The Winter Solstice 2020

The winter solstice in the Northern hemisphere happens tomorrow, Monday 21st December, at 10.02 Irish Time. Among other things, this means that tomorrow is the shortest day of the year in the Northern hemisphere. Days will get steadily longer from then until the Summer Solstice next June.  The longest night – defined by the interval between sunset and sunrise – is tonight and the shortest day – defined by the interval between sunrise and sunset – will be tomorrow. The day tomorrow will be two seconds shorter than today, while the interval between sunrise and sunset on Tuesday 22nd December will be four seconds longer than tomorrow.

This does not, however,  mean that sunrise will happen earlier tomorrow than it did this morning. Actually, sunrise will carry on getting later until the new year, the length of the day nevertheless increasing because sunset occurs later. Sunrise this morning (20th December was at 08.37 Dublin Time while tomorrow it will be at 08.38. Sunset tonight will be at 16.07 and sunset tomorrow will be at 16.08.

These complications arise 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).

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 shape 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 winter solstice is the lowermost point on this curve and the summer solstice is at the top. These two turning points define the time of the solstices much more precisely that the “shortest day” or  “longest night”.

Incidentally, the Tropic of Capricorn is the circle of latitude (about 23.5°, the declination of the Sun at the Winter Solstice) that contains the subsolar point at the December solstice. This is therefore the most southerly latitude on Earth where one can see the Sun directly overhead.

Anyway, 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.

Using a more rapid calculational tool (Google), I found a table of the local mean times of sunrise and sunset for Dublin around the 2020  winter solstice. This shows that tomorrow is indeed the shortest day (with a time between sunrise and sunset of 7 hours 29 minutes and 57 seconds).  The table also shows that sunset already started occurring later in the day from 17th December,  before the winter solstice, and sunrise will continue to happen later  after the solstice, notwithstanding the fact that the interval between sunrise and sunset gets longer from tomorrow onwards.

I hope this clarifies the situation.

Follow @telescoper

Domhnach na Fola

In the days before lockdown I would often travel past Croke Park on the train from Maynooth into Dublin Connolly station. It’s a magnificent stadium, with a capacity over 80,000, its stands towering up on all sides of the playing field which is used for major sporting events organized by the Gaelic Athletics Association (GAA), chiefly hurling and gaelic football. It’s located quite close to Drumcondra Station, the last stop before Connolly on the way into Dublin. I’ve never actually been inside the ground, and you can’t see much of the interior from the train because of the stands, but I do hope to see a match there one day.

Croke Park looked very different a hundred years ago today, on November 21st 1920 (which was a Sunday).

Croke Park, looking towards Hill 16, taken on the day of November 21st 1920.

Incidentally, the low hill you can see in the background is Hill 16. There’s a story that this was built up using rubble from buildings destroyed during the 1916 Easter Rising, but this seems to be apocryphal.

Anyway, as you can see, there wasn’t much in the way of buildings around the playing field in those days, and not much to give spectators cover if they were trying to flee from gunfire.

A Gaelic football match between Dublin and Tipperary started in Croke Park at 2.45 pm on November 21st. About ten minutes into the game, armed police (including members of the regular Royal Irish Constabulary, Auxiliaries, and some Black and Tans) suddenly arrived at the southern end of the park, panicking some of the spectators who tried to run away. Without warning the police opened fire on the crowd. The first to die was 11 year old William Robinson who was sitting in a tree outside the ground to get a better view. Overall the firing lasted about 90 seconds. Thirteen people were killed outright and another died of his wounds later. Others were injured either by gunfire or in the crush resulting from the panic.

Among the dead was Tipperary’s star player Michael Hogan, who was shot dead on the playing field as he tried to find cover. Information from post-mortems released many years after the event revealed that most of the victims had been shot in the back.

Michael Hogan, star player and Captain for the Tipperary team at Croke Park on Bloody Sunday. He died that day.

The massacre could have been even worse had the British forces at the other end of the ground, who had an armoured car with a machine gun, shown more restraint. The machine gun was fired above the heads of the people running towards this contingent. They didn’t shoot anyone but they did force the crowd back towards the gunfire from the other end of the ground. Had they opened fire at the crowd there would have been a massacre on the scale of Amritsar, where hundreds died.

Witnesses also said that while the security forces let all the Dublin players go, they lined up the entire Tipperary team against a fence and were preparing to shoot them all when a junior officer intervened and ordered them to be released. Tipperary was perceived to be a hotbed of IRA activity. Michael Hogan was in fact a member of the Irish Volunteers.

So what on Earth had happened to trigger this indiscriminate slaughter, on the day known now as Bloody Sunday (Irish: Domhnach na Fola)

The overall context is the Irish War of Independence which started in 1919 and was largely a guerilla campaign waged in rural areas. There had not been large-scale eruptions of violence in Dublin. That changed on November 21st 1920. That morning, members of the Irish Republican Army under the direction of Michael Collins, had carried out an operation across Dublin intended to eliminate the ability of the British forces to gather intelligence on the IRA. Hit squads entered the homes of known or suspected British intelligence operatives across the town and shot them. Fifteen people were killed that morning, including at least two innocent civilians in the process.

The IRA members responsible for the killings on Sunday morning melted away into the city. Once again the police and security services seemed to be fighting an invisible enemy. However, knowing that there was a football match going on that afternoon, and that at least some of those involved with the GAA had strong Republican leanings and may indeed be active IRA members, they decided to search all the spectators at the match of which there were over 10,000. The hope was, presumably, to find in the crowd at least some of those responsible for the morning’s assassinations. Instructions were given that anyone who ran away when the search operation began should be presumed guilty and shot.

News about the morning’s events had spread through Dublin that morning and it was widely anticipated that the British would carry out reprisal killings, probably in their usual indiscriminate fashion they had employed previously. When armed men arrived in vehicles outside the ground, the instinct of many spectators was therefore to run even before the searching began. Nervous and trigger-happy police deployed in a harebrained plan to make the slaughter inevitable. Nobody has ever been brought to justice for the murders at Croke Park.

Later that day two members of the IRA were caught by the security services, taken to Dublin Castle, beaten and then shot under the pretext that they were trying to escape. These killings brought the death toll past thirty. Bloody Sunday indeed.

The events in Croke Park handed a major propaganda victory to the IRA and also sparked an escalation of the violence. Just a week later, at Kilmichael in County Cork, the IRA ambushed two trucks carrying a total of 18 Auxiliaries, killing 17 of them and leaving the other for dead. On December 11th the British burned down a large part of the city of Cork in retaliation against another attack on their forces. And so it went on into 1921 to the point where the British eventually realized that Ireland had become ungovernable (by them) and a process was started that brought about independence (at least for part of Ireland).

As you can imagine there have been many commemorations of the grim events of a century ago. I watched a very interesting documentary on the TV earlier this week and there have been many articles in the newspapers and elsewhere about it, taking different angles. Those I found the most moving were those that dealt with the memory of the innocent lives lost. One very poignant idea was to stage 14 very short plays around Croke Park about each of the victims.

Here is a sort of trailer, featuring the heartbreaking story of Jane Boyle – the only woman to die on Bloody Sunday. Her death was particularly tragic as she was due to marry her fiancé Daniel Byron the following week. The couple went to mass at St Kevin’s Church on Harrington Street on Sunday morning and proceeded to Croke Park afterwards. When the firing started, they fled. In the scramble for safety, Daniel felt Jane’s hand go limp; she had been shot in the back and died instantly. She was buried later that week in her wedding gown.

Follow @telescoper

A Revolutionary Manhole Cover

I must have walked dozens of times past the above manhole cover on Maynooth University’s North Campus without paying too much attention. Then I noticed a post on Twitter of another such cover in County Kerry, in the thread following which someone mentioned one on Maynooth campus so I thought I’d take a picture of it. They must have been made for the centenary commemorations in 2016. There’s more than a hint of Soviet-style design in the artwork.

The figure depicts Eamon Bulfin raising the flag of Irish Republic above the GPO on Easter Monday 1916, the start of the Easter Rising. After the end of the rising Bulfin was condemned to death, but his sentence was commuted and, after being imprisoned in Britain for a time, he was deported to Argentina. He returned to Ireland when the Irish Free State in 1922 where he lived until his death in 1968.

Follow @telescoper

 

The Summer Solstice 2020

The Summer Solstice in the Northern hemisphere happens this evening, Saturday 20th June 2020, at 22:43 Irish Time (21.43 UTC). Among other things, this means that today is the longest day of the year. This is an earlier day in June than you might expect, primarily because 2020 is a leap year.

Days will get shorter from today until the Winter Solstice in December, although this does not mean that sunset will necessarily happen earlier tomorrow than it does today. In fact it is a little later. 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 2020 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 21st June is actually a bit later than this evening, but sunrise is also bit later so the day is indeed (slightly) shorter.

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.

Follow @telescoper

#PoetryDayIRL: ‘Dublin’, by Louis MacNeice

Here is another poem for Ireland’s National Poetry Day. This one is called Dublin and it was written by Louis MacNeice.

Grey brick upon brick,
Declamatory bronze
On sombre pedestals –
O’Connell, Grattan, Moore –
And the brewery tugs and the swans
On the balustraded stream
And the bare bones of a fanlight
Over a hungry door
And the air soft on the cheek
And porter running from the taps
With a head of yellow cream
And Nelson on his pillar
Watching his world collapse.

This never was my town,
I was not born or bred
Nor schooled here and she will not
Have me alive or dead
But yet she holds my mind
With her seedy elegance,
With her gentle veils of rain
And all her ghosts that walk
And all that hide behind
Her Georgian facades –
The catcalls and the pain,
The glamour of her squalor,
The bravado of her talk.

The lights jig in the river
With a concertina movement
And the sun comes up in the morning
Like barley-sugar on the water
And the mist on the Wicklow hills
Is close, as close
As the peasantry were to the landlord,
As the Irish to the Anglo-Irish,
As the killer is close one moment
To the man he kills,
Or as the moment itself
Is close to the next moment.

She is not an Irish town
And she is not English,
Historic with guns and vermin
And the cold renown
Of a fragment of Church latin,
Of an oratorical phrase.
But oh the days are soft,
Soft enough to forget
The lesson better learnt,
The bullet on the wet
Streets, the crooked deal,
The steel behind the laugh,
The Four Courts burnt.

Fort of the Dane,
Garrison of the Saxon,
Augustan capital
Of a Gaelic nation,
Appropriating all
The alien brought,
You give me time for thought
And by a juggler’s trick
You poise the toppling hour –
O greyness run to flower,
Grey stone, grey water,
And brick upon grey brick.

Follow @telescoper

Wagner & Bruckner at the National Concert Hall

I had to brave some very inclement weather on the way to last night’s performance at the National Concert Hall in Dublin for a performance by the RTÉ National Symphony Orchestra, under the direction of Mihhail Gerts (deputising for Natalie Stutzmann who had to withdraw “due to unforeseen circumstances”). The concert consisted of the Prelude to Act I and the Good Friday Music from the Opera Parsifal by Richard Wagner followed by Symphony No. 7 by Anton Bruckner. To my surprise these pieces were performed without a wine break interval.

As was the case a couple of weeks ago for Bruckner 8, a big orchestra was required, including a quartet of Wagnertuben.

While not everyone likes Wagnerian Opera performed in entirety there must be very few people who don’t enjoy the overtures. A programme consisting entirely of Richard Wagner’s Preludes would make for a wonderful concert, and the Prelude to Act I of Parsifal, although very familiar, is so beautiful that it bears repeated listening. Whenever I hear it I can’t help thinking of the poignant last scene of the very last episode of Inspector Morse: `Goodbye Sir’, says Lewis and kisses the dead Morse on the forehead to the accompaniment of this music from Parsifal.

The Good Friday Music occurs at the start of the Third Act of Parsifal so is in a sense also a Prelude. Even out of the context of the Opera, it provides a wonderful opportunity for reflection and contemplation because it is so subtle and understated, somewhat uncharacteristically for Wagner.

These two pieces last about half an hour, and normally one would expect an interval after them, especially since the Symphony is over an hour in duration. I’m not sure what the reason was for playing the Bruckner straight after the Wagner, but it seems to have been a last minute decision. The printed programme contains the usual `INTERVAL_ 20 minutes’ so I had ordered a drink for the interval; nobody had told the bar staff there wouldn’t be one. I got my money back, though.

One positive aspect of the lack of a pause was that it made the connection between Bruckner’s composition and Wagner even more obvious. The radiant first movement of Bruckner’s Seventh Symphony, with its noble melody soaring over shimmering violin tremolos is very reminiscent of Wagner, as is much of the rest of the Symphony (including the orchestration). Bruckner famously idolized Wagner and this composition is at least partly a tribute to his musical hero. It is said that Bruckner had a premonition of Wagner’s death in 1883 and the cymbal crash during the second (slow) movement symbolizes the moment that he found out that his premonition had come true. That whole movement (marked Sehr feierlich und sehr langsam; very solemn and very slow) is very moving: sombre though not excessively mournful. The third movement Scherzo is marked Sehr Schnell (very fast) but I found the tempo last night rather restrained. I was expecting something a bit wilder. The last movement actually sounded to me more like Mahler than Wagner.

The Seventh is probably Bruckner’s best known and most performed Symphony. It was certainly a big hit for him when it was first performed in 1884. I enjoyed last night’s performance. Usually videos of these concerts are put on the Lyric FM Youtube channel shortly after the performance, but when I looked just now last night’s wasn’t there yet. I’ll put a link up as soon as it appears.

UPDATE: Here, as promised, is the recording:

 

The picture above was taken a while before the performance and, although quite a few more people came in before it started, there were still quite a few empty seats. The National Concert Hall posted a (small) financial loss last year. I do the best I can to support it by attending as frequently as I can, but I am always saddened a bit to see so many empty seats. Anyway, I shall be back there this evening for a special event which is part of the Beethoven 250 celebrations, so watch this space!

Follow @telescoper

Bruckner: Symphony No. 8

Last night I once again found myself settling into a seat at the National Concert Hall in Dublin for a performance by the RTÉ National Symphony Orchestra, this time under the direction of Mihhail Gerts. There was only one item on the menu – the Symphony No. 8 by Anton Bruckner – but what a feast it turned out to be!

Bruckner had a habit of making multiple revisions to his scores, and the Eighth Symphony is no exception to this. There are two major versions (usually referred to as the 1887 and 1890 versions) but also numerous edited variations of these two. For the record last night we heard the edition made by Robert Haas, based mainly on the 1890 version, but replacing some pieces which had been edited out of the 1887, perhaps most notably a quiet passage in the Third (Adagio) Movement.

This is a colossal work, lasting about 90 minutes in performance and requiring a huge orchestra so the stage was very crowded when the concert got under way.

As well as larger than usual string sections, the brass section comprises no less than eight horns, three trumpets, three trombones and a tuba as well as a quartet of Wagnertuben which you don’t often see in a symphony orchestra. These instruments have a sound somewhere between that of the horns and the trombones and they add an immense solidity to the section that produces a wall of sound that has an extraordinary effect when heard live, especially during the fortissimo passages (of which there are several in this work).

Woodwinds include a bass clarinet and a contrabassoon alongside the more usual clarinets and flutes, and there are three harps and percussion. A special mention must be made of the timpanist (Grahame King) who was given a huge amount to do, and did it all exceptionally well.

The work is structured in four movements, each of which involves a shift from minor to major (the piece opens in C minor) but each covers a very varied musical landscape. The overall atmosphere of the work varies too. At times it is tranquil (or perhaps merely resigned) but it often evokes a sense of conflict and sometimes even terror. It does, however, end in a glorious crescendo that gives a sense of triumph. Along the way there is some truly memorable passages: a gorgeous dialogue between flutes and clarinets in the 2nd Movement (Scherzo) comes to mind, and the Adagio as a whole is just magnificent.

I have never heard this work performed live, and have to admit I got completely lost in the performance. Despite the length of the concert, I never looked at my watch once during the whole thing. Congratulations to Mihhail Gerts and the entire orchestra for taking us on such an epic journey. I enjoyed every second of it, and so I think did the rest of the audience, because the end was greeted with a standing ovation.

But you don’t need to rely on my opinion. You can’t beat live music, but the entire concert is here for you to enjoy as live on the Lyric FM stream. Enjoy!

Follow @telescoper

The Winter Solstice 2019

The winter solstice in the Northern hemisphere happens tomorrow, Sunday 22nd December 2019, at 04.19 Irish Time (04.19 UTC). Among other things, this means that tomorrow is the shortest day of the year in the Northern hemisphere. Days will get steadily longer from now until the Summer Solstice next June.  In fact, the interval between sunrise and sunset tomorrow will be a whole second longer tomorrow than it is today. Yippee!

This does not mean that sunrise will happen earlier tomorrow than it did this morning, however. Actually, sunrise will carry on getting later until the new year. 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).

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 shape 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 winter solstice is the lowermost point on this curve and the summer solstice is at the top. 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.

Using a more rapid calculational tool (Google), I found a table of the local mean times of sunrise and sunset for Dublin around the 2019 winter solstice. This shows that tomorrow is indeed the shortest day (with a time between sunrise and sunset of 7 hours 29 minutes and 58 seconds).  The table also shows that sunset already started occurring later in the day before the winter solstice, and sunrise will continue to happen later for a few days after the solstice, notwithstanding the fact that the interval between sunrise and sunset gets longer from today onwards.

I hope this clarifies the situation.

Follow @telescoper

Arrival of Storm Atiyah

I was a bit alarmed when I saw this weather forecast map on Friday. At first I thought it meant that Ireland was about to be swallowed by a black hole but when I realised it was Storm Atiyah I had the lesser but still significant concern that my flight home from Cardiff would be disrupted.

As it happened the flight was on time, though the blustery winds at Dublin Airport ahead of the storm made for a more than slightly bumpy landing.

I was in one of these:

It’s a Bombardier Dash-8 Q400 operated by FlyBe. I had a window seat on the right hand side so had a good view as we bobbled around on the way in to land. The wings being above the level of the cabin and my seat being next to the starboard engine I could see the right undercarriage come down as we approached. We weren’t quite level when we reached the runway though and I felt and heard the left set of wheels touch down while the ones on the right I could see were still in the air. I could also see weren’t moving exactly parallel to the runway but slightly crosswise. We travelled for quite a few seconds on one set of wheels before we had both feet on the ground, so to speak. During that time I thought we might go off the side of the runway. When the right set of wheels did touch down, however, causing a big splash of water, only a slight correction was needed to point us in the right direction and all was well.

Pilots are if course trained to cope with windy conditions and I’m sure everything was always under control but I bet pilots do have to concentrate hard on such occasions.

Follow @telescoper

Happy Birthday, Quaternions!

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.

Follow @telescoper