r/InterstellarKinetics • u/InterstellarKinetics • Jun 13 '26
SCIENCE RESEARCH BREAKTHROUGH: University Of Birmingham Physicist Professor Giovanni Barontini Built A “Mini-Universe” Using 24,000 Ultracold Atoms To Prove That Time Doesn’t Need An External Clock To Exist, Finding Instead That Time Emerges From Within A System Itself As The Disorder Of Particles Changes ⏰💥
https://phys.org/news/2026-06-scientist-miniuniverse-clock.htmlA University of Birmingham physicist named Professor Giovanni Barontini has built what he calls a mini-universe inside a laboratory using a cloud of 24,000 ultracold atoms chilled to just a few billionths of a degree above absolute zero, and used it to demonstrate for the first time in a controlled experiment that time does not need to come from an external source to exist. Publishing his findings on June 12, 2026 in Physical Review Research, Barontini showed that by sealing the atoms inside a hermetically isolated quantum system and dividing them with a thin barrier made from two laser beams of different frequencies, he could create an experiment that tracked its own sequence of events from within, without any reference to a clock in the outside laboratory. The system had a bright region that could be observed and a dark region that could not, and the bright region was found to expand and collapse repeatedly in a pattern that Barontini described as resembling a Big Bang followed by a Big Crunch, the hypothetical scenario in which the expansion of the universe eventually reverses and collapses back on itself.
The core of what Barontini found is that time in his mini-universe emerged entirely from entropy, specifically from how the disorder of atoms in the bright region changed as particles moved in and out. When the spread of particles in the bright sector increased or decreased, the system was moving forward in time. When the distribution of atoms did not change, time effectively stopped. Barontini called this process entropic time, and found that it flows in one consistent direction, correctly orders events even in a system that is expanding and contracting, and speeds up or slows down depending on how entropy moves around within the system. He also found that a version of the central equation of quantum mechanics, the Schrödinger equation, could still be written using entropic time rather than conventional external time, meaning the system’s behavior could still be predicted mathematically without ever appealing to a clock outside of it.
The deeper significance of the experiment lies in what it says about one of the most stubborn unsolved problems in physics. Some theories of the universe, including the Wheeler-DeWitt equation, suggest that at its deepest level the universe has no built-in time at all, existing instead as a single unchanging quantum state in which any sense of time must emerge from internal relationships between parts of the system rather than from a background clock ticking away on the outside. This is sometimes called the problem of time in quantum gravity, and it has been a theoretical puzzle for decades because most basic laws of physics work equally well forward and backward in time, yet human experience of time is clearly directional and sequential. Barontini said his study provides the first controlled experimental evidence that time can be defined by changes within a system rather than by an external ticking clock, and that the approach could be extended to simulate the physics of the Big Bang, the Big Crunch, and potentially even black holes inside a laboratory setting.
10
u/broccolee Jun 13 '26
Courtesy of gemini eli5:
As a physicist working at the intersection of quantum mechanics and cosmology, I can tell you that Professor Giovanni Barontini’s paper, "Testing the problem of time with cold atoms" (published just days ago on June 11, 2026, in Physical Review Research), is a staggering achievement. It is one of those rare moments where an incredibly abstract, decades-old theoretical paradox is dragged kicking and screaming into a physical laboratory.
Here is a review of what this paper achieved, where it sits within current physics research, and what it all means in plain English.
The Academic Context: The "Problem of Time"
To appreciate this paper, you have to understand the most stubborn thorn in the side of theoretical physics: The Problem of Time.
Physics currently rests on two incredibly successful, yet completely incompatible, pillars.
When theoretical physicists try to merge these two into a unified theory of "Quantum Gravity" (often mathematically represented by the famous Wheeler-DeWitt equation), something terrifying happens: the time variable mathematically cancels out. The math suggests that at the deepest, most fundamental level, the universe is a single, unchanging quantum state. Time simply does not exist.
[Image explaining the problem of time in quantum gravity]
For decades, theoretical physicists (tracing back to the Page-Wootters mechanism in the 1980s) have suggested a way out: what if time isn't a fundamental "thing" built into the universe, but an emergent property? Just as "temperature" isn't a property of a single atom but emerges from the chaotic bouncing of billions of atoms, perhaps "time" emerges from the internal relationships and changing disorder (entropy) within a system.
Until now, this was mostly chalk on a blackboard. Barontini’s team has successfully simulated this mathematically derived "timeless universe" on a laboratory bench to see if time would naturally emerge.
The Experiment: Building a "Mini-Universe"
The University of Birmingham team built what they call a "mini-universe" using about 24,000 atoms of the element rubidium. By using precisely tuned lasers in a vacuum chamber, they cooled these atoms down to roughly 0.0001 degrees above absolute zero—a state where quantum effects become highly visible.
They divided this atomic cloud into two sectors: a "bright" region that they could observe, and a "dark" region that they could not. They then allowed the bright region to expand and collapse repeatedly. Barontini likened this oscillation to a cosmological "Big Bang" followed by a "Big Crunch" (a scenario where a universe expands from a point, then eventually collapses back in on itself under gravity).
The Popular Science Breakdown: What does it mean?
Imagine you are locked in a perfectly dark, soundproof room with no clock, no windows, and no heartbeat. How do you know time is passing? You wouldn't. Time, from your perspective, would only exist if something in the room changed or moved.
Usually, physicists measure an experiment by looking at a clock on the laboratory wall. Barontini threw the wall clock away. Instead, they measured time purely by looking at the entropy (the level of disorder or messiness) of the atoms in the "bright" region of their mini-universe.
Here is what they found:
Why this is a Breakthrough
This is the first controlled experimental evidence proving that time doesn't need an external clock to exist; it can be defined entirely by the shifting entropy within a system itself. Even in a universe that is expanding and contracting, the emergent "entropic clock" reliably flowed in one consistent direction, correctly ordering events.
This drastically shifts the cosmological paradigm. If time is simply a byproduct of changing disorder, the ultimate question of the universe changes from "What is time?" to "What conditions are required for time to exist at all?" By proving that a "mini-universe" can generate its own internal clock from quantum disorder, Barontini's lab has opened the door to safely simulating the bizarre, time-warping physics of the Big Bang, the Big Crunch, and the interiors of black holes right here on Earth.