Simulating the first billion years of our universe's history

Space · Published 21 October 2026 Swipe more like this →

In short: How do we understand the birth of the cosmos when we cannot travel back in time? Scientists are using the world's most powerful supercomputers to recreate the first billion years of the universe, tracing how microscopic quantum fluctuations expanded into the massive cosmic web we see today.

Researchers at the U.S. Two massive cosmological simulations were finished by the Argonne National Laboratory, part of the Department of Energy. A span of 28.6 billion light-years was covered by these models, which followed 13.4 trillion dark matter particles. Because dark matter is invisible to telescopes, these particles serve as tracers to map how gravity shaped the universe's large-scale structures over billions of years.

To examine cosmic inflation—a concept regarding the early universe's sudden, fast expansion—these simulations were designed. Scientists believe inflation stretched microscopic quantum fluctuations into tiny density variations, which gravity then amplified. By simulating these processes, researchers can look for clues about the early universe's physics, which remain uncertain today. The team used the Aurora exascale machine, which draws on 8,100 nodes and roughly 50,000 GPUs to perform over a quintillion calculations per second.

This work builds on the Hardware/Hybrid Accelerated Cosmology Code (HACC), developed about 15 years ago. HACC was designed to be adaptable, moving from petascale computers like Summit to modern exascale machines like Frontier and Aurora. While Frontier was the world's fastest supercomputer until November 2024, when El Capitan took the lead, these machines allow for 'cosmological hydrodynamics' tests that were previously impossible. These simulations help astronomers validate the standard model of cosmology by comparing digital evolution against real-world observations.

The project also allows for 'what-if' scenarios. For example, previous simulations named after Star Trek planets explored different universes, such as one with massive neutrinos or one where dark energy changed over time rather than remaining constant. By manipulating these variables in a digital environment, scientists can better understand the fundamental constants that govern our own reality.

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