The Valley Prize winner making sense of the world’s fastest fluids

At its fastest, the water in the Niagara Falls flows at 30 meters per second. Lorenzo Gavassino, the 2026 recipient of APS’ George E. Valley Jr. Prize, studies fluids that move a million times faster. The prize, awarded annually to an early-career individual for an outstanding scientific contribution to physics, honors Gavassino’s theoretical research insights into these so-called relativistic fluids.

Relativistic fluids are “substances that move very fast, close to the speed of light,” or exist in extreme environments, like under intense gravity, says Gavassino, 30, a postdoctoral researcher at Cambridge University in the UK.

These substances may seem otherworldly, but physicists have had experimental access to relativistic fluids for more than two decades. In 2000, researchers at the Relativistic Heavy Ion Collider in New York and the Large Hadron Collider in Switzerland created the first lab-based quark-gluon plasmas, which are extremely hot states of matter whose constituent quarks and gluons move near the speed of light. Since then, physicists have regularly created quark-gluon plasmas at both colliders.

By studying quark-gluon plasmas, researchers can better understand the early universe, which, according to standard cosmology theory, was filled with the material within a few microseconds after the Big Bang. This quark-gluon plasma then condensed into the matter-filled universe we know today.

More recently, the observation of gravitational waves also sparked momentum in relativistic fluid dynamics research. In 2017, the Laser Interferometer Gravitational-Wave Observatory collaboration detected a gravitational wave from two neutron stars colliding for the first time. The interior of a neutron star, which is under immense gravity, qualifies as a relativistic fluid.

As a theorist, Gavassino builds the mathematical framework to explain experimental results and observations and guide future hypotheses. Unlike conventional fluid dynamics, researchers can’t just study relativistic fluids in a beaker. “All the measurements are very indirect,” says Gavassino. “There are many things to clarify still, due to the fact that we have less experimental control.”

Sometimes, his projects aim to explain a specific experiment or observation. Other times, he studies general scenarios involving relativistic fluids meant to probe their fundamental behavior.

In 2022, while a Ph.D. student at the Nicolaus Copernicus Astronomical Center in Warsaw, Poland, Gavassino caught the attention of other researchers when he solved a long-standing fundamental problem in relativistic fluid dynamics. Because the equations that govern relativistic fluids are so complex, researchers use approximations to solve them. However, many conventionally used approximate equations implied strange results — imagine a glass of water that accelerates close to the speed of light. The equations implied that the water would explode “without any clear reason,” says Gavassino.

In his work, Gavassino showed that these explosions were a consequence of the equations permitting signals in the fluid to travel faster than the speed of light. Previously, researchers had thought this was permissible as long as the signals were weak. “I proved that no matter how small it is, the very fact that [signals travel faster than light] is the cause for the explosions,” says Gavassino. With his paper, he resolved a problem that researchers have puzzled over since the 1980s.

Yet his entry into relativistic fluid dynamics research was “complete randomness,” he says.

As a child growing up in Saronno, Italy, near Milan, Gavassino was drawn to wide-ranging topics, from dinosaurs to Greek mythology. He attended a science-focused high school. Philosophy was an early interest: he studied Kant, Schopenhauer, and Kierkegaard, among others. But the wide-ranging ideas were “confusing,” he says. Different philosophers offered opposing pictures of the world, “sometimes in ways that are almost irreconcilable,” he says. Philosophers are, for example, still debating the basic definition of existence.

Physics felt like steadier ground. “Progress in physics means I create a new understanding that contains all the previous ones,” says Gavassino. “There is not a rejection of the previous idea. The vision of Einstein contains the vision of Newton.”

He sees science as “a branch of philosophy whose way of going about things I find satisfactory and more relaxing, and less confusing,” he says.

Gavassino attended the University of Milan for his undergraduate and master’s degree. He started his master’s studies doing research in biophysics. After the project didn’t pan out, he asked Pierre Pizzochero, a professor in nuclear astrophysics, if they could work together. “He said, ‘Sure, open this book. If you find something in there that interests you, I can find a thesis for you,’” says Gavassino.

The book was on relativistic fluid dynamics. “I liked it,” says Gavassino. “There was not a big plan behind it. I started, and then I continued.”

To Gavassino, science is meaningful regardless of its potential for technology. “I do science because, for me, knowledge is an end,” he says.

In fact, he published a paper on time travel in 2024, while a postdoc at Vanderbilt University. “It was a fun exercise that I did in my spare time,” he says. He investigated a hypothetical space-time that curves on itself to form a closed loop, enabling a traveler on this loop to time travel.

But time travel should be impossible, as illustrated by the well-known grandfather paradox: If you went back in time and killed your grandfather before your parents were born, you would prevent your own birth. But if you were never born, you could never travel back in time in the first place.

Gavassino resolved the paradox for this loop. Using arguments involving entropy and quantum mechanics, he showed that in such a warped spacetime, seemingly irreversible events like a grandfather’s death could be temporary. Discover and Popular Mechanics featured the work, while physicists largely ignored it. “All these journalists contacted me about this, whereas I never had a single discussion about it with a colleague,” he says. “For me, it was just a game. It’s not particularly useful for anything.”

Still, Gavassino takes the game seriously. The time travel paper includes rigorous proofs and formal equations, just as he does in his more mainstream relativistic fluids research. “I think that the creation of knowledge, the understanding of the universe, is something of intrinsic value,” he says. “It's something to pursue for the thing itself.”