Archive for November, 2023

The Atwood Machine

Posted in Barcelona, Cute Problems, Education, Maynooth with tags , , , on November 14, 2023 by telescoper

In the foyer of the Physics Department at the University of Barcelona you will find, as well as a fine refracting telescope, an example of the Atwood Machine. For some years before my current sabbatical I have been teaching Newtonian Mechanics to first-year students in Maynooth and used this as a simple worked example. I have to admit I’ve never seen an actual Atwood machine before, and what I’ve done in lectures is the simplified form on the right rather than the actual machine on the left.

The illustration on the right depicts the essential elements, but you can can see that the actual machine has a ruler which, together with a timing device, can be used to determine the acceleration of the suspended mass and how that varies with the other mass. You can work this out quite easily in the simplest case of a frictionless pulley by letting the tension in the string (which is light and inextensible) be T (say) and then eliminating it from the equations of motion for the two masses. I leave the rest as an exercise for the reader. A more interesting problem, for the advanced student, is when you have to take into account the rotational motion of the pulley wheel…

In fernem Land – Leo Slezak

Posted in Literature, Opera with tags , , , on November 13, 2023 by telescoper

The book I’m currently reading in the evenings contains a scene in which members of a family listen to a gramophone record of Leo Slezak singing In fernem Land from the opera Lohengrin by Richard Wagner. Being the anorak I am I searched around the many recordings made by Slezak and I reckon it must be this one. The sound quality isn’t great, but then it was recorded way back in 1907 and it always amazes me that you can hear anything at all from over a century ago. It’s an interesting performance because it’s taken at quite a slow tempo and Slezak’s voice sounds to my ears more like a lyric tenor than the Heldentenor one normally associates with Wagnerian roles. Anyway, it’s well worth a listen as there’s much to appreciate and it’s very different from modern renditions.

Now that you’ve heard the record, I wonder if you can guess the book I’m reading? Answers through the comments box please!

Astrophysics & Cosmology Masterclass at Maynooth

Posted in Maynooth, The Universe and Stuff with tags , , , on November 13, 2023 by telescoper

Both my regular readers may remember that for the last couple of years at this time of year there has been an Astrophysics & Cosmology Masterclass at Maynooth; see here and here for the previous incarnations. Not being in Maynooth I almost forgot about this year’s Masterclass, which has a different line-up with Dr Paddy Kavanagh adding some observational content alongside Dr John Regan.

This event is online only from 10am to 12pm on Friday 17th November 2023 and you can find out more details and register here.

Demonstration!

Posted in Barcelona, Politics with tags , on November 12, 2023 by telescoper
A demonstration went past my apartment in Barcelona today

The march was a right-wing protest against a proposed amnesty for Catalan separatists. Judging by the time it took to pass my apartment, I’d say there were a few thousand people on it and it passed off peacefully as far as I could tell.

P.S. it’s warmer again today, about 21°C.

Three New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , , , , , on November 12, 2023 by telescoper

It’s been a busy week generally, and specifically at the  Open Journal of Astrophysics. In fact, this week we have published three papers, which I didn’t have time to post here at the time we published them but now present to you. These take the count in Volume 6 (2023) up to 44 and the total published by OJAp up to 109. With many more in the pipeline we’re still on for 50 by the end of the year.

In chronological order, the three papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so. All three of these papers are in the folder Cosmology and Nongalactic Astrophysics.

First one up is “On the degeneracies between baryons, massive neutrinos and f(R) gravity in Stage IV cosmic shear analyses” by Alessio Spurio Mancini (Mullard Space Sciences Laboratory, University College London, UK) and Benjamin Bose (Royal Observatory Edinburgh, UK). This presents a fast nonlinear matter power spectrum emulator for f(R) gravity with massive neutrinos, coupled with a baryon feedback emulator forecasts for a cosmic shear experiment with typical Stage IV specifications. This paper was published on 6th November 2023.

Here is a screen grab of the overlay, which includes the abstract:

You can find the officially accepted version of the paper on the arXiv here.

The second paper to announce is “” by Marika Asgari (Hull, UK), Alexander Mead (Bochum, Germany) and Catherine Heymans (Edinburgh, UK).  This presents a thorough discussion of the popular halo model for cosmological structure with applications, accompanied by the release of a software suite called pyhalomodel (which you can download here). The paper was also published on 7th November 2023 and you can see the overlay here:

 

 

The accepted version of this paper can be found on the arXiv here.

The last paper of this batch is  entitled “Dissecting the Thermal SZ Power Spectrum by Halo Mass and Redshift in SPT-SZ Data and Simulations” and the authors are: by Josemanuel Hernandez (Chicago), Lindsey Bleem (Chicago) , Thomas Crawford (Chicago), Nicholas Huang (Berkeley), Yuuki Omori (Chicago), Srinivasan Raghunathan (NCSA, Urbana) & Christian Reichardt (Melbourne). This paper, a study of the mass and redshift dependence of the thermal Sunyaev-Zeldovich effect in South Pole Telescope data and a comparison thereof with theoretical calculations, was published on 9th November 2023.

Here is the overlay:

 

 

You can find the full text for this one on the arXiv here.

The Geometry of Barcelona

Posted in Architecture, Barcelona, Biographical with tags , , , on November 11, 2023 by telescoper

Having a lazy Saturday morning before going out to do some shopping I thought I’d do a silly post about a few random things that struck me about Barcelona. As I have mentioned before, I am resident in area of the city known as Eixample. Most of this zone was built in the 19th and early 20th centuries and its layout was very carefully planned, as you can see from this aerial picture:

I initially thought that the name Eixample related to the exemplary nature of the area, but in fact it means something like “extension”; the “ample” has a similar sense to the English “ample”.

To orient yourself, the Sagrada Familia is towards the bottom left. In the middle of the top you can see Plaza de Cataluña. Near that there is a junction of two wide tree-lined roads; the one running from SW to NE (relative to the picture) is the Gran Via de les Corts Catalanes (which is actually 8 miles long altogether); the one perpendicular to the Gran Via is Passeig de Gràcia. My apartment is a few blocks SW of this junction. You can see to the top left how the pattern of streets changes, as you approach the older part of town, the harbour and the sea.

Anyway, the street plan of Eixample is generally rectangular but if you look carefully you will note that the footprint of the blocks is not quite rectangular; the corners are shaved off to make them octagonal. This is a very nice feature because it means that visibility around the corners is very good and there is a lot of pavement space near the entrances. Many of these buildings now have a bar or restaurant on the ground floor and there is plenty of room for seated areas. Above all, combined with the wide boulevard-type roads, this gives this densely-populated area a much less claustrophobic feel than other cities with rectilinear street layouts, such as New York. Note also that each block encloses a communal space which contains private gardens, play areas, etc, though some appear to have been built over especially.

The road passing diagonally through the picture is called, um, Avenida Diagonal. It plays a rather similar role to Broadway in Manhattan.

As well as A. Diagonal, Barcelona has A. Parallel. In Spanish this is called Avenida del Paralelo; in Catalan it is Avinguda del Paral·lel. The signs on the Metro are all in Catalan so the one on the Metro station on this road says Paral·lel. I was puzzled for some time by the dot between the two letters “l” but it’s quite straightforward. In Catalan (and Spanish) the diagraph “ll” (which used to be listed a separate letter of the alphabet) is pronounced like the English letter “y”, e.g. in paella and amontillado. The dot in Paral·lel is there to indicate that it’s not the letter “ll” in the middle but two letters “l” next to each other and is pronounced para-lel rather than para-yel. The Spanish word “Paralelo” avoids this problem by simply dropping an “l”.

Now it’s nearly time to get ready to go out. The temperature here has fallen noticeably over the last few weeks. It was around 15° last week with a stiff westerly breeze. That was enough to persuade some of the locals to put on their winter coats, scarves and woolly hats although to me it still felt warm when in the sun. Today is about 19° C. The cooler weather makes it far less sweaty and much more pleasant to walk about. It’s also noticeable that there are fewer tourists around, which has two advantages: (a) one’s mean free path between people is longer and (b) it’s much easier to get into places of interest. I hope to ramp up my visits to museums and art galleries between now and Christmas.

University Management Salaries

Posted in Barcelona, Maynooth on November 10, 2023 by telescoper

I have long believed that the hierarchical management structure of modern universities, especially in the UK and Ireland, is wrong and damaging. One aspect of this is the unjustifiably high salaries paid to the people at the very top. I can see no good reason for any university President, Vice-Chancellor, Rector, or whatever else their name is, to receive a salary above the standard scale for professors.
The problem with the high salaries these people get nowadays is not only the expense (which is considerable) but the fact that it sends out the message that they are much more important than they actually are and that the people who actually carry out the core work of a third-level institution – the academics and related staff – are mere subordinates. Moving into management should really be regarded as a sideways move, not an advance.

Incidentally, I would also argue that nobody should be employed in a senior management role in a university who neither teaches nor does research. How can someone who is not active in these areas know the reality of the situation facing staff who are?

Anyway, these thoughts came back into my mind after an informal chat with some people here in the ICC. It turns out that the salary of the Rector of the University of Barcelona, Joan Guàrdia Olmos, is in the public domain. It is made up from various components but the grand total is €124,619.58 (2022 figure). That would be well below the bottom level of the Professor A scale in Maynooth. Contrast that with the President of Maynooth University, Eeva Leinonen, who is paid a salary of €208,509, which is considerably higher than the top of the Professor A scale at Maynooth. Professor Leinonen also receives €13,500 benefit in kind for rent-free accommodation.

You can contrast these salaries with the respective institutions, both of which are public universities. The University of Barcelona has around 63,000 students and about 5000 staff; it is widely regarded as the top University in Spain (pop. 47 million). Maynooth University has about 15,000 students and about 900 staff; it is not regarded by anybody as the top University in Ireland (pop. 5 million).
I think you get the point.

Northern Lights over Maynooth

Posted in Maynooth, The Universe and Stuff with tags , , on November 9, 2023 by telescoper
It seems the Northern Lights have been seen over Maynooth! 

(picture by @_fidel_astro on Instagram)

Yet another problem with Journal Impact Factors

Posted in Open Access with tags , , , on November 9, 2023 by telescoper

I was at a meeting this morning in which the vexed issue of the journal Impact Factor (IF) came up. That reminded me of something that struck me when I was checking the NASA/ADS entry for a paper recently published by the Open Journal of Astrophysics, and I thought it would be worth sharing it here. First of all, here’s a handy slide showing how the Impact Factor (IF) for a journal is calculated for a given year:

It’s a fairly straightforward piece of information to calculate, which is one of its few virtues.

Now consider this paper we recently published in the Open Journal of Astrophysics:

As of today, according to the wonderful NASA/ADS system, this paper has 36 citations. That’s no bad considering that it was published less than a month ago. It’s obviously already quite an impactful paper. The problem is that if you look at the recipe given above you will see that none of those 36 citations – nor any more that this paper receives this year – will ever be included in the calculation of the Impact Factor for the Open Journal of Astrophysics. Only citations to this paper garnered in 2024 and 2025 will count to the impact factors (for 2025 and 2026 respectively). There’s every reason to think this paper will get plenty of citations over the next two years, but I think this demonstrates another bit of silliness to add to the already long list of silly things about the IF as a measure of citation impact.

My view of citation numbers is that they do contain some (limited) information about an article’s impact, but if you want to use them you should just use the citations for the article itself, not a peculiar and arbitrarily-constructed proxy like the IF. It is so easy to get article-level citation data that there is simply no need to use a journal-level metric for anything at all.

Euclid, the Perseus Cluster, and Beyond!

Posted in Euclid, The Universe and Stuff with tags , , , on November 8, 2023 by telescoper

I see that the Euclid Early Release Observation of the Perseus Cluster is today’s Astronomy Picture of the Day:

The Perseus Cluster seen by Euclid

The Perseus Cluster (Abell 426) – a dense concentration of over a thousand galaxies with a total mass of about 1.2 × 1015 M – is impressive in its own right, especially because the picture was taken in a single exposure, but the staggering thing about this image is that it contains hundreds of thousands of galaxies. In other words there are as many galaxies in this picture as there are words in a book. Most of these galaxies are in the background, not associated with the cluster, and many of them extremely distant. With so many objects in one field, you can perhaps see how much data we will get from the entire survey, which will last more than 6 years. It is these distant sources – billions of them – that Euclid will survey to glean information about the expansion history of the Universe.

P.S. Yesterday’s press conference resulted in a lot of media attention worldwide, even some in Ireland. There is a piece on the RTÉ website, for example, and another on Silicon Republic (which includes a quote from yours truly).