How did we get here? We humans are not the only ones racing around the pale blue dot, racing around a star, racing around a supermassive black hole, racing inside the local cluster. So how did the dot, star, black hole and cluster get here? How did the incomprehensible magnitude of everything come from incredible nothingness billions of years ago to what it is today?

This is really the question of questions. As part of the largest project of its kind to date, astronomers are trying to find answers by performing computer simulations of the entire universe.

These are called FLAMINGO simulations (full-scale all-sky mapping structure simulations for next-generation observational interpretation) run on a supercomputer at the DiRAC facility in the UK.

These simulations are intense. They were designed to calculate the evolution of all known components of the universe. This means normal matter: stars; galaxies; everything we could touch (it could kill us, but we could); dark matter is a mysterious mass that creates a strange additional gravity; and dark energy, the mysterious force accelerating the expansion of the universe.

The largest of these simulations contains 300 billion particles, the mass of a small galaxy, in a 10 billion light-year-wide cubic volume of space.

“To make this simulation possible, we developed a new SWIFT code that efficiently distributes the computational work among 30,000 processors,” explains astronomer Mathieu Schaller from Leiden University.

The first results were published in three papers: the first describing the methods, the second describing the simulations, and the third describing the large-scale structure of the universe in cold dark matter.

The third article looked specifically at something called sigma 8 or S8 voltage. This is based on a measurement of the universe’s so-called cosmic microwave background (the weak microwave radiation that has filled the universe since the period just after the Big Bang). Analysis of this light suggests that the universe must be more harmonious than it currently is.

Since this tension is a major challenge for the cold dark matter model of the universe where clustering must occur, researchers hope FLAMINGO may provide some answers.

So far they haven’t been able to resolve this tension—which would be big news for cosmology—but they do know something about running simulations: Both ordinary matter and neutrinos are required for accurate predictions.

“Although dark matter dominates the gravitational force, the contribution of ordinary matter can no longer be ignored,” says study leader and astronomer Joop Schae from Leiden University, “because this contribution may be similar to deviations between models and observations.”

A simulation involving ordinary matter is more difficult to run. Dark matter is known to interact with the universe only gravitationally; Ordinary matter also interacts with pressures such as radiation pressure and galactic winds, which are unpredictable and difficult to model. It requires a lot more processing power to run, so we’ll have to wait a little longer for FLAMINGO’s answers regarding S8 voltage.

But the researchers ran a series of simulations tracking the formation of the universe’s structure in dark matter, normal matter, and neutrinos, varying the parameters of all three to see how this affected the final outcome.

“The influence of galactic winds was calibrated using machine learning by comparing predictions from many different simulations on relatively small volumes with observed galaxy masses and gas distributions in galaxy clusters,” explains astronomer Roy Kugel of Leiden University.

The team has not yet released the FLAMINGO data as it is several petabytes in size. Anyone interested is encouraged to send a polite question to the corresponding author. Source