## A quiz of marginal interest

November 20, 2013

Two things we know.

(1) Scientific terminology is burdened with the baggage of history, which now makes no logical sense. So… early type galaxies are the ones with late type stars? Errr… And which of these terms relates to a sequence in time? Neither. Right. Very helpful.

(2) When you have to teach something, you finally figure out things that have been bugging you for years.

(3) Nobody expects the … oh. Anyway. Often (1) and (2) combine to make a particularly thick fog.

For some time the term “marginalisation” had been nagging at me, but I ignored it because I had other stuff to get on with. I am referring to the term in statistics. You have a probability density function of two variables, f(x,y), but decide that y is “interesting” and x is “uninteresting”. You then integrate over x to get a PDF p(y) for y alone. This known as “marginalising over x”.

So here is the quiz. My guess is only about seven people will want to take it, but I can’t resist it.

Rule (a) Andrew Liddle is not allowed because I already told him the answer in the pub. Rule (b) No Googling. Rule (c) Never talk about  Stats Club.

## Ten Thousand Torches

December 30, 2007

My coat will smell of smoke for a month. Last night we took the in-laws and the kidlums on the annual Torchlight Procession, part of Edinburgh’s long festive excess. This town is good at circuses. Thousands upon thousands of Edinburgh citizens and Hogmanay visitors holding up two-foot burning torches and marching through the town, up to Calton Hill, burning stuff, and ooohhhing at the fireworks. Several mystified Americans asked me “what is it in aid of ?”, and “why are those people dressed as vikings ?”, and “how come they are burning a twelve foot model of a stag ?” ???? Well hell I don’t know. We just do this stuff.

The Old Observatory is on Calton Hill, and being Regius Professor of Astronomy I tend to explain pompously to anybody in earshot that in 1789 that would have been my house. Luckily my partner Debbie is normally on hand to point out that in 1789 a lower class oik like me would never have been a University Professor. Walking down off the hill, as the torches go out and the smoke temporarily parts, I can see Orion, Betelgeuse glaring orange across a distance I can write down but not really grasp.

Back home to bacon butties for eight and Christmas Special Type Telly. Perfect.