Monday, August 27, 2012

Of air and water and light - solar halos over China

My flight to Japan was a remarkably comfortable one. Last week saw me in the sky for over 70 hours and thoughts of DVT played heavy on my mind as I got ready for the last leg of a rather mammoth few days. Days that I would however repeat, travel included, given the chance. Thankfully on changing at Amsterdam airport the ground staff took pity on my grizzled face and booked me into a seat with two spares next to it so I could finally stretch out.

I managed a couple of hours sleep on the 11 hour journey which is not a bad proportion for me, given that I normally manage none at all. After a recent flight where, on asking for a whiskey, I was presented with a good half pint of the stuff, I have been staying away from alcohol on flights. The whiskey did knock me out, but it also gave me a horrendous hangover for the waking hours of the journey.

Anyway, I was up to watch the sunrise over China and managed to see the faintest of green flashes, though sadly didn't get it on camera this time.

Later on in the flight however as we neared Japan the air at 30,000+ ft became filled with ice clouds and the interplay of light and ice made for a truly spectacular display.

The conditions were very interesting. Around the plane was a thin layer of cirrus clouds, with a high density of ice crystals, and below us where much thicker clouds, also packed full of ice crystals, many of them plate-like. Plate-like hexagonal ice crystals like to lie flat in the sky and act like mirrors to the sun. These are the crystals that cause sun pillars:

ice pillar
and sub-suns (the reflection of the sun off ice crystals in the clouds below):
halo and subsun from a plane
This time however the display was a lot more complex. The column crystals in the clouds around us caused a 22 degree halo while the plate crystals gave a faint sundog (also known as a parhelion). In the thick clouds below however things got more interesting. The plate crystals below gave an effect that I'd never seen before. Not only did the light refract as it was passing through the sides of the crystals, but it also bounced off the bottom face, and back up, acting like a mirror to give a so called subparhelion. Moreover, because of the high density of crystals in the lower layers there was a strong 46 degree halo coming from a rather rare dynamic of light through the end of column crystals. It seems that this may not have been photographed before.

Here is the almost undoctored photo:
sundog of subsun and Lowitz arcs with supralateral arc
and here is a rather more doctored one just to enhance the effect to see the different arcs more clearly:
sundog of subsun and Lowitz arcs with supralateral arc

The reason that the circle around the sun is so distorted is because it's from the edge of a very wide-angle lens (Sigma 10-20mm at 10mm).

I sent this through to Les at Atopics who has been my source of knowledge and inspiration in the subject over the last few years and he sent me back a ray-trace computer simulation of what was going on. This is the simulation of the particular conditions so you can compare with the images above (click to view the full image):

The 46 degree arc in the clouds below seems to be an extremely rare event and the infralateral arc is also something rather special. All in all one of the best halo displays I've ever seen.

I've seen halo displays a few dozen times when flying now. Take some sunglasses with you, look out the plane and see if you can spot them next time...they're are there to be marveled at.

Now in Japan for the next 3 weeks. 2 weeks at a machine learning summer school and then a few days at the Yukawa institute where I will be giving a talk and hopefully chatting with some of the experts on entanglement entropy in holography. There are some ideas I need to talk with them about...

Wednesday, August 15, 2012


I've been silent here for a long time. I've also been in a bit of a reboot phase for the last few months, probably since around the end of June. I have a confession to make, that the reason for this was that the first six months of this year I simply took on too much. I'm not very good at saying no in general and have always loved the buzz of being busy. To be bored is a waste of the incredibly short time we have here and I find myself frustrated by all the other things that I wish I could pack into the hours of the day and of the night.

A couple of posts ago I wrote about the incredible new explosion in online learning tools (take a look for links), from Khan Academy to Coursera and Udacity and now with EdX in the mix, there are more and more courses online every day, for free, for anybody connected to the web. Some of the best teachers in the world offering their services in a fascinating business model to bring highly advanced skills to the masses. On Coursera alone there are now over 100 courses, from Natural Language Processing to Sociology, from Vaccines to Computer Vision and from Automata theory to the study of Modern and Contemporary American poetry.

The opportunity was too much to miss and I jumped on board in a big way. I signed up to every course that looked interesting, and dove in, head first. I new from the start that it was going to be busy, but didn't know quite what I was taking on or how I wasn't going to be able to say no to finishing the assignments, even if it meant sleepless nights. And that it did. In fact I spent a good few months at the beginning of the year working 18 hour days. I was working in the office during the day, working on assignments and watching course videos at night and then at the weekends working on  other projects, some of which are now finished and some of which are ongoing (working on interdisciplinary areas has been enormously fun!). It was a huge buzz to be doing this and I felt in a great zone. The courses finished off one by one but as they did so a new one started.

South Africa came in the middle of all this and I was teaching a course on a subject I'd never taught before, while giving lectures about my work as well as working on the courses at night. It was all a bit too much.

From South Africa I came back and went off to Denmark, then to the UK then back to Germany, then somehow the Netherlands crept in and I spent a few days in Leiden after a trip through Köln and Neijmegen. Again, more talks, more work, more courses. I don't really remember July, it came and went in a flash with Strings at the end

The next week is going to be the most ridiculous of all time in terms of travel, the last piece of it will be a trip to Japan in about 8 days to spend two weeks at a summer school before spending a few days at the Yukawa Institute where I will give a talk and hopefully be able to discuss with some of the world experts on a problem I'm looking at at the moment.

There are also plans afoot for next year but I'm going to keep these somewhat hidden for the moment. When there is any movement I will talk about it.

So, After working for the first six months like crazy, the courses slowly trickled off and my concentration span trickled off with them. I emerged from this intense period in a completely hyperactive state and unable to concentrate on any one thing for more than a fraction of the time I'd normally be able to commit. I found myself easily distracted and even the simple pleasure of reading a book, which is my normal wind-down activity didn't seem to be happening.

A few weeks passed by like this and I knew that I really needed a break, things were not improving, I felt fully burnt out. There are friends around the world that I would love to have seen, but I knew that this time it had to be a holiday of withdrawal, a trip where I could get away from everything and reboot. I wanted to go somewhere with very little to do, with beautiful streets and cafes where I could sit and read. More than anything I wanted somewhere that I didn't have to fly to! After a little searching I settled on Ljubljana, Slovenia, a mere six hour train ride from Munich. I was recommended this by a Slovenian friend and at the same time was told of all the fantastic natural wonders to go and visit in the country. Normally I would jump at such photo opportunities, but this time I simply wanted a week or so of doing nothing!

And that's what I managed to get. I spent 9 days in Ljubljana doing nothing but sitting in cafes and reading, occasionally talking with street musicians who I would see every day as I wandered around, ate some good food and spent the afternoons exercising. It felt like a true retreat. I didn't have to speak to anyone, I didn't have to think about emails or facebook or traveling from one place to another. I read some great books, probably my favourites being The Brothers Karamazov, Religion For Atheists and Cosmic Anger, the biography of Abdus Salam. I sat in the castle at night under the stars watching the open air cinema, I sat and did nothing, it was perfect!

So, I am back now. Now I go away again and and will be gone for a few weeks, but I'm feeling a lot more ready to get my head down and concentrate, to finish the projects that are ongoing and to start some new ones, as well as to try and figure out a bit more what next year may hold.

For now I'll leave you with a photo from Ljubljana castle. The city is surrounded by mountains and as the yellow light of the sunset cut through the valleys, this castle was bathed in the glow:

church in the hills in the sunset