Archive for Leiden

The Cosmological Evidence – 25 Years Ago

Posted in Biographical, The Universe and Stuff with tags , , , on July 15, 2020 by telescoper

Today Facebook reminded me that the picture below is now 25 years old. I have posted it before and it has done the rounds at a number of cosmology conferences (usually to the accompaniment of lots of laughter), but I thought I’d circulate again as a bit of nostalgia and also to embarrass all concerned with this image. The picture was taken at a graduate school in cosmology in Leiden (in The Netherlands) in July 1995. In my memory that was a sweltering hot summer, which is my excuse for the informality of my attire.

Anyway, various shady characters masquerading as “experts” were asked by the audience of graduate students at a summer school to give their favoured values for the cosmological parameters. from from top to bottom these are:

  • the Hubble constant H0;
  • density parameter Ω0 (not split into dark matter and `ordinary’  matter as is now customary);
  • cosmological constant Λ0,
  • curvature parameter k
  • and age of the Universe t0.

 

From left to right we have Alain Blanchard (AB), Bernard Jones (BJ, standing), John Peacock (JP), me (yes, with a beard and a pony tail – the shame of it), Vincent Icke (VI), Rien van de Weygaert (RW) and Peter Katgert (PK, standing). You can see on the hi-tech digital display screen blackboard that the only one to get anywhere close to correctly predicting the parameters of what would become the standard cosmological model was, in fact, Rien van de Weygaert. Actually he was the only one of us to include a non-zero cosmological constant. My own favourite model at the time was a low-density model with negative spatial curvature.

Nobody is suggesting that panel discussions are the right way to settle scientific questions, of course, but it is interesting to see the diversity of opinions that were around in 1995.

P.S. Note that not all the combinations of parameters presented there are consistent with a Friedman model, but nobody said they had to be!

 

Cosmology – Confusion on a Higher Level?

Posted in Biographical, The Universe and Stuff with tags , , , , , on January 19, 2015 by telescoper

I’ve already posted the picture below, which was taken at a conference in Leiden (Netherlands) in 1995. Various shady characters masquerading as “experts” were asked by the audience of graduate students at a summer school to give their favoured values for the cosmological parameters (from top to bottom: the Hubble constant, density parameter, cosmological constant, curvature parameter and age of the Universe).

From left to right we have Alain Blanchard (AB), Bernard Jones (BJ, standing), John Peacock (JP), me (yes, with a beard and a pony tail – the shame of it), Vincent Icke (VI), Rien van de Weygaert (RW) and Peter Katgert (PK, standing). You can see on the blackboard that the only one to get anywhere close to correctly predicting the parameters of what would become the standard cosmological model was, in fact, Rien van de Weygaert.

Well, my excuse for posting this again is the fact that a similar discussion was held at a meeting in Oslo (Norway) at which a panel of experts and Alan Heavens did a similar thing. I wasn’t there myself but grabbed the evidence from facebook:

experts

I’ll leave it as an exercise for the reader to identify the contributors. The 2015 version of the results is considerably more high-tech than the 1995 one, but in case you can’t read what is on the screen here are the responses:

panel_vote

The emphasis here is on possible departures from the standard model, whereas in 1995 the standard model hadn’t yet been established. I’m not sure exactly what questions were asked but I think my answers would have been: 3+1;  maybe; maybe; don’t know but (probably) not CDM; something indistinguishable from GR given current experiments; Lambda; and maybe. I’ve clearly become a skeptic in my old age.

Anyway, this “progress” reminded me of a quote I used to have on my office door when I was a graduate student in the Astronomy Centre at the University of Sussex many years ago:

We have not succeeded in answering all our problems. The answers we have found only serve to raise a whole set of new questions. In some ways we feel we are as confused as ever, but we believe we are confused on a higher level and about more important things.

The attribution of that quote is far from certain, but I was told that it was posted outside the mathematics reading room, Tromsø University. Which is in Norway. Apt, or what?

The Evidence

Posted in Biographical, The Universe and Stuff with tags , , , on September 25, 2009 by telescoper

Further to my recent post about the evidence for a low-density Universe, I thought I’d embarrass all concerned with this image, taken in Leiden in 1995.

Various shady characters masquerading as “experts” were asked by the audience of graduate students at a summer school to give their favoured values for the cosmological parameters (from top to bottom: the Hubble constant, density parameter, cosmological constant, curvature parameter and age of the Universe).

From left to right we have Alain Blanchard (AB), Bernard Jones (BJ, standing), John Peacock (JP), me (yes, with a beard and a pony tail – the shame of it), Vincent Icke (VI), Rien van de Weygaert (RW) and Peter Katgert (PK, standing). You can see on the blackboard that the only one to get anywhere close to correctly predicting the parameters of what would become the standard cosmological model was, in fact, Rien van de Weygaert.