Episode 4, in which I show that spiral galaxies are very grubby – they contain huge amounts of dust. And not only galaxies – astronomical dust is everywhere we look. The Universe may be big, but it sure is dirty..
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Watch “Why the Universe is quite disappointing, really – Episode 4” on YouTube
Posted in The Universe and Stuff, YouTube with tags astronomy, dust, galaxies, M31, M64 on May 19, 2020 by telescoperHubble Tension in Perspective
Posted in The Universe and Stuff with tags Cosmology, Durham, Hubble constant, Richard Ellis on May 18, 2020 by telescoperIn my office today for the first time in a couple of months I stumbled across a folder containing the notes from the summer school for new Astronomy PhD students I attended in Durham in 1985. Yes, that’s thirty five years ago..
Among the lectures was a set given by Richard Ellis on Observational Cosmology from which I’ve taken this little snippet about the Hubble Constant:
It’s not only a trip down memory lane but also up the cosmological distance ladder! You will see that there were two main estimates, one low and one high. Both turned out to be about three sigma away from the currently-favoured value of around 70.
Plus ça change, plus c’est la même chose…
Does this change your mind about today’s tension between another pair of “low” (67) and “high” (73) values?
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Posted in Biographical, Covid-19 on May 18, 2020 by telescoper
So here we are then. Phase One of the relaxation of Ireland’s Covid-19 restrictions begins today. The focus will be on the extent to which people continue to follow the rules while the modest loosening of restrictions takes place.
Here is the most recent log plot summarising the Covid-19 epidemic in Ireland. I’m keeping track of the numbers here.
Yesterday only 64 new cases were reported, the lowest since mid-March, along with 10 deaths.
Here is a plot of new cases on a linear scale so you can see the decline more easily.
And the mortality figures look like this:
Data and explanatory notes can be found here.
The signs are thus optimistic but I think its very sensible to take this in slow stages. It remains perfectly possible for infection to spread again if the remaining precautions are not taken seriously. By and large, though, people have been sensible so far and I’m hopeful.
I shall shortly be attempting to remember where my office is so I can go in and deal with some online assessments.
I suppose it won’t be long until we start getting instructions on how to prepare for Phase 2.
Update: I made it into the Department where I noticed the evidence of the last time I was there!
One down, Thirteen to go..
Posted in Education, Maynooth with tags Department of Theoretical Physics, Examinations, Maynooth University on May 17, 2020 by telescoper
As I mentioned in a recent post, Saturday saw the first of our new-fangled examinations online timed assessments in the Department of Theoretical Physics at Maynooth University. Despite all the planning I was quite nervous as the time for that test approached and it wasn’t even one of my examinations on that occasion!
Happily the event went ahead without any significant technical hitches and all students who took the paper managed to upload answers.
The type of mathematical problems we set in the Department of Theoretical Physics means that students will work out their answers by hand on paper which then requires scanning and converting to a PDF. That’s not very hard to do but it’s not as easy as writing an essay on a laptop then uploading a document file which is what some subjects involve.
In this sense, I think we ask a bit more of our students than many other Departments, and I very much appreciate the effort they have made to master an unfamiliar system. That goes for the staff too – this is all new for all of us!
I thought that anything significant was going to go wrong it would do so in the first one, so the fact that nothing broke not only brings relief but also builds confidence for the thirteen further examinations we have over the next two weeks.
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Posted in Cute Problems, The Universe and Stuff with tags circular orbits, geostationary satellite, Gravity, satellite on May 16, 2020 by telescoperI’m was mucking out this blog’s blocked comments folder and unsurprisingly found a few from Mr Hine, a regular if sadly deranged correspondent.
One of his blocked comments begins
In the forlorn hope that Mr Hine might some day learn something scientifically correct I thought I’d repost this problem, which is very easy if you have a high school education in physics or applied mathematics but no doubt very difficult if you’re Mr Hine.
Verify that the radius of a circular geostationary orbit around the Earth is about 42,000 km, i.e. find the radius of a circular orbit around the Earth which has a period of 24 hours so that its orbital period matches the Earth’s rotation period, thus ensuring that an object travelling in such an orbit in the same direction as the Earth’s rotation is always above the same point on the Earth’s surface.
(You will need to look up the mass of the Earth.)
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Posted in Biographical, Covid-19, Education, Maynooth with tags Covid-19 on May 16, 2020 by telescoper
Yesterday (Friday 15th May) the Government of Ireland announced that Phase 1 of the Roadmap for relaxation of its Covid-19 restrictions would commence as planned on Monday 18th May.
This won’t make a huge difference to those people working in third level institutions because it means that anyone who can work from home should continue to do so. As you can see in the graphic above, though, some (limited) access to buildings will be available to allow staff access “to facilitate remote learning”.
Here at Maynooth University our teaching term is over and we’re into the examination period, so there is no actual teaching going on. There are exams, however, and some staff (including myself) will be going onto campus to oversee these, including sitting by their office phones in case of emergency. It is a great relief that we can do this during the examination period as things would have been far more complicated otherwise, especially for those of us who don’t have full internet access at home.
Access for this purpose will be strictly limited and in general the campus is not open. The rules for those coming into campus are quite strict. These are excerpts from the instructions sent out by the University last night:
- Everyone who can work effectively from home should continue to do so, and non-essential travel should not be undertaken.
- The campus is not open, and there is no general access, but you may access your office in limited circumstances if you cannot otherwise prepare for or deliver remote teaching and assessment. Approval from your Head of Department is required in all instances.
- Always observe physical distancing of 2m and ensure thorough hand hygiene. These are key individual responsibilities to minimise the spread of the virus.
- Employees should wash their hands when they arrive and leave.
- Essential access will be limited to an individual’s office, provided it is not shared. If you work in a shared office, you should co-ordinate with your colleagues to make sure that you are not there at the same time.
- There will be no general access to any shared facilities, except toilets. Toilets will be cleaned every evening, but it is the responsibility of every individual to ensure personal hand hygiene on leaving the toilets.
- Anyone who does require access to their office should make their way directly to their office and avoid congregating in groups. Once the essential work is complete, you should leave the campus directly.
A more general ‘return-to-work’ will start in Phase 2 (in three weeks’ time) but several things related to health and safety will need to be organised before that. In the meantime I expect the Department of Theoretical Physics will continue to be empty apart from occasional visits by myself and one or two other members of staff.
Anyway, we need to take life one phase at a time. My main priority on Monday will be trying to remember where my office is, as I haven’t been there for nine weeks!
P. S. Schools in Ireland will not reopen until the start of the new school year, in August.
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Posted in The Universe and Stuff with tags Adam Riess, arXiv:2005.02445, Cepheid varfiables, Cosmology, Hubble constant, Shaun Hotchkiss on May 15, 2020 by telescoperHere’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.
Follow @telescoperNearly Time for Timed Assessments
Posted in Astrohype, Covid-19, Maynooth on May 14, 2020 by telescoperFriday 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!
Follow @telescoperHow to Solve Physics Problems
Posted in Cute Problems, Education, Maynooth, The Universe and Stuff, YouTube with tags education, How to Solve Physics Problems, Physics on May 14, 2020 by telescoperSince 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.
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Posted in Art, Biographical, Covid-19, Mental Health with tags Art, Coronavirus, Covid-19, dreams, Nigel Farage, Salvador Dalí, The Dream 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!
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In the Dark 