I ventured onto Maynooth University Campus today and guess who I found there? He seems fine although he wasn’t exactly a busy bee when I paid him a visit. No doubt he’s taking it easy ahead of the new academic year.
At least he’s keeping himself clean!
One of the many highlights of the 2024 Olympics was the amazing achievement of Armand Duplantis in winning the Gold Medal in Pole Vault and in the process breaking his own world record at a height of 6.25m. Here he is
He seemed to clear that height quite comfortably, actually, so I dare say he’ll break quite a few more records in his time. On the other hand, when I first wrote about this back in 2011 the world record for the pole vault was held by the legendary Ukrainian athlete Sergey Bubka at a height of 6.14m which he achieved in 1994. That record stood for almost 20 years but has since been broken several times since. The fact that the world record has only increased by 11 cm in 30 years tells you that the elite pole vaulters are working at the limits of what the human body can achieve. A little bit of first-year mechanics will convince you why, as I have pointed out in previous posts (e.g. here).
What a pole-vaulter does is rather complicated and requires a lot of strength, flexibility and skill, but as in many physics problems one can bypass the complications and just look at the beginning and the end and use an energy conservation argument. Basically, the pole is a device that converts the horizontal kinetic energy of the vaulter 
Now assume that the approach is at the speed of a sprinter, i.e. about 
This suggests that 6.25 metres should not just be at, but beyond, the limit of a human vaulter, unless the pole were super-elastic. However, there are two things that help. The first is that the centre of mass of the combined vaulter-plus-pole does not start at ground level; it is at a height of a bit less than 1m for an an average-sized person. Note also that the centre of mass of pole (which weighs about 15 kg and is about 5 m long) only ends up about 2.5 m off the ground when it is vertical, so there’s a significant effect there. Note also that the centre of mass of the vaulter does not actually pass over the bar after letting go of the pole. That doesn’t happen in the high jump, either. Owing to the flexibility of the athlete’s back, the arc is such that the centre of mass remains under the bar while the different parts of the athlete’s body go over it.
Moreover, it’s not just the kinetic energy related to the horizontal motion of the vaulter that’s involved. A human can jump vertically from a standing position using elastic energy stored in muscles. In fact the world record for the standing high jump is an astonishing 1.9m. In the context of the pole vault it seems likely to me that this accounts for at least a few tens of centimetres.
Despite these complications, it is clear that pole vaulters are remarkably efficient athletes. And not a little brave either – as someone who is scared of heights I can tell you that I’d be absolutely terrified being shot up to 6.25 metres on the end of a bendy stick, even with something soft to land on!
And now, some poetry…
It’s Saturday so it’s time once again for another roundup of business at the Open Journal of Astrophysics. After last week’s summer lull, this week I have three papers to announce, which brings the total we have published so far this year (Vol. 7) to 67 and the total published by OJAp to 182.
First one up, published on 7th August 2024, is “Brightest Cluster Galaxy Offsets in Cold Dark Matter” by Jonathan Katz of Washington University (St Louis, Missouri, USA), a simulation-based study of the distribution of the position of brightest cluster galaxies relative to the dark matter distribution and its possible use as a cosmological probe. The authors are Cian Roche (MIT), Michael McDonald (MIT), Josh Borrow (MIT), Mark Vogelsberger (MIT), Xuejian Shen (MIT), Volker Springel (MPA Garching), Lars Hernquist (Harvard), Ruediger Pakmor (Harvard), Sownak Bose (Durham, UK) and Rahul Kannan (York U., Canada). This paper is in the folder marked Astrophysics of Galaxies.
Here is a screen grab of the overlay, which includes the abstract:
You can read the paper directly on arXiv here.
The second paper to present is “LAMOST J1010+2358 is not a Pair-Instability Supernova Relic” by five authors based in the USA: Pierre Thibodeaux (Chicago), Alexander P. Ji (Chicago), William Cerny (Yale), Evan N. Kirby (Notre Dame) and Joshua D. Simon (Carnegie Observatories) . As the title makes clear, the paper presents arguments against previous claims that a particular star is not a pair-instability supernova relic. This paper is in the folder marked Solar and Stellar Astrophysics. It was published on Friday August 9th 2024.
The overlay looks like this:
You can read this paper directly on the arXiv here.
Last, but by no means least, comes “A Pilot Search for Gravitational Self-Lensing Binaries with the Zwicky Transient Facility“, results of a trial search for signals of gravitational lensing of one component in a binary system by a compact companion, with a discussion of future prospects for larger surveys. This one, which was also published on 9th August, is in the folder marked High-Energy Astrophysical Phenomena. The authors are Allison Crossland & Eric C Bellm (U. Washington), Courtney Klein (UC Irvine), James R. A. Davenport (U. Washington), Thomas Kupfer (Hamburg Observatory) and Steven L. Groom, Russ R. Laher & Reed Riddle (Caltech).
Here is a screengrab of the overlay:
To read the accepted version of this on the arXiv please go here.
That’s it for this week. I hope to post another update next weekend.
I’ve taken the liberty of reblogging this post from a blog that I follow, as it is a question that interests me. As far as I know I have never contracted Covid-19, but I think I’m a rare case. I know many people who have had it multiple times. The most I think is five. There was an outbreak at the Euclid Meeting in Rome too, which affected over sixty people. I am hearing through the grapevine that case numbers are rather high at the moment, both in Europe and the USA, but in the absence of any systematic testing it is difficult to know the precise situation.
A couple of months ago I had a nasty cough which I thought might have been Covid-19 but repeated tests came back negative.
In the interest of full disclosure, I am fully vaccinated and boosted. I suppose another booster will be available in the autumn and I’ll take that too.
Anyway, I’d be interested to hear through the comments from anyone who has never had Covid-19 if you feel like divulging such information.
I have seen many comments on social media to the effect that the 2024 Paris Olympics have gone “woke”. I agree. Many sports are now mere shadows of what they were a few decades ago let alone the original Greek ideals. Gymnastics for example, the name of which is derived from the Greek gymnós meaning “naked”, nowadays involves competitors with their naughty bits covered up. How woke is that? And the boxers even wear gloves! They’ve all gone soft!
Another example is the fencing. I’m not an expert on this but I did watch quite a lot when I was younger – admittedly not on live TV, but in the form of film recordings. The modern Olympic version of fencing is boring compared with how it used to be. Here are two photographs that illustrate how fencing has gone woke.
For a start, just look at all the protective gear worn by the namby-pamby competitors on the left! And they don’t even use proper swords! It’s health and safety gone mad!
Also, where are the fancy costumes, the stone staircases to run up and down, the chandeliers to swing from, the elaborate hanging tapestries to climb, or the long banqueting tables covered in expensive items there to be trashed? Pathetic!
(P.S. Basil Rathbone (in the still on the right) was actually a seriously good fencer, twice British Army champion in fact, unlike his opponent in the picture Errol Flynn who was so useless that he was a danger to other members of the cast, including Rathbone.)
Is Shakespeare’s play Coriolanus different when performed in the Southern Hemisphere?
As it was foretold on Saturday, this afternoon I gave a talk at the 32nd General Assembly of the International Astronomical Union currently taking place in Cape Town, or rather at a side event thereof called Open Access Encounters: The Good, The Bad and the Ugly. I actually gave the last talk in the session, which may or may not mean that I was representing The Ugly…
About 50 people attended online plus an unknown number in person, so it was quite a decent size of audiance.
I’m not sure if Slideshare is still working on WordPress, but if not here is a PDF of the slides.
As I’ve mentioned before on this blog, one of my English teachers at school would occasionally give us exercises in creative writing inspired by `Only Connect’ – the epigraph of the novel Howard’s End by E.M. Forster. We were given two apparently disconnected things (usually news items), asked to think of a possible connection between them and write an story joining them together. From time to time when trying to think of something to write about I’ve resorted to playing the same game and am going to do it today.
This time, I thought I would connect two of my own recent blog posts, one about the case of female boxer Imane Khelife and the other about about the death of theoretical physicist TD Lee. What could the connection be?
Tsung-Dao Lee’s most famous work – for which he won the 1957 Nobel Prize with was on parity violation, which was detected experimentally by Chien-Shiung Wu in 1956. Parity is a conserved quantity in classical physics (e.g. in electromagnetism and gravity) and it was believed until the mid-20th century that it would be conserved in the quantum theory of nuclear interactions too. Wolfgang Pauli, for example, criticized Hermann Weyl’s suggestion of a two-component weakly interacting massless particle because it implied parity violation.
The experimental proof of parity violation in some weak interactions led to a much deeper understanding of fundamental physics, including the the idea of chiral gauge interactions, and the development of the standard model of particle physics. Parity is violated in some strong interactions too. Our simple-minded view of how things are changed as a result of an exception to a widely-held assumption. That’s how progress happens.
You might think now that I’m going to write about the fact that double-helix structure of DNA is right-handed, i.e. that it exhibits a form of parity violation, but that’s not it. Or only a little bit. You see, not all DNA is right-handed…
What does this have to do with Olympic boxing? Well, much of the furore about about Imane Khelif is about the (unproven) assertion that she has XY chromosome and is therefore male and should not be allowed to box in the women’s competition. A ‘biological’ female would have XX chromosomes.
It is true in the vast majority of cases that men have XY chromosomes and women have XX chromosomes, but if you read any reasonably modern book on human biology, the statement that ‘females have XX chromosomes’ is preceded by a “usually” or “in most cases”. But there exceptions: some women have XY chromosomes and some men have XX chromosomes; there are also individuals who have an extra chromosome and are XXY.
How can a person be said to be female if they have XY chromosomes? Well, that is because there is a very long journey between the information encoded in genetic material and the expression of that information in form and function. That entire process determines whether an athlete may nor not have an advantage over another. In a rare, sensible article about the Imane Khelif case I found this
Alun Williams, professor of sports and exercise genomics at Manchester Metropolitan University, said that when considering if a person had an unfair advantage it was necessary to look at chromosomes, levels of testosterone and other hormones, as well as the body’s response to testosterone.
“That then is a clinical assessment, which is really very invasive,” Williams said. “Simply looking at someone’s sex chromosomes … is incomplete.”
In most cases individuals with XY chromosomes develop “male” characteristics and those with XX chromosomes develop “female” but there are exceptions. For example, there are women – with ovaries, a uterus and no male sex organs – who have XY chromosomes. These are biologically female, even if their karyotype indicates otherwise. There is much more to biology than genetics, just as there is much more to physics than electromagnetism and gravity.
I don’t know whether Imane Khelif has XY chromosomes or not, and frankly I don’t care. The fact is that she was assigned female gender at birth, has been raised as female, and her gender is female as on her passport. She is a woman. I won’t use the phrase biological woman, because it is silly: every human being is biological. Caster Semenya is female too.
You might not care about this case and prefer top stick to the rigid definition that XX=male and XY=female. I don’t think that’s appropriate in sports: chromosomes don’t compete in sports, people do. I’ve also been accused of being ‘unscientific’ for accepting that the exceptions to a rule. On the contrary, I think such exceptions are how our understanding improves, not only in scientific terms but also in our respect for our fellow human beings.
In the Dark 