The race for computational supremacy continues to yield remarkable scientific advancements. Frontier, a behemoth of a supercomputer residing at Oak Ridge National Laboratory, recently achieved a milestone: generating the most detailed and complex computer simulation of the universe ever created. Until recently holding the title of the world’s fastest, it was surpassed in November 2024 by El Capitan at the Lawrence Livermore National Laboratory, boasting an impressive 1.742 exaFLOPS. Even so, Frontier’s 1.1 exaFLOPS (1.1 quintillion floating-point operations per second) – achieved through an astounding 9,472 AMD CPUs and 37,888 AMD GPUs – remains a testament to its extraordinary processing power.
This ambitious project utilized the Hardware/Hybrid Accelerated Cosmology Code (HACC), developed over 15 years. HACC’s design is inherently scalable, making it adaptable to the fastest supercomputers available at any given time. This adaptability is key, as the demands of simulating the universe are immense. Previously, the Argonne National Laboratory team, led by Salman Habib, utilized HACC on petascale computers, like Summit (the world’s fastest from November 2018 to June 2020). These earlier simulations, while groundbreaking, were limited to ‘gravity-only’ approximations, omitting other crucial forces and effects.
On Summit, three simulations, playfully named after Star Trek planets (Qo’nos, Vulcan, and Ferenginar), explored different cosmological scenarios. These included variations in dark energy and the inclusion of massive neutrinos. The results highlighted the impact of varying dark energy on early universe galaxy clustering, a finding verifiable through high-redshift galaxy surveys. However, even Summit’s capabilities proved insufficient for incorporating the complexity of baryonic matter (the stuff that makes up you and me), hot gas, star formation, black holes and galaxy formation – all crucial elements of a truly comprehensive model.
The Frontier simulation, funded by the Department of Energy’s $1.8 billion ExaSky project, represents a significant leap forward. The ExaSky project mandated that HACC run at least 50 times faster on Frontier than on Titan (the world’s fastest in 2012). Frontier exceeded expectations, achieving a nearly 300-fold speed increase. Bronson Messer, director of science at the Oak Ridge Leadership Computing Facility, described the resulting simulation, which incorporates ‘baryons and all the other dynamic physics,’ as a “true tour de force.”
This massive undertaking aims to tackle some of cosmology’s most enduring mysteries. By simulating the interplay of dark matter, dark energy, and baryonic matter, the simulation allows researchers to test various cosmological models, including alternative theories of gravity like Modified Newtonian Dynamics (MOND). The results will be made available to the astronomical community, providing a powerful resource for comparison with observational data from astronomical surveys like the Sloan Digital Sky Survey and the upcoming Vera C. Rubin Observatory. This will help determine which models best reflect the observed universe.
The implications of this achievement are profound. The increasing power of supercomputers enables ever more detailed and accurate simulations of the universe, raising fundamental questions about the nature of reality itself. If computational power continues to advance, eventually reaching the point where simulations become indistinguishable from reality, what does that say about our own existence? The possibility that we ourselves might be living within a simulation, a concept explored in science fiction and scientific thought, becomes increasingly intriguing as our ability to simulate the universe approaches the complexity of reality itself.
