Scientists at the University of Zurich have created the largest simulation of the Universe using a powerful supercomputer. It contains 25 billion virtual galaxies and was created with a simple goal in mind: train the next big mission from the European Space Agency (ESA).
Writing such a complex simulation is far from easy and there are difficulties from both the physical and computational side of the problem. The code, known as PKDGRAV3, was recently published in Computational Astrophysics and Cosmology and took about three years to develope and optimize.
The code runs in about 80 hours and its starting point is a universe with 2 trillion “macro-particles” of dark matter. The macro-particles represent giant blobs of dark matter, and while that is a very coarse approximation, it allows them to produce a pretty good virtual universe.
This simulated cosmos is currently being used to train Euclid, the ESA mission that hopes to uncover the secrets of dark matter and dark energy. The mission, set to fly in 2020, will image billions of galaxies to study what effects the dark side of the universe has on the paths of the photons.
"That is comparable to the distortion of light by a somewhat uneven glass pane," co-author Joachim Stadel, from the Institute for Computational Science of the UZH, said in a statement. "Euclid will perform a tomographic map of our universe, tracing back in time more than 10-billion-years of evolution in the cosmos."
Dark energy is the cause of the accelerated expansion of the universe. Dark matter, instead, is responsible for how galaxies keep their shape. Although we don’t know exactly what they are, we can see what they do. Their effect on the universe is evident and that’s what the researchers used in the simulation.
The struggle for the researchers was to create a virtual universe with galaxies as small as one-tenth of the Milky Way, while having billions of galaxies in the simulation. This was a specific requirement to help calibrate Euclid's suite of instruments. This means the macro-particles had to be small enough to merge into small galaxies and numerous enough to produce enough galaxies to study.
But the researchers were able to deliver it. Using the virtual universe, the Euclid team will be able to tweak the observational strategy so that Euclid will have fewer sources of error. The mission will collect data for six years, and scientists hope that it will finally shed some light on the “dark” side of the cosmos.