The Universe, being the Universe, is massive. It's so massive that if we created a virtual model of just what we know of it on a standard PC, it would take about 2,000 years to properly simulate it. Astrophysicists have access to computers that are somewhat more powerful than a standard PC, and they've used them to create an entire Universe simulation over the course of just three months, and it’s a thing of beauty.
The simulation, titled Illustris, took nearly five years to program using over 8,000 CPUs. It's the most realistic simulation to date of the Universe (as we know it) and works in everything from how dark matter evolved to how stars and galaxies form. The final result is in line with previous observations, including what we know about how galaxies align with each other to how the cosmic web of dim matter connects them all. All of this is possible thanks to what we know about the composition of the Universe: ordinary matter, dark matter, and the strange dark energy that plays a part in the Universe’s expansion.
Illustris covers about 350 million light-years of the Universe and includes over 40,000 galaxies. It shows a series of cosmic explosions over the course of 13 billion years that eventually formed galaxies. Although there have been similar simulations before, Illustris is the first this large, and it also has much more detail than previous models and lets us see each individual galaxy and its evolution.
The importance of Illustris is that it gives us the ability to go back in time and watch the beginnings of the Universe, as well as the beginnings of galaxies. The simulation lets you zoom in and study each detail, lending us more understanding about what eventually put the Universe in place. The simulation has already led to one discovery: Illustris shows that stars in smaller galaxies formed earlier than we originally thought. With more time and study, Illustris is sure to unlock more mysteries of the Universe.