanently faces away from Earth, remains directly exposed to undisturbed solar wind, allowing ions to penetrate deeper into the regolith.
The researchers suggest that approximately 25% of the total solar-wind exposure at the Chang’e-5 landing site was influenced by this decelerated solar wind, whereas the Chang’e-6 landing site experienced no such shielding effect.
By providing the first direct empirical evidence from lunar far-side samples, this study confirms the speed-governing effect of Earth’s magnetosphere on solar-wind implantation into the lunar surface, an effect permanently preserved in both the implantation-depth distributions and isotopic signatures of noble gases within the regolith.
Furthermore, the researchers noted that heavy noble gases in lunar soils may serve as “fossil records” of past interactions between Earth’s magnetosphere and the solar wind, offering a novel approach for reconstructing the long-term evolution of Earth’s magnetosphere when combined with paleomagnetic records.
The findings also show that interactions within the Sun–Earth–Moon system are more complex than previously recognized. According to the researchers, these results open a new window into these ancient dynamics, revealing that Earth’s nearest celestial neighbor preserves previously unknown records of these interactions.
Journal
Nature Geoscience
Article Title
Deeper solar wind penetration on the Moon’s farside from noble gas records
Article Publication Date
15-Jul-2026
A source of extremely high-energy particles in the Milky Way identified
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Observation by NASA’s Fermi Gamma-ray Space Telescope identified GeV gamma-ray excess toward LHAASO J1912+1014u and confirmed it to be a proton PeVatron through multiwavelength observations and modeling. The source is marked by a solid circle and is largely extended, with a diameter of more than 1 degree. For comparison, the size of the Moon is indicated by a dashed circle. (Adapted from Tsunefumi Mizuno, et al. The Astrophysical Journal. July 16, 2026)
view moreCredit: Adapted from Tsunefumi Mizuno, et al. The Astrophysical Journal. July 16, 2026
An accelerator of the highest-energy protons in our galaxy has been identified; it could help scientists better understand the nature of these fast-moving particles that fill the space between stars.
Cosmic rays are made primarily of protons with a few electrons sprinkled in, and they can reach energies even higher than what human-made accelerators can produce. Considering human-made accelerators, such as the Large Hadron Collider on the border of Switzerland and France, can move protons to near the speed of light, it’s no wonder that these super-energetic particles can influence cosmic events across the galaxy.
An accelerator of the highest-energy cosmic-ray protons in our galaxy has been identified conclusively, thanks to a Hiroshima University-led international team of researchers assessing data from three major observatories on Earth and in space. This could help scientists better understand the nature of these fast-moving particles that fill the space between stars and influence cosmic events across the Milky Way galaxy.
The findings were published in The Astrophysical Journal on July 16, 2026.
“This immense energy makes cosmic rays important in astronomy and astrophysics,” said first and corresponding author of the study Tsunefumi Mizuno, associate professor at Hiroshima University’s Hiroshima Astrophysical Science Center. He explained that these energies are measured in electron volts — the energy an electron gains when it moves from a resting state and increases its electrical potential by one volt. “The highest energy of galactic cosmic rays can reach and exceed one quadrillion (1015) electron volts, or a peta electron volt (PeV). Finding a cosmic-ray proton accelerator above that PeV level, called a proton PeVatron, is one of the most exciting topics in modern astrophysics, and we identified one such object previously known as LHAASO J1912+1014u.”
The Tibet AS gamma experiment, a project led by Japan and China since 1990, and later China’s Large High Altitude Air Shower Observatory (LHAASO) found dozens of gamma-ray sources above 0.1 PeV, including one named LHAASO J1912+1014u. These gamma-rays, which are the most energetic electromagnetic radiation and can originate from cosmic-ray sources, have energies about one-tenth of their parent cosmic-ray particles. Accordingly, these sub-PeV gamma-ray sources, including the one named LHAASO J1912+1014u, are potential cosmic ray PeVatron candidates. Previous studies in the field propose that the source might be a pulsar wind nebula or other debris from a massive star explosion.
“However, data from Tibet AS gamma and LHAASO experiments alone cannot clearly identify proton PeVatrons because PeV cosmic ray electrons can also produce the lower energy gamma-rays,” Mizuno said, explaining that the experiments’ image resolution is limited, so researchers cannot delve deeply enough to confirm a proton PeVatron.
But data had been collected by other experiments: Fermi Large Area Telescope (Fermi-LAT), led by NASA and to which Hiroshima University contributed to the instrumentation development and operation; the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN), led by Japan; and the Chandra X-ray Observatory, led by NASA.
LHAASO J1912+1014u was discovered in 2024, and is located within the constellation Aquila, and close to Altair, a famous star constituting the Summer Triangle. It was originally considered a supernova remnant, until emissions above 100 TeV were detected.
“With data from multiple experiments, we have studied LHAASO J1912+1014u in detail,” Mizuno said. He noted that the experiments provide data across a wide wavelength range from radio to gamma-rays, enabling this broad investigation with comprehensive multiwavelength modeling.
The gamma-ray data from Fermi-LAT clocked in with energies around a giga electron volt (GeV), or one billion electron volts; while Chandra provided data on lower energies and FUGIN with still lower energies. By combining this data with information in a tera electron volt (TeV) from instruments including LHAASO, the researchers could paint a detailed picture of LHAASO J1912+1014u as a proton PeVatron and rule out other possible scenarios.
First, the gamma-ray emission smoothly extends from over 100 trillion electron volts down to 400 million electron volts, making the possible explanation that LHAASO J1912+1014u is an electron accelerator unlikely based on energy arguments, according to Mizuno. Second, the GeV gamma-ray map matches well with the distribution of interstellar gas traced by FUGIN radio data, which strongly supports the proton PeVatron scenario. Third, Chandra X-ray data revealed that diffuse X-ray emission is very weak, further reinforcing the scenario.
“This research is achieved by team effort. There is an old Japanese saying: ‘One arrow is easy to break, but three arrows bundled together are not,’” Mizuno said. “In this study, three arrows — Fermi-LAT GeV gamma-ray data, FUGIN radio data and Chandra X-ray data — are bundled together through a detailed multiwavelength modeling, revealing that our target, LHAASO J1912+1014u, is a cosmic-ray proton PeVatron.”
Mizuno also emphasized that their study not only identified a proton PeVatron, but characterized properties of the accelerated particles. This is crucial to understand the nature of the source. According to him, there are dozens of cosmic-ray proton PeVatron candidates in the Milky Way. The researchers plan to comprehensively examine other potential PeVatron sources next.
Naoto Nakahara at Hiroshima University; Hidetoshi Sano & Takeru Murase at Gifu University; Tomohiko Oka at Julius-Maximilians-Universität Würzburg; and Hiromasa Suzuki at Miyazaki University co-authored the study.
The Fermi LAT Collaboration acknowledges generous ongoing support from the National Aeronautics and Space Administration (NASA) and the Department of Energy (DOE) in the United States; the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules in France; the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy; the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan; and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis from the Istituto Nazionale di Astrofisica in Italy; and the Centre National d’Études Spatiales in France is gratefully acknowledged.
This work was performed in part under US Department of Energy (DOE) Contract DE-AC02-76SF00515. This work was also supported in part by a University Research Support Grant from the National Astronomical Observatory of Japan (NAOJ); the Japan Society for the Promotion of Science (JSPS) KAKENHI (23K25882, 23H04895, 22H00152, 24H00246, 24K17093).
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About Hiroshima University
Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 5 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en
Journal
The Astrophysical Journal
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT γ-ray Data and FUGIN CO Data
Article Publication Date
16-Jul-2026
