2017.10.09; Computer_Simulation_Recreates_the_Universe-Seeker

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Mind-Blowing Computer Simulation Recreates Our Universe

After 3 months of number-crunching, 8,000 computer processors working in parallel have recreated the evolution of our Universe in unprecedented detail.
May 7, 2014
8:58 PM EDT
Photo: Large scale projection through the Illustris volume at z=0, centered on the most massive cluster, 15 Mpc/h deep. Shows dark matter density overlaid with the gas velocity field. Credit: Illustris Collaboration Astronomers have a pretty good idea how the universe began and the near-14 billion years of evolution after, but throwing all our knowledge behind one grand computer simulation has been hard. The task at hand is simply too huge for any one computer to handle.
Today, however, astronomers have announced the results of three months of computer number-crunching, combining 8,000 CPUs all running in parallel, modeling our evolving universe. If the same simulation was carried out on your office desktop computer, the simulation would take 2,000 years to recreate.
"Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously," said Mark Vogelsberger of the Harvard-Smithsonian Center for Astrophysics and lead scientist of the study.
Previous work has either focused on a tiny portion of cosmic volume or had been too low a resolution. This study, however, has created a cube 350 million light-years across and over 13 billion years of simulated time at an unprecedented resolution. This work has been published in the May 8 edition of the journal Nature.
In the model, the effects soon after the Big Bang are considered where the hot soup of primordial matter cools to form the first stars and young galaxies. Dark matter is also included in the calculations, which dominates the "cosmic web," anchoring clusters of galaxies at its gravitational nodes.
The effects of supernovae enriching the interstellar and intergalactic volume with increasingly heavier elements is also modeled, providing us with an insight as to the building blocks of other stars, planets and, eventually, the organic chemistry that is the foundation for life.
The most striking thing about this virtual universe is its uncanny resemblance to observations made by today's observatories. The recreation of the array of galaxies we see deep in the furthest-most reaches of the universe form in strikingly familiar shapes and sizes.
The model only uses equations from theories constructed from decades (even centuries) of astronomical observations and allowed to evolve with time. The result is nothing short of breathtaking and it can be hard to distinguish the model from real observations.
The model, called Illustris, created a 3-D space filled with 12 billion pixels, all calculating the fundamental equations that govern normal (and dark) matter. The researchers can now zoom in on regions of interest to focus on different mechanisms as they unfold. When they kicked off the simulation 12 million simulated years after the Big Bang, some 41,000 galaxies condensed into numerous galactic cluster from the seemingly chaotic churning of matter.
"Illustris is like a time machine. We can go forward and backward in time. We can pause the simulation and zoom into a single galaxy or galaxy cluster to see what's really going on," added co-author Shy Genel, also of the CfA.
As noted in the Nature video accompanying the announcement of this study (below), there are some anomalies in the simulation that don't match our observations, but this is what science is all about; formulating hypotheses, testing theories and comparing them with observations. If something doesn't match up, there's something lacking in our understanding as to how the Cosmos works and astronomers will doggedly try to find answers to the mind-boggling questions the universe asks of us.
RELATED PHOTOS: Watching the Universe Grow Inside a Supercomputer
Imagine if you could assemble all known physics, throw it into a powerful supercomputer and watch a virtual universe evolve. Well, that's exactly what a team of physicists at Stanford University's Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) have done. This mammoth task has culminated in a part-physics/part-art exhibit that is being showcased in 3D videos playing at a theater on the SLAC National Accelerator Laboratory and featured at planetariums in New York City and San Francisco. In the videos, everything from dark matter to star formation is simulated. One simulation even demonstrates the majestic collision between two galaxies just as they merge to become one. Here's a sneak peek of a few of the stunning scenes showcased in the simulations.
Dark Matter The KIPAC team have simulated everything from the first few milliseconds of a supernova detonation to the 13.75 billion years of cosmic evolution and condensed the trillions of bytes of data into short animations lasting only minutes. "I'm trying to predict the past -- how the universe came to be the way that it is today," said Tom Abel, an associate professor of physics at Stanford University and head of KIPAC's computational physics department. Of particular interest to cosmologists is the science behind mysterious dark matter -- the "invisible" stuff that is theorized to pervade the whole cosmos, supplying the majority of the Universe's mass. Therefore, to visualize the early formation of large-scale dark matter structure (pictured here) isn't only a beautiful sight, it's also of paramount scientific importance.
Galactic Mergers In one simulation, the gravitational effects of two spiral galaxies colliding is envisioned. Before they merge as one, the pair undergo an orbital dance, scattering stars as they go. Astrophysicists have predicted and observed rapid star birth inside galactic mergers, so far from being destructive events, galaxy collisions can kick-start star formation.
Dwarf Galaxies Another simulation shows the formation of some of the earliest galaxies. Only a couple of hundred million years after the Big Bang, dwarf galaxies started to appear. It is thought that these galaxies eventually clumped together, forming the foundation of larger galaxies we see today -- like the Milky Way.
The First Stars The first stars to form were very massive, feeding off and ionizing their proto-galaxies' supply of hydrogen. These stars lived fast and died young, exploding as powerful supernovae. The KIPAC simulations take the viewer on an immersive tour of these powerful events using computational power that hasn't been available till now. "Creating these animations is a real joy these days because computers and software are so much more powerful today," Abel said. "Not long ago it took us weeks to produce a single animation. Now we can do one in an afternoon. "It's an immersive environment," he continued. "You can explore three-dimensional data, 'Avatar'-style. It's wonderful to have the sensation of being inside the cosmological data."
Not Just a Pretty Picture Astrophysicists work by taking observations and then they try to understand what they are seeing by creating a model. The model will use known physics in an attempt to replicate the observations. Now researchers have Hollywood budget-busting visualization tools in the laboratory, producing mind-blowing simulations of astrophysical phenomena, they are able to chase-down some of the most complex mechanisms that shape the cosmos. For example, the KIPAC visualizations helped Stanford colleagues understand the formation and structure of galactic clusters by simulating the formation of 100 clusters within a virtual cube measuring 4.5 billion light-years per side. So these may be pretty animations, but there is a strong scientific motivation behind their creation.
"These videos aren't just screensavers. They show us how the universe really works," concluded Oliver Hahn, KIPAC post-doctoral researcher, who is using this visualization tool to support his work.
For more information, images and videos of these simulations, see the KIPAC project pages.
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