Posts Tagged ‘simulation’

Realistic Simulation of the Formation of a Milky Way-Like Galaxy

August 31, 2011 1 comment

The first realistic simulation of a spiral galaxy similar to our own Milky Way has been generated by researchers at the University of California, Santa Cruz, and the Institute for Theoretical Physics in Zurich.

The simulation, called ERIS, took 1.4 million processor hours to complete. And that was on the 7th most powerful supercomputer in the world, NASA’s Pleiades supercomputer, which runs at 1.09 petaflops per second.

The simulation follows the formation of a galaxy equivalent to 7.9 × 1011 solar masses (1 solar mass is equal to the mass of our Sun) and has a total of 18.6 million particles.

The resulting galaxy has a radius of 2.5 kilo-parsecs (about 7.7 × 1016 kilometers). Previous attempts at simulating a realistic galaxy have failed, resulting in simulated galaxies which have too large of a central bulge. The finding of this study, which has been accepted for publication in Astrophysical Journal, found that,

A high star formation threshold appears therefore key in obtaining realistic late-type galaxies, as it enables the development of an inhomogeneous interstellar medium where star formation and heating by supernovae occur in a clustered fashion. The resulting outflows at high redshifts reduce the baryonic content of galaxies and preferentially remove low angular momentum gas, decreasing the mass of the bulge component.

Another important result of this work is that it supports the idea that cold dark matter constitutes a large portion of the mass in the universe.

Turning Boring Data Into Awesome Movies

January 21, 2011 Leave a comment

As reported today on Scientific American, the Advanced Visualization Laboratory at the National Center for Supercomputing Applications (NCSA), turn terabytes worth of data into majestic astronomic visual treats.

They talk more about the process in the Scientific American piece.  For me though, sometimes you just want to see the Universe in all its awesomeness, and leave the data analysis to the experts. (That last statement is a bit ironic since I am a data analyst, but that’s not important right now…)

The first mini-galaxies formed when the universe was just a few hundred million years old. Over time, these small galaxies interacted and merged to build up ever larger galaxies, including big spirals like our own Milky Way. Credit: NCSA/NASA/B. O’Shea (MSU) and M. Norman (UC San Diego)

Two spiral galaxies undergo a protracted crash lasting two billion years, eventually merging into a single elliptical galaxy. Credit: NCSA/NASA/B. Robertson (Caltech) and L. Hernquist (Harvard Univ.)

Beginning when the universe is about 20 million years old and continuing to the present day, this visualization provides a glimpse of how the cosmic web may have developed. Credit: NCSA/NASA/R. Cen and J. Ostriker, (Princeton Univ.)

You can see a few more videos like these at the James Webb Telescope page.

How Facebook Connects the World: A Visual

December 14, 2010 1 comment
A Stunning Visualization of Facebook Friend Connections – Click to Enlarge

This beautiful simulation was created by a Facebook intern named Paul Butler. He is an intern on Facebook’s data infrastructure engineering team.

Using a sample of 10 million friend pairs, he wanted to see how those friends were connected geographically. How did he do it?

He explains in a Facebook note, but it is a little bit technical, so I will attempt to translate for the lay reader.

First he started with his 10 million sample pairs. Then he sorted them out by adding up how many friends each city has with each other. For example, how many friends do people in New York have in Chicago? How many friends do people in Los Angeles have in Tokyo? And so on.

So then he tried plotting lines between those cities. Pairs of cities that had more friends between them would have brighter lines. But this turned out to be a bit of a problem. When he tried this,

…a big white blob appeared in the center of the map. Some of the outer edges of the blob vaguely resembled the continents, but it was clear that I had too much data to get interesting results just by drawing lines. I thought that making the lines semi-transparent would do the trick, but I quickly realized that my graphing environment couldn’t handle enough shades of color for it to work the way I wanted.

His graph simply did not have enough shades of blue to make an accurate representation of the numbers. But since he sounds like a very smart guy, he came up with a solution:

I defined weights for each pair of cities as a function of the Euclidean distance between them and the number of friends between them. Then I plotted lines between the pairs by weight, so that pairs of cities with the most friendships between them were drawn on top of the others.

So cities that were closer together got brighter lines. So the line between New York and Chicago is brighter than the line between Los Angeles and Tokyo. Next, he chose to plot lines between cities that have more friendships between them on top of other lines. So the line from New York to Chicago is plotted on top of the line from New York to Scranton.

And Voila! A really nice map of the world drawn entirely with friendships. Paul Butler had some deep thoughts on it:

It’s not just a pretty picture, it’s a reaffirmation of the impact we have in connecting people, even across oceans and borders.

Facebook has gotten some bad press lately. And frankly, I was getting sick of people clogging up my News Feed with Farmville.

But damn, that picture is cool.