Researchers are using high-powered computer simulations to help understand one of the most puzzling phenomena in science–how the universe is expanding faster than ever.

Ever since 1929, when Edwin Hubble first theorized the Big Bang, cosmologists have been hard at work to define what it all means. Over the course of the 20th century, scientists have come to realize that the universe is comprised of numerous galaxies made up of stars, planets, black holes, gas, and dust, as well as mysterious and invisible dark matter with gravitational properties. More recently, they have hypothesized that the expansion is accelerating due to dark energy, a little-understood cosmic force. The universe is estimated to be made up of approximately 70% dark energy, 25% dark matter, and only 5% normal matter, also called baryons (that includes the galaxies themselves, Earth and we humans).

Despite this explosion of new theories, cosmologists are still struggling to understand the real causes of this accelerated pace of expansion. One way for them to arrive at reasonable and informative conclusions about the true nature of the universe is through the application of sophisticated computer codes and technology that simulates the cosmos. They can then compare such simulations to telescopic observations.

Now, a team of eight U.S. Department of Energy researchers has run a cosmological computer simulation that provides one of the largest, high-resolution portrayals of the expanding universe ever displayed, called the Q Continuum Simulation. The results of their work were outlined in a study subtitled “Harnessing the Power of GPU Accelerated Supercomputers,” published in August by the Astrophysical Journal Supplement Series of the American Astronomical Society.

The unique simulation was created on the DOE’s Oak Ridge National Laboratory’s Titan supercomputer—one of the world’s most powerful that became available to researchers in early 2013— using a code developed since 2008, called the Hardware/Hybrid Accelerated Cosmology Code (HACC), also known for being the only cosmological simulation code that can run on multiple supercomputer platforms worldwide.

“We wanted to create a very detailed synthetic map of the universe that we can use as a cosmic laboratory,” says Katrin Heitmann, an Argonne physicist who led the project. “Also, we wanted to answer questions about how the structures that we observe actually formed. From the observational information we have right now, we set up initial conditions that we put on a computer. We ran this simulated model and can compare the results to observations from telescopes.”

Overall, the simulation shows the formation of structure over time and how gravity acts on dark matter, causing a clumping that leads to so-called halos, where galaxies form. “This is a very rich simulation,” Heitmann adds. “We can use the data to look at how galaxies are distributed, as well as the fundamental physics of structure formation itself.”