Category Archives: Astronomy

A conference in Paris

This week I’m in Paris, attending a conference in memory of the outstanding British astronomer and theoretician Arthur Stanley Eddington. The conference, which is taking place at the Observatoire de Paris, is designed to celebrate the centenary of Eddington’s famous measurement of the bending of distant starlight by the sun.  a key experiment that offered important early support for Einstein’s general theory of relativity. However, there are talks on lots of different topics, from Eddington’s philosophy of science to his work on the physics of stars, from his work in cosmology to his search for a unified field theory. The conference website and programme is here.


The view from my hotel in Denfert-Rochereau

All of the sessions of the conference were excellent, but today was a particular treat with four outstanding talks on the 1919 expedition. In ‘Eddington, Dyson and the Eclipse of 1919’, Daniel Kennefick of the University of Arkansas gave a superb overview of his recent book on the subject. In ‘The 1919 May 29 Eclipse: On Accuracy and Precision’, David Valls-Gabaud of the Observatoire de Paris gave a forensic analysis of Eddington’s calculations. In ‘The 1919 Eclipse; Were the Results Robust?’ Gerry Gilmore of the University of Cambridge described how recent reconstructions of the expedition measurements gave confidence in the results; and in ‘Chasing Mare’s Nests ; Eddington and the Early Reception of General Relativity among Astronomers’, Jeffrey Crelinsten of the University of Toronto summarized the doubts expressed by major American astronomical groups in the early 1920s, as described in his excellent book.

Image result for no shadow of a doubt by daniel kennefick        Image result for einstein's jury

I won’t describe the other sessions, but just note a few things that made this conference the sort of meeting I like best. All speakers were allocated the same speaking time (30 mins including questions); most speakers were familiar with each other’s work; many speakers spoke on the same topic, giving different perspectives; there was plenty of time for further questions and comments at the end of each day. So a superb conference organised by Florian Laguens of the IPC and David Valls-Gabaud of the Observatoire de Paris.


On the way to the conference

In my own case, I gave a talk on Eddington’s role in the discovery of the expanding universe. I have long been puzzled by the fact that Eddington, an outstanding astronomer and strong proponent of the general theory of relativity, paid no attention when his brilliant former student Georges Lemaître suggested that a universe of expanding universe could be derived from general relativity, a phenomenon that could account for the redshifts of the spiral nebulae, the biggest astronomical puzzle of the age. After considering some standard explanations (Lemaître’s status as an early-career researcher, the journal he chose to publish in and the language of the paper), I added two considerations of my own: (i) the theoretical analysis in Lemaître’s 1927 paper would have been very demanding for a 1927 reader and (ii) the astronomical data that Lemaître relied upon were quite preliminary (Lemaître’s calculation of a redshift/distance coefficient for the nebulae relied upon astronomical distances from Hubble that were established using the method of apparent magnitude, a method that was much less reliable than Hubble’s later observations using the method of Cepheid variables).


Making my points at the Eddington Conference

It’s an interesting puzzle because it is thought that Lemaitre sent a copy of his paper to Eddington in 1927 – however I finished by admitting that there is a distinct possibility that Eddington simply didn’t take the time to read his former student’s paper. Sometimes the most boring explanation is the right one! The slides for my talk can be found here.

All in all, a superb conference.


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Filed under Astronomy, Cosmology (general), History and philosophy of science

The joys of mid term

Thank God for mid-term, or ‘reading week’ as it is known in some colleges. Time was I would have spent the week on the ski slopes, but these days I see the mid-term break as a precious opportunity to catch up – a nice relaxed week in which I can concentrate on correcting assessments, preparing teaching notes and setting end-of-semester exams. There is a lot of satisfaction in getting on top of things, if only temporarily!

Then there’s the research. To top the week off nicely, I heard this morning that my proposal to give a talk at the forthcoming Authur Eddington conference  in Paris has been accepted; this is great news as the conference will mark the centenary of Eddington’s measurement of the bending of starlight by the sun, an experiment that provided key evidence in support Einstein’s general theory of relativity. To this day, some historians question the accuracy of Eddington’s result, while most physicists believe his findings were justified, so it should make for an interesting conference .



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Einstein’s unfinished symphony in the media

Our recent discovery of an unpublished model of the cosmos by Albert Einstein (see last post or here for a preprint of our paper) is receiving a lot of media attention, it’s very humbling. First off the mark was Davide Castelvecchi with a very nice article in Nature. Davide’s article was quickly reproduced in various outlets, from Scientific American here to the Huffington Post here. Trawling over the internet, I see newspaper and magazine articles describing our discovery in a dozen languages. It’s nice to see historical material receiving this sort of attention, I guess everyone loves an Einstein story.


I’m also intrigued that it was the traditional media that picked up the story – with the exception of Peter Woit, no-one in the blogosphere seemed to notice our preprint or even a blogpost I wrote describing our paper. Perhaps we bloggers need the imprimateur of respected print journals more than we care to admit!

I notice one slightly misleading point in the electronic version of the Nature article is getting repeated everywhere. It’s probably not quite correct to frame Einstein’s attempt at a steady-state model of the cosmos in terms of a resistance to ‘big bang’ theories; there is no reference to the problem of origins in Einstein’s manuscript. Indeed, one of the most interesting aspects of the manuscript is that it appears to have been written in early 1931, at a time when the first tentative astronomical evidence for an expanding universe was emerging but the issue of an explosive beginning for the cosmos had yet to come into focus (e.g. the great debate between Eddington and Lemaitre later in 1931). It’s interesting that the initial mention in Nature of resistance to ‘big bang’ theories  is repeated in almost all other outlets, one can’t help wondering how many science journalists read our abstract. An honorable exception here is John Farrell at Forbes Magazine. John certainly noticed the discrepancy and no wonder – John has written an excellent book on Lemaitre.


All in all, it’s been a lot of fun so far. I’m getting quite a few emails from distinguished colleagues pointing out that Einstein’s model is trivial because it didn’t work, which is of course true. However, our view is that what Einstein is trying to do is very interesting from a philosophical point of view  – and what is even more interesting is that he apparently abandoned the project when he realised that a consistent steady-state model would require an amendment to the field equations. In short, it seems the Great Master conducted an internal debate between steady-state and evolving models of the cosmos decades before the rest of the community…


There is a very nice video describing our discovery here.


Filed under Astronomy, Cosmology (general), History and philosophy of science

VM Slipher and the expanding universe

In an earlier post, I mentioned an upcoming  conference in Arizona to celebrate the pioneering work of the American astronomer Vesto Slipher. As mentioned previously, 2012 marks the centenary of Slipher’s observation that light from the Andromeda nebula was Doppler shifted, a finding he interpreted as evidence of a radial velocity for the nebula. By 1917, he had established that the light from many of the distant nebulae is redshifted, i.e. shifted to lower frequency than normal. This was the first  indication that the most distant objects in the sky are moving away at significant speed, and it was an important step on the way to the discovery of the expanding universe.

Vesto Melvin Slipher (1875-1969)

The conference turned out to be very informative and enjoyable, with lots of interesting presentations from astronomers, historians and science writers. It’s hard to pick out particular talks from such a great lineup, but three highlights for me were Einstein, Eddington and the 1919 Eclipse Expedition by Peter Coles, Georges Lemaitre: A Personal Profile by John Farrell and Slipher’s redshifts as support for de Sitter’s universe? by Harry Nussbaumer. The latter compared the importance of the contributions of Slipher, Hubble, Einstein, De Sitter, Friedmann and Lemaitre (to mention but a few) and was a focal point for the conference. My own talk ‘Who discovered the expanding universe? – an open bus tour’ was quite similar to Harry’s , with some philosophy of science thrown in, while Micheal Way’s talk Dismantling Hubble’s Legacy? also touched on similar ground.  However, there was little danger of overlap since viewpoints and conclusions drawn from the material varied quite widely! You can see the conference program here.

A slide from Peter Cole’s talk on the Eddington eclipse experiment

A slide from John Farrell’s talk showing a postcard from Lemaitre to Slipher, announcing the former’s visit to the Lowell observatory

Harr Nussbaumer, author of ‘The Discovery of the Expanding Universe’,  in action

Front slide of my own presentation

The best aspect of the conference was the question and answer session after each talk. There was quite a divergence of opinion amongst the delegates concerning the relative importance of the various scientists in the story, which made for great discussions (though I suspect that much of the argument arises from differing views concerning the role of the theoretician vs the role of the experimentalist). You can see a list of speakers and abstracts for the talks here and the slides for my own talk are here.

There was plenty of material here for the relativist; indeed, quite a bit of discussion concerned the relative contributions of Friedmann and Lemaitre (told you it was a good conference). In particular, the Israeli mathematician Ari Belenkiy gave a defence of Friedmann’s work in his talk Alexander Friedmann and the Origin of Modern Cosmology, pointing out that the common assertion that Friedmann took no interest in practical matters is simply untrue, given his work in meteorology, and that the relevant astronomical data was not widely available to Europeans at the time. I must admit I share Ari’s view to some extent; I’m always somewhat in awe of a theoretician who describes all possible solutions to a problem (in this case the universe), as opposed to one solution that seems to chime with experiments of the day.

Title slide of Ari’s talk on Friedmann

The conference also included a trip to the Lowell observatory, including a view of the spectrograph used by Slipher for his groundbreaking measurements and a peep through the famous 24-inch Clark telescope which remains in operation to this day. We were also treated to a few scenes from Dava Sobel’s upcoming play based on her book on Copernicus, read by Dava herself and the eminent Harvard science historian Owen Gingerich.

The famous spectograph, perfectly preserved

Slipher’s telescope remains in use today

Dava Sobel and Professor Owen Gingerich reading from her new play at the Lowell observatory

All in all, a superb conference, definitely worth the long trip (Dublin-Chicago-Phoenix-Flagstaff). Earlier in the week, I gave a longer version of my talk at the BEYOND centre at Arizona State University in Phoenix; I was afraid some of the theoreticians in Larry Krauss’s  group might find it a bit equation-free, but they seemed to enjoy it. Larry and Paul Davies have a fantastic operation going on at the BEYOND centre, but I have to say the ambience and surroundings  at Flagstaff are probably more suitable for a European – much nicer weather!

Many thanks to Ari Belenkiy for the photographs. You can find more descriptions of the conference on John Farrell’s Forbes blog, and on Peter Coles’s  In The Dark blog.


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September conference: origins of the expanding universe

A conference next month will celebrate the pioneering work of the American astronomer Vesto Slipher. On September 13-15th, the Lowell Observatory in Flagstaff, Arizona, will host the conference The Origins of the Expanding Universe to commemmorate the hundredth anniversary of Slipher’s measurements of the motion of the distant nebulae; see here for the conference website.

As readers of this blog will know, Slipher observed that the light from many of the distant nebulae was redshifted, i.e. shifted to lower frequency than normal. This was the first  indication that the distant nebulae are moving away at significant speed and it was an important hint that some nebulae are in fact distinct galaxies far beyond our own Milky Way (see cosmology 101 section). A few years later, Edwin Hubble combined Slipher’s redshift results with his own measurements of distance to establish that there is a linear relation between the distance to a galaxy and its rate of recession; the relation became known as Hubble’s law although it probably should be called the Hubble/Slipher law.

The Hubble/Slipher discovery of the recession of the galaxies  was a key step along the road to the discovery of the expanding universe, but the two are not quite the same thing; for the latter, one needs to situate the phenomenon in the context of the general theory of relativity (according to relativity, the galaxies appear to be moving away from one another because space is expanding). The Belgian physicist Georges Lemaitre was the first to make the connection between the relativistic universe and the observed recession of the galaxies, although his contribution is often overlooked. A major thrust of the conference is to explore exactly such distinctions; looking at the lineup, it looks like an intriguing mixture of cosmologists, astronomers and historians.

All this is highly relevant to my yet-to-be-completed book so after a long, wet summer at WIT, I’m off to sunny Arizona next month!  My own talk is titled ‘Who discovered the expanding universe?’ and I intend to compare and contrast the contributions of various pioneers such as Slipher, Hubble, Humason, Friedmann and Lemaitre. You can see a list of speakers and abstracts for the talks here.

Many thanks to Peter Coles of In the Dark for drawing the conference to my attention.


Going on holiday just as classes start back? Nice job – Ed.

Sigh. I haven’t had a day off all summer and this is not a holiday.


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A letter to the Minister for Education

On Friday evening, I gave a public talk on the big bang at Blackrock Castle in Cork. I always enjoy giving public science talks, but this one was special (slides here). The venue was a beautiful castle overlooking the sea and I was enormously impressed with the science outreach work being done there by Dr Niall Smith, director of research at Cork Institute of Technology. I was equally impressed with the new observatory at the castle and the astronomy program of Niall and his postgraduate students. Superb work in a fantastic location, surely an inspiration for generations of young students.

Blackrock Castle in Cork: the white dome above the tower is the observatory

I left Cork early on Saturday morning in order to travel to Dublin to catch the High Flyers conference of the Institute of Physics (this is what physicists get up to on bank holiday weekends!). On my way to the meeting, I heard the Irish Minister for Education interviewed on RTE Radio One (Marian Finucane show, May 5th). The Minister had many interesting things to say on subjects such as RTE, the Catholic Church, a recent libel case in Ireland and the near-paralysis of political process in the United States (the latter is a most unusual topic for a politician over here). However, I was taken aback to hear him refer to “problems of productivity in the third level sector, particularly in the Institutes of Technology”, and disappointed that the interviewer didn’t seek some clarification on the comment.

I would very much like to know what the Minister meant by this comment. What do we understand by ‘productivity’ in the context of the third level education? How is it measured? Is it the number of students taught? Number of Noble prizes for research?  Perhaps some Soviet-style quota of engineers graduated? Like all Institute lecturers, I have a heavy teaching load; we produce legions of exactly the sort of science, computing and engineering graduates that Ireland so desperately needs. I must say I grow weary of generalizations like this about third level academics from journalists and politicians, and such a comment from the top man in education is pretty serious. Not a scintilla of evidence was offered by the Minister in support of his remark, just a casually delivered public insult to my colleagues and I.

Here’s the thing, Minister Quinn: like almost all lecturers in the Institutes of Technology (IoTs), I teach between four and five different courses per semester to degree level, a larger teaching load than any third level college in the world as far as I know; add research and outreach activity to this and it is no surprise I am in the office until 9 pm at least four days a week. In terms of prep, each semester typically presents at least one new module to teach, involving months of preparation over the summer, where I would hope to be concentrating on research, finishing my book and attending conferences. (I teach diverse courses in mathematics and physics to students in the departments of computing, engineering and science, not to mention more specialized modules in quantum physics, cosmology and particle physics – how many Harvard professors can boast such a wide teaching portfolio?).

‘Yes, but what about other IoT lecturers?’, the Minister will ask. I imagine I have a more accurate view of the work of my colleagues than the Minister’s advisors and I have no complaints. Indeed, the limited time I have for research arises because other lecturers take on the bulk of student administration (the large number of classes in the IoTs necessitates a great deal of admin; Year Tutors and Course Leaders spend a great deal of time keeping track of attendance, assessments, lab performance  and exam results). There are no easy lecturing jobs.

I love my job and stopped counting the overtime years ago. However, it is frustrating to hear the work of lecturers in the institutes and the universities denigrated by politicians who know nothing of what we do. The tragedy is, I suspect the binary system of universities and institutes has served Ireland very well, although few in charge of education seem to realize it. As they consider the future of the third level sector, I hope politicians and their advisors will make an effort to understand the current system, rather than indulge in unsupported generalizations.


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Astronomy and cosmology at Birr Castle

Yesterday, I travelled to historic Birr Castle in the centre of Ireland in order to catch the end of the annual meeting of the Astronomical Science Group of Ireland. Birr Castle is a great setting for an astronomy meeting –  not only is it a beautiful castle with fantastic grounds, it is also an important landmark in the history of astronomy. The castle was the home of the famous Leviathan, a reflecting telescope that was the largest instrument of its kind in the world for many years. The telescope was built in the 1840s by Lord Parsons, the third Earl of Rosse, and featured  a 72-inch mirror, a marvel of engineering at the time.  He made many important discoveries with the instrument, not least the first observation of the spiral structure of some of the distant nebulae and the detection of stars within the nebulae. Indeed, the Earl was one of the first to propose that the nebulae were entire galaxies distinct from our own, a hypothesis that was not definitely established until Hubble’s measurements with the 100-inch Hooker telescope at Mt Wilson in California.

Birr Castle in Co.Offaly

The Leviathan telescope at Birr castle

There were a great many interesting talks over the two days of the meeting (see program here), but I was there to catch ‘The Search for Polarization Fluctuations in the Cosmic Microwave Background’ by Creidhe O’Sullivan of NUI Maynooth. Creidhe started with a basic overview of the cosmic microwave background (CMB), explaining its importance as evidence in support of the big bang model and describing the measurements of temperature fluctuations in the radiation by the COBE and WMAP satellites. (The CMB is the primordial radiation left over from the time that atoms first began to form. Cosmologists and astronomers spend a great deal of time studying the tiny temperature fluctuations imprinted in the CMB, as this gives information on the density and geometry of the early universe, see the Cosmology 101 section of this blog.)

Creidhe then moved on to explain the study of polarization in the background radiation. The CMB radiation is expected to be polarized because it comprises light that has been scattered by many particles; when light is scattered, it gets polarized into different planes of vibration. (Polaroid sunglasses operate on the same principle; they cut down on light by allowing only light polarised in one plane to pass through). Hence cosmologists search for fluctuations in polarization as well as temperature in the CMB, although the polarization fluctuations are much smaller. Mathematically speaking, the polarization is divided into two modes: electric (E –mode) and magnetic (B-mode) polarisation. E-modes have been detected since 2003; the analysis of these modes has become a major area of research in cosmology. Creidhe gave a superb overview of the instruments used to analyse the E- modes, including the work of her own group with the QuaD experiment at the South Pole.

The QUaD experiment at the South Pole

She finished the talk by explaining that the next big challenge in cosmology is the detection of B–mode polarization in the background radiation. B-modes present a great challenge as they are yet more difficult to detect. The great hope here is that the PlANCK satellite telescope, with its improved resolution. Just as the COBE satellite results were a watershed in our view of the early universe, the resolution of B-mode polarization in the CMB by PLANCK would give yet more support for the big bang model and cosmic inflation, and even offer evidence for the existence of gravity waves.

The Planck satellite telescope

That is not to say terrestrial experiments will not have their place. After Creidhe’s talk, another member of the Maynooth group, Stephen Scully, gave a brief overview of the team’s work on the QUBIC experiment. This is a new type of the bolometric interferometer that will be used in the next generation of terrestrial measurements at the South Pole.

All in all, a most informative afternoon. After the talks, we were shown the site in the castle grounds where a new radiotelescope is to be situated. This will form the Irish node of the international LOFAR astronomy project, bringing Birr castle up to date with modern astronomy – more on this in the next post.

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