Archive for June, 2019

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More Vain Human Fake (Cosmology) Science

Posted in The Universe and Stuff with tags , on June 24, 2019 by telescoper

I haven’t mucked out my spam folder for a while and when I did so just now I found that a long-term irritant of mine, a certain Mr David Hine, had attempted to post another comment:

I have to admit that I’m not well up on the biblical references so I looked them up. Isaiah Chapter 40 Verse 22

He sits enthroned above the circle of the earth, and its people are like grasshoppers. He stretches out the heavens like a canopy, and spreads them out like a tent to live in.

I don’t see any mention of the Hubble constant, nor indeed any statement that the stretching of the heavens follows a linear relation (Hubble’s Law).

As for Psalm 2, in the New International Version, Verse 1 reads:

Why do the nations conspire
    and the peoples plot in vain?

I have only just now realized that the second part of this verse refers to the construction of graphs. Personally, I never plot in vain. I normally use python.

UPDATE: I have now received further information of the derivation of the Hubble constant straight from the horse’s arse mouth:

 

Unfortunately I am so lacking in mental equipment I can’t really understand this equation. It’s not even an equation actually because it doesn’t equate anything with anything.

Anyway, let’s look at the expression given in the above comment. A Megaparsec has the units of length. The speed of light has units of length/time, so  whatever the formula calculates has units of length2 time-1, which is dimensionally incorrect for the Hubble constant, which has units of time-1.

Moreover, if I put values for c, π, 21 and 2 into the equation I don’t even get anything like 70.98047:

π21 ≈ 2.75 × 1010 (dimensionless).

2 × `a Mpc’ × c ≈ 2 × 3.086 ×1022 m × 3 × 108 m s-1 ≈ 1.83 × 1031 m2 s-1.

Thus the full expression has a value approximately 6.66 × 1020 m2 s-1.

The correct value for the Hubble constant is about 2.2 × 10−18 s−1.

Completely wrong value and completely wrong dimensions. The first three figures of the answer may be significant however.

Here’s some reasoned criticism:

 

I’ve checked the above calculation and don’t see any mistakes. Perhaps I forgot to take away the number I first thought of…

 

 

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Birds of Play

Posted in Biographical, Maynooth with tags , , on June 23, 2019 by telescoper

As if it weren’t enough to have a celebrity cat, Maynooth University now also has a celebrity bird. Or birds. I’m not absolutely sure that it’s the same Jackdaw that is a frequent visitor to offices on the South Campus, as they are so many around, but here are a few pictures taken from Twitter which may or may not be the same critter:

I’ll assume for the purpose of this blog that it is the same bird, but I don’t know whether it’s male or female so I’ll just say call it `it’. As you can see, it is very trusting of humans.

Jackdaws are extremely characterful, intelligent and inquisitive birds. These traits are not unrelated. In fact this is true in general of the family Corvidae which includes the genus Corvus (crows, rooks, ravens, and jackdaws) as well as magpies, jays, nutcrackers and a number of other species: this family has about the same ratio of brain to body weight as the great apes and cetaceans.

One of the characteristics of this family is their propensity to indulge in various forms of play. I imagine most people know that magpies and other Corvidae like to steal and hoard shiny things, but they also engage in even stranger behaviour. I saw some crows sliding down a roof on campus during the winter snows, which is one of their favourite games. They also like to hang upside down from branches, washing lines and telephone wires. Another thing I’ve seen groups of campus jackdaws do is collect sticks and arrange them in patterns on the ground. I’m not at all sure of the rules of the game they were playing, but they seemed to be taking it very seriously, which made it all the funnier to watch.

I’ve heard various reports of what the Jackdaw above gets up to when visiting staff offices. Most of its activities cause considerable chaos. It seems to be fascinated by string, elastic bands and tissue paper which it pulls out of any container that it can and scatters about. It also has a particular interest in pencils, a fascination which may be related to the stick game I mentioned in the previous paragraph, and it delights in pulling them out of containers to play with.

I’m not aware of any jackdaws coming into offices on the North Campus (where my office is situated), which is a shame because they provide a great deal of amusement.I imagine it took quite a long time to build up a sufficient level of trust for this one to feel comfortable indoors because, outside, they seem rather wary of humans.

I can add one personal anecdote though. Some weeks ago I went for a walk along the canal and at one point sat down on a bench on the towpath. I wasn’t there long until a Jackdaw appeared on the ground and began tugging at the shoelaces on my left foot. I assumed it thought they were something edible such as worms or perhaps spaghetti so just watched in amusement as it tugged more and more frantically. It was only then that I realized that there another Jackdaw had appeared to my right hand side on the bench and was busy trying to get into my bag. This was clearly an attempted distraction theft, but I refrained from calling the Gardaí..

P.S. Here’s a hooded crow trying much the same trick.

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Summer Open Day

Posted in Biographical, Education, Maynooth with tags , on June 22, 2019 by telescoper


This morning I made my way onto campus to  represent the Department of Theoretical Physics at Maynooth University’s Summer Open Day which took place today. Naturally I encountered Maynooth Library Cat on the way. I’ve never seen him in that location amid the shrubs before, and when I saw him heading for that place I thought he might be about to do a poo in the mulch (which looks a bit like a litter tray). Instead of that he just flopped into the position shown in the photo. It was quite sunny early on today and I think he was happy to have found a spot in the shade.

Despite the good weather, the Open Day wasn’t as busy as the last couple I’ve been involved with, probably because this year’s Leaving Certificate examinations haven’t quite finished. Nevertheless we had a reasonable number of prospective students visit the stall in Iontas, shown here with Rebekah (a current student in the Department on a summer research project):

Later on I gave a talk. The audience was fairly small but quite a few people took the opportunity to ask questions at the end, so I think it was useful for those who attended.

At least today the weather was nice, even if the occurrence of the solstice yesterday means that the nights are now drawing in…

I find these occasions always bring a bit of a flashback to Sussex days, actually, when I used to have to do this sort of thing quite regularly on Saturdays throughout the year. It’s almost three years since I left there. Can it really be so long already?

 

 

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On Bumfodder

Posted in Books, History with tags , , on June 21, 2019 by telescoper

It’s not quite the end of the week for me, as I am on duty all day tomorrow for the Summer Open Day at Maynooth University, but I thought I’d end the penultimate working day of this week with a post about a piece I read in the Times Literary Supplement a few weeks ago. I subscribe to this mainly for the crossword, but also because some of the reviews are extremely interesting.

In the May 31st issue of said organ, I came across a review of a book charmingly entitled Bellies, bowels and entrails in the eighteenth century, which is published by Manchester University Press. I’m not planning to buy a copy as it costs £96, but it I was intrigued by the review, which includes such vivid insights as

Stomachs and bellies, hiccups and flatulence dominate the last third of the book…

The thing that really caught my attention however was the issue of toilet paper. As far as I am aware, paper in a form specifically designed for the use of wiping one’s bits clean after defecation wasn’t introduced until the middle of the 19th century, but waste paper was commonly used for that purpose much earlier. In the 18th century it was apparently commonplace to tear pages out of cheap books to use as lavatory tissue, and it appears some people would buy books both to read when on the job and for cleaning up afterwards.

This practice gave rise to the word bumfodder, which the Oxford English Dictionary defines as:

  1. Toilet paper. Also occasionally: a piece of this.

  2. attributive and allusively. Worthless or inferior literature; any written or printed material that is perceived as useless, tedious, or unnecessary.

In case you didn’t know, this is also the origin of the word bumf, which the OED gives as

  1. slang (originally in British public schools). Paper (of any kind). Now rare.

  2. Toilet paper. Now somewhat archaic.

  3. orig. Military slang. Written or printed material that is perceived as useless, tedious, or unnecessary, as bureaucratic paperwork, advertising, etc. Also occasionally: worthless or inferior literature.

I have to admit I’ve used the word `bumf’ in the third sense on a number of occasions without realizing quite how indelicate is its origin.

The first instances of `bumfodder’ quoted in the OED date from the mid-17th Century, which surprises me a little because I was under the impression that paper was an expensive commodity then. By the 18th century, however, it was obviously much cheaper, presumably because of mass production, and so consequently books and newspapers were much less expensive. Waste paper was then used quite frequently not only as toilet paper but also for wrapping groceries and other goods. I should mention, however, that paper was used at toilet tissue in China as far back as the 6th Century AD, so Europe was obviously a bit behind on the matter.

Anyone who has read any 18th Century literature – the humour in which is often rather coarse – will not be surprised by the number of scatalogical jokes about bumfodder going around. Obviously I couldn’t repeat any here.

P.S. Now wash your hands please.

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The Summer Solstice 2019

Posted in Uncategorized with tags , , , , , , on June 21, 2019 by telescoper

The Summer Solstice in the Northern hemisphere happens today, Friday 21st June 2019, at 16.54 Irish Time (15.54 UTC). Among other things, this means that today is the longest day of the year. Days will get shorter from now until the Winter Solstice in December. Saturday June 22nd will be two seconds shorter than today!

This does not mean that sunset will necessarily happen earlier tomorrow than it does today however.  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 2019 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 22nd June is actually a bit later than this evening, while sunrise is a bit later.

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:

maxresdefault

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.

 

 

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Vain Human Fake (Cosmology) Science

Posted in Uncategorized with tags on June 20, 2019 by telescoper

I haven’t mucked out my spam folder for a while and when I did so just now I found that a long-term irritant of mine, a certain Mr David Hine, had attempted to post another comment:

I have to admit that I’m not well up on the biblical references so I looked them up. Isaiah Chapter 40 Verse 22

He sits enthroned above the circle of the earth, and its people are like grasshoppers. He stretches out the heavens like a canopy, and spreads them out like a tent to live in.

I don’t see any mention of the Hubble constant, nor indeed any statement that the stretching of the heavens follows a linear relation (Hubble’s Law).

As for Psalm 2. In the New International Version, Verse 1 reads:

Why do the nations conspire
    and the peoples plot in vain?

I have only just now realized that the second part of this verse refers to the construction of graphs. Personally, I never plot in vain. I normally use python.

 

 

 

4 Comments »

Margaret Skinnider – in her own words

Posted in History with tags , , on June 20, 2019 by telescoper

A few weeks ago, occasioned by a stroll around St Stephen’s Green in Dublin, I put up a post that included the the remarkable story of Margaret Skinnider.

Before the 1916 Easter Rising Margaret Skinnider was a school teacher. During the hostilities she initially acted as a scout and a runner, carrying messages to and from the GPO, but when given the chance she proved herself a crack shot with a rifle and showed conspicuous courage during the heavy fighting in and around St Stephen’s Green. In particular, on 27th April she lead a squad of men in an extremely dangerous mission against a British machine gun position, during which she was hit three times by rifle bullets and very badly wounded.

Anyway, I found this fascinating recording of Margaret Skinnider herself telling the story of her part in the 1916 Easter Rising.

After the War of Independence and the subsequent Civil War were over, Margaret Skinnider returned to her career as a primary school teacher. She died in 1971.

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While Tories distract us with Brexit, the NHS has just slipped out its first price list for treatments

Posted in Uncategorized on June 19, 2019 by telescoper

Don’t say you weren’t warned.

Tom Pride's avatarPride's Purge

Please don’t say you weren’t warned.

Because you’ve been warned time and time and time again the Tories are stealthily privatising the NHS.

This doesn’t mean just handing over hospitals and NHS services to private firms.

It means stealthily introducing actual charges to NHS patients at point of need.

This is all totally ignored by the mainstream press of course.

NHS trusts are now so confident they’ll get away with it, they are openly publishing the very first price lists since the formation of the NHS – for NHS operations, NHS procedures and NHS consultations (see here):

nhs charges 1

PLEASE SHARE if you care about the NHS. Thanks.

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Atmospheric Muons as an Imaging Tool

Posted in The Universe and Stuff with tags , , on June 19, 2019 by telescoper

The other day I came across an interesting paper with the above title on the arXiv. The abstract reads:

Imaging methods based on the absorption or scattering of atmospheric muons, collectively named under the neologism “muography”, exploit the abundant natural flux of muons produced from cosmic-ray interactions in the atmosphere. Recent years have seen a steep rise in the development of muography methods in a variety of innovative multidisciplinary approaches to study the interior of natural or man-made structures, establishing synergies between usually disconnected academic disciplines such as particle physics, geology, and archaeology. Muography also bears promise of immediate societal impact through geotechnical investigations, nuclear waste surveys, homeland security, and natural hazard monitoring. Our aim is to provide an introduction to this vibrant research area, starting from the physical principles at the basis of the methods and reviewing several recent developments in the application of muography methods to specific use cases, without any pretence of exhaustiveness. We then describe the main detector technologies and imaging methods, including their combination with conventional techniques from other disciplines, where appropriate. Finally, we discuss critically some outstanding issues that affect a broad variety of applications, and the current state of the art in addressing them.

This isn’t a new field, but it’s new to me and this paper provides a very nice introduction to it. I’ve taken the liberty of reproducing Figure 3 here to show one application of `muography’..

 

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Physics Lectureship in Maynooth!

Posted in Maynooth with tags , , , , , on June 18, 2019 by telescoper

Every now and then I have the opportunity to use the medium of this blog to draw the attention of my vast readership (both of them) to employment opportunities. Today is another such occasion, so I am happy to point out that my colleagues in the Department of Experimental Physics are advertising a lectureship. For full details, see here, but I draw your attention in particular to this paragraph:

The Department of Experimental Physics is seeking candidates with the potential to build on the research strengths of the Department in the areas of either terahertz optics or atmospheric physics. The Department is especially interested in candidates with research experience that could broaden the scope of current research activity. This could include for example terahertz applications in space, imaging, remote sensing and communications or applications of atmospheric physics related to monitoring and modelling climate change. It would be an advantage if the candidate’s research involved international collaboration with the potential for interdisciplinary initiatives with other University institutes and departments.

The deadline for applications is Sunday 28 July 2019 at 11.30pm.

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