Cosmology Conundrum

March 26, 2013

Some colleagues have suggested that my posting on Planck Day was overly frivolous, given the huge importance of what Planck has achieved. (Nicely written up by Andrew Jaffe.) Other colleagues have suggested that Planck Day was bad press, as it was such a huge public non-event, with a big fuss about mild parameter adjustment. I find both these things true, leaving a weird sense of tension and excitement. I’d better explain myself.

First, lets be clear about the technical achievement. Planck is an absolute triumph of technology, engineering, management, and organisation. An amazing machine that has worked beautifully. It also represents a stunning scientific achievement. The lamda-CDM model, and its beautifully articulated engine of prediction, is a conceptual and analytic triumph. Of course this triumph belongs not just to the Planck team, but represents the accumulated achievement of many scientists all over the world over a number of years.

Lets just look at that power spectrum fit. It is not just a question of the theoretical curve going vaguely up and down, in more or less the same way as the data. The detailed agreement is gob-smacking – multiple peaks, their positions, their sizes, their widths, their second and third order curvature. Any scientist will look at this and think “no way is this a fluke”. Don’t let doubters trot out that coffee-time stuff about being able to fit anything with enough parameters. Firstly, that old chestnut is largely nonsense, and secondly, the fit quality is way beyond that.

Parfait. Everybody love parfait

And yet – outside the world of the CMB, the CDM paradigm has problems, as we were reminded here at ROE the day after Planck Day, in a nice wee coffee talk by Jorge Penarrubia.The best known problems are that CDM predicts far too many dwarf galaxies, and galaxy profiles that are much cuspier than observed,  but there are other claims, such as the existence of a very unlikely polar structure of dwarfs surrounding the Milky Way,  and of suspicious uniformities in galaxy rotation curves. All these problems may still get patched up by astrophysical fixes to do with feedback, IMF games, etc… but we don’t know yet.

Its common to hear people say that Particle Physics and Cosmology are in a similar situation – a model rather than a theory – a perfect fit but with no explanation. Why do all those parameters have those particular values? It seems so arbitrary. And what are dark matter and dark energy anyway? In this view, even the boringly successful fit is tantalising because it tells us there must be a deeper theory in waiting that will explain the perfect fit.

That may describe particle physics, but it doesn’t describe cosmology. Rather, what we have is perfect but fishy. How can the model be so perfect in some places and so poor in others? Have we missed something simple? It may well be that the astrophysical fixes do the trick, and then cosmology does look indeed like particle physics – successful but unsatisfying. Or it could be that some conceptual change is needed, and a revolution is waiting.

I’d give the revolution 2:1 against. But thats good enough odds that your eyes are glued to the table… Mesdames et Messieurs, faites vos jeux.


George, God, and the Grapefruit : Ten Things I Learned

March 21, 2013

Been watching the ESA Planck live press junket George show thingy. Well, everybody and his hairdresser will be writing up their well considered Planck thoughts over the next hour and a half, so I thought I would just summarise some personal lessons. The follow-on press release is here. Apparently there will be more serious stuff about lunchtime, and here in Embra our very own Andrew Liddle will give a seminar this afternoon. Actual science papers on ArXiv tomorrow. Meanwhile, lets keep it light.

The title is ruthlessly stolen from a a Tweet by Professor R.Ivison.

(1) George’s taste in ties continues to improve.

(2) George would give his children away for the Planck map. According to their Mum, they didn’t hear this because they are in school.

(3) The Universe is a bit like a grapefruit. Roundish, mostly very smooth, but with tinnsy-winnsy dimples

(4) When a Twitter hashtag starts trending, it becomes cloggged up with porno-tweets. This is annoying. Well, unless thats what you are after of course. (Am I missing some kind of filter?)

(5) You can’t mention God, unless you mention that you are not mentioning Him. Her. It.

(6) The Universe is EVEN MORE BORING than WMAP told us. Perfect fit to simple inflation.

(7) EXCEPT … for (a) the ten degree dip, and (b) the preferred direction, aka the axis of evil

(8) The axis of evil lines up with the ecliptic plane. Woahh !  But as ex-Edinbuggerer Tom Kitching said to me, that sounds like zodiacal dust… so maybe when that correction is improved the UNIVERSE IS EVEN MORE BORING

(9) The Hubble constant is exactly what Michael Rowan-Robinson told us years ago (67) without the aid of extreme coolants

(10) Talking of which, ESA say they created the coldest place in space, at 0.1K. Now that is definitely quite cute.


Wild Northern Skies

March 19, 2013

Only connect, as Goethe said. Or was it E.MForster? Or did I already already use that gag in an earlier post? Anyhoo. Two or so weeks ago commenters on my own nuclear blog post made me eat humble pie , liberally sprinkled with Thorium. Last week I was in Thurso, in the far distant north of our fair land. “Thurso” ought to mean  to Thor’s town, but sadly it doesn’t, actually meaning “Bull’s River” or some such. However, it is just down the road from Dounreay, for many years the home of Britain’s development programme in fast breeder reactors. The last Dounreay reactor, the “Prototype Fast Reactor” was shut down in 1994, but the plant still employs large numbers of people, because of the extended decomissioning programme. The aim is to return to a brownfield site by 2036..  Nuclear power ain’t simple. Also, the MoD still run some experiments there. Its all quite nicely explained in this wikipedia page on Dounreay.

Anyway, forMilky Way from Loch More, Caithness2012 Oct 7thGordon Mackie a such a remote area, with a population of a few tens of thousands, Caithness has a substantial sprinkling of high-tech and generally educated folk, who work for Dounreay and related activities, and an active and lively Astronomical Society – the Caithness Astronomy Group. These nice folk invited me up. Being in the distant north, it takes a whole day to get there even from Edinbrr, so I was there for several days, talking to multiple primary schools and doing a public talk as well as the usual astro-soc talk.

Caithness is a great place for amateur astronomy. Its as cloudy as most of Britain, but its DARK. When I asked the primary school kids who had seen a shooting star, 80% of the hands went up. I have never seen that in Edinburgh or London … and a large fraction of the populace have seen the Milky Way. You just walk out and there it is. The CAG chairbeing, Gordon Mackie, sent me the shot you can see to the left, taken at Loch More.

Aurora over Thurso CastleGordon Mackie2011 Aug 6th Caithness is also a great place for seeing the Northern Lights. Frustratingly, there was a massive CME arriving while I was there, but it was raining … Here is another Gordon Mackie shot to make up for it. Another ace astro-photographer is Stewart Watt. You can see his collection at “Under Highland Skies“.

But possibly the most exciting is Maciej Winiarczyk, who specialises in time-lapse astrophotography. He has lots of stuff on both YouTube and Vimeo. Take a look at this. But first pour a glass of Old Pulteney, sit back, and relax.

Oh, and its a nice place for a holiday.