Gravity may not operate exactly as physicists have long assumed. By rebuilding gravity from the principles of thermodynamics instead of Einstein’s traditional framework, researchers have developed an unconventional theory that naturally produces the universe’s accelerating expansion without requiring dark energy or a cosmological constant. Although still speculative, the work offers a fresh way to tackle one of cosmology’s longest-standing puzzles.
Gravity has long been understood through Albert Einstein’s theory of general relativity, which describes the force not as a traditional pull but as the curvature of spacetime. The theory has transformed modern physics and successfully explains a wide range of cosmic phenomena. Yet it also leaves behind major unanswered questions, including one of the biggest mysteries in cosmology: the cosmological constant problem.
Now, researchers at Imperial College London have proposed a radically different way of thinking about gravity. Rather than treating gravity as a geometric property of spacetime, they explored whether it could instead emerge from the laws of thermodynamics—the branch of physics that describes how heat and energy behave.
Their findings, published in Physical Review Letters, build on an influential idea introduced nearly three decades ago while taking it in an entirely new direction.
Turning an Old Idea Into a New Theory
The research traces its origins to a landmark 1995 paper by theoretical physicist Ted Jacobson. Instead of assuming gravity comes first and then assigning it thermodynamic properties such as temperature and entropy, Jacobson reversed the logic by using thermal physics to derive Einstein’s theory of gravity.
João Magueijo, the study’s senior author, said the concept had fascinated him since shortly after completing his Ph.D.
For years, however, every attempt to extend the idea failed.
That changed during a vacation on a remote Greek island, where limited internet access gave him uninterrupted time to think about the problem from a different perspective. He realized that previous efforts had largely tried to fit existing theories of gravity into Jacobson’s framework rather than allowing a completely new theory to emerge naturally from thermodynamics itself.
Instead of asking what kind of gravity should result, Magueijo decided to begin solely with thermal physics and let the mathematics determine the outcome.
Looking at Gravity Like a Heat Engine
To develop the idea further, Magueijo partnered with his Ph.D. student Ray Isichei at Imperial College London.
Together, they examined gravity using the concept of an Otto cycle, the thermodynamic process commonly used to describe how gasoline engines operate.
The researchers argued that ordinary thermodynamics rarely involves heat alone. Real physical systems often include additional processes such as expansion, work, or chemical reactions. They therefore introduced an extra thermodynamic contribution into the mathematical framework without assuming what consequences it would have for gravity.
That decision produced an unexpected result.
An Unexpected Challenge to Conservation Laws
The new gravitational theory suggested that matter and energy could be continuously created or destroyed under certain conditions.
This directly conflicts with the familiar conservation laws that form one of the foundations of modern physics.
The result was so surprising that the researchers nearly abandoned the project altogether.
However, they soon realized that this apparent flaw became remarkably interesting when applied to the universe as a whole.
Instead of requiring dark energy, a cosmological constant, or other commonly proposed ingredients to explain why the universe’s expansion is accelerating, their model generated that acceleration on its own.
According to Magueijo, ordinary matter is normally expected to slow the expansion of the universe because standard conservation laws remain in effect. In their new framework, however, modifying those conservation laws allows continuously created matter to drive accelerated cosmic expansion instead.
A Different Approach to a Persistent Cosmological Puzzle
One of the biggest motivations behind the study is the cosmological constant problem.
Current physics struggles to explain why the observed energy of empty space differs so dramatically from the much larger values predicted by quantum theories.
The newly proposed framework suggests that a conventional cosmological constant may not be necessary at all. If gravity truly emerges from thermodynamic processes in the way the researchers propose, it could offer a completely different route toward understanding the universe’s accelerating expansion.
The theory also raises the possibility that Einstein’s description of gravity might itself be interpreted as part of a broader thermodynamic process rather than as the final description of gravity.
Much More Testing Still Lies Ahead
Despite its intriguing implications, the researchers emphasize that the work remains highly speculative.
The proposed theory has not yet been established as a replacement for general relativity, and substantial work remains before its predictions can be evaluated against real observations.
The next stage of research will involve comparing the model with available cosmological evidence and experimental data to determine whether it accurately describes the universe.
Magueijo noted that cosmology has changed dramatically since he began his Ph.D. in 1990. At that time, limited observational data allowed many theoretical ideas to remain viable. Today, by contrast, cosmology has become an extremely precise, data-driven science in which every new proposal must withstand careful observational testing.
Why This Matters
Gravity remains one of the most fundamental yet mysterious forces in nature. While general relativity continues to serve as the cornerstone of modern gravitational physics, unresolved questions—including the cosmological constant problem—show that the current picture may still be incomplete.
By deriving gravity from thermodynamics rather than assuming Einstein’s framework from the outset, the new study opens a novel line of theoretical investigation. Although the model is still in its earliest stages and requires extensive observational testing, it offers an unconventional explanation for the universe’s accelerating expansion without relying on dark energy or a traditional cosmological constant. Whether the idea ultimately survives that scrutiny or not, it introduces a fresh perspective on one of physics’ deepest and most enduring mysteries.
