Gravity From Entropy: Why the Universe Never Rests

Every cup of coffee ever left on a counter has obeyed one rule without fail: it cools down and never heats itself back up. That is the second law of thermodynamics, and it says disorder always grows. So how did orderly things like galaxies, planets, and brains ever form inside a universe that is supposedly falling apart? A new gravity from entropy theory, published in Physical Review D by physicist Ginestra Bianconi at Queen Mary University of London, offers a strange but elegant answer: the universe can build local order and get messier overall at the very same time.

What the Gravity From Entropy Theory Actually Says

Picture two maps of the same city, one drawn from satellite photos and one built from traffic reports. They rarely line up perfectly, and the gap between them is information you can measure. The gravity from entropy theory, often shortened to GfE, treats spacetime the same way. It compares the true shape of spacetime with a second shape implied by everything sitting inside it, matter, radiation, and curvature. The gap between the two, a quantity called quantum relative entropy, becomes the driving force behind gravity itself. When the gap is small, the theory folds neatly back into ordinary Einstein gravity.

This is what makes the gravity from entropy theory so different. It does not add gravity on top of thermodynamics as an afterthought. It builds gravity directly out of the bookkeeping of disorder. That single choice is about to make cosmology a lot stranger.

Why Physicists Have Struggled to Connect Gravity and Heat

For fifty years, the main bridge between gravity and heat has run through black holes. Jacob Bekenstein and later Stephen Hawking showed that a black hole's event horizon carries entropy proportional to its surface area, an idea later stretched to cover the edges of the observable universe itself. That approach works beautifully for black holes and cosmic horizons. It leaves an awkward gap for everyday cosmology, though, because most of space, including the room a reader sits in right now, has no horizon nearby to hang entropy on.

The gravity from entropy theory sidesteps that requirement entirely. Instead of hiding entropy at a distant boundary, it assigns a little bit of temperature and pressure to every single point in spacetime.

That shift sounds technical, but it changes the entire question physicists can ask. Instead of only asking how hot a black hole's edge is, they can now ask how hot ordinary, empty-looking space is. What happens when you actually run those numbers turns out to be the most surprising part of the whole paper.

How Can Local Order Grow While the Universe Gets Messier?

Here is the twist. Bianconi's calculations show that entropy density, the amount of disorder packed into each cubic meter of space, actually falls as the universe ages. For a universe dominated by ordinary matter or radiation, that local density drops roughly in step with the square of cosmic time. On its own, that sounds like it should violate the second law.

It does not, because space itself keeps stretching far faster than the density is shrinking. Multiply a falling density by an exploding volume, and the grand total, the entropy of the entire universe, keeps climbing without pause. Local tidiness and global disorder turn out to be two sides of the same expanding coin.

That single line resolves a puzzle that has quietly bothered cosmologists for decades: how a universe racing toward disorder can still leave room for stars, planets, and life to organize themselves along the way.

What This Means Beyond the Equations

If the gravity from entropy theory holds up, it reframes one of cosmology's biggest mysteries: dark energy, the mysterious push that is speeding up the universe's expansion. Instead of treating that acceleration as a fixed number bolted onto the equations by hand, GfE lets an effective dark energy term emerge naturally from the same entropy bookkeeping that drives gravity itself. That single move could eventually help explain why the observed acceleration is so puzzlingly small, without needing a separate fudge factor.

The theory also hands scientists a new accounting tool for a question that sounds almost philosophical: why complicated things are allowed to exist at all inside a universe built to decay.

The Questions Gravity From Entropy Still Has to Answer

Bianconi is candid about how far this framework still has to go. The thermodynamic results rely on approximating GfE universes with standard Friedmann cosmology, a stand-in solution rather than an exact one, valid only once the universe is old enough for the approximation to hold safely. Whether GfE predicts anything measurably different from ordinary general relativity, and whether it avoids the Big Bang singularity altogether, remains an open question.

The next steps are testing the theory against real astrophysical data and working out how to quantize it, likely using an unconventional mathematical toolkit called contact geometry rather than the textbook methods built for older gravity theories.

• Order and disorder coexist — Local regions can shed entropy even while the universe's grand total keeps climbing without end.
• No horizon required — GfE assigns temperature and entropy to ordinary space, not only to black holes or cosmic horizons.
• Dark energy might not be fixed — The theory lets cosmic acceleration emerge from entropy bookkeeping instead of a hardcoded constant.

It hints that in this universe, tidiness in one corner was never the enemy of the bigger story. It was always part of how the story keeps moving forward.

"Cosmological dynamics can accommodate local ordering while remaining fully consistent with the second law." — G. Bianconi, Physical Review D, 2026.