Newgrange and JWST

Posted in History, The Universe and Stuff with tags , , 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.

Leave a comment »

Barabbas was a Publisher

Posted in Literature, Television with tags , , , on August 17, 2024 by telescoper

I couldn’t resist sharing the following, which I found here.

One day Lord Byron gave his publisher, John Murray, a handsomely bound Bible, its cover graced with a flattering inscription. Murray proudly displayed the book on a table where it would be seen by his many guests.

One day a visitor, admiring the book, noticed that at John 18:40, in the line ‘Now Barabbas was a robber,’ Byron had crossed out the word ‘robber’ and substituted… ‘publisher’.

You can probably figure out why I found it amusing!

The post from which I got the quote cites anecdotage.com as the source, but other websites dispute the attribution to Bryon. The Oxford Book of Essential Quotations, for example, gives:

Now Barabbas was a publisher.
 
also attributed, wrongly, to Byron

Thomas Campbell 1777–1844 Scottish poet: attributed, in Samuel Smiles A Publisher and his Friends: Memoir and Correspondence of the late John Murray (1891) vol. 1, ch. 14; see Bible

This goes to show two things: one is that not everything you find on the internet is true; the other is that very often the things that aren’t true really should be.

P.S. Fans of the classic TV series Tinker Tailor Soldier Spy will no doubt remember in Episode 1 that George Smiley uses the variation “Barabbas was a bookseller” when he is making a purchase in an antiquarian bookshop before he notices that he is being followed by Peter Guillam…

Leave a comment »

New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , on August 17, 2024 by telescoper

It’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.

Leave a comment »

Back to A-level Again

Posted in Cardiff, Covid-19, Education with tags , , , on August 16, 2024 by telescoper

Yesterday 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.

Leave a comment »

Evolving Dark Energy or Supernovae Systematics?

Posted in The Universe and Stuff with tags , , , , , , , on August 15, 2024 by telescoper

A 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.

1 Comment »

Hubble Tension Reduced?

Posted in The Universe and Stuff with tags , , , , on August 14, 2024 by telescoper

Back 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!

1 Comment »

Maynooth University Library Cat Update

Posted in Maynooth with tags , on August 13, 2024 by telescoper

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.

Site icon
Maynooth University Library Cat Update

At least he’s keeping himself clean!

Leave a comment »

In the Dark on Social Media

Posted in Biographical, Politics with tags , , , , , , on August 12, 2024 by telescoper

It’s almost a year since I deactivated my Twitter account. Or should I call it X? Anyway, it doesn’t matter because I don’t use it any more. Over the past few weeks it seems quite a few more – especially in the UK – have had enough of the antics of Elon Musk (aka Space Karen), especially with his attempts to fan the flames of the recent Farage riots by spreading misinformation. The first thing I noticed was that my BlueSky account was suddenly getting quite a lot of new followers. I now have about 850, still a long way short of the over 7000 I used to have on Twitter, but the level of engagement is far higher. That’s because the algorithm Space Karen introduced on X makes it difficult for your own followers. let alone anyone else, to see your tweets. The one disadvantage of BlueSky is that it doesn’t have an API that allows me to post directly from this blog when I publish a post, so I have to copy the URL by hand.

I also have an account on Mastodon where I have over 1200 followers and similarly good engagement. When I first started there a couple of years ago it didn’t have a WordPress API but it does now, so everything I write here gets posted automatically on my feed. Not only that, this blog is now also now fully federated which means that there is an autonomous feed for the blog posts. Not just a link to each post, as the API produces, but the whole post. This is a nice feature because if I change a post on this WordPress platform it automatically gets changed on the Mastodon feed.

I also have a Facebook Page on which these

And now there’s Threads, which is like a version of Twitter bolted onto Instagram. When this first came out last year it wasn’t available in the EU for data protection issues so I didn’t bother with it. I only just found out at the weekend that has been available since December 2023 but I wasn’t paying much attention to social media then so didn’t catch the news. Anyway, since I already have a (very quiet) Instagram account so I set up a Threads account which you can find here if you like that sort of thing. My first impressions of Threads are not very favourable, but let’s see how it goes. At least it’s not as bad as Twitter. I still think it is indefensible that my employer, along with most other universities, has decided to maintain a presence on that site.

1 Comment »

The Mechanics of the Pole Vault

Posted in Sport, The Universe and Stuff with tags , , , on August 11, 2024 by telescoper

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 \frac{1}{2} m v^2,  as he/she runs in, to the gravitational potential energy m g h acquired at the apex of his/her  vertical motion, i.e. at the top of the vault.

Now assume that the approach is at the speed of a sprinter, i.e. about 10 ms^{-1}, and work out the height h = v^2/2g that the vaulter can gain if the kinetic energy is converted with 100% efficiency. Since g = 9.8 \, ms^{-2} the answer to that little sum turns out to be about 5 metres.

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!

3 Comments »

Wine in a Can – Marcel Lucont

Posted in Poetry with tags , , on August 10, 2024 by telescoper

And now, some poetry…

Leave a comment »

« Older Entries
Newer Entries »