Devastating news from Cape Town

Posted in Biographical with tags , , , on April 18, 2021 by telescoper

(Pictures from here.)

A devastating fire that seems to have started somewhere on Table Mountain has swept onto the upper campus of the University of Cape Town, even engulfing the splendid library (last picture; that’s the special collections part in flames).

It’s terrible to see a place you know go up in flames but at least the campus was evacuated before the fire reached it.

I’ve been to UCT several times, including a long visit in 1995 when I wrote a book with George Ellis. The last time was in 2012; see here. During those visits I was based in the Department of Applied Mathematics, which is on the Upper Campus. From what I’ve seen that building has been completely destroyed by the fire, which seems to be out of control.

I’ve not heard any reports of casualties – thank goodness – but it’s still devastating.

UPDATE: Here is an update on the situation in the Library

UPDATE: I’ve heard from George Ellis that the fires are now out: the Maths and Physics & Astronomy buildings have survived.

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Gardener’s Question Time

Posted in Biographical, Maynooth on April 18, 2021 by telescoper

A spell of good weather last week meant that I was able at last to get out and mow the lawns to front and rear of my house. I had tried to do that a while ago but just as I was about to start a hailstorm came down and I abandoned the plan.

By the time I got round to actually mowing it the grass was quite long and still a bit damp which, combined with the poor quality of the old lawnmower I have, meant that I had to do a rough cut followed a couple of dry days later by a closer trim. The lawnmower, incidentally, was left behind in the shed by the previous owner of the house. I was slightly surprised to find that it works at all but I should get myself a new one.

I was joined on the first mow by a little robin who was no doubt on the lookout for bugs disturbed by the grass cutting. I was a bit worried I might accidentally hit the bird with the mower, but he (or she) was fearless, at one point jumping on my foot and pecking at my shoe laces, presumably thinking they were worms.

The rear garden is now looking a bit tidier.

This is a very secluded and quiet space, nice for having lunch al fresco which I did yesterday. The sound of the birdsong around was really delightful. I couldn’t see many birds but they were making a lot of noise wherever they were hiding!

Come to think of it they were probably warning each other about the human weirdo invading their territory. They will have eggs and/or chicks in their nests right now.

Anyway the above bush is in my rear garden, beside the wall next to the, seating area. Does anyone know what it is?

Answers through the comments box please!

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Will we return to on-campus teaching next academic year?

Posted in Biographical, Covid-19, Education, Maynooth on April 17, 2021 by telescoper

As we approach the end of the 20/21 academic year during which most of our teaching has been online rather than face-to-face, a number of students have been asking me whether we will “get back to normal” next September for the start of next teaching year.

The answer I give to this is that I don’t know. It depends entirely on the progress of the battle against the Covid-19 pandemic and that has so far proved to be difficult to predict.

Over the last week, however, the news has made me lean very strongly towards a negative answer. I am now quite confident that there will be no (or at most minimal) in-person teaching at Irish universities in September 2021.

The reason I feel this is the shambolic state of Ireland’s vaccination programme. According to the updates page, as of 15th April, Ireland has administered 1,155,599 vaccine doses, including 814,470 first doses and 341,129 second doses. The figure for total doses on 1st April was 893,375. That means in the first two weeks of April just 262,224 doses have been given. The HSE’s target for April is 800,000 doses; to reach that the daily rate of dishing out vaccinations has to more than double in the second half of the month.

The slowness of the rollout is partly due to a pause in use of the AstraZeneca vaccine because of concerns about blood clots and a decision by Johnson & Johnson not to deliver its promised doses for similar reasons, leaving a shortfall in supply. But that’s not the only reason. If it were then the vaccination programme in Ireland would not be stalling at the same time as Germany’s has been accelerating.

There has been an absurd amount of dithering and disorganization in the Health Service Executive and at Ministerial level which, together with incoherent messaging, has led to administrative chaos.

The AstraZeneca vaccine will in future only be offered to those over the age of 60, with an impact on the timetable for other age cohorts. Last week the HSE announced that Irish people in the general population under the age of 60 will not get their first jab (presumably either Pfizer or Moderna) until June “at the earliest”. It seems – to say the least – unlikely that 80% of the population will receive a vaccine dose by the end of June (the official target) if they’re not going to start on the under-60s until the beginning of that month.

More recently it has been announced that the HSE is also considering changing the correct rollout programme yet again, this time moving people aged 18-30 up the batting order. (Currently the scheme for the general population is organized by age; those in the 65-69 cohort are currently registering.)

I can see the argument for doing that. Younger people tend to have a bigger cross-section for interaction, as it were, and therefore contribute more to the spread of the virus. Prioritizing them would therefore lower the rate of community transmission. On the other hand, moving younger people to a higher priority will have the effect of moving older people down it. But surely this should have been considered long before now?

If the decision is taken to do this people aged 30-50 will not get even their first dose until much later than they would under the current programme, possibly not until the autumn. The vaccination programme plays two roles: one is to protect individuals from serious illness and the other is to slow the transmission of the virus. The former approach means to prioritize the older cohorts while the second pushes in the opposite direction. It’s a difficult question and I think it’s sensible to consider moving younger adults up, though it’s not obvious to me that on balance it would be advantageous.

All of which brings me to the reason I think we won’t be doing on-campus teaching next year, at least for the first Semester. If students (who are mainly aged 18-30) are vaccinated first then most academic staff will probably not be vaccinated by September. If most academic staff are vaccinated by September then probably most students won’t be. Either way it doesn’t look good for a return to campus. I know for a fact that some Irish Universities are already planning for online teaching at the start of the 21/22 academic year. I don’t know what the plans are at my own institution.

I can’t speak for anyone other than myself, but there is I am not going to support a return to face-to-face teaching on campus unless and until a majority of staff and students have been vaccinated. And I am certainly not going to return to campus until I have had both jabs. I am in the 55-60 cohort and may therefore get my first shot in June and second doses by September (although, to be honest, I wouldn’t bet on either of those possibilities).

Of course there are much wider issues to be taken into consideration than what happens in third-level institutions so I’m not saying that this should be a main policy driver, but it’s important to be aware of the ramifications. In previous manifestations of the rollout programme, those involved in delivering education where in a high priority group, but they are no longer. In lowering the priority for vaccination teaching staff, the Government has to accept that it is lowering the priority for a return to campus in September.

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Oh Larmor! Energy in Electromagnetic Waves

Posted in Cute Problems, The Universe and Stuff with tags , , , on April 16, 2021 by telescoper

This week I started the bit of my Advanced Electromagnetism module that deals with electromagnetic radiation, including deriving the famous Larmor Formula. It reminded me of this little physics riddle, which I thought I’d share again here.

As you all know, electromagnetic radiation consists of oscillating electric and magnetic fields rather like this:

Figure10.1

(Graphic stolen from here.) The polarization state of the wave is defined by the direction of the Electric field, in this case vertically upwards.

Now the energy carried by an electromagnetic wave of a given wavelength is proportional to the square of its amplitude, denoted in the Figure by A, so the energy is of the form kA2 in this case with k constant. Two separate electromagnetic waves with the same amplitude and wavelength would thus carry an energy = 2kA2.

But now consider what happens if you superpose two waves in phase, each having the same wavelength, polarization and amplitude to generate a single wave with amplitude 2A. The energy carried now is k(2A)2 = 4kA2, which is twice the value obtained for two separate waves.

Where does the extra energy come from?

Answers through the Comments Box please!

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April is the cruellest month

Posted in Poetry with tags , , , , on April 15, 2021 by telescoper
April is the cruellest month, breeding
Lilacs out of the dead land, mixing
Memory and desire, stirring
Dull roots with spring rain.
Winter kept us warm, covering
Earth in forgetful snow, feeding
A little life with dried tubers.

So begins Part I, The Burial of the Dead from The Waste Land by T.S. Eliot. I thought of it yesterday when I was working in the garden, though I have no lilacs.

The poem is rightly regarded as one of the most important poems of the 20th Century and Eliot one of the most important poets but in my opinion one thing he wasn’t good at was reading his own work. I always found his readings of his own work rather flat and dreary. He’s not the only poet I think that of either, but perhaps that’s just me.

Anyway, here is T.S. Eliot reading all of The Waste Land so you can make your own mind up:

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A New Horizon

Posted in Covid-19, Maynooth on April 14, 2021 by telescoper

With the (very slight) relaxation in Covid-19 restrictions in Ireland starting this week my horizon had increased from the previous 5km to a new 20km radius:

In fact the new rule says “You can travel within your county or up to 20 km from your home”. I could therefore travel even beyond Naas* remaining within County Kildare, and almost to Dublin City Centre or up to Ashbourne in County Dublin and County Meath respectively. The excitement of it all!

*Naas is the location of the hospital where I get my knee treatment, but they’re not doing routine procedures right now so I’ve got no reason to go there.

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The Moon and Blackrock Castle

Posted in Art, The Universe and Stuff with tags , on April 14, 2021 by telescoper

Picture Credit: Cian O’Regan

This image of February’s Full Moon (the “Snow Moon”) by Blackrock Castle Observatory in Cork is by Cian O’Regan. Prints of this and other beautiful images can be bought from his website here.

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Testing Cosmological Reciprocity

Posted in The Universe and Stuff with tags , , on April 13, 2021 by telescoper

I have posted a few times about Etherington’s Reciprocity Theorem in cosmology, largely in connection with the Hubble constant tension – see, e.g., here.

The point is that if the Universe is described by a space-time with the Robertson-Walker Metric (which is the case if the Cosmological Principle applies in the framework of General Relativity) then angular diameter distances and luminosity distances can differ only by a factor of (1+z)2 where z is the redshift: DL=DA(1+z)2.

I’ve included here some slides from undergraduate course notes to add more detail to this if you’re interested:

The result DL=DA(1+z)2 is an example of Etherington’s Reciprocity Theorem and it does not depend on a particular energy-momentum tensor; the redshift of a source just depends on the scale factor when light is emitted and the scale factor when it is received, not how it evolves in between.

Etherington’s theorem requires light rays to be described by null geodesics which would not be the case if photons had mass, so introducing massive photons would violate the theorem. It also requires photon numbers to be conserved, so some mysterious way of making photons disappear might do the trick, so adding some exotic field that interacts with light in a peculiar way is another possibility, as is the possibility of having a space-time with torsion, i.e. a non-Riemannian space-time.

Another possibility you might think of is to abandon the Robertson-Walker metric. We know that the Universe is not exactly homogeneous and isotropic, so one could appeal to the gravitational lensing effect of lumpiness to provide a departure from the simple relationship given above. In fact a inhomogeneous cosmological model based on GR does not in itself violate Etherington’s theorem, but it means that the relation DL=DA(1+z)2 is no longer global. In such models there is no way of defining a global scale factor a(t) so the reciprocity relation applies only locally, in a different form for each source and observer. In order to test this idea one would have to have luminosity distances and angular diameter distances for each source. The most distant objects for which we have luminosity distance measures are supernovae, and we don’t usually have angular-diameter distances for them.

Anyway, these thoughts popped back into my head when I saw a new paper on the arXiv by Holanda et al, the abstract of which is here:

Here we have an example of a set of sources (galaxy clusters) for which we can estimate both luminosity and angular-diameter distances (the latter using gravitational lensing) and thus test the reciprocity relation (called the cosmic distance duality relation in the paper). The statistics aren’t great but the result is consistent with the standard theory, as are previous studies mentioned in the paper. So there’s no need yet to turn the Hubble tension into torsion!

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Spring Return

Posted in Biographical, Covid-19, Education, Maynooth on April 12, 2021 by telescoper

After a few days off last week following the Easter Bank Holiday weekend it’s time to get back into the swing of things for the four weeks of teaching term that remain. It’s back to school today for all school students in Ireland too, so good luck to them on their first day in the classroom since Christmas!

As well as (remote) lectures the next four weeks will involve us getting our papers ready for the examination period which starts on 14th May this year. All our examinations will be remote online timed assessments (as indeed they were last year). I’ve been teaching three modules this Semester so have no fewer than six examinations to write: three main exams plus three repeat papers for the resit period in August. The decision has already been made to make all the repeat exams online so at least these will be of similar style to the original May versions.

Then it will be marking and Exam Boards and various other things heading into the summer break. Hopefully I will get some holiday this summer as I didn’t get any at all last year. On the other hand there’s a strong likelihood that Senior Management will think of something else for Heads of Department to do that will make this impossible.

What happens at the end of summer all depends on Covid-19 of course, and specifically how Ireland’s vaccination programme goes. My personal opinion is that we should continue with remote teaching until all staff and students have had their jabs, which is unlikely to be the case before September at the current rate, but you never know. The speed of vaccination shows signs of increasing though, so we might be able to do it.

Despite the more rapid progress with immunisation over the other side of the Irish Sea, UK university bosses are apparently complaining that they haven’t got a date for returning to campus. This surprises me as they run on roughly the same calendar as here in Ireland so there are only a few weeks of teaching left there too. Why bother to go back at such a late stage? Unless of course it’s so they can charge students for a full term’s accommodation…

 

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Grand National Takeaway

Posted in mathematics, Sport with tags , , , on April 11, 2021 by telescoper

Congratulations to Rachael Blackmore for becoming the first female jockey ever to ride the winner Minella Times of the Grand National yesterday. It was a good race for Ireland generally as the top five were all Irish horses.

The race was led for a long time by 80-1 outsider Jett who at one point was about 10 lengths clear of the field but you could see that about three fences from home the horse was very tired, fading badly over the final stages of the race to finish in eighth place.

At 11-1, Minella Times would have netted quite a few people a good return on their investment. I wasn’t so lucky but had a modest success. After studying the form carefully (i.e. sticking a pin in the list of runners), I settled on Any Second Now, also at 11-1, betting €25 each way. I was pleased yesterday to see the odds shortening to 15/2 at the start, which meant quite a lot of people were backing the same horse.

In the event Any Second Now finished 3rd which was a great result given that it was badly hampered by a faller (Double Shuffle) at the 12th fence. A thing like that is normally difficult to recover from but jockey Mark Walsh did well to get back in contention, though he was too far back and too tired to catch the winner, who ran a perfect race.

The Grand National is one race where I think an each-way bet is a sensible strategy. As a handicap with 40 runners (and a very tough race for which the probability of a horse not making it to the finish line is quite high) the odds are usually pretty long even on the favourite, and most bookies pay out for a place down to sixth. I bet €25 each way, which means €25 to win outright at 11-1 and €25 for a place at one-fifth the odds, i.e. 2.2 to 1. I lost the first €25 but won €55 on the place (plus the stake). My net result was therefore €50 staked for an €80, more than enough profit to pay for last night’s takeaway dinner.

The point is that if you want the place to cover the loss on the win the starting price has to be good. If the odds are N:1 they will only cover the loss if N/5 ≥1 with the equality meaning that you break even. In a race in which the odds are much shorter the place bet is usually not worth very much at all. In yesterday’s Grand National the favourite was 5-1.

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