Easter. The grave clothes of winter
are still here, but the sepulchre
is empty. A messenger
from the tomb tells us
how a stone has been rolled
from the mind, and a tree lightens
the darkness with its blossom.
There are travellers upon the road
who have heard music blown
from a bare bough, and a child
tells us how the accident
of last year, a machine stranded
beside the way for lack
of petrol, is crowned with flowers.
by R.S. Thomas (1913-2000)
Follow @telescoperIf in that Syrian garden, ages slain,
You sleep, and know not you are dead in vain,
Nor even in dreams behold how dark and bright
Ascends in smoke and fire by day and night
The hate you died to quench and could but fan,
Sleep well and see no morning, son of man.
But if, the grave rent and the stone rolled by,
At the right hand of majesty on high
You sit, and sitting so remember yet
Your tears, your agony and bloody sweat,
Your cross and passion and the life you gave,
Bow hither out of heaven and see and save.
by A.E. Housman (1859-1936)
Housman was an atheist. This poem was not published in his lifetime, but is the first poem in More Poems which was published shortly after his death.
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As as Astronomist I am often asked “How do they calculate the date of Easter?”, to which my answer is usually “Look it up on Wikipedia!“.
The simple answer is that Easter Sunday is on the first Sunday after the first full Moon on or after the Vernal equinox. The Vernal Equinox took place this year on March 20th and the more observant among you will have noticed that yesterday was (a) Sunday and (b) a Full Moon. Yesterday was not Easter Sunday because the rule says Easter is on the first Sunday after the first full Moon on or after the Vernal equinox, which does not include a Full Moon on the first Sunday on or after the vernal equinox. Accordingly Easter 2021 is next Sunday 4th April. If the Full Moon had happened on Saturday, yesterday would have been Easter Sunday.
That is just as well really because next weekend is when the holidays and sporting events have been arranged.
I say “simple” answer above because it isn’t quite how the date of Easter is reckoned for purposes of the liturgical calendar.
For a start the ecclesiastical calculation of the date for Easter – the computus – assumes that the Vernal Equinox is always on March 21st, while in reality it can be a day or two either side of that. This year it was on March 20th.
On top of that there’s the issue of what reference time and date to use. The equinox is a precisely timed astronomical event but it occurs at different times and possibly on different days in different time zones. Likewise the full Moon. In the ecclesiastical calculation the “full moon” does not currently correspond directly to any astronomical event, but is instead the 14th day of a lunar month, as determined from tables (see below). It may differ from the date of the actual full moon by up to two days.
There have been years (1974, for example) where the official date of Easter does not coincide with the date determined by the simple rule given above. The actual rule is a complicated business involving Golden Numbers and Metonic cycles and whatnot.
I’m grateful to Graham Pointer on Twitter for sending this excerpt from the Book of Common Prayer that sheweth how to determine the date of Easter for any year up to 2199:
I don’t care what happens after that as I’ll be retired by then. If you apply this method to 2021 you will find it is an 8C. Next year will be a 9B. Further calculations are left as an exercise to the reader.
Follow @telescoperIt is 9.37am Local Time in Ireland on Saturday 20th March 2021 which means that the Vernal Equinox or Spring Equinox (in the Northern hemisphere) is taking place right now!
The Spring Equinox jumped back a day last year because 2020 was a leap year and now is gradually moving forward again. Of course the actual date depends on where you are in the world. The date last year was 20th March (early in the morning) in Ireland, but 19th March (late at night) in New York.
People sometimes ask me how one can define the `equinox’ so precisely when surely it just refers to a day on which day and night are of equal length, implying that it’s a day not a specific time?
The answer is that the equinox is defined by a specific event, the event in question being when the plane defined by Earth’s equator passes through the centre of the Sun’s disk (or, if you prefer, when the centre of the Sun passes through the plane defined by Earth’s equator). Day and night are not necessarily exactly equal on the equinox, but they’re the closest they get. From now until the Autumnal Equinox days in the Northern hemisphere will be longer than nights, and they’ll get longer until the Summer Solstice before beginning to shorten again.
Loughcrew (County Meath), near Newgrange, an ancient burial site and a traditional place to observe the sunrise at the Equinox
Here in Ireland we celebrated Saint Patrick’s day on March 17th, the reputed date of his death in 461 AD. Nobody really knows where St Patrick was born, though, so it would be surprising if the when were any better known.
In any case, it wasn’t until the 17th Century that Saint Patrick’s feast day was placed on the universal liturgical calendar in the Catholic Church. In the thousand years that passed any memory of the actual date was probably lost, so the Equinox was perhaps rebranded for the purpose.
The early Christian church in Ireland incorporated many pre-Christian traditions that survived until roughly the 12th century, including the ancient festival of Ēostre (or Ostara), the goddess of spring associated with the spring equinox after whom Easter is named. During this festival, eggs were used a symbol of rebirth and the beginning of new life and a hare or rabbit was the symbol of the goddess and fertility. In turn the Celtic people of Ireland probably adapted their own beliefs to absorb much older influences dating back to the stone age. St Patrick’s Day and Easter therefore probably both have their roots in prehistoric traditions around the Spring Equinox, although the direct connection has long been lost.
Follow @telescoperWith everything else going on I quite forgot that the Vernal Equinox or Spring Equinox (in the Northern hemisphere) took place today (Friday 20th March) at 3.49am (Irish Time). This is in fact the earliest Spring Equinox for 124 years, the fact that 2020 is a leap year moving it a day earlier in our calendar. It’s a lovely day in Maynooth too!
People sometimes ask me how one can define the `equinox’ so precisely when surely it just refers to a day on which day and night are of equal length, implying that it’s a day not a specific time?
The answer is that the equinox is defined by a specific event, the event in question being when the plane defined by Earth’s equator passes through the centre of the Sun’s disk (or, if you prefer, when the centre of the Sun passes through the plane defined by Earth’s equator). Day and night are not necessarily exactly equal on the equinox, but they’re the closest they get. From now until the Autumnal Equinox days in the Northern hemisphere will be longer than nights, and they’ll get longer until the Summer Solstice before beginning to shorten again.
Loughcrew (County Meath), near Newgrange, an ancient burial site and a traditional place to observe the sunrise at the Equinox
Here in Ireland we celebrated Saint Patrick’s day on March 17th, the reputed date of his death in 461 AD. Nobody really knows where St Patrick was born, though, so it would be surprising if the when were any better known.
In any case, it wasn’t until the 17th Century that Saint Patrick’s feast day was placed on the universal liturgical calendar in the Catholic Church. In the thousand years that passed any memory of the actual date was probably lost, so the Equinox was perhaps rebranded for the purpose.
The early Christian church in Ireland incorporated many pre-Christian traditions that survived until roughly the 12th century, including the ancient festival of Ēostre (or Ostara), the goddess of spring associated with the spring equinox after whom Easter is named. During this festival, eggs were used a symbol of rebirth and the beginning of new life and a hare or rabbit was the symbol of the goddess and fertility. In turn the Celtic people of Ireland probably adapted their own beliefs to absorb much older influences dating back to the stone age.
St Patrick’s Day and Easter therefore probably both have their roots in prehistoric traditions around the Spring Equinox, although the direct connection has long been lost.
Follow @telescoperSo here we are, then. The term is finally over. Lectures officially finished yesterday, and there’s now another week or so before examinations start (next Friday, 17th May). The examinations for my two modules take place on Tuesday 21st and Wednesday 22nd May, and after that I’ll be busy with marking for a while. In fact, I’ll probably be getting much busier in general pretty soon, but more of that in due course…
Marking doesn’t just mean written examinations. I have been teaching a module on Computational Physics to 3rd Year students here in Maynooth, and 40% of the assessment for that is a mini-project (usually done in groups of two or three). Early on the term, I put up a list of a dozen or so projects and ask them to pick first second and third choices so I can form groups in such a way that most students get to work on a project they like the look of. This year I made up a new set of projects, but I feel a bit sorry for one of them (`Scattering in a Spherical Potential’), which didn’t appear anywhere \at all on any student’s list of preferences. That’s a shame as I thought it was a well-rounded project, with lots of potential. Hopefully it will prove more popular next year…
Anyway, the deadline for projects to be handed in came yesterday so I’ve got a stack of those to mark which, you will realise, why I am indulging in a displacement activity by writing this blog post. My plan is to mark these next week so that they’re done before the written examinations come in.
Before I get on with what I should be doing I’ll just mention another thing that happened yesterday: the President of Ireland (Uachtarán na hÉireann), Michael D. Higgins visited Maynooth University yesterday:
That’s him at the front, on the right, of course. The reason for his visit was to attend a memorial service.
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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!
Follow @telescoperThis is Week 11, which is the last week of teaching here at Cardiff University before the Easter break. In the early hours of this morning I finished marking my last set of coursework for the term and later on delivered my last (2-hour) lecture on the Physics of the Early Universe.
I’ve booked two weeks of annual leave from Friday and am really looking forward to a bit of rest, though I will have quite a few private matters to deal with while I’m away from work.
Such is the topsy-turvy world we live in that I note that this month’s meeting of the Royal Astronomical Society is on this Friday, 7th April. This is contrary to the settled order of Nature, as these meetings are always on the second Friday of the month. This year, however, the 2nd Friday of April is Good Friday. This, after all, is Eastertide, when Christians celebrate the invention of the chocolate egg by doing arms deals with despotic middle-eastern governments.
I’m only joking. Of course. Chocolate eggs have nothing to do with the true message of Easter, which is depicted in the following.
Anyway, it’s the fact that Easter moves about in the calendar that is the reason this term has been so long and I am tired and grumpy. I don’t like chocolate either.
On the bright side I did receive two pieces of good news today in between the other stuff. I hope to be able to pass them on tomorrow, or at any rate before I go off on my hols…
Follow @telescoperToday is Palm Sunday, the start of what Christians call “Holy Week”, which culiminates in Easter. It’s also the birthday of the great Welsh poet R.S. Thomas, who was born on this day in 1913. Thomas spent much of his life as an Anglican priest. I’m not a Christian but I am drawn to the religious verse of R.S. Thomas not only for its directness and lack of artifice but also the honesty with which he addresses the problems his faith sets him. There are many atheists who think religion is some kind of soft option for those who can’t cope with life in an unfriendly universe, but reading R.S. Thomas, whose faith was neither cosy nor comfortable, led me to realise that is very far from the case. I recommend him as an antidote to the simple-minded antagonism of people like Richard Dawkins. There are questions that science alone will never answer, so we should respect people who search for a truth we ourselves cannot understand.
And whether or not it is clear to you, no doubt the universe is unfolding as it should. Therefore be at peace with God, whatever you conceive Him to be.
I will be offline for the Easter holiday so I thought I’d post a poem that I find appropriate to the time of year. You can read it as Praise for God, or for Nature, or for both. I don’t think it matters.
I praise you because
you are artist and scientist
in one. When I am somewhat
fearful of your power,
your ability to work miracles
with a set-square, I hear
you murmuring to yourself
in a notation Beethoven
dreamed of but never achieved.
You run off your scales of
rain water and sea water, play
the chords of the morning
and evening light, sculpture
with shadow, join together leaf
by leaf, when spring
comes, the stanzas of
an immense poem. You speak
all languages and none,
answering our most complex
prayers with the simplicity
of a flower, confronting
us, when we would domesticate you
to our uses, with the rioting
viruses under our lens.
So here we are, then. The last day of term has finally arrived. Many of our students will be out partying tonight before they start a three-week break with little to disturb their relaxation but project reports, assignments and examination revision. Probably not all that relaxing at all then, especially for the final-year students.
For various reasons I’ve found this term very heavy going and am looking forward to spending some time away over the next couple of weeks. More about that in due course, assuming I have internet access…
The curious thing about the academic year is that since most UK universities switched to a semester system we’ve had to cope with the fact that Easter isn’t on a fixed calendar date. Last year, Easter was rather late so we managed to squeeze in a full 11 weeks teaching in before the vacation started. This year we’ve only got time for 9 weeks, so we resume teaching in three weeks’ time for another two weeks, followed by a revision week and the examination period. I think most students probably agree with me that this hiatus is extremely annoying.
This year Good Friday is on 6th April (a week today) and Easter Monday on 9th April; both are statutory (“bank”) holidays in the UK. Most universities have felt obliged to move their recess so that these two holidays occur outside term-time.
If I had my way we would have fixed semester dates so this nonsense of a 9+2 week teaching semester wouldn’t happen. Last year’s 11-week uninterrupted run was a slog, but I much prefer it over the stop-start affair we’re having this year.
I was a visiting professor at an American university over one Easter period many years ago. Given the fact that the Christian lobby is far more powerful over there than it is here I was quite surprised by the fact that there’s no real interruption for Easter. Lectures were held on Good Friday and there’s no Easter Monday holiday. Easter Sunday was definitely observed, but that had no effect on teaching.
The two Bank Holidays are a bit of a problem, of course, especially because they are followed by two more in May. However, when I was an undergraduate at Cambridge, we had lectures as normal on bank holidays. I’m not sure whether that practice was restricted to Oxbridge colleges – where term dates are different to elsewhere anyway – or some other Universities did the same. I don’t even know if Oxbridge still carries on over bank holidays today…
A better solution would be to distribute the statutory holidays more evenly through the year so they weren’t concentrated so inconveniently in Spring. There would be nothing to stop Christians taking a day’s leave in order to observe Good Friday, of course.
But since only a minority of British people are practising Christians, why are the rest of us forced to arrange our calendars according to archaic and irrelevant rituals? Far better, in my opinion, to give us all a day off for the start of the cricket season…
Grumble over, it just remains for me to wish my loyal readers (Sid and Doris Bonkers) all the best for the recess, and I hope it’s a good night at the Student Ball tonight!
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In the Dark 