Primacks’ Premium Simulations

After spending a week debating with myself about various Many Worlds philosophy issues  and other quantum cosmology questions, today I saw Joel Primack’s presentation at the Philosophy of Cosmology International Conference, on the topic of Cosmological Structure Formation. And so for a change I was speechless.

Thus I doubt I can write much that illumines Primack’s talk better than if I tell you just to go and watch it.

He, and colleagues, have run supercomputer simulations of gravitating dark matter in our universe. From their public website Bolshoi Cosmological Simulations they note: “The simulations took 6 million cpu hours to run on the Pleiades supercomputer — recently ranked as seventh fastest of the world’s top 500 supercomputers — at NASA Ames Research Center.”

To get straight to all the videos from the Bolshoi simulation go here (


MD4 Gas density distribution of the most massive galaxy cluster (cluster 001) in a high resolution resimulation, x-y-projection. (Kristin Riebe, from the Bolshoi Cosmological Simulations.)

The filamentous structure formation is awesome to behold. At times they look like living cellular structures in the movies that Primack has produced. Only the time steps in his simulations are probably about 1 million year steps. for example, on simulation is called the Bolshio-Planck Cosmological Simulation — Merger Tree of a Large Halo. If I am reading this page correctly these simulations visualize 10 billion Sun sized halos.  The unit they say they resolve is “1010 Msun halos”. Astronomers will often use a symbol M to represent a unit of one solar mass (equal to our Sun’s mass). But I have never seen that unit “M halo” used before, so I’m just guessing it means the finest structure resolvable in their movie still images would be maybe a Sun-sized object, or a solar system sized bunch of stuff. This is dark matter they are visualizing, so the stars and planets we can see just get completely obscured in these simulations (since the star-like matter is less than a few percent of the mass).

True to my word, that’s all I will write for now about this piece of beauty. I need to get my speech back.

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Oh, but I do just want to hasten to say the image above I pasted in there is NOTHING compared to the movies of the simulations. You gotta watch the Bolshoi Cosmology movies to see the beauty!

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