Archive for Dublin

Happy Birthday, Quaternions!

Posted in History, mathematics with tags , , , , on October 16, 2019 by telescoper

Sir William Rowan Hamilton (1805-1865)

Today, October 16th, is Hamilton day! It was on this day 176 years ago, in 1843, that  William Rowan Hamilton first wrote down the fundamental result of quaternions. Apparently he was walking from his residence at Dunsink Observatory into Dublin when he had a sudden flash of inspiration  and wrote the result down on the spot, now marked by a plaque:


Picture Credit: Brian Dolan

This episode  is commemorated by an annual Hamilton Walk. Sadly,  Broombridge (Droichead Broome) is near the bridge (Broom Bridge) where Hamilton had his Eureka moment and it is on the main commuter line from Maynooth into Dublin. This is ironic because Quaternion algebra does not commute. (Geddit?)

Although it is quite easy to reach Broombridge from Maynooth, I sadly can’t attend the walk this year because I’m teaching this afternoon.

P.S. Maynooth is also home to the Hamilton Institute which promotes and facilitates research links between mathematics and other fields.

The Summer Solstice 2019

Posted in Uncategorized with tags , , , , , , on June 21, 2019 by telescoper

The Summer Solstice in the Northern hemisphere happens today, Friday 21st June 2019, at 16.54 Irish Time (15.54 UTC). Among other things, this means that today is the longest day of the year. Days will get shorter from now until the Winter Solstice in December. Saturday June 22nd will be two seconds shorter than today!

This does not mean that sunset will necessarily happen earlier tomorrow than it does today however.  This is because there is a difference between mean solar time (measured by clocks) and apparent solar time (defined by the position of the Sun in the sky), so that a solar day does not always last exactly 24 hours. A description of apparent and mean time was given by Nevil Maskelyne in the Nautical Almanac for 1767:

Apparent Time is that deduced immediately from the Sun, whether from the Observation of his passing the Meridian, or from his observed Rising or Setting. This Time is different from that shewn by Clocks and Watches well regulated at Land, which is called equated or mean Time.

The discrepancy between mean time and apparent time arises because of the Earth’s axial tilt and the fact that it travels around the Sun in an elliptical orbit in which its orbital speed varies with time of year (being faster at perihelion than at aphelion).

Using a rapid calculational tool (Google), I found a table of the local mean times of sunrise and sunset for Dublin around the 2019 summer solstice. This shows that today is indeed the longest day (with a time between sunrise and sunset of 17 hours and 10 seconds), but sunset on 22nd June is actually a bit later than this evening, while sunrise is a bit later.

In fact if you plot the position of the Sun in the sky at a fixed time each day from a fixed location on the Earth you get a thing called an analemma, which is a sort of figure-of-eight curve whose shape depends on the observer’s latitude. Here’s a photographic version taken in Edmonton, with photographs of the Sun’s position taken from the same position at the same time on different days over the course of a year:


The summer solstice is the uppermost point on this curve and the winter solstice is at the bottom. The north–south component of the analemma is the Sun’s declination, and the east–west component is the so-called equation of time which quantifies the difference between mean solar time and apparent solar time. This curve can be used to calculate the earliest and/or latest sunrise and/or sunset.



The End of the Common Travel Area?

Posted in Biographical, Cardiff, Politics with tags , , on June 14, 2019 by telescoper

I’m back in Cardiff for a couple of days after flying from Dublin this morning.

When my flight arrived at Cardiff Airport there was yet again a full passport and immigration check on all passengers.

There is supposed to be a Common Travel Area including the UK and Ireland (as well as the Channel Islands and the Isle of Man), and passport checks are not supposed to be made routinely at borders within the CTA.

I have noticed passport checks happening at Cardiff Airport before (e.g. here and here) but I’ve previously imagined there was some specific reason for them. Passport checks have, however, been carried out every time I have arrived in Cardiff recently and it is now abundantly clear that there has been a material change of policy.

When I got to the desk and handed over my passport I asked the Officer whether these checks were being imposed all the time now. She said yes: there are now full passport and immigration checks on all flights to Cardiff from Dublin.

This is from the UK Government’s website:

Well, if they check all passengers on all flights then that sounds like ‘routine’ to me. In other words the British authorities are violating the Common Travel Area agreement just weeks after undertaking to uphold it.

Did someone say ‘Perfidious Albion’?

A Story of St Stephen’s Green

Posted in History with tags , , , , , on May 26, 2019 by telescoper

I had a bit of spare time before the Opera on Friday and the weather was fine so I decided to go for a walk around the park in St Stephen’s Green.

I have walked past St Stephen’s Green many times but have never previously been inside, or if I have it was so long ago that I’ve now forgotten.

On my way around I noticed that there are posters here and there marking the events of the 1916 Easter Rising. Here’s an example:

The artwork is a bit ‘Boy’s Comic’ style but the descriptions are fascinating especially because the Park and the area around it are pretty much unchanged in more than a hundred years since the momentous events of 1916 so it’s not difficult to imagine the scene as it was then. There are still bullet holes in the Fusiliers Arch at the North West Corner of the Green, as there are in a number of other locations around Dublin.

St Stephen’s Green is inside the area marked ‘Citizens Army‘. One look at the map will tell you why this was considered an important location to control as it is at the junction of several main roads. On the other hand if you actually visit the location you will see a big problem, namely that the Green itself is surrounded on all sides by very tall buildings, including the swanky Shelbourne Hotel to the North.

When a contingent of about 120 members of the Citizens Army arrived in St Stephen’s Green on Easter Monday, 24th April 1916, they immediately began erecting barricades outside, and digging trenches inside, the Park. They did not, however, have the numbers needed to seize and hold the buildings around it except for the Royal College of Surgeons building to the West.

The following morning, Tuesday 25th April, the British moved two machine guns into position, one in the Shelbourne Hotel and the other in the United Services club, along with numerous snipers. From these vantage points British soldiers could shoot down into the Park making it impossible for the rebels to move around.

The position inside the Green being untenable the Rebels effected an orderly (but perilous) withdrawal to the Royal College of Surgeons which they had fortified for the purpose. And that’s where they stayed until the end of the Rising.

The British realised that there was no need to assault the RCS building, as the force inside was contained and offered no real threat. From the roof of the building the Rebels watched helplessly as the British systematically reduced the resistance around the Rebel Headquarters in the GPO Building to the North, using artillery fired from College Green. Smoke rose into the sky as one entire side of O’Connell Street went up in flames and the perimeter slowly tightened around the GPO.

In the early hours of the morning of Thursday 27th April the occupants of the RCS were alarmed to see that British soldiers had installed another machine gun on the roof of the University Church on the South side of St Stephen’s Green along with snipers in adjacent buildings.

This was a very dangerous development that required a rapid response. A plan was devised that involved sending a squad of about 30 to break into buildings on the South side of the Green and start fires therein that would force the British to withdraw. This action is the subject of the poster shown above.

This is a photograph of the remarkable Margaret Skinnider, who is shown in the graphic leading the attempted assault. Before the Rising she was a school teacher. During the hostilities she initially acted as a scout and a runner, carrying messages to and from the GPO, but when given the chance she proved herself a crack shot with a rifle and showed conspicuous courage during the heavy fighting in and around St Stephen’s Green.

Skinnider insisted on leading the assault on Thursday 27th April despite the obviously high risk as it would involve running about 30 yards in full view of the machine gun position.

Under the cover of darkness, the detachment made its way out of the RCS to the South West corner of the Green safely enough but when men began breaking windows in Harcourt Street in order to gain entry to buildings there, the sound alerted the British soldiers who realised what was happening and opened fire as the Rebels made their move. Margaret Skinnider was leading from the front and she was inevitably among the casualties: she was hit three times by rifle bullets and very badly wounded.

Such was the volume of fire that the assault was abandoned and the surviving members of the squad retreated to the RCS where they remained until the general surrender on Saturday (29th April).

Skinnider was taken to hospital after the Rising ended but escaped and made her way to Scotland. She later returned to Ireland to take part in the War of Independence and subsequent Civil War. When the latter ended, in 1923, she went back to her job as a teacher in a primary school. She passed away in 1971 at the age of 79.

Irish Quantum Foundations and Other Matters

Posted in Biographical, The Universe and Stuff with tags , , on May 23, 2019 by telescoper

So here I am then, at Irish Quantum Foundations (IQF) 2019 which is being held in the Hamilton Building (shown above), and hosted by the School of Mathematics of the College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin, which is sometimes known as Trinity College, Dublin for short.

I got here a bit later than I originally planned as some last-minute things came up this morning to do with next week’s events. I’ll have to skip tomorrow morning too, for similar reasons. When I did get going this morning I had to stand all the way from Maynooth to Connolly because the train was packed. At least it was reasonably on time though.

Anyway, the schedule of IQF 2019 is rather varied and I’m looking forward to the parts of it that I can attend.

Among the things I have been dealing with to do with next week are  submitting the final version of pedagogical piece about the Eclipse Expeditions of 2019 which should be published very soon in Contemporary Physics (at least in the online version) and writing a short piece for RTÉ Brainstorm (which will appear on Monday 27th May), and sorting out an appearance on Newstalk Radio next week. How I’ll get time to finish my exam marking in the middle of all this I don’t know!


Back to Sunny Ireland

Posted in Biographical, Cardiff, Maynooth with tags , , , , , on April 22, 2019 by telescoper

Well here I am, back in Maynooth, after a week’s restful leave in Cardiff. The weather here is just as nice as it was in Wales when I left yesterday: sunny and about 20 degrees. I’m enjoying the warm weather very much indeed, as my arthritis seems to have eased off considerably.

I was planning to return to Ireland today (Monday) but the flights were far cheaper yesterday. The plane I took yesterday (Sunday) less than half full. Incidentally, after their recent rescue and restructuring FlyBe have announced that after this summer they will no longer operate jets from Cardiff. Flights to Dublin will therefore be by their smaller Bombardier turboprops rather than the Embraer aircraft that I took yesterday.

Today is a Bank holiday in Ireland, as it is in the UK, but after that the Easter break is over; I’m officially back to work tomorrow. This semester will have been divided into three pieces, firstly by the half-term study week (around St Patrick’s Day) and now by a one-week Easter break. Last year these two breaks were contiguous, but Easter is quite late this year so they are separate this time.

Anyway, we now have three weeks of teaching left followed by the May examination period and, of course, the inevitable Marking of the Scripts.

The three remaining weeks include two Bank Holiday Mondays including today, Easter Monday, and the May Day Holiday on 6th May). I have lectures on Mondays I will miss two sessions, leaving only seven lectures remaining for Engineering Mathematics. I’d better make sure that in the short time remaining I cover everything that is in the examination!

Anyway, although it’s a holiday I’ve got to get my lecture together for tomorrow morning so I’d better get to work. It’s a shame not to be out and about in the sunshine but there you go. That is the price you pay for having a week off. No doubt there is a ton of emails to reply to as well; I’ve tried not to look at my inbox while I’ve been off. I’ve made that a rule for holidays now: put the out of office message on and leave the email alone!

Technical Problems

Posted in Biographical, Cardiff with tags , , , , on March 10, 2019 by telescoper

This morning I got up early to travel to Cardiff Airport to get a flight back to Dublin.

We boarded the plane on time, left the gate on time and arrived at the end of the runway, apparently about to take off. We then sat there for 20 minutes before the pilot explained that there was a problem with the instruments on the flight deck. The plane then taxied back to the terminal, and an engineer got on, but he was unable to fix the problem so we all got off the plane which is clearly going nowhere soon.

A FlyBe Embraer 175 actually flying.

I’m currently sitting in the departure lounge drinking a coffee and wondering when (if) I’ll get to Dublin.

We’re told a plane will arrive from Edinburgh in half an hour and that will take us to Dublin. I’m not convinced. I think there’s a significant probability that my flight will be cancelled, but you never know..

The service with FlyBe has deteriorated in recent weeks almost as quickly as its fares have gone up. The airline has only recently been rescued from collapse and I suspect a major reorganisation is coming up.

Anyway, I know it’s safety first and all that, but my main concern is that we got all the way to the runway before anyone noticed there was a problem. Don’t they check before leaving the gate?

Update: we arrived in Dublin on Plane Number Two at 12.30, two hours and twenty minutes late but all in one piece.