Cosmology Talks: Adam Riess on Cepheid Crowding and the Hubble Tension

Posted in The Universe and Stuff with tags , , , , , on May 15, 2020 by telescoper

Here’s another example from the series of cosmology talks being curated by Shaun Hotchkiss. In this one, esteemed astronomer and Nobel Prize winner Adam Riess talks about what he and collaborators considered to be the leading candidate for a systematic error in the SHOES measurement of the expansion rate of the Universe. This is “Cepheid crowding”, the possibility that background sources change our interpretation of Cepheid brightness, ruining one step in the SHOES distance ladder. Riess and collaborators devise a nice way to test whether the crowding is correctly accounted for and find that it is, so crowding cannot be the “explanation” of an error in the distance ladder measurement of H0. Riess also stresses that both the early and late universe measurements of H0 are now backed up by multiple different measurements. Accordingly, if the resolution isn’t fundamental physics, then no single systematic can entirely solve the tension.

P. S. The paper that accompanies this talk can be found on the arXiv here.

Nearly Time for Timed Assessments

Posted in Astrohype, Covid-19, Maynooth on May 14, 2020 by telescoper

Friday 15th May is the first day of the summer examination period at Maynooth University. I’ve written posts at the start of every examination period I’ve been involved with over the 11 years or so I’ve been blogging but this is definitely the strangest.

Owing to the restrictions imposed by the Irish Government to deal with the Covid-19 emergency, exams in the Department of Theoretical Physics this year will be unsupervised timed assessments, similar to traditional exams but done by remotely by the students and then uploaded to our virtual learning environment, Moodle. I posted about this a few weeks ago here.

The duration of these examinations is the same as usual (2 hours in most cases) and the students should be able to use past examinations to prepare reasonably well for them. The questions, however, have been set in the knowledge that students will have access to notes and textbooks so there there is a lot less ‘bookwork’ in the papers and a greater emphasis on problem solving.

Students have extra time added to scan and upload their answers and have been given detailed instructions on the entire process. Staff across the University have worked very hard to develop this new method of assessment in the short time available and to give as much instruction as possible about the technology needed.

Our overriding concern is to be as fair as possible in giving students to demonstrate what they have learnt. There are contingency plans in case things go wrong and staff will be available for consultation during the assessments in case there are problems. The intention is to ensure as much as possible that no student is penalised for circumstances beyond their control. I honestly think that we have done everything that could have been expected of us in the circumstances to make this new system work.

Nevertheless I don’t mind admitting I’m still a bit apprehensive about the forthcoming tests. A famous General once said that “no plan of battle survives first contact with the enemy*” and some improvisation may be required. Our first examination in Theoretical Physics will not be until Saturday (16th) so at least we will find out what befell Departments in the first wave tomorrow before taking our turn.

At times like this I think the best advice for examiners and examinees alike comes from Douglas Adams.

*In this context the enemy is the technology rather than the students!

How to Solve Physics Problems

Posted in Cute Problems, Education, Maynooth, The Universe and Stuff, YouTube with tags , , on May 14, 2020 by telescoper

Since the examination period here at Maynooth University begins tomorrow I thought I would use the opportunity provided by my brand new YouTube channel to present a video version of a post I did a few years ago about how to solve Physics problems. These are intended for the type of problems students might encounter at high school or undergraduate level either in examinations or in homework. I’ve tried to keep the advice as general as possible though so hopefully students in other fields might find this useful too.

Dream Time

Posted in Art, Biographical, Covid-19, Mental Health with tags , , , , , , on May 13, 2020 by telescoper

The Dream (Salvador Dali, 1931)

I know I’m not alone during this strange and unsettling Coronavirus period in having extraordinarily vivid dreams almost every night.

I’m grateful for two things related to this. One is that I’m sleeping much better than usual, with not a trace of the insomnia I’ve experienced in the past during times of stress. The other is that these dreams are very far from being nightmares. Most of them are benign, and some are laugh-out-loud hilarious.

The other day, for example, I had a dream in which Nigel Farage returned from his recent trip to Dover in search of migrants publicity to find his house filled with asylum seekers singing the theme from The Dambusters. There was also a cameo appearance by Nigella Lawson in that dream but I forget the context.

I’ve written about dreams a few times before (e.g. here) and don’t intend to repeat myself here. It does seem to me however that dreams are probably a byproduct of the unconscious brain’s processing of notable recent events and this activity is heightened because the current times are filled with unfamiliar experiences.

I know some people are having far worse nocturnal experiences than me, and I don’t really understand why I’m having a relatively easy ride when my past history suggests I’d be prime candidate for cracking up. Perhaps I’ve had enough practice at dealing with anxiety in the past (not always very satisfactorily)? Perhaps the sense of detachment I’ve experienced over the past few weeks is part of some sort of defence mechanism I’ve acquired?

Anyway, don’t have nightmares!

Watch “Why the Universe is quite disappointing, really – Episode 3” on YouTube

Posted in The Universe and Stuff, YouTube on May 12, 2020 by telescoper

Why the Universe is quite disappointing really – Episode 3, in which I give two examples of biological systems that are inefficient and poorly designed. If these are the product of intelligent design, the designer clearly wasn’t concentrating.

Remembering Johnny Hodges – Jeep’s Blues (Live at Newport, 1956)

Posted in Jazz with tags , , , , on May 11, 2020 by telescoper

The great alto saxophonist and long-term mainstay of the Duke Ellington Orchestra Johnny Hodges passed away 50 years ago today, on 11th May 1970.

Here’s the piece that was his signature tune, Jeep’s Blues – played during a very famous live concert by the Ellington band at the Newport Jazz Festival in 1956.

Feast your ears on that huge soulful sound that was perfect for playing the blues!

Calculating the UK COVID Alert Level

Posted in Covid-19, mathematics, Politics with tags , , , on May 11, 2020 by telescoper

I didn’t watch yesterday’s broadcast by the UK’s Clown-in-Chief Bozo Johnson but I gather that he delivered an address that was every bit as coherent and lucid as one might have expected.

I for one am delighted that at last there is some clarity in the UK Government’s position and that they have applied the necessary level of mathematical rigour to their treatment of the Covid-19 Pandemic.

Catching up on these pronouncements via Twitter I was impressed to see, for example, to see this precise formulation of the calculation required to establish the COVID Alert Level.

Let me take you through a detailed calculation using this important formula.

As far as I know the best estimate of the basic reproduction number R in the UK is around 0.8.

As of this morning (11th May) the number of confirmed Covid-19 infections in the UK is 219,183.

Applying the formula I obtain a value

COVID Alert Level = 219183.8

That seems a big number. I thought it should only go up to 11. Have I slipped up somewhere?

Azed 2500

Posted in Biographical, Crosswords on May 10, 2020 by telescoper

Long before this Covid-19 lockdown started I had been planning to attend a lunch, due to take place last weekend, on Saturday 2nd May, at Wadham College Oxford, in honour of Jonathan Crowther who, under the pseudonym Azed, has been setting cryptic crosswords in the Observer for the best part of 50 years. The occasion for this planned shindig was the publication of the 2500th Azed Crossword. I went to a similar celebration about a decade ago when the 2000th Azed puzzle came out and enjoyed it a lot.

Sadly, but of course understandably, the Azed 2500 lunch was cancelled (or at least postponed until September) but the crossword appeared today (above). It looks a bit tricky, but it will have to wait until later because I have many other things to do.

I haven’t been doing crosswords as regularly as usual during this period. The main reason for that is lack of time and energy caused by my current workload, but it’s also the case that most newspapers are no longer running their competitions: without the possibility of a prize I don’t feel do enthusiastic about solving the puzzles. The Azed Competition is still running, though, so I’ll definitely give this one a go.

Anyway let me take this opportunity to thank Azed for all the challenging yet enjoyable crosswords he has set over the years!

Update: I managed to solve the puzzle, which was indeed tricky: it took me a good couple of hours! Now to compose a clue for 34 across!

Leaving Off

Posted in Education, Maynooth with tags , , , on May 9, 2020 by telescoper

So yesterday the Government of Ireland announced that this year’s Leaving Certificate examinations will be cancelled. That decision seems to have surprised quite a few people but to me it looked inevitable once the Covid-19 Roadmap was published last Friday. If you recall these examinations would normally take place in June but this year had been initially been postponed to happen in late July and into August. Now they’re cancelled altogether.

Not many details are available about the scheme proposed to replace the examinations but it will be based on an assessment made by schoolteachers based on previous performance moderated in some way by the Department for Education & Skills, which has oversight of the process.

Most of the reaction I’ve seen on social media from students is that they’re delighted they won’t have to sit the examinations. Questions arise however about how fair the new system will be, especially given that it is being assembled at such short notice.

I note that the Government press release states that

Students will also retain the right to the sit the 2020 Leaving Certificate examinations at a date in the future when it is deemed safe for state examinations to be held.

The Leaving Certificate isn’t just about entry into Third Level Education but it does raise specific issues for that sector. One is how many students who would potentially enter Higher Education in September will defer until they can take the Leaving Certificate proper. If many do that then the implications for University finances in the short term are significant.

Another issue is that Universities have been planning on the basis that because of the delayed Leaving Certificate, newly enrolled students would not be arriving until November. Now it looks like they will come in September along with the returning students, so we now need a Plan B.

On the face of it, it seems good news that we will no longer have the staggered academic year required in Plan B to contend with. On the other hand, if institutions have to operate with strict social distancing measures in place when they reopen, as is likely, the increased number of students in September will make this even more difficult – especially since first-year classes are the usually larger ones. I can’t see any way of coping unless a significant part of our teaching is done remotely. Recorded lectures and virtual tutorials look set to be part of the “new normal” for some time.

The decision to cancel the Leaving Certificate raises other questions but I don’t want to get into a discussion of the rights and wrongs of that decision (in which it seems Ireland’s universities had very little influence) . All I will say – and I’m sure that I speak for all my colleagues at Maynooth University – is that we will do our utmost to operate the new admissions system in a way that is as fair as possible to potential students, and to deliver the best education we can with the resources available within whatever constraints we are under in September. Whatever we do won’t be perfect, but we’ll do our best.

Until then there is no need for students or staff to get even more stressed than we are already, so I hereby invoke the calming influence of Maynooth University Library Cat.

Watch “Why the Universe is quite disappointing really – Episode 2” on YouTube

Posted in The Universe and Stuff, YouTube with tags , , on May 8, 2020 by telescoper

Episode 2, in which I explain how stars limp along unimpressively, making very poor use of the resources available to them, not doing a very good job at what they’re supposed to be doing, and then they die.

Just like people really…