Tag Archives: Astronomy

May 27, 2019 · 7:39 pm

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.

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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.

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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).

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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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March 2, 2018 · 1:44 pm

Snowbound academics are better academics

Like most people in Ireland, I am working at home today. We got quite a dump of snow in the last two days, and there is no question of going anywhere until the roads clear. Worse, our college closed quite abruptly and I was caught on the hop – there are a lot of things (flash drives, books and papers) sitting smugly in my office that I need for my usual research.

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The college on Monday evening

That said, I must admit I’m finding it all quite refreshing. For the first time in years, I have time to read interesting things in my daily email; all those postings from academic listings that I never seem to get time to read normally. I’m enjoying it so much, I wonder how much stuff I miss the rest of the time.

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The view from my window as I write this

This morning, I thoroughly enjoyed a paper by Nicholas Campion on the representation of astronomy and cosmology in the works of William Shakespeare. I’ve often wondered about this as Shakespeare lived long enough to know of Galileo’s ground-breaking astronomical observations. However, anyone expecting coded references to new ideas about the universe in Shakespeare’s sonnets and plays will be disappointed; apparently he mainly sticks to classical ideas, with a few vague references to the changing order.

I’m also reading about early attempts to measure the parallax of light from a comet, especially by the great Danish astronomer Tycho de Brahe. This paper comes courtesy of the History of Astronomy Discussion Group listings, a really useful resource for anyone interested in the history of astronomy.

While I’m reading all this, I’m also trying to keep abreast of a thoroughly modern debate taking place worldwide, concerning the veracity of an exciting new result in cosmology on the formation of the first stars. It seems a group studying the cosmic microwave background think they have found evidence of a signal representing the absorption of radiation from the first stars. This is exciting enough if correct, but the dramatic part is that the signal is much larger than expected, and one explanation is that this effect may be due to the presence of Dark Matter.

If true, the result would be a major step in our understanding of the formation of stars,  plus a major step in the demonstration of the existence of Dark Matter. However, it’s early days – there are many possible sources of a spurious signal and signals that are larger than expected have a poor history in modern physics! There is a nice article on this in The Guardian, and you can see some of the debate on Peter Coles’s blog In the Dark.  Right or wrong, it’s a good example of how scientific discovery works – if the team can show they have taken all possible spurious results into account, and if other groups find the same result, skepticism will soon be converted into excited acceptance.

All in all, a great day so far. My only concern is that this is the way academia should be – with our day-to-day commitments in teaching and research, it’s easy to forget there is a larger academic world out there.

Update

Of course, the best part is the walk into the village when it finally stops chucking down. can’t believe my local pub is open!

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Dunmore East in the snow today

 

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March 12, 2013 · 4:39 pm

Cosmic fingerprints at Trinity College Dublin

I was back in my alma mater Trinity College Dublin on Monday evening in order to catch a superb public lecture, ‘ Fingerprinting the Universe’ , by Andrew Liddle, Professor of Astrophysics at the University of Edinburgh. The talk was presented by Astronomy Ireland, Ireland’s largest astronomy club and there was a capacity audience (despite the threat of snow) in the famous Schrödinger lecture theatre in the Fitzgerald Building, Trinity’s physics department.

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Professor Liddle was introduced by David Moore, Chairman of Astronomy Ireland, who also presented an update of the club’s recent activities  (David and I participated in a discussion of the life and science of Sir Isaac Newton on NEWSTALK radio station the evening before, you can hear a podcast of the show here). Anyone with an interest in cosmology will be familiar with Andrew Liddle’s seminal textbook ‘ An Introduction to Modern Cosmology’, (not to mention several other books) and the ensuing lecture certainly didn’t disappoint.

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Starting with a tribute to the work of both Schrödinger and Fitzgerald, Andrew gave a brief outline of today’s cosmology, showing how it has moved from a rather speculative subject to a mature field of study. He attributed this progress to key advances in three main areas: precision observations by satellite, sophisticated theoretical models and high performance computing for both analysis and simulation.

He then described five specific challenges that any successful model of the cosmos must address –  the expanding universe;  the formation of structure (galaxies etc);  the age of the universe; the composition of the universe (baryonic matter, radiation, neutrinos, dark matter and dark energy);  a consistent description of the very early universe (cosmic inflation or alternatives).

As ever, many in the audience were surprised to hear that, while dark energy is estimated to make up about 73% of the mass-energy content of the universe, we have very little idea of the nature of this phenomenon!

In the second part of the lecture, Andrew focused on the cosmic microwave background (CMB), explaining how the study of this ‘fossil radiation’  gives precious information on the early universe,  and in particular describing how tiny non-uniformities (or anisotropies) imprinted on the radiation formed the seeds of today’s galaxies (‘cosmic finger-printing’). There followed a swift description of results of CMB studies by the COBE and WMAP satellite missions, with a reminder that more recent measurements by the European Space Agency’s   PLANCK Satellite Observatory  will be announced next week. He also reminded us how, amongst other triumphs, the theory of inflation gives a very satisfactory explanation for the origin of the variations in the background radiation terms of quantum fluctuations in the very early universe. This link between inflation and galaxy formation is often under-stated in the popular literature; in answer to a query from me question time, Andrew confirmed that non-inflationary explanations for the origins of the observed variations in the microwave background have not been very successful. It’s pretty impressive that inflation can give an explanation for the origin of structure, given that this was not part of the original motivation for the theory.

ESA's Planck mission

The ESA’s PLANCK Satellite will report new measurements of the cosmic microwave background on March 21st this month

All in all, a fantastic talk, well worth the trip; afterwards, we all repaired to a nearby pub for sandwiches and further discussion of the universe over hot ports and Guinness…

P.S. In his discussion of the discovery of the expanding universe, I was pleased to see Professor Liddle refer to the work of Vesto Slipher; it seems that recent historical work on the important contribution of Slipher is finding its way into the mainstream community.

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April 20, 2012 · 2:02 pm

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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April 28, 2009 · 11:52 am

Astronomy Ireland and IYA

Last Saturday, Astronomy Ireland hosted an extraordinary national meeting at the Science Gallery at Trinity College Dublin, in order to draw members’ attention to planned events to mark the UN International Year of Astronomy.

Astronomy Ireland (AI) is Ireland’s premier astronomy club and it promotes astronomy, space interest and science education all over the country. I first became aware of the club when I attended some great cosmology talks they hosted last year (see post on a lecture onThe Cosmological Distance Ladder by Micheal Rowan-Robinson here and on Dark Matter by Tim Sumner here); AI also organise observing sessions and other astronomy events nationwide, not to mention running astronomy classes in various institutions around the country. I attended their astronomy classes in our own college this semester and found them excellent (well done Emmet Mordaunt!).

Saturday’s meeting offered a packed program of talks, short films and discussions. First up was film producer and director Ginita Jimenez of film company Father Films, who described how she came to make a short film about Venetia Phair, the 11-year old Oxford schoolgirl who named the planet Pluto. I missed the beginning of Ginita’s talk, but her description of reading a short newspaper article on the topic and her subsequent discovery that Venetia had never actually seen the planet, was fascinating: with the demotion of Pluto to ‘dwarf planet’ status, she knew she had to make a film about the whole affair.

After Ginita’s introduction, we were treated to the Irish premiere of ‘Naming Pluto’. Sure enough, it was a beautiful little film: the discovery of a new planet from the perturbations in the orbit of Uranus, the naming of the planet by Venetia, granddaughter of Falconer Madan, ex-Head of Oxford University’s Bodleian Library, the subsequent passing of the name to the powers that be in Flagstaff USA, it was all there. (I’m not sure how many of our students would have 11-year old Venetia’s knowledge of both astronomy and classical mythology – planets are generally named after Roman gods and Venetia suggested Pluto as he is the Roman god of the underworld). The second part of the film described an older Venetia’s visit to uber-astronomer Patrick Moore, a failed sighting, and then her first sighting of the planet she named all those years ago at the Science Observatory in Hertsmonceaux at age 89. The film finished with some moving shots of an aged Venetia telling her story to a group of wide-eyed students – straight out of C.S. Lewis, you could see them trying to imagine her as an 11-year old! If you want to know more, there is a summary of the story here and a nice trailer of the film on YouTube here; better still, why don’t you buy the film here.  

Robert Hill of the Armagh Planetarium and Northern Ireland Space Office then gave a lively overview of activities worldwide that are taking place to mark the International Year of Astronomy. The sort of activities involved are:

100 hours of astronomy: a round-the-clock event that features live webcasts from research observatories around the world

The Galileoscope ; the distribution of thousands of easy-to-assemble, easy-to-use telescopes to budding astronomers around the world: each telescope has about the same power as that available to Galileo

Cosmic Diary: an astronomy blog featuring regular posts by diverse professional astronomers

Portal to the universe; a one-stop web portal for astronomy that will feature astronomy content, acting as an index for press, educators and scientists

Dark Skies Awareness: a project promoting the awareness of light pollution

It was a great talk and you can find out more about the various activites on the IYA website.

AI founder and chairman David Moore also gave a talk, describing the activites of Astronomy Ireland for the year that’s in it, in particular the school lecture program and the teacher training program. He also described what individual members could do, from voluntary work to lobbying public representatives. A change of mission was highlighted: instead of confining itself to promoting astronomy, David sees AI as promoting a science culture in Ireland. He pointed out that while Ireland has a great culture in both arts and sports, it has no such culture in science, despite a great heritage in the subject. I think he is absolutely right in this and it strikes me that astronomy is a very good place to start to address the problem..you can find a list of the planned AI activities here or on the AI website.

David Moore (R) in interview at the Young Scientist Exhibition

After David’s talk, we were treated to another short film. 3-d glasses were handed out and Robert Hill presented a short spectroscopic tour of the universe. I won’t attempt to summarize the film, but there were some stunning graphics. You can get a flavour of it by taking the tour on the website of Celestia. As usual, I came away thinking just how insignificant our own little galaxy is in the wider scheme of things.

All in all, the meeting was a lively and informative event, with a serious mission behind it. Afterwards, we left the beautiful Science Gallery for some hot food and drinks at the pub across the road (it was an Irish meeting after all). There, discussions on the promotion of science continued for many hours…

Update:

I just heard from Ginita that Venetia died last week at the age of 90. Sad news, but I’m sure she enjoyed seeing the film in her final days. You can find a nice NYT obituary here. Ar dheis De do raibh a h-anam

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February 10, 2009 · 2:06 pm

ESA Mission to Mars

This week is Engineering Week in Ireland and it got off to a great start at WIT with a talk on space exploration at the European Space Agency (ESA) by Micheal McKay, the Belfast-born engineer who has acted as Flight Operations Director for ESA lunar and Mars missions. (The seminar was presented by CALMAST, the Centre for the Advancement of Learning of Mathematics, Science and Technology at WIT, see here for other science/engineering events this week).

Dr McKay started with a superb outline of space exploration in general and of the work of the European Space Agency in particular. He put great emphasis on practical applications such as:

– the monitoring of the earth’s climate via the ESA ERS satellites:

– the forthcoming ESA Galileo GPS network, an independent European satellite telecommuncations network, vital for air traffic contol and for air/sea rescue:

– the SOHO mission, a study of the interaction of solar output with the earth’s magnetic field with the ESA SOHO satellite:

– observations of the most distant galaxies using Far Object Cameras mounted on ESA satellities:

– the study of the atmosphere of Venus using an ESA satellite, gathering vital information on the greenhouse effect and its implications for the earth.

One of the ESA’s earth-monitoring satellites

A schematic of the ESA’s Galileo GPS system

McKay then went on to talk about the ESA’s greatest success – the Mars Express Orbiter. He gave a superb overview of the information got from the orbiter, despite the loss of the Beagle II Lander. Indeed, McKay spent a good deal of time on the Mars mission, explaining carefully that it was the Mars Express that established the first firm evidence for substantial ice/water at the south pole. At this point, the speaker described two great examples of the sort of thinking-outside-the box engineering solutions  necessary in his  job  – the slow rotation of the Mars orbiter into sunlight to free up a jammed hinge on one of the antennae, and a software ‘sunglasses’ patch to protect a sensitive detector from excess sun…both successfully completed from hundreds of millions of miles away!

The Mars Express Orbiter

McKay also spent some time explaining the next ESA Mars project, a  manned mission to Mars in 2030.  I won’t describe this part in detail, but you can find details of the Aurora mission here;

This ws a fine seminar and there were a few general themes  I liked a lot:

(i) ‘you too can do this’ – like so many at the top, the speaker continually emphasised to the students that they too had the potential for a great career in space exploration

(ii) the outstanding success of a relatively young European space agency (currently accounts for 40% of the global space market) and the fact that European citizens are not always aware of it

(iii) the spectacular benefits of European co-operation, and of the co-operation between ESA and NASA and other space agencies – nations seem to co-operate better in space than down here!

(iv) the importance of space exploration in its own terms for our knowlege of our universe, plus the beneficial spinoffs such as the ERS  earth observation missions

(v) the success of Ireland’s membership of ESA: not just in terms of commercial contracts gained, but the payback in terms of experience and knowledge brought back to Ireland, and the potential for fantastic careers in space exploration for the next generation of Irish science and engineering students

Interesting that many of these themes are precisely the advantages that I, and others, refer to as the potential benefits of Irish membership of CERN – see earlier post on CERN and Ireland.

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At question time, I asked the speaker the stock question – given the expense of building the space station necessary for manned expeditions to Mars, what can a manned mission discover that robotics cannot? He answered this in detail, carefully listing the problems of communication and contol of robots. It will be interesting to see what happens in the context of the current recession..

All in all, this was an inspiring seminar for our students given by a top expert in the field.  For me, the highlights were a music video showing the docking of the ESA vessel Columbus to the International Space Station, and the description of the solutions to engineering problems with the Mars Express orbiter – from a software patch to protect a detector from excess sun, to the rotation of the station into sunlight to free up a jammed hinge!

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