The Bolshoi Simulation - visualization of dark matter

October 2, 2011 5:35 AM

Visualization of the dark matter in 1/1000 of the gigantic Bolshoi cosmological simulation, zooming in on a region centered on the dark matter halo of a very large cluster of galaxies. ... The Bolshoi simulation is the most accurate cosmological simulation of the evolution of the large-scale structure of the universe yet made (“bolshoi” is the Russian word for “great” or “grand”). (The Formation of the Milky Way and its Neighbors is cool too.)
posted by nickyskye (6 comments total)

So, is the distinctive thing about the Bolshoi simulation an innovative or unique methodology, or as the name kind of implies is it just a matter of scale that's making it effective in getting similar statistics to observational data?

Also - with the observational data, in about half of the field there's very sparse data, with a very distinct line dividing the two halves. I always guessed that this appearance of large-scale charts of the cosmos was because the core of the Milky Way obstructs observations in one direction, is that true?
posted by XMLicious at 5:57 AM on October 2, 2011

XMLicious, I think the answers to your questions can be found on the Bolshoi Simulation site FAQs and about the Bolshoi simulation on Astronomy.com.
posted by nickyskye at 6:13 AM on October 2, 2011 [2 favorites]

From the FAQ:

The Bolshoi simulation clock started about 24 million years after the Big Bang, based on a highly accurate calculation of the evolution of the universe to that time. The Bolshoi simulation then followed the evolution of 8.6 billion particles, each particle representing an amount of dark matter with a mass about 200 million times the mass of the sun (about 1/5000th [??] the mass of the Milky Way dark matter halo). 180 times during the simulated evolution of the universe, the resulting picture of all the dark matter particles and their motions was captured and stored like a frame in a monumental three-dimensional movie. These stored time steps will allow astrophysicists to explore the three-dimensional model of the universe and study how dark matter halos, their galaxies, and clusters of galaxies coalesced and evolved....

Bolshoi is the most accurate and highest-resolution large cosmological simulation run to date. Its results—including merger trees (basically the family trees) of dark matter halos and galaxies—will be made available this fall and winter to the world’s astronomers in a series of phased releases.

All available data suggest that dark energy is a cosmological constant, a possibility first proposed by Albert Einstein, who called it by the Greek capital letter lambda [Λ]. That is what the Bolshoi simulations assume.

(Not An Astrophysicist, Not Your Astrophysicist)

I think it's important to note that (IMHO) the point of this kind of simulation is really to give a general framework for making observations. What makes this grand is that they are attempting to

A) start reasonably close to the CMB
B) attempt to build up the large-scale distribution of galaxies by particles which are smaller than galaxies so it builds in some models of how galaxies themselves are formed and presumably the kinds of observational artifacts to look for.

It's nice that the end-state looks like the modern snapshot of the distribution of galaxies, but it doesn't really give a basis for saying anything about the underlying physics of the models used to produce the simulation. However, given the huge scale (in both time and space) of the processes involved, actually knowing what to the try to observe is crucial. Physics is dynamic i.e. it's about change, but all observations in astrophysics are snapshots of these dynamics events which we will never be able to observe because they occur over time-scales too huge to really even comprehend. The simulation allows you to tie in a snapshot to an sequence of snapshots (an event!) and gives the observer some clues about how the observed structure is changing and the physics involved.
posted by ennui.bz at 7:18 AM on October 2, 2011

If they can't see the matter because it's too dark, can't they just turn on the light?
posted by goethean at 7:49 AM on October 2, 2011

They could, but their grant runs out before the billions of years it will take for the light to bounce off the dark matter that they're trying to study. Think about that the next time you turn the lights off when you leave a room.
posted by Kid Charlemagne at 8:45 AM on October 2, 2011 [1 favorite]

As simulations of the universe get more and more accurate, the greater the probability becomes that our universe is just such a simulation. I find this existentially vexing, as it implies some sort of outside observer, or at least some universe-generating framework capable of creating the simulation and extracting data from it. It also implies the possibility of nested simulated universes, which leads to the kind of recursion that plants me right on the couch with a cool cloth over my forehead.
posted by BitterOldPunk at 12:54 PM on October 2, 2011 [6 favorites]