Flying Backwards Through Time

I've tried to make this video as self-explanatory as possible, so here it is without further ado :

This will be a short post just to give a bit more detail and some static images.

I was feeling really inspired and motivated by the recent solarigraphy meeting. I haven't made any dedicated data visualisation projects in a while, but one that's been gestating in the back of my mind is to try and show the dark matter in galaxy simulations... I think showing this as trails (a la the Sun in solarigraphic images) might look interesting.

But first, there's much lower-hanging fruit to pluck, though in a tangentially similar vein. Back in 2018, I decided it might be fun to try a time lapse from the office. Specifically, here, looking down the Jihozápadní V avenue.

Red X marks the spot.

So each time I went to the office, for the next ~16 months, I took a photo on my mobile phone, which was then a Huawei P10 lite. I tried to keep things as stable as I could, trying to get myself in the same position each time and lining things up in a similar way, but this was all done very quickly and by hand. I decided to do this particular view basically on a whim : it's somewhere I was present regularly and reliably at about the same time, it's quite a nice view, and looking in the other direction (towards the institute itself) you don't see so much. From the other direction, where you enter the avenue to go towards the institute, at certain times of year one gets a very nice "Stonehenge" effect :

Looking in the other direction avoids the sun being in the frame and I'm not sure if this was the right decision or not. I do wish I'd gone for landscape format, but having to avoid the tops of the trees would probably have annoyed me quite intensely.

Anyway, I didn't always manage to take a photograph every day. Sometimes I just forgot, occasionally going back later when I remembered (or if there were inconveniently-placed people that I hoped would bugger off if I left it for a bit). Sometimes I was away for conferences or holidays* (maybe even working from home from time to time !), and of course I wasn't there on weekends at all. Also the time of day varied considerably, from 7:45 am (God knows what that was all about) to 5:36 pm (probably I forgot to take the picture in the morning). The median time was 9:47 am, with a standard deviation of 1 hour. 

* Worst of all for this project, I tend to take holidays in the spring an autumn, so the most crucial moments of seasonal change are missing !

This is about as good as can be expected from a real-world side-project, where it's just not possible to keep things more controlled. So not only does the camera position vary quite a bit, but so does the lighting - and of course, this varies dramatically depending on the weather.

The result is the first sequence in the video - not much more than an unpleasant mess. We need not dwell on it any longer.

I was expecting as much. I knew I'd probably have to manually align the images to get a nice result, but somehow I just never got around to doing it... until now. So I imported all the images in Blender as transparent planes and manually aligned them by adjusting their scaling, rotation and location. If we show all the images together, here's the unaligned result :

Which explains why the animated sequence is such a mess. Here's the version after doing all the corrections :

Little bit of contrast adjustment on this one.

Much better. Probably there are better ways to do this; certainly there are a few cases where I didn't align things as well as I could, probably it could even be automated. But I enjoyed the process, so never mind. I'm also pleased with the way the colour turned out, and the blur gives it an air of authenticity, like it's from an archaic film camera instead of a modern electronic gizmo. Still, while the resulting animation sequence is far more bearable than the raw version, it's not quite as good as I was hoping for.

But together with all the long-exposure stuff I'd seen in the solarigraphy meeting, this gave me ideas of how to process the images differently. Why stop with a simple, traditional sequence of images ? These combined images are in effect pseudo-long-exposure photographs, compressing 16 months into single stills. They're not the same as proper solarigraphs of course, but the overall effect is similar in that you see multiple times all at once.

So I tried combining the images in different ways for the animation. The simplest approach, which gives a result I quite like, is to give all the images the same level of transparency, such that only when they're all combined do they become completely opaque. That's what's shown in still images above. In the animation, it gives very a much smoother animation than the original, and you still get a satisfying sense of change as it progresses. 

But why insist we see all the images ? If we restrict it so that only 30 images (one month) are ever shown on screen, and their transparency is such that their sum is fully opaque, then we get the best of both worlds : a nice smooth transition but with a more pronounced sense of change.

Choosing four images to give an obligatory "four season" compilation. We had a particularly hot and dry summer that year, with all the grass dead and even the trees looking unhealthy. Fortunately we also had a cold, snowy winter.

Finally, using the same technique I do for astronomy data visualisations, we can also show the data as a pseudo-3D volume. In effect this has been done already : the images are all separated along the into-the-screen axis, it's just you can't see this because the rendering disables perspective. If we enable it, we get this funky volumetric effect. I really like this in the animation, you get a sense of movement that's only partially true... the camera moves back from the images, but that's not the same as really moving through the street. It's actually moving backwards through time, a weird quasi-movement away from the images but not through the street itself, all the while showing images from longer and longer ago.

Or equivalently, in this image you're looking into the future by looking at the centre, and into the past by looking at the edges. Time is treated as a spatial dimension.

This concludes my brief foray into experimental photography. You may go about your business, and I'll get back to the world of astronomy.

Working On Sunshine

Staring At The Sun With Solarigraphy

Image by Diego López Calvín. Always reminds me of the time travel sequence in The Time Machine.

Alas, I can't take credit for the post title. It's something I once heard someone joke should be the official anthem of solar astronomers, though I've long since forgotten who it was. Anyway, last week I was lucky enough to attend a conference on solarigraphy, and I think this is worth a post.

Now as an extragalactic astronomer the Sun is our great foe in the sky that does naught but blind us all and make us wince in pain and fear. And to be honest, professionally my interest in the Sun is practically zero. Furthermore I'm somewhat averse to stepping so far outside my astronomical lane that I end up in a subject which is really another topic all together; some people even call solar science a branch of geophysics.

But this meeting was arranged as a combination of science, art and education. And there things get much more interesting to me, which is how I came to be on the local organising committee.

Solarigraphy is an unusual photographic technique which is at once incredibly simple and incredibly subtle. On the first day we had a little workshop where we made our own cameras. It consists of cutting open a can (in this case a beer can from our sponsor), making a pinhole*, adding in some photographic paper on the opposite side, and then – and this is the only tricky bit – quickly taping it in place before it gets a significant level of light exposure, and finally sealing the can back up with more tape.

* With a pin.

The small piece of tape on the lower part of the can (right image) is a shutter, to stop the camera from exposing before it's ready.

This incredibly simple device can produce remarkable images. You have to leave them for an extended period – typically six months – but the results can be fascinating.

The basic idea is to capture the paths the Sun makes through the sky, which varies throughout the year. With just a pinhole and a sheet of paper, you can capture both the solar tracks but also the landscape. The phenomenally long exposures (one claimant for the record is eight years) means you get something which is essentially the reverse of the T-Rex's vision in Jurassic Park : solarigraphy can only see things which don't move. Unless something appears consistently in the same place, you won't usually see it in the final image.

On the other hand, a predator from which you can run but never rest could be pretty damn threatening too. 

There are a lot of nuances to the technique and I'll describe a few of them in the course of recapping the meeting. The cameras themselves, though, really do tend to be extremely simple. The difficulties of using them are pragmatic : you have to find somewhere to place them where they won't be disturbed for a long time, you have to orient them so the rainwater can drain out, you have to fix them securely so they don't move about on their own. You don't need to develop the paper though : it does that all by itself. Instead you just digitally scan and process the sheet when you're ready. 

Depending on what goes right and what goes wrong, you can get an incredible diversity in the final results. Some look like professional-grade photographs whereas some look like Jackson Pollock caught the norovirus from a vomiting unicorn. As someone said, if you place two identical cameras in the same location for the same time, you'll still get two completely different results.

Without further ado, here's my summary of the meeting and the bits I found most interesting.

The Meeting

Day One

The 2nd International Solarigraphy Meeting took place in Ondřejov, a small village about 40 km from Prague. The only feature of note here is that it's home to Ondřejov Observatory, the much larger half and headquarters of the Astronomical Institute which employs me, and it's where the main meeting organisers are based.

We began with a talk by head honcho Maciek Zapior who introduced the topic (you can see some of his own solarigraphs on his web page). This was great for muggins here, as probably the only participant who'd never attempted any solarigraphy. Maciek covered not just the technique but also the wider context of the intersection of art and science : there's a search for beauty and truth, arguably, in both. Now personally I think the Universe is a great big bloody mess, but that the topic was raised was far more important than agreement, with these kinds of discussions for me being generally limited to online stuff. Incidentally, the name comes from the 1961 novel Solaris.

Next we had a talk by Cezary Bartczak about camera construction, especially pinhole cameras in general, which can range from the simple can constructions* to heavy-duty 3D printed versions. They're really quite satisfying objects in their own right, and now I wish I'd tried the "make your own pinhole camera" sets when I was younger. Note that pinhole photography in general does rely on chemically developing the image, whereas solarigraphy does not.

* Why IN GOD'S NAME don't we have a website called Only Cans ???

Following this we had the "build-a-solarigraph" session for which you've already seen my efforts above. It's going to be tough to find somewhere I can put this, but I'll have to try. Then there was an exhibition of a solarigraph contest which featured some very impressive images, which starts to introduce how flexible this technique can be :

See the link above for details. Some of these images were taken on a bicycle (!) and with a rotating turntable to produce intersecting solar trails rather than the usual continuous set.

This one is from Krzysztof Winciorek which shows a building in construction. I love this weird partial transparency, showing multiple times all at once.

I believe this one, by Łukasz Ciesielski, is of a car hubcap.

In the afternoon we had the online session. Apart from the first speaker, who didn't want to be recorded, you can watch the whole thing below, or just continue reading for my summary of the highlights. As a session all from non-scientists, I found this to have some of the most interesting talks of all. 

We began with Tarja Trygg, who initiated a Global Solarigraphy Project to image solar trails at different latitudes : at the equator the Sun goes vertically overhead, while at the poles it's almost horizontal. She noted that colours appear even on black and white paper, on which more later, and that solarigraphy makes the invisible visible (like imaging wavelengths we can't see directly, but in a very different way). Weirdly, when she started the project she asked people if the photographic technique was viable and was greeted with extreme skepticism. Why this should be, I don't know.

Next was Pablo Giori, one of the directors of the Experimental Photo Festival. This was very art-heavy and not all of it was to my taste... I can't say I'm ever going to "get" Dadaism; to me this looks like the cartoons in Monty Python. More interesting was his history of photography as a process of revolution, homogenisation, and democratisation. I normally find the latter word is heavily overused but in this case it's absolutely appropriate : photography today is available to everyone. Pablo noted that experimental photography is in the mindset, not the technique, with most photos today being "visual rubbish" of no artistic value. 

In this I think he's right but missing the point : most photos today are taken for communication and shared experience, not for artistic value at all. I take pictures when I visit famous landmarks not because I expect to do better than the thousands of professional photos that already exist, but because (a) there's no point in not taking them given how easy it is, (b) to have something that is mine, to remember what I saw. Pablo's talk was also very anti-capitalist, and though I tend to sympathise, I think he might be rather heavily overstating the case. I'm just not convinced that there's any sort of malevolence at work when it comes to Big Photo.

After a break we resumed with photographer and lecturer Justin Quinnel. I think this was probably the most fun presentation of all of them, full of engaging anecdotes of successes and failures. While I strongly agree with the need for outreach and education, I disagree that this shouldn't be digital : digital exploration is absolutely as valid as any other medium.

Possibly my favourite talk was by Michael Wesely for the clear presentation and sheer quality of the images, which are technically amazing. I liked very much his description of standard short exposures as presenting an illusion of stability : the reality is that all things are in constant (though varying degrees) of motion, and in some ways the long exposure photographs actually present a more correct view of the world – they aren't just a blur, they encode all the time information, events and stories as well as brief moments. I really liked some of the images where the buildings were in the process of construction, giving a powerful effect of seeing through time.

It's also worth noting that these are inherently privacy friendly because unless you're dead*, you won't show up well at all in a solarigraph. Wesely took an eight hour exposure of himself (which I think must have been agony), but only with strenuous effort did he appear as anything more than a blur. The vast majority of people show up only as interesting trails. The next talk, by Corine Dufresne-Deslières, picked up on this theme, also noting how if data is unlocatable, it's also unaccountable.

* If we really want to get noticed, we could try doing (a) solarigraphic porn or (b) going full Channel 4 and doing a solarigraph of a decaying corpse.

The final talk of the session was by artist and teacher Heather Palecek, who initially had no realisation that solarigraphy was an astronomical technique but approached it from the perspective of nature. In contrary to the more typical approach of striving for technical perfection, she likes the effects of nature interfering with the images : dirt, mould and water can all influence the colours that develop on the paper, sometimes leading to very surreal but striking images. This all made me wonder if there are any animals that experience time in this greatly sped-up way – I know some experience the world at a much faster pace than we do (hence their incredible reaction times), but I wonder if maybe snails have solarigraph-like vision...

Day Two

Maciej kicked off with a review of the current state of the art. He showed some more novel uses of the images, such as exposures of a single day where you get just one, dramatic-looking solar trail. Others used manual recolouring to give a more realistic appearance, which divided audience opinion. Some thought this meant it was "just a graphic" (whatever that means) while others thought it was clearly the better image. I lean towards the latter, as long as the process is clearly explained. While I do think that any art should have some immediate, self-explanatory value (hence that stupid, moronic painting of a can of soup is just the work of an ultra-pretentious tit, in my view), knowing the process behind it can at least add value.

He also mentioned https://analemma.pl/, especially their NxN project. This hammers home the importance of post-processing, with different artists coming up with very different versions of the same raw image. It's even possible to do solarigraph time lapses, although who claims the title of the "first" is open to debate (Maciej is not a fan of the superlative contests, and I tend to agree - that eight-year exposure image looks quite nice but is nothing extraordinary compared to some much shorter images). Finally he mentioned that you can buy pre-made solarigraph cameras for €20 online, which is just insane considering the total manufacturing cost is probably more like €2 and it takes ~5 minutes.

The afternoon social events included the obligatory visit to the telescopes, another solarigraphy exhibition, but also something much more unusual : a saxophone performance inside the dome of the 2m telescope. In the dark, with the saxophonist accompanied by Maciej who walked around with a torch looking for pieces of sheet music. Well, that's something I've certainly never experienced before.

The cars are very interesting. Here there were different cars parking at approximately the same spot each day, resulting in what Maciej calls a "generalised" car. In other images you can see sun reflections from moving cars in the parking areas.

In the evening we went to a nearby village for dinner, where I was sat with a wickedly mischievous older Polish gentleman. He spoke, very, very slowly and deliberately, and proceeded to tell me how he personally had helped convince Sean Connery to become a Scottish nationalist. For this reason, when the next day in the discussion session he declared that, "there's no emotion in art, that's all rubbish", and that solarigraphy is evidence that the Sun goes around the Earth... he probably wasn't being entirely serious.

On returning to Ondřejov I found it was a very nice evening so I went to the field of radio telescopes to watch the sunset.

In keeping with the experimental photography vibe, here's the Sun through a radio telescope.

Day Three

The morning session was pretty intense. We kicked off Łukasz Rogiński and Jakub Pacuk, who shared their first year of experience in solarigraphy – some of these images were really impressive, and I wish I could find them online. Grzegorz Hussak then showed us a solarigraph taken using a glass negative instead of the usual photographic paper, and while the contrast is extremely low – barely visible – on the physical glass itself, the digital scan was certainly clear enough. 

Maciej took over the next slot due to our only cancellation, resuming the discussion of the current state of solarigraphy. Again, many more amazing images – the single solar track during the eclipse was particularly nice – and more anecdotes of how people respond when they find the cameras in the wild. Some think they're part of geocaching and leave stuff inside. A few people, weirdly, take them away only to return them again. Some leave notes apologising. He moved on to solarigraphy as both an art and science, wherein art is free to treat time as a substance while in astronomy it can be thought of as an angle. He concluded with using automated shutters to trace analemmas and create more arbitrary patterns in the sky.

Next, Alexandre Sampaio – a professional theatre director and photographer – gave us a description of a solarigraphic tour of some Spanish islands he's doing... well, it's nice work if you can get it. Some of his images were great, especially one with a fountain where you could see both the water and solar trails at once. He also gave us a delightful naming contest for alternatives to solarigraphy* : the winner was "let-it-go-let-it-go-graphy", but I much preferred, "it's-a-blur-but-I-call-it-art-agraphy". Oh well, can't win 'em all.

* I can pronounce solarigraphy just fine in my head, but I always stumble on it physically. I find solargraphy very much easier.

Finally, chemistry researcher Tomáš Slanina gave us a really interesting, totally different talk on the chemistry that makes solarigraphy work, and photoreactivty more generally. He gave a few amazing demos where he mixed different chemicals in beakers and you could see them shining in UV light. For photographic paper, light causes silver nitrate to solidify, which makes it opaque. Why the different colours appear I'm not sure, but this appears to be the result of something more complex.

After a break, professional artist Helena Jiráková began the final session with a talk on art in astronomy. She covered the works of many artists besides herself, including Nancy Holt's Sun Tunnels,  James Turrell's Skyspaces and Roden Crater, Chris McCaw's use of the Sun to literally burn tracks in film, and perhaps my favourite, Olafur Eliasson's spectacular artificial indoor sun made of hundreds of lamps with a mist of sugar water.

Then it was my turn; I've put my slides online here. There was very little new content here but I assembled it in a different way for a different audience. I began with a very brief overview of galaxies and described how radio data tells us about the invisible dark matter, using that old exploding galaxy sim to start things off. I described how radio receivers work and the importance of understanding that they're spectrographs, so they collect frequency data as well as brightness. Receiving 4,096 frequency channels all at once somewhat compensates for having only seven spatial pixels to work with... and it also means you have a lot of freedom to choose how you render the data.

I began with the standard approach of channel maps, in which each frequency channel creates a different image, moving on to volumetric rendering by way of the glass cube and a 3D movie. Then I tried to address Maciej's comments about truth by showing the exact same data set rendered in four different ways : channel maps, height maps, volumetrically, and isosurfaces. You really do get different information from the data if you just look at it differently.

Pablo Giori had said that art isn't in the business of truth; Michael Wesley that it was all about stories, and various others that it's all about different perspectives, self-discovery, empowerment etc*. My take is similar. How you visualise your data really does affect how you interpret it, not just aesthetically but also scientifically : some information is far easier to discern using one technique than another. I think none has a claim to be more valid or true than another, but each can be more appropriate for tackling different questions. I ended with an overview of my efforts to turn HI data into art, which I don't need to recount here because you can just see that link instead.

* It was a very, very woke meeting.

It's always fun to see audiences looking silly.

People seemed very enthusiastic about all this and I came away with an adrenaline buzz that always accompanies a successful talk. In fact, it's inspired me to pick up a project that's been on hold for four years – with luck, that should be the next post here in a couple of weeks or thereabouts, so watch this space.

The final talk was Zbigniew Makarewicz on science as art and politics. This was interesting, though at times hard to follow (what he meant by saying that art was aristocratic I'm not sure). He began quite delightfully with something along the lines of, "Thank you all for indulging my sadistic tendencies, especially Mr. Taylor for speaking English". He proceeded to say that painting is not art, that an artist is someone who creates something of special quality. Art, science, technology and politics, he said, are all interconnected in common culture : they are separate endeavours but do not exist in isolation. And again, he noted that artists and scientists view the same data in different ways, resulting in different works. Einstein viewed the world as equations, Bohr as something more poetical. 

It was all very heady stuff. I liked it a lot, even though so many speakers had the unfathomably bizarre tendency of having laptops with desktops in which every available space was occupied with an icon. It's all well and good to meet new people and get different perspectives, but there are limits. So for now, it's back to science I go.