Cosmological Simulations down Memory Lane

On Friday I have to be in London to give a keynote talk at this year’s LGBT+ STEMinar, which is taking place at the new Institute of Physics Building near King’s Cross. I’ve been struggling to think what to say but a conversation this afternoon with some of our PhD students gave me an idea. I won’t spoil it for those going to the event by giving too much detail away, but it involves going over the past 30 years of cosmology and LGBT+ rights alongside each other, pointing out that in both areas there has been great progress but there is also still very much to do.

Anyway, in the course of this I had a look at my thesis (vintage 1988) and came up with the following pictures, in glorious monochrome:

You can click on them to make them bigger. When I started my graduate studies in 1985 my thesis was supposed to be about the statistical analysis of the cosmic microwave background. The problem was that way back then there weren’t any measurements, so I had to make simulations to test various analysis methods on. The above images are examples that ended up in a published paper.

You have no idea what a pain it was to make these images. I had very limited access to a graphics terminal so I had to send these to a special printer in the computer room  (which was behind closed doors and an airlock) and then wait (sometimes for days) for the operators to process the files and produce a the printout. If they came out wrong the process had to be repeated. It was all frustratingly slow as my programs were quite buggy, at least to begin with.

For those of you interested, these simulations were made using a (two-dimensional) Fast-Fourier Transform method, using a pseudo-random number generator to set up appropriate amplitudes and phases for the Fourier modes. The only even remotely clever bit was to find a way of generating Gaussian and non-Gaussian maps with the same two-point correlations.

In all it took me several months of work to complete the work that went into that paper (which was essentially a thesis chapter). When I look back on it I think if I’d been cleverer – and had a decent graphics screen like you find on a modern PC – I could have done it all in a couple of days!

And now, of course, we have real data as well as simulations!

My point is that things that seem very difficult at the time often look extremely easy in retrospect. And that’s not just the case in cosmology.

 

 

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6 Responses to “Cosmological Simulations down Memory Lane”

  1. “the past 30 years of cosmology and LGBT+ rights alongside each other”

    How about an old photo of Davis, Efstathiou, Frenk, and White and an astronomy lookalikes involving Freddie Mercury?

    Did George ever sport a mustache?

  2. […] Anyway, back to the talk. What I then tried to do – actually for most of the presentation – was to outline the progress that has been made over the last thirty years in cosmology. When I started in 1985 there was hardly any data. There were some small redshift surveys of the order of a thousand galaxies, but my thesis was supposed to be about the pattern of fluctuations in the cosmic microwave background and there were no relevant measurements back then. I had to rely on simulations, as I mentioned here a few days ago. […]

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