In the Dark

The Summer Solstice in the Northern hemisphere takes place later today, Wednesday 21st June 2022, at 15.58 Irish Time (14.58 UTC) or 16.58 local time here in Copenhagen.

Among other things, this means that today is the longest day of the year around these parts. Incidentally, the latitude of Copenhagen is 55.6761° N, which is a little bit South of Edinburgh. I had thought it was further North, but I was wrong.

According to this website, the interval between sunrise and sunset in Copenhagen today will be 17 hours 32  minutes and 18 seconds. which is 5 seconds longer than yesterday while tomorrow will be two whole seconds shorter than that.

It’s all downhill from now on.

In the Northern hemisphere, days will get shorter from tomorrow until the Winter Solstice in December, although this does not mean that sunset will necessarily happen earlier on 22nd than it does tomorrow. In fact it is a little later. Nor does it mean that sunrise will happen later tomorrow; in fact it is a little earlier.

This arises 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).

Anyway, here’s a  picture of four sixty-somethings – myself, John Peacock, Per Lilje and Ofer Lahav – on our way to dinner last night (including a toast to the memory of Nick Kaiser)

Picture courtesy of Ofer Lahav

The building in the background is Københavns Domhus (the Copenhagen Court House). The restaurant we went to, Puk, is highly recommended.

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It’s Sunday morning, I’ve just had breakfast, and shortly I’ll be throwing a few things into a bag and heading off to Dublin Airport on the Hopper Bus which is back running after being suspended for a considerable time owing to the pandemic. It’s by far the most convenient way to get to the Airport from Maynooth. I’m all checked in and ready to go, although my flight is not until this evening and it takes less than an hour to get to the airport. You can put this down to nerves!

I realized last night that this will be the first trip I’ve taken outside the UK/Ireland Common Travel Area since I went to the Euclid Consortium Meeting in Helsinki in June 2019, just over four year ago. I was made Head of Department in 2019 and the pandemic descended on us in March 2020, so I couldn’t have travelled even if I’d had the time (which I didn’t).

After such a big gap I’m very out of practice with all this travelling malarkey so am actually quite nervous, which is ridiculous, especially since I’m going to a familiar destination, Copenhagen, and will only be there for a few days. I had a short panic this morning because I’d forgotten where I’d put my passport after all this time. On the other hand, it’s good to be getting back into the swing of things with a little trip before a much bigger one later in the year.

Anyway, the reason for this trip is this year’s Euclid Consortium Meeting which will be the last before Euclid is launched next month. It promises to be a very exciting event which I can enjoy without the tension of having to do a talk.

There’s a good chance that the actual launch date for Euclid will be announced during this meeting. At the moment, all we know is that it’s between July 1st and July 15th. The announcement of the date will be made 10 days in advance so if it’s early in that two-week window, we will be told next week.

UPDATE: I took an earlier Airport Hopper than I really needed to, in case of traffic delays and/or queues at security, but the bus arrived dead on time at Maynooth and slightly ahead of schedule at the Airport. Then it only took 15 minutes to get through security. Then I found it my flight was delayed on its inbound journey so I ended up having to wait about three hours. I arrived in Copenhagen about an hour later than I’d expected but that’s not too bad really. I was a bit disappointed that I didn’t get full value from my EU passport at arrivals, however, as the “All Passports” booths were a lot less busy than the EU/EEA/ETC ones so I went through one of them as I would have done if I’d been travelling on my British passport. Anyway, the public transport here is very good so I got to my hotel not far from the Central Railway Station very easily. Now I just have to settle in and find out where I have to be tomorrow and when I need to get there!