From out Earthly perspective, the universe appears to be unchanging. But of course, it isn’t.
From out Earthly perspective, the universe appears to be unchanging. But of course, it isn’t; the universe is a dynamic and evolving place even if we can’t see so with our own eyes. A new set of visualizations published today by the journal Nature shows the universe evolving in stunning detail, far more than we’ve seen before.
We know a fair bit about the universe’s formation and evolution, yet there remain a number of mysteries in its history as well. We now know the universe has a "foamy" structure, and that the galaxies that make up the visible universe create a massively complex scaffold-like network that spreads throughout the expansive cosmic void.
We know that the the unseen dark matter in our universe makes up roughly 27 percent of its matter-energy content, and that the exact properties of dark matter are still pretty mysterious. But knowing about these material structures and how they interact with one another helps us understand the processes by which the universe formed and evolves. This is what simulations of the universe endeavor to show.
Simulations of the universe typically show the web of galaxies that we see in the universe today, and they typically answer the main questions about the its evolution: how were the first stars and galaxies created, and how did this go on to influence later stellar and planetary formation.
Description from the paper: "Time evolution of a 10Mpc (comoving) region within Illustris from the start of the simulation to z=0. The movie transitions between the dark matter density field, gas temperature (blue: cold, green: warm: white: hot), and gas metallicity." Video: Illustris Collaboration/Illustris Simulation
In 2011, scientists from NASA’s Ames Research Centre used the Pleiades supercomputer and the "Bolshoi" simulation code to generate the largest and most realistic cosmological simulation of the evolving universe we had ever seen. The result modeled the distribution of dark matter across one billion light years, and the simulation was sufficiently detailed that researchers hoped it would help explain how large structures in the universe changed following the Big Bang. Running the code took millions of hours of computer time over 18 days and generated staggering amounts of data.
The new simulation, created by a team led by Mark Vogelsberger from the Massachusetts Institute of Technology, shows the evolution of the universe with galactic distribution and composition more accurately represented than any previous simulation. This simulation starts 12 million years after the Big Bang and brings 13 billion years of cosmic evolution to life. It shows a mix of spiral and elliptical galaxies with hydrogen and metal content that corresponds to recent observational data.
"Basically, our program follows step by step and follows the universe from when it was 12 million years old and ends up at the present day," said Shy Genel, a post-doctoral fellow at the Harvard-Smithsonian Center for Astrophysics and coauthor of the new work. "We take those initial conditions and put them in our computer program that uses what we know about the laws of nature, expansion of the universe, dynamics, formation of stars and black holes, and energy and radiation that starts from black holes, and follow it from there. We find that, naturally, it has galaxies that form and they look just like our real galaxies."
It’s the first to correctly predict characteristics we’ve learned about from observational studies, marking a considerable advance in modeling galaxy formation. But it also shows something previous simulations haven’t: the mixed populations of galaxies as well as their gas and metal content. That the program could model universe formation in such detail is evidence that what we currently think about the laws of nature are correct.
"It’s not hard proof because there could always be an alternative model that comes up, but I think this is really good evidence we have the basic properties and components of the universe that operate on these scales—we have them quite under control," Genel said. "there are still fine details that require a lot of future work."
Vogelsberger’s team attributes their success to advances in computing power, improved numerical algorithms, and a better understanding and available models of the physics that ties into and shapes galactic evolution. They were able to model the evolution the visible matter in the universe as well as the dark matter. And it’s not just a gorgeous movie. The interaction between light and dark might prove to be important in future studies of the universe’s evolution.