- Frontier ran the first cosmological simulation combining gas, stars, and black holes with dark matter.
- The HACC code ran nearly 300 times faster on Frontier than on its predecessor Titan.
- These simulations can test whether dark energy's strength has changed over cosmic time.
Salman Habib has probably spent more hours than most trying to fit the universe into a computer. The problem isn't just scale. It's everything that happens between the galaxies.
Previous simulations could track dark matter's gravitational pull across cosmic distances. They showed how galaxies cluster and voids form.
But they left out the messy physics of ordinary matter.
Now Habib's team at Argonne National Laboratory has run the most complete simulation of cosmic evolution ever attempted. Their code captures not just gravity, but gas dynamics, star formation, and black hole growth.
Key figure
300×
How much faster ExaSky ran on Frontier than on its predecessor Titan
The Limits of Gravity-Only Models
Dark matter dominates the universe's mass budget. It shapes the cosmic web. Simulating its gravitational effects alone gets you reasonably accurate large-scale structure.
But galaxies aren't just dark matter halos.
Hot gas flows between them. Stars explode and seed the intergalactic medium with heavy elements. Supermassive black holes launch jets that heat surrounding gas for millions of light-years.
These baryonic processes - everything made of ordinary atoms - are computationally expensive to model. Most cosmological simulations simply ignored them.
Exascale Computing Changes the Equation
The Frontier supercomputer at Oak Ridge National Laboratory performs 1.1 quintillion calculations per second. That's exascale computing, a thousand petaflops.
What is exascale computing?
Exascale means a billion billion calculations per second - or one quintillion operations. It's roughly the processing power of a million laptops working together. Until 2022, no computer had crossed this threshold.
Habib's team used it to run their Hardware/Hybrid Accelerated Cosmology Code, known as HACC. The code has been refined over fifteen years specifically to exploit massively parallel architectures.
On Frontier, the ExaSky simulation ran nearly 300 times faster than on its predecessor, Titan.
That speed made full cosmological hydrodynamics practical for the first time.
Testing Dark Energy and Alternative Gravity
"If we want to know what the universe is up to, we need to simulate both," Habib explained. Dark matter and dark energy interact with ordinary matter in ways that gravity-only models miss entirely.
The new simulations will let researchers test whether dark energy's strength has changed over cosmic time. They can compare alternative gravity theories against the same initial conditions. Each model makes different predictions about how structure forms.
The team plans to make their simulation data available to astronomers worldwide. Researchers can compare the synthetic universe against real observations from surveys like the Dark Energy Spectroscopic Instrument.
Related reading
Can Math Finally Prove We Live in a Simulation? It's Complicated
A physicist proves that self-simulation is possible. Another team proves it is impossible. Both may be right.
→Pushing Into Earlier Epochs
The ExaSky project continues to push resolution higher. Future runs will track smaller structures and earlier cosmic epochs.
Each improvement narrows the gap between simulation and observation. When the synthetic and real universes match, the underlying physics is probably right.
When they don't, something fundamental is missing from our models.
Sources
- Primary Source: World's 2nd fastest supercomputer runs largest-ever simulation of the universe (Space.com)
- Additional Context:
- Argonne National Laboratory - HACC cosmology code developmentOak Ridge Leadership Computing Facility - Frontier supercomputer
Fact Check: Claim-by-Claim Verification Verified
The recap closely follows the source article and institutional descriptions of the project, with only mild rhetorical embellishment and no substantive scientific distortions.
Commentary
- The phrase “most complete simulation of cosmic evolution ever attempted” and “first time” for “full cosmological hydrodynamics” are consistent with how DOE and Space.com describe this specific Frontier/ExaSky run (largest and most complex cosmological hydrodynamics simulation at this scale), but they should be understood as referring to scale and detail rather than to the first inclusion of gas, stars, and black holes in any cosmological simulation, since earlier large hydrodynamical simulations (e.g., Illustris, EAGLE) have also modeled such physics on smaller volumes.
Sources used for verification
Academic/Peer-reviewed:
- Cosmological Hydrodynamics at Exascale: A Trillion-Particle Leap with HACC on Frontier - arxiv.org
- At the Frontier: DOE Supercomputing Launches the Exascale Era - energy.gov
- Record-Breaking Run on Frontier Sets New Bar for Simulating the Universe in the Exascale Era - olcf.ornl.gov
Other reliable sources:
- World's 2nd fastest supercomputer runs largest-ever simulation of the universe - space.com
- Frontier supercomputer hits new highs in third year of exascale - eurekalert.org
- Largest-Ever Universe Simulation Up for Supercomputing's Highest Prize - olcf.ornl.gov
- Supercomputer runs largest and most complicated simulation of the universe ever - livescience.com
Fact-checked by Perplexity Sonar Pro on 2026-01-09
