by Bridget Riley (1994, 1576 × 2278 mm, Oil on Canvas, Private Collection)
From Here – Bridget Riley
Posted in Art with tags Art, Bridget Riley, From Here, painting on August 21, 2024 by telescoperAn Exercise in Bayesian Probability
Posted in Bad Statistics with tags Fraud, Mile Lynch on August 20, 2024 by telescoper
A businessman is on a luxury yacht, celebrating his recent acquittal in a high-profile fraud trial, when the yacht sinks in mysterious circumstances off the coast of Sicily. The businessman is one of six people on board who are missing, presumed dead. Just last week, the businessman’s co-defendant in the aforementioned fraud trial died in a mysterious road accident while out running in Cambridgeshire.
Using Bayesian methods, calculate the probability of these two events being a coincidence. Show your working. To the police.
Update: An investigation into possible manslaughter has been opened by the authorities in Italy.
Quasar – The Jimmy Giuffre 4
Posted in Jazz with tags Four Brothers, Jazz, Jimmy Giuffre, quasar, The Train and the River on August 19, 2024 by telescoperJimmy Giuffre (1921-2008) was an immensely gifted saxophonist and clarinet player who was also an accomplished arranger and composer who worked for many big bands. His most famous piece as an arranger was Four Brothers which he wrote for Woody Herman’s fantastic saxophone section of Stan Getz, Zoot Sims, Serge Chaloff and Herb Steward. My first encounter with Giuffre as an instrumentalist was in the opening track of the 1958 film Jazz on a Summer’s Day playing a tune called The Train and the River which has been a favourite of mine for many years. Back then he had a quite accessible style that blended jazz with folk elements, but he later developed a freer and more “modern” approach, including the use of electronic instruments and elements of jazz/rock fusion. I recently read a biographical article about him and – for obvious reasons – was intrigued that in 1985 he made an album called Quasar so I thought I’d share the title track here. Giuffre is on soprano sax on this one.
Newgrange and JWST
Posted in History, The Universe and Stuff with tags JWST, Newgrange, Tom Ray on August 18, 2024 by telescoper
Although I won’t myself be able to attend, I’m happy to be able to use the medium of this blog to advertise the above public event which is taking place in the first week of September on the back of a week-long conference to celebrate the career of Professor Tom Ray of the Dublin Institute for Advanced Studies. That in turn follows hard on the heels of the Irish National Astronomy Meeting (INAM) which takes place in Galway on 29th and 30th August.
Anyway, the public event on 3rd September is free to attend but you need to register here, where it is described thusly:
The Newgrange Passage Tomb, a prehistoric monument in County Meath, Ireland, is one of the most remarkable examples of Neolithic art and architecture, dating back to around 3200 BC. This ancient structure, with its intricate stone carvings and precise alignment with the winter solstice sunrise, reflects the sophisticated astronomical knowledge of its builders.
With starkly different technology, the James Webb Space Telescope (JWST), launched in 2021, represents the pinnacle of modern astronomical achievement. JWST is designed to peer into the farthest reaches of the universe, capturing images and data from the formation of the earliest galaxies to the atmospheres of planets outside of/beyond our solar system.
Despite being separated by millennia, both Newgrange and JWST underscore humanity’s enduring quest to understand our place in the cosmos through the study of the stars and the universe.
As part of the celebration of the career of Professor Tom Ray the Dublin Institute for Advanced Studies and the Institute of Physics are delighted to host a public event on Newgrange and JWST. This is in recognition of Tom’s long interest in archaeoastronomy and Newgrange in particular, and his involvement with the JWST through the Mid-Infrared instrument (MIRI).
The talk will be delivered by Dr. Frank Prendergast, archaeoastronomer and Emeritus Research Fellow at Technological University Dublin, and Professor Gillian Wright, European Principal Investigator of MIRI and Director of the UK Astronomy Technology Centre in Edinburgh.
New Publication at the Open Journal of Astrophysics
Posted in OJAp Papers, Open Access, The Universe and Stuff with tags arXiv:2404.15698v2, Astrophysics of Galaxies, Diamond Open Access, dwarf galaxies, Open Journal of Astrophysics, Star Clusters on August 17, 2024 by telescoperIt’s Saturday morning and time for the usual weekly update of publications at the Open Journal of Astrophysics. This will be a short post because there is only one paper to report this week, being the 68th paper in Volume 7 (2024) and the 183rd altogether. It was published on Thursday August 15th 2024.
The title of the latest paper is is “Spatial segregation of massive clusters in a simulation of colliding dwarf galaxies” and it is in the folder marked Astrophysics of Galaxies. The authors are Bruce Elmegreen (IBM, NY, USA) and Natalia Lahen (MPA Garching, Germany); the paper presents a numerical study of the properties and spatial distribution of star clusters resulting from a collision between dwarf galaxies.
Here is the overlay of the paper containing the abstract:
You can click on the image of the overlay to make it larger should you wish to do so. You can also find the officially accepted version of the paper on the arXiv here.
Back to A-level Again
Posted in Cardiff, Covid-19, Education with tags A-level, A-level Results, Physics, University Admissions on August 16, 2024 by telescoperYesterday was the day that students in United Kingdom received this year’s A-level results. It seems the number of students getting the highest grades went up in England but down in Wales and Northern Ireland. That difference could be because of the timing of the transition from Covid-19 adjustments, with marks in Wales and Northern Ireland only returning to pre-pandemic levels this year; this may disadvantage applicants to universities this year, of course.
Another thing worth mentioning is that the number of students taking Physics A-level has increased by 12% this year, reversing a recent downward trend. In Physics, 31.5 per cent of students achieved the top grades. This was an increase from last year when 30.8 per cent were awarded an A or A*. That probably means that most students who applied to do Physics at university will get a place in their first-choice institution.
As always my advice to students who got disappointing results is
There’s always the clearing system and there’s every chance you can find a place somewhere good. If you’re reading this blog you might be interested in Physics and/or Astronomy so I’ll just mention that both Cardiff and Sussex have places in clearing and both are excellent choices.
At least you’ve got your results; students here in Ireland will have to wait next Friday (23rd August) to get to get theirs – not in the form of GCE A-levels, of course, but the School Leaving Certificate. I have been away all year so don’t know how admissions have been going for Maynooth but the intention seems to be to increase student numbers in any way possible despite the already huge student-staff ratio (the highest in Ireland) and lack of student accommodation. Anyway, Covid-19 adjustments are still in place in Ireland so the artificial inflation of Leaving Certificate grades will continue. It seems the Government doesn’t know how to get out of the system it has locked itself into and is intent on leaving it for the next Government to sort out.
Evolving Dark Energy or Supernovae Systematics?
Posted in The Universe and Stuff with tags Cosmology, Dark Energy, Dark Energy Spectroscopic Instrument, Dark Energy Survey, DES, DESI, evolving dark energy, Pantheon on August 15, 2024 by telescoperA few months ago I posted an item about the release new results from the Dark Energy Spectroscopic Instrument (DESI). That was then followed by a presentation explaining the details which you can find here to find out more about the techniques involved. At the time the new DESI results garnered a lot of media attention much of it about claims that the measurements provided evidence for “New Physics”, such as evolving dark energy. Note that the DESI results themselves did not imply this. Only when combined with supernova measurements did this suggestion arise.
Now there’s a new preprint out by George Efstathiou of Cambridge. The abstract is here:
Recent results from the Dark Energy Spectroscopic Instrument (DESI) collaboration have been interpreted as evidence for evolving dark energy. However, this interpretation is strongly dependent on which Type Ia supernova (SN) sample is combined with DESI measurements of baryon acoustic oscillations (BAO) and observations of the cosmic microwave background (CMB) radiation. The strength of the evidence for evolving dark energy ranges from ~3.9 sigma for the Dark Energy 5 year (DES5Y) SN sample to ~ 2.5 sigma for the Pantheon+ sample. Here I compare SN common to both the DES5Y and Pantheon+ compilations finding evidence for an offset of ~0.04 mag. between low and high redshifts. Correcting for this offset brings the DES5Y sample into very good agreement with the Planck LCDM cosmology. Given that most of the parameter range favoured by the uncorrected DES5Y sample is discrepant with many other cosmological datasets, I conclude that the evidence for evolving dark energy is most likely a result of systematics in the DES5Y sample.
Here are a couple of figures from the paper illustrating the difference in parameter constraints using the uncorrected (left) and corrected (right) Dark Energy (Survey) 5 year Supernova sample.
The y-axis shows a parameter wa, which is zero in the standard model with non-evolving dark energy; the non-zero value implied by the left hand panel using the uncorrected data.
Just as with the Hubble Tension I blogged about yesterday, the evidence for a fundamental revision of our standard model may be nothing of the sort but some kind of systematic error. I think we can expect a response from the Dark Energy Survey (DES) team. Grab your popcorn.
Hubble Tension Reduced?
Posted in The Universe and Stuff with tags arXiv:2408.06153, Hubble constant, Hubble Tension, JWST, Wendy Freedman on August 14, 2024 by telescoperBack in April I posted about a meeting at the Royal Society in London called Challenging the Standard Cosmological Model, some of which I attended virtually. In that post I mentioned that Wendy Freedman gave a talk related to the ongoing issue of the Hubble Tension, i.e. the discrepancy between different types of measurement of the Hubble Constant, usually characterized as local measurements (using stellar distance indicators) and larger-scale measurements (chiefly Planck). There are quite a few posts about this issue on this blog. Anyway, Wendy Freedman mention in her talk that her latest work on stellar distances suggested a value of 69.1 ± km s-1 Mpc-1, which reduces the tension with Planck significantly. At the time, however, there was no paper explaining how this number was derived.
Yesterday there appeared on arXiv a preprint by Freedman et al. which summarizes the recent results. The abstract is here:
We present the latest results from the Chicago Carnegie Hubble Program ( CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae (SNe Ia), suitable for measuring the Hubble constant (H0). It also includes NGC 4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of H0 = 69.85 ± 1.75 (stat) ± 1.54 (sys) for the TRGB, H0 = 67.96 ± 1.85 (stat) ± 1.90 (sys) km s-1 Mpc-1 for the JAGB, and H0 = 72.05 ± 1.86 (stat) ± 3.10 (sys) for Cepheids. Tying into SNe Ia, and combining these methods adopting a flat prior, yields our current estimate of H0 = 69.96 ± 1.05 (stat) ± 1.12 (sys) km s-1 Mpc-1. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of H0 based on these two methods with JWST data alone is H0 = 69.03 ± 1.75 (total error) km s-1 Mpc-1. These numbers are consistent with the current standard ΛCDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.
You can read the full paper on arXiv here. A summary of the summary is that of the three methods they use, two give lower values of the Hubble constant and one (Cepheids) gives a higher value but with larger errors. The number quoted in the Royal Society talk was presumably preliminary as it doesn’t match any of the numbers in the abstract, but the point remains.
You can see the reduction in scatter in the new JWST measurements in this Figure (old on the left and new on the right).
On the face of it, these results suggest that the Hubble tension is greatly reduced. I am sure, however, that advocates of a higher value will have been preparing their ripostes and it’s just a matter of time before they arrive on the arXiv too!
Maynooth University Library Cat Update
Posted in Maynooth with tags Maynooth University, Maynooth University Library Cat on August 13, 2024 by telescoperI 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!
In the Dark 