Archive for Copenhagen

Cardiff, City of Cycling?

Posted in Bute Park with tags , , , , , , , on February 22, 2017 by telescoper

Two recent news items about Cardiff caught my attention so I thought I’d do a quick post. The first piece was about the terrible state of traffic congestion in the city. This doesn’t affect me directly as I normally work to work and back, but it has definitely got much worse in the last few years. The roads are regularly gridlocked, a situation made worse by the interminable and apparently pointless roadworks going on everywhere as well as absurdly slow and dysfunctional traffic lights. There’s a common view around these parts that this is being allowed to happen – or even engineered – so that Cardiff City Council can justify the introduction of congestion charging. This would be an unpopular move among motorists, but I think a congestion charge would not be a bad idea at all, as what the city really needs is to reduce the number of motor vehicles on its streets, to deal with the growing problem of pollution and long journey times.

One day, about six years ago,  I was almost run over three different times by three different vehicles. The first was near the car park in Sophia Gardens, where there are signs and road marking clearly indicating that there is a speed limit of 5 mph but where the normal speed of cars is probably more like 35; the guy who nearly killed me was doing about 60.

Next, in Bute Park, a heavy lorry belonging to the Council, engaged in some sort of “tree-management” business, thundered along the footpath past me. These paths used to be marked 5mph too, but the Council removed all the signs when it decided to build a huge road into the Park and encourage more vehicles to drive around inside. The lorry wasn’t going as fast as the Boy Racer of Sophia Gardens, but the size of the truck made it just as scary.

Finally, using a green light at the pedestrian crossing at Park Place I was narrowly missed by another car who had clearly jumped a red light to get onto the dual carriageway (Dumfries Place) leading to Newport Road.

I have to say things like this aren’t at all unusual, but that is the only time I’ve had three close encounters in one day! Although most car drivers behave responsibly, there seems to be a strong concentration of idiots in Cardiff whose antics are exacerbated by the hare-brained Highways Department of the local council. There are many things to enjoy about living in Cardiff, and the quality of life here is very good for a wide range of reasons, but of all the cities I’ve lived in it is by a long way the least friendly to pedestrians and cyclists.

Which brings me to the second news item, which is about Cardiff City Council’s ambitious new Cycling Strategy, which aims to double the number of trips made using cyclists over the next ten years. That still wouldn’t reach the level of Cambridge, where 30% of all journeys in the city are done by bicycle.

Cardiff has a long way to go to match Cambridge and further still to be like Copenhagen, one of the loveliest and most livable cities I’ve ever experienced, partly because of its traffic policies.

In the interest of balance I should also point out that I was once actually hit on a pedestrian crossing in Cardiff by a bicycle steered by a maniac who went through a red light. In this case, however, I did manage to push him off his bike as he tried to get away, so he ended up more seriously hurt than I was. I was hoping that a friendly car would run over his bike, which was lying in the road, but sadly that didn’t happen.

I hope in their desire to increase the number of cyclists, the town planners don’t forget those of us who travel on foot!

Lognormality Revisited (Again)

Posted in Biographical, Science Politics, The Universe and Stuff with tags , , , , , , , on May 10, 2016 by telescoper

Today provided me with a (sadly rare) opportunity to join in our weekly Cosmology Journal Club at the University of Sussex. I don’t often get to go because of meetings and other commitments. Anyway, one of the papers we looked at (by Clerkin et al.) was entitled Testing the Lognormality of the Galaxy Distribution and weak lensing convergence distributions from Dark Energy Survey maps. This provides yet more examples of the unreasonable effectiveness of the lognormal distribution in cosmology. Here’s one of the diagrams, just to illustrate the point:

Log_galaxy_countsThe points here are from MICE simulations. Not simulations of mice, of course, but simulations of MICE (Marenostrum Institut de Ciencies de l’Espai). Note how well the curves from a simple lognormal model fit the calculations that need a supercomputer to perform them!

The lognormal model used in the paper is basically the same as the one I developed in 1990 with  Bernard Jones in what has turned out to be  my most-cited paper. In fact the whole project was conceived, work done, written up and submitted in the space of a couple of months during a lovely visit to the fine city of Copenhagen. I’ve never been very good at grabbing citations – I’m more likely to fall off bandwagons rather than jump onto them – but this little paper seems to keep getting citations. It hasn’t got that many by the standards of some papers, but it’s carried on being referred to for almost twenty years, which I’m quite proud of; you can see the citations-per-year statistics even seen to be have increased recently. The model we proposed turned out to be extremely useful in a range of situations, which I suppose accounts for the citation longevity:

nph-ref_historyCitations die away for most papers, but this one is actually attracting more interest as time goes on! I don’t think this is my best paper, but it’s definitely the one I had most fun working on. I remember we had the idea of doing something with lognormal distributions over coffee one day,  and just a few weeks later the paper was finished. In some ways it’s the most simple-minded paper I’ve ever written – and that’s up against some pretty stiff competition – but there you go.

Lognormal_abstract

The lognormal seemed an interesting idea to explore because it applies to non-linear processes in much the same way as the normal distribution does to linear ones. What I mean is that if you have a quantity Y which is the sum of n independent effects, Y=X1+X2+…+Xn, then the distribution of Y tends to be normal by virtue of the Central Limit Theorem regardless of what the distribution of the Xi is  If, however, the process is multiplicative so  Y=X1×X2×…×Xn then since log Y = log X1 + log X2 + …+log Xn then the Central Limit Theorem tends to make log Y normal, which is what the lognormal distribution means.

The lognormal is a good distribution for things produced by multiplicative processes, such as hierarchical fragmentation or coagulation processes: the distribution of sizes of the pebbles on Brighton beach  is quite a good example. It also crops up quite often in the theory of turbulence.

I’ll mention one other thing  about this distribution, just because it’s fun. The lognormal distribution is an example of a distribution that’s not completely determined by knowledge of its moments. Most people assume that if you know all the moments of a distribution then that has to specify the distribution uniquely, but it ain’t necessarily so.

If you’re wondering why I mentioned citations, it’s because they’re playing an increasing role in attempts to measure the quality of research done in UK universities. Citations definitely contain some information, but interpreting them isn’t at all straightforward. Different disciplines have hugely different citation rates, for one thing. Should one count self-citations?. Also how do you apportion citations to multi-author papers? Suppose a paper with a thousand citations has 25 authors. Does each of them get the thousand citations, or should each get 1000/25? Or, put it another way, how does a single-author paper with 100 citations compare to a 50 author paper with 101?

Or perhaps a better metric would be the logarithm of the number of citations?

Lognormality Revisited

Posted in Biographical, Science Politics, The Universe and Stuff with tags , , , , , on January 14, 2015 by telescoper

I was looking up the reference for an old paper of mine on ADS yesterday and was surprised to find that it is continuing to attract citations. Thinking about the paper reminds me off the fun time I had in Copenhagen while it was written.   I was invited there in 1990 by Bernard Jones, who used to work at the Niels Bohr Institute.  I stayed there several weeks over the May/June period which is the best time of year  for Denmark; it’s sufficiently far North (about the same latitude as Aberdeen) that the summer days are very long, and when it’s light until almost midnight it’s very tempting to spend a lot of time out late at night..

As well as being great fun, that little visit also produced what has turned out to be  my most-cited paper. In fact the whole project was conceived, work done, written up and submitted in the space of a couple of months. I’ve never been very good at grabbing citations – I’m more likely to fall off bandwagons rather than jump onto them – but this little paper seems to keep getting citations. It hasn’t got that many by the standards of some papers, but it’s carried on being referred to for almost twenty years, which I’m quite proud of; you can see the citations-per-year statistics even seen to be have increased recently. The model we proposed turned out to be extremely useful in a range of situations, which I suppose accounts for the citation longevity:

lognormal

I don’t think this is my best paper, but it’s definitely the one I had most fun working on. I remember we had the idea of doing something with lognormal distributions over coffee one day,  and just a few weeks later the paper was  finished. In some ways it’s the most simple-minded paper I’ve ever written – and that’s up against some pretty stiff competition – but there you go.

Picture1

The lognormal seemed an interesting idea to explore because it applies to non-linear processes in much the same way as the normal distribution does to linear ones. What I mean is that if you have a quantity Y which is the sum of n independent effects, Y=X1+X2+…+Xn, then the distribution of Y tends to be normal by virtue of the Central Limit Theorem regardless of what the distribution of the Xi is  If, however, the process is multiplicative so  Y=X1×X2×…×Xn then since log Y = log X1 + log X2 + …+log Xn then the Central Limit Theorem tends to make log Y normal, which is what the lognormal distribution means.

The lognormal is a good distribution for things produced by multiplicative processes, such as hierarchical fragmentation or coagulation processes: the distribution of sizes of the pebbles on Brighton beach  is quite a good example. It also crops up quite often in the theory of turbulence.

I’ll mention one other thing  about this distribution, just because it’s fun. The lognormal distribution is an example of a distribution that’s not completely determined by knowledge of its moments. Most people assume that if you know all the moments of a distribution then that has to specify the distribution uniquely, but it ain’t necessarily so.

If you’re wondering why I mentioned citations, it’s because it looks like they’re going to play a big part in the Research Excellence Framework, yet another new bureaucratical exercise to attempt to measure the quality of research done in UK universities. Unfortunately, using citations isn’t straightforward. Different disciplines have hugely different citation rates, for one thing. Should one count self-citations?. Also how do you aportion citations to multi-author papers? Suppose a paper with a thousand citations has 25 authors. Does each of them get the thousand citations, or should each get 1000/25? Or, put it another way, how does a single-author paper with 100 citations compare to a 50 author paper with 101?

Or perhaps the REF panels should use the logarithm of the number of citations instead?

Ice Watch

Posted in Art, Politics with tags , , , , , , on October 30, 2014 by telescoper

I thought I’d share this video about an installation called Ice Watch, which involves one hundred tonnes of inland ice from Greenland meltinging on the Radhusplads, Copenhagen’s City Hall Square. With Ice Watch, Olafur Eliasson and Minik Rosing direct attention to the publication of the IPCC’s 5th Assessment Report on the Earth’s Climate. The ice now melted, which happened faster than expected owing to the unusually warm weather for this time of year…

 

 

 

Riverbed

Posted in Art with tags , , , , on August 20, 2014 by telescoper

Yesterday afternoon I skived off the last session of the workshop I’m attending and took the train to the small town of Humlebæk, which is about 35 north of Copenhagen and is the site of the Louisiana Museum of Modern Art. The purpose of my visit was to attend an invitation-only preview of a new installation by Olafur Eliasson called Riverbed. The invitation to this came relatively recently and it was only the coincidence of my being here at this workshop that made it possible for me to attend.

As it turned out, I arrived quite early and the weather was fine, so I took the chance to wander around the sculpture park before the main event. There are many fine works there. This, for example, is by Henry Moore:

SAMSUNG DIGITAL CAMERA

This one is by Henri Laurens

SAMSUNG DIGITAL CAMERA

And so to Riverbed. This is a large work featuring boulders and gravel, brought all the way from Iceland, which have been used to recreate a section of the landscape of Olafur’s native land. The distinctive colouring and granularity of the raw material produces terrain of a texture that must look very alien to anyone who has never been to Iceland. The installation is contained within a space which is contained within and divided by stark white-painted walls, with rectangular gaps where necessary to let the water through from room to room. These boundaries, with their geometrically precise edges, affect the experience of the naturalistic landscape in a very interesting way. The Riverbed itself may look “natural” but the structures surrounding it constantly remind you that it isn’t. Viewers are permitted to wander through the piece wherever they like and interact however they please, sitting down on a boulder, paddling in the stream or even just watching the other people (which is mainly what I did). I don’t know what’s more interesting, the work itself or the way people behave when inside it!

Here are some pictures I took, just to give you a flavour:

SAMSUNG DIGITAL CAMERA
SAMSUNG DIGITAL CAMERASAMSUNG DIGITAL CAMERASAMSUNG DIGITAL CAMERA
SAMSUNG DIGITAL CAMERA

Anyway, after that we adjourned for a drinks reception and a splendid dinner in the Boat House, which part of the Louisiana complex. Being neither an artist nor an art critic I felt a bit of an outsider, but I did get the chance to chat to quite a few interesting people including, by sheer coincidence, a recent graduate of the University of Sussex. The Boat House looks out towards the island of Hven, home of the observatory of Tycho Brahe, so naturally I took the opportunity to drink a toast to his memory:

Bvat-UeCAAA9u4p

After that I had to return to Copenhagen to write my talk, as I was on first this morning at 9.30. This afternoon we have a bit of a break before the conference excursion and dinner this evening. The excursion happens to be to Louisiana Museum of Modern Art (although we’re all going by bus this time); dinner is in the cafeteria rather than the Boat House, though..

On Problems

Posted in Poetry, The Universe and Stuff with tags , , , on August 19, 2014 by telescoper

Since I’m in Denmark I thought I’d put up one of the wonderfully witty little poems written by Danish mathematician Piet Hein. He called each of these verses a “grook” (or actually, in Danish, the word is gruk) and he wrote thousands of them over his long life. I’ve posted one of these before but this one is even shorter but it makes a deep point, the danger of becoming be trapped by your own assumptions. I won’t comment on the relevance of this to the cosmology workshop I’m attending…

Our choicest plans
have fallen through
our airiest castles
tumbled over
because of lines
we neatly drew
and later neatly
stumbled over.

by Piet Hein (1905-1996).

A Psychological Tip

Posted in Biographical, Poetry with tags , , , , on November 16, 2012 by telescoper

So here I am, then, in Copenhagen. Yesterday evening, as far as I’m concerned, at least, my wavefunction collapsed along with the rest of me into a definite location. Ibsen’s Hotel, in fact. I had a pleasantly uneventful journey to Heathrow by train. The plane thence arrived in Copenhagen twenty minutes ahead of time, and then I had the chance to marvel at wonderful Copenhagen’s wonderfully efficient public transport in the form of the Metro that took me to about 100 metres from my hotel. All very relaxed and stress-free.

This morning I got up bright and early, determined to avoid the queues at breakfast, but was inevitably foiled by dozens of uber-efficient Germans who were already there at 7am when it opened. Fortunately I managed to find a quiet place in the corner to drink my coffee while they basked in their own smugness and barked orders at the waitresses.

Anyway, it’s still pretty dark outside so I thought I’d post something before walking to the Niels Bohr Institute for the day’s business. Since I’m in Denmark I thought I’d put up one of the wonderfully witty little poems written by Danish mathematician Piet Hein. He called each of these verses a “grook” (or actually, in Danish, the word is gruk) and he wrote thousands of them over his long life. Many, like this one, are utterly brilliant.

Whenever you’re called on to make up your mind,
and you’re hampered by not having any,
the best way to solve the dilemma, you’ll find,
is simply by spinning a penny.

No – not so that chance shall decide the affair
while you’re passively standing there moping;
but the moment the penny is up in the air,
you suddenly know what you’re hoping.

by Piet Hein (1905-1996).