Big doesn’t quite cover this blog post.

For the past few weeks in my role as a demonstrator in the first year undergraduates lab, I have been supervising the experiment titled Large Scale Structure of the Universe. The experiment itself is a slightly painful exercise involving a series of simulated optical telescopes on an odd piece of software installed on the lab computers. The students have to find the galaxies, which I give to them on a piece of paper, and then take a fake spectrograph reading for each one. This enables them to dot-by-dot create a small, 3D slice of the universe where they can see how far away each galaxy is from Earth and the structure the galaxies take on the largest scales.
They are, understandably, not too thrilled at this. Lab takes four hours and the preamble to this experiment takes a good hour on its own. When it is complete, and they have say, an hour remaining of lab, in which they must answer a series of questions based upon the data they have taken and the completed set of many more galaxies printed in their lab book already.

Now ignoring the fact that they seem to have taken the data for no reason at all and that this is a sure-fire way of ensuring they learn to loathe astronomy as a boring, long-winded science, what they end up with is quite interesting. Naturally none of them see it as interesting as they have been steadily bored by it for a whole afternoon, which is a great shame.

The reason it is so interesting is that on the very largest scales, the Universe has a structure. When one looks into the sky and sees the myriad of stars, nebula and galaxies one could be forgiven for thinking that the universe was pretty randomly distributed. Yet given a little thought this doesn’t seem obvious at all because eveything we have yet discovered seems to have an order.

The Earth goes around the Sun, the Sun around the centre of the galaxy. The galaxy itself is part of a larger collection of gravitationall bound galaxies called the Local Group. The Local Group is part of a larger collection known as a cluster. The clusters collect into super-clusters. There is structure at all levels. Yet at its highest order of size, the Universe still shows form and shape.

Taking every galaxy as simply a dot and then assembling all the dots together into a picture containing millions upon millions of galaxies we see the Universe looks a bit like foam. The matter (i.e. all the galaxies) mostly exisitng on the surface of bubbles, within which lies great voids of space. These regions are unimaginable large and if you were to sit at the centre of them it would be incredibly dark as there would be no stars to light things up.

There are many people studying the structure of the universe at this level. There is a survey, as a good example, called the Two degrees of freedom galaxy redshift survey, or the 2DF Survey which you can read more about at this link

What I wanted to post here though was deatils of the Millennium Simulation. In the words of the Virgo Consortium that carried out the simulation, it is

“…the largest [computer] Simulation ever carried out, containign over 10 billion particles. The simulation was carried out by the Virgo Consortium using the a cluster of 512 processors located at the Max Planck Institute for Astrophysics in Garching, Germany. The simulations took a total of 28 days (~600 hours) of wall clock time, and thus consumed around 343000 hours worth of cpu-time.”

What the simulation produced, amongst other things, was a series of movies and images from a simulated Universe. In these animations the camera flies around the universe, showing in rich detail the current best model for what the universe looks like at such large scales. It is quite beautiful to watch and I suggest you do. There are two versions of it: a 60 MB version called the Fast Flythru and then a 120 MB version which is the same journey but done more slowly so you can take more in. Both are DivX files.

A whole host of video and images are available on this website, which outlines what you’re looking at as well. You can look at the Universe as it is now or watch it evolve from its early stages to the present day.

Obviously even at 10 billion particles, the Millennium Simulation doesn’t even start to approach the actual resolution of the Universe but this is worth a look and certainly gives you an idea of exactly how teeny tiny we are here on Earth and how remarkable it is that we are able to discover such enormous ideas.