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On Fourier Series

Posted in mathematics, Maynooth, The Universe and Stuff with tags , , , , , , on November 30, 2021 by telescoper

So here we are, in the antepenultimate week of the Autumn Semester, and once again I find myself limbering up for the “and” bit of my second-year module on Vector Calculus and Fourier Series, i.e. Fourier Series.

As I have observed periodically, I don’t like to present the two topics mentioned in the title of this module as completely disconnected, so I linked them in a lecture in which I used the divergence theorem of vector calculus to derive the heat equation, the solution of which led Joseph Fourier to devise his series in Mémoire sur la propagation de la chaleur dans les corps solides (1807), a truly remarkable work for its time that inspired so many subsequent developments.

 

Anyway I was looking for nice demonstrations of Fourier series to help my class get to grips with them when I remembered this little video recommended to me some time ago by esteemed Professor George Ellis. It’s a nice illustration of the principles of Fourier series, by which any periodic function can be decomposed into a series of sine and cosine functions.

This reminds me of a point I’ve made a few times in popular talks about astronomy. It’s a common view that Kepler’s laws of planetary motion according to which which the planets move in elliptical motion around the Sun, is a completely different formulation from the previous Ptolemaic system which involved epicycles and deferents and which is generally held to have been much more complicated.

The video demonstrates however that epicycles and deferents can be viewed as the elements used in the construction of a Fourier series. Since elliptical orbits are periodic, it is perfectly valid to present them in the form a Fourier series. Therefore, in a sense, there’s nothing so very wrong with epicycles. I admit, however, that a closed-form expression for such an orbit is considerably more compact and elegant than a Fourier representation, and also encapsulates a deeper level of physical understanding.

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Great News for Astrophysics & Cosmology at Maynooth!

Posted in Education, Maynooth, Science Politics, The Universe and Stuff with tags , , , on November 29, 2021 by telescoper

I couldn’t resist a quick post in reaction to the announcement by the Irish Government of ten new senior professorial positions under the Strategic Academic Leadership Initiative (SALI). I blogged about this scheme here. Among the positions just announced is a new Chair in Observational Astrophysics or Cosmology at Maynooth University. You can find Maynooth University’s official response to the announcement here.

The pandemic has played havoc with my sense of the passage of time so I had to check my documents folder to see when we completed the application. It turns out to have been January this year; the deadline was 29th January 2021. It has taken much longer than expected to for the outcome of this, the second, round to emerge but I suppose it’s better late than never!

The key rationale for these SALI positions is clear from the statement from Simon Harris, the Minister responsible for Third Level education in Ireland:

“Championing equality and diversity is one of the key goals of my department. The Senior Academic Leadership Initiative (SALI) is an important initiative aimed at advancing gender equality and the representation of women at the highest levels in our higher education institutions.

We have a particular problem with gender balance among the staff in Physics in Maynooth, especially un Theoretical Physics where all the permanent staff are male, and the lack of role models has a clear effect on our ability to encourage more female students to study with us.

The wider strategic case for this Chair revolves around broader developments in the area of astrophysics and cosmology at Maynooth. Currently there are two groups active in research in these areas, one in the Department of Experimental Physics (which is largely focussed on astronomical instrumentation) and the other, in the Department of Theoretical Physics, which is theoretical and computational. We want to promote closer collaboration between these research strands. The idea with the new position is that the holder will nucleate and lead a new research programme in the area between these existing groups as well as getting involved in outreach and public engagement.

The next step will be to launch a recruitment campaign, and more details will be available when the position is formally advertised. Let me just say for now that we intend the position to appeal not only to people who have their own observational programmes (e.g. using facilities provided by ESO, which Ireland recently joined) but also working on data from space missions, multi-messenger astrophysics, gravitational waves, and so on.

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A Pembrokeshire Dangler

Posted in Biographical, Maynooth, The Universe and Stuff on November 28, 2021 by telescoper

I checked the weather app on my phone last night and noticed the unmistakable cloud formation over the Irish Sea known as a Pembrokshire Dangler:

The Dangler is the strip of rain  over the Irish Sea extending North from the Pembrokeshire coast in Wales. I knew I had mentioned this phenomenon before on this blog and when I check it turns out to have been almost exactly four years ago. That’s not very surprising as winter is definitely the season for dangling. There has been a northerly airflow over Ireland for a few days now, which is why it has been so cold here, though in relatively sheltered Maynooth we have been spared the worst of the effects of Storm Arwen.

The situation required for the formation of a Pembrokeshire Dangler (which quite often involves snow rather than rain) is a cold northerly airflow down into the Irish Sea from the Arctic. This combines with slightly warmer air in the form of land breezes from the Irish coast to the North West and the Scottish coast to the North East, funneling the airflow into a narrow channel over the Irish Sea in which convection cells form, leading to precipitation. The configuration is quite stable as long as the dominant northerly airflow continues so although the strip of cloud tends to persist for some time once it has formed.

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A Free Online Course in Cosmology from SISSA

Posted in Education, The Universe and Stuff with tags , , , , on November 25, 2021 by telescoper

The nice people at the Scuola Internazionale Superiore di Studi Avanzati (known to its friends as SISSA for short) have made available a free online course in cosmology. You can get all of it on Youtube.

The course comprises 16 professionally edited video-lectures delivered by lecturers of the SISSA Astrophysical and Cosmology and Astroparticle PhD Programs and some of their collaborators. I know some of the participants personally, including Paulo Salucci (who introduces the course though I haven’t met him in person for ages so it was nice to see him on camera.

Cosmology is a big subject, of course, and a short-ish course can’t cover everything so there is an emphasis on the research topics covered by SISSA scientists. I haven’t watched all the videos but those I have seen are pretty good. There are actually 17 videos in the playlist below but that includes a very short prelude to introduce the series. The others are between about 25 and 45 minutes in length so you probably don’t want to watch them all in one sitting!

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Clusters and Superclusters of Galaxies 1991

Posted in Biographical, The Universe and Stuff with tags , , on November 23, 2021 by telescoper

As part of an occasional series of blasts from the past down memory lane of days gone by I present this, which was taken in Cambridge in July 1991 – 30 years ago!!! – at the NATO ASI Clusters and Superclusters of Galaxies:

Picture Credit: Alberto Fernandez Soto

There are no prices for putting names to faces because the names are all along the bottom but it’s still fun to try doing it without looking at the answers!

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The Curious Incident of the JWST and the Clamp Band…

Posted in The Universe and Stuff with tags , , , on November 23, 2021 by telescoper

 

Just a quick newsflash to pass on the news that the launch of the James Webb Space Telescope has been pushed back until at least 22nd December 2021 owing to an “incident” that occurred during preparations for its launch.

It seems the sudden release of a “clamp band” – or is it band clamp? – caused unwanted vibrations through the observatory and it now has to be thoroughly checked before it can be declared safe for launch.

This is not the news anyone wanted to hear, but the previous launch date was 18th December, so hopefully the few days’ delay won’t cause too much difficulty.

I was going say that for JWST to work there has to be something incident on its mirror, but on reflection I decided that wasn’t a very good joke.

 

 

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Astrophysics & Cosmology Masterclass – The Video!

Posted in Education, Maynooth, The Universe and Stuff, YouTube with tags , , , on November 15, 2021 by telescoper

As promised here is the video recording of the Astrophysics & Cosmology Masterclass we held by Zoom last Friday.

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That Was The Masterclass That Was

Posted in Education, Maynooth, The Universe and Stuff with tags , , , on November 12, 2021 by telescoper

This morning we did the Astrophysics and Cosmology Masterclass advertised here. I think it went quite well. Apparently we had over sixty schools registered – at least one in every County – about a 1,000 schoolkids altogether. Certainly there were lots and lots of questions, which is a good sign!

Here is a screen grab of part of the event. I didn’t realize my camera was a bit wonky!

In case anyone is interested here are the slides I used for my part of the talk:

I’ll post a recording of the whole event when it becomes available. Here is the recording of the workshop:

I had to leave before the end to go to a vector calculus lecture that was interrupted by the arrival of the Power Rangers, but that’s a different story…

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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , on November 5, 2021 by telescoper

Time to announce yet another publication in the Open Journal of Astrophysics. This one is the 14th paper in Volume 4 (2021) and the 45th in all.

The latest publication is entitled  Ultra Fast Astronomy: Optimized Detection of Multimessenger Transients, and is in the section marked Instrumentation and Methods for Astrophysics.  The authors are Mikhail Denissenya of Nazarbayev University (Kazakhstan) and Eric V. Linder of the University of California at Berkeley (USA).

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

You can find the paper on the Open Journal of Astrophysics site here and can also read it directly on the arXiv here.

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The 2020 Decadal Survey

Posted in Science Politics, The Universe and Stuff with tags , , on November 4, 2021 by telescoper

Delayed by a year, the 2020 US Decadal Survey of Astronomy -full title Pathways to Discovery in Astronomy and Astrophysics for the 2020s – is now out.

It’s a hefty document of more than 600 pages so I haven’t had time to do anything but skim it. The top priority for NASA for the next decade seems to be a 6-m class space telescope capable of imaging Earth-like worlds orbiting sun-like stars, something that can’t be done with much larger telescopes from the ground though the plan does involve bringing very large ground-based telescopes (the Giant Magellan Telescope in Chile and the Thirty Metre Telescope in Hawaii) into service more quickly than currently scheduled. Any new space telescope won’t be built and launched on the timescale of course: it probably won’t fly until the 2040s by which time I’ll probably be retired,

I also noticed in the section on the Cosmic Microwave Background we have

Recommendation: The National Science Foundation and the Department of Energy should jointly pursue the design and implementation of the next generation ground-based cosmic microwave background experiment (CMB-S4).The panel suggests that third-generation CMB experiments aligned with CMB-S4―specifically, the SPO (South Pole Observatory) and the “nominal” version of the SO (Simons Observatory)―be high priorities for federal support.

The clarifications in parentheses are my additions.

The shopping list is a lot longer than these items however. There is plenty of discussion in the media already. See, for example, here. I may comment further if time allows.

UPDATE: there is a very user-friendly interactive overview of the survey here.

This is of course an American survey but Astronomy is a truly international enterprise so astronomers all round the globe will be studying it and trying to work out its implications for their own research environment.

And of course there’s a box below for comments from you!

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