“Scientists Release Most Accurate Simulation of the Universe to Date”

A new computer simulation out of New Mexico State University, running on NASA’s Pleiades supercomputer, has become the new hotness in universe simulation. Called the Bolshoi, it’s based off of data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), which measures variation in cosmic microwave radiation remaining from the Big Bang. The Bolshoi’s predecessor, the Millennium Run, used an older version of WMAP data that has since been shown to be inaccurate. 

From ScienceDaily:

The simulation traces the evolution of the large-scale structure of the universe, including the evolution and distribution of the dark matter halos in which galaxies coalesced and grew. Initial studies show good agreement between the simulation’s predictions and astronomers’ observations.

The standard explanation for how the universe evolved after the Big Bang is known as the Lambda Cold Dark Matter model, and it is the theoretical basis for the Bolshoi simulation. According to this model, gravity acted initially on slight density fluctuations present shortly after the Big Bang to pull together the first clumps of dark matter. These grew into larger and larger clumps through the hierarchical merging of smaller progenitors. Although the nature of dark matter remains a mystery, it accounts for about 82 percent of the matter in the universe. As a result, the evolution of structure in the universe has been driven by the gravitational interactions of dark matter. The ordinary matter that forms stars and planets has fallen into the “gravitational wells” created by clumps of dark matter, giving rise to galaxies in the centers of dark matter halos.

A principal purpose of the Bolshoi simulation is to compute and model the evolution of dark matter halos…

The Bolshoi simulation focused on a representative section of the universe, computing the evolution of a cubic volume measuring about one billion light-years on a side and following the interactions of 8.6 billion particles of dark matter. It took 6 million CPU-hours to run the full computation on the Pleiades supercomputer, recently ranked as the seventh fastest supercomputer in the world.

A note about that last sentence: keep in mind that supercomputers progress in leaps and bounds. The Pleiades is the seventh fastest supercomputer in the world, but it’s about 1/8 as fast as the fastest supercomputer (which is still in production, in Japan), and less than 1/2 as fast as the fastest supercomputer that’s actually completed (in China). 

About dark matter: it’s matter that does not interact with electromagnetic radiation (like light, radio waves or infrared), which means as yet we haven’t been able to actually detect it. The reason scientists think it exists is because it’s the most likely explanation for cosmological gravitational effects they’ve observed; the matter we can detect doesn’t explain all the gravity we detect. 

Finally… I don’t know what’s up with the astronomy world, but one individual wrote the code for this simulation, which I find odd. Did he have some kind of monopoly on the data? It takes teams of programmers to make a video game world, but only one to simulate a universe, apparently. 


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