Delicate Tension – Wassily Kandinsky

Posted in Art with tags , , on December 26, 2023 by telescoper
Zarte Spannung (Delicate Tension) No. 85

by Wassily Kandinsky (1923, watercolor and ink on paper, 35.5 x 25.2 cm, Museo Nacional Thyssen-Bornemisza, Madrid)

Nollaig Shona Daoibh Go Léir!

Posted in Uncategorized on December 25, 2023 by telescoper

Here we are then, Christmas Day. I thought I’d do a quick yule blog before (late) breakfast. I can’t possibly compete with my post of yesterday featuring Miggledy Higgins, so I’ll keep it brief. Let me just wish you all a Merry Christmas, Nadolig Llawen, Nollaig Shona, Fröhliche Weihnachten, Joyeux Noël, Buon Natale, Feliz Navidad, Feliç Nadal, etc.

I’m not in Barcelona at the moment but I thought you might enjoy this old traditional carol from Catalonia called Fum, fum, fum.

 

And in the words of a traditional Irish toast:

Go mbeirimid beo ag an am seo arís!

(“May we all live to see this time next year”)

A Christmas Message from the President of Ireland

Posted in Politics with tags , , on December 24, 2023 by telescoper

It’s Christmas Eve so I thought I’d share this Christmas message from the President of Ireland (Uachtarán na hÉireann) Michael D. Higgins, a person I admire greatly and am proud to call my President. He is a rare example of a politician who is also a decent and likeable human being.

The whole speech is worth listening to, but I draw your attention in particular to this excerpt:

… may I express my gratitude to the migrants who now call Ireland their home. Their presence enriches our culture, contributes to our society, bringing as they do experiences, traditions, and perspectives that make us stronger as a nation.

It’s such a refreshing change to hear such words, contrasting with the toxic rhetoric being spewed out by so many politicians across the world. Well said, Michael Higgins!

Newton’s Third Law Illustrated

Posted in The Universe and Stuff with tags , on December 23, 2023 by telescoper
"To every Action Man...

R.I.P. Alexei Starobinsky (1948-2023)

Posted in Covid-19, R.I.P., The Universe and Stuff with tags , , , on December 22, 2023 by telescoper
Alexei Starobinsky, pictured in 2013.

I’m very sorry, especially just before Christmas, to pass on the news of the death of Russian physicist and cosmologist Alexei Starobinsky who died yesterday (21st December 2023) of complications resulting from Covid-19. I heard this morning, but have been travelling all day and only just found time to write something in appreciation.

Starobinsky was one of the many academic descendants of the great Zeldovich; he did particularly important work on the physics of the early Universe in which field his ideas prefigured the theory that came to be known as cosmic inflation. Although Starobinsky’s seminal (1979) work on this topic was not well known outside the Soviet Union at the time Alan Guth wrote his paper on inflation (1981), it did later gained wider appreciation, and led to numerous awards, including the Gruber Prize in 2013 and the Kavli Prize in 2014 (together with Guth and Andrei Linde). 

I do have one rather fond personal memory of Starobinsky, from when we were coincidentally both visiting IUCAA in Pune at the same time back in the Nineties. We ended up going on a shopping trip together during which he revealed himself to be hopeless at the kind of light-hearted haggling that was the norm in the places we visited. He ended up paying way over the odds for everything he bought. He didn’t seem to mind though, and apparently found it all quite amusing. I only met him a few times and didn’t get to know him well at all, but he struck me as a very nice man as well as a fine physicist of the old-school Russian type.

Rest in peace, Alexei Alexandrovich Starobinsky (1948-2023).

Hasta la vista, Barcelona!

Posted in Barcelona, Biographical with tags , , , , on December 22, 2023 by telescoper

I’m reliably informed that Spanish people don’t really say “hasta la vista” very often, but it seemed an appropriate title. I’m writing this post in the Departure Lounge at Barcelona Airport, having got here in very good time for my flight. Last time I checked in here the check-in staff were so slow that it took two hours to drop my bag at the desk and I only just made it to the gate in time for my flight. This time I arrived three hours ahead of time and it only took about 15 minutes to get processed so now I’ve got ages until I leave.

Yesterday, my last day in the office, we had a “Christmas Toast” in the foyer of the Physics Faculty building which consisted of a couple of inaudible speeches, followed by drinks and snacks in the company of a Grubb Telescope, an Atwood Machine, and many physicists.

This morning I said goodbye the flat I’ve been in for most of the past three months. I’ll be back in Barcelona in 2024, of course, but I’ll be in a different apartment when I return. Although my time in Barcelona is not over, I’d like to thank my hosts – especially Licia and Raul – for what has been a very enjoyable stay so far.

I’ll be back!

P.S. The last arXiv mailing before Christmas brought news of the accepted version of a paper for the Open Journal of Astrophysics, so I’ve just made the overlay and published the paper. That means that we finish 2023 with a half-century of articles in Volume 6. Roll on, Volume 7 (2024)!

UPDATE: I arrived safely in not-Barcelona and am looking forward to spend the next couple of weeks very lazily.

The Winter Solstice 2023

Posted in The Universe and Stuff with tags , , , on December 21, 2023 by telescoper
Sunlight at dawn on the Winter Solstice at Newgrange

Just a quick note to point out that the Winter Solstice in the Northern hemisphere happens tomorrow, Friday 22nd December 2023, at 4.27 am CET (3.27 UT). I am posting this in advance as although I am will be getting up quite early to catch a flight, it won’t be that early…

People often think that the Winter Solstice is defined to be the “shortest day” or the “longest night” of the year. The Solstice is actually defined in astronomical terms much more precisely than that. It happens when the axial tilt of the Earth away from the Sun is greatest, so that the Sun appears in the sky with its lowest maximum elevation. The timing of this event can be calculated with great precision.

In Barcelona, sunrise today (21st December) is at 8.13 am and sunset at 5.24 pm, while tomorrow the sunrise is at 8.14 am and sunset at 5.25 pm. The Solstice therefore occurs before sunrise tomorrow morning and the interval between sunrise and sunset tomorrow will be very close to that today; the interval between sunrise and sunset on 20th December (yesterday) was four whole seconds longer than on 22nd (today); the shortest day is therefore today rather than tomorrow. Moreover, the Solstice marks neither the latest sunrise nor the earliest sunset: sunrise will carry on getting later until the new year, the length of the day nevertheless increasing because sunset occurs even later. For a full explanation of this, see last year’s Winter Solstice post.

Merry Christmas from Barcelona!

Posted in Barcelona on December 19, 2023 by telescoper

Yet more high-z galaxies from JWST…

Posted in The Universe and Stuff with tags , , , , , , , on December 19, 2023 by telescoper

I noticed a paper on arXiv yesterday, by Robertson et al., with the abstract:

You can click on this to make it larger if you find it difficult to read.

This is the latest in a number of studies by the JWST Advanced Deep Extragalactic Survey (JADES), which is aiming to detect galaxies that formed in the very early Universe; for a previous example see here. The latest batch can be seen in this figure:

There is an important caveat here, which is that these are photometric redshifts, based on the overall shape of the spectrum of the galaxy rather than on spectral lines which give a more accurate result. Follow-up spectroscopy is needed to firmly identify the redshift of the sources. Past experience suggests that some of these candidates may not actually be at as high a redshift as is claimed. If confirmed, however, the existence of large galaxies at redshifts of order 15 will put greater pressure on models of galaxy formation. A recent OJAp publication has shown that galaxies at redshift 10 are consistent with current theoretical ideas, but much larger will increase the tension on theorists. I can imagine quite a few people around the world replotting their graphs right now!