Simulating The First 80 Days of Our Universe

By Roland Piquepaille

In "Scientists Set to Change Face of Cosmology," the Korea Times writes that "a team of Korean scientists conducted the largest-ever simulation experiment to understand the evolution of the universe. The simulation, which involved 8.6 billion mass particles distributed just like after the Big Bang, took 4 years of computation. But here, I'm confused. Last September, in "Simulating the Whole Universe," I mentioned another simulation done by the Virgo Consortium which used 10 billion mass points. The goals were different. The Virgo team wanted to simulate the entire life of our universe while the Korean team is trying to understand the evolution of the universe during its first 80 days. Still, the Virgo simulation used more mass particles than the Korean one. Am I missing something here?

Let's start with some details about the Korean simulation.

The scientists, led by Korea Institute for Advanced Study (KIAS) professor Park Chang-bom, said Friday their team carried out the four-year project using a supercomputer.

Park's team used 8.6 billion massive particles that were distributed just like after the Big Bang and calculated the formation and evolution of the universe thereafter during 80 days.

The simulation is about eight times larger than the previous largest test and about 2,000 times bigger than Park's first trial based on 4-million particles in 1990, the largest back then.

"We will finish analyzing the calculation for the next two years through early 2007 and the analysis might completely change the face of the current cosmological model," Park predicted.

But here is a short quote of the August 2004 issue of IEEE Spectrum that I mentioned last September (see above for the link).

An international group of cosmologists, the Virgo Consortium, has realized the first simulation of the entire universe, starting 380,000 years after the Big Bang and going up to now.

The fundamental challenge for the Virgo team is to approximate that reality in a way that is both feasible to compute and fine-grained enough to yield useful insights. The Virgo astrophysicists have tackled it by coming up with a representation of that epoch's distribution of matter using 10 billion mass points, many more than any other simulation has ever attempted to use.

I hope some alert reader will help me to understand how 8.6 billion is larger than 10 billion...

Now, it's time to return to the Korean simulation and to some of its puzzling results.

The analysis of Park's team might conflict against the discovery of the Sloan Great Wall, a series of clusters of galaxies with a size of 1.4 billion light-years, by the Sloan Digital Sky Survey (SDSS).

"The likelihood that such big clusters of galaxies exists is just about 2 percent under the legacy model, insinuating it might be dead wrong. If more conflicting proof emerges, the old model will need to be overhauled," he said.

The Park's team is going to represent Korea in the SDSS project, where he will join other researchers from the U.S., Europe and Japan.

Finally, and just for your viewing pleasure, below is an image of Messier 44, a cluster of stars in our galaxy. Here is a link to a larger version.

"Messier 44, also know as Praesepe and the beehive clusters, is a famous cluster of stars in our own Milky Way galaxy. It is at a distance of about 180 parsecs in the constellation Cancer. The stars all formed at nearly the same time, about 800 million years ago. The cluster includes many different types of stars, including main sequence stars, red giants, and white dwarfs, and is often studied by astronomers." (Credit: SDSS, Caption by Steve Kent).

Sources: Kim Tae-gyu, The Korea Times, January 7, 2005; and various websites

Related stories can be found in the following categories.

• Astronomy
  
• Space
  
• Supercomputers