Prague Castle 2 : The Sequel

As I've previously reported, people flock in droves to the Charles Bridge to the point where it becomes invisible. This is undoubtedly the peak of the population density in Prague, but on the surrounding streets the flow of tourists is still torrential. Yet, walk for merely a minute - or less - orthogonal to this living human filament and the streets are practically empty.

It isn't that the towers and spires of the city are mere fronts, disguising some kind of foul city-wide cesspit. In fact the rest of central Prague is no less beautiful than the army-ant tourist route, though it is, perhaps, less iconic. Even this isn't true of Vysehrad, Prague's second castle. It's accessible by a short, very easy (i.e. flat) walk from a metro station, is about a thousand years old and has sweeping panoramic views of the city. And yet on a sunny Saturday afternoon there were no more than a handful of visitors in the whole, extensive site.

What's wrong with people ? The site is only two metro stops from the city center - so it's basically still in the city center. A city with a population of 1.3 million, yet it almost feels like somewhere rural. This is wonderful. In fact, I'm wary of promoting it, in case it too is swallowed whole by the voracious human wyrm.

It's also cheaper than Prague Castle (which itself it not very expensive). Entering the cathedral is about £1 (St Vitus is free to simply enter but costs about £5 to walk around - still, admittedly, a bargain) while the spacious grounds are entirely free. As is the cemetery, where the great and good of Czech society are buried. As I understand it, the nearest British equivalent would be Westminster Abbey.

It's a fascinating place to explore, though the only name I recognized was Dvorak. Even so, I would have spent longer had I not already been around the site for about 3 or 4 hours. I kept getting distracted by just how lovely the place is.

If you want landscapes, go to Switzerland. For skyscrapers go to America, and for castles go to Wales. But for churches, go to Prague. So far I'm convinced that the city could no more allow an ugly church than a Greenpeace activist would eat a  whale burger with a side order of dolphin fins. Vysehrad is not as magnificent as St Vitus or as ornate as Our Lady Before Tyn. But it is cheaper than St Vitus and far less crowded. It's not free, unlike Tyn, but they do let you take photos (unlike Tyn). The interior is certainly remarkable, and well worth seeing, being entirely covered in paintings.

One could be forgiven for walking through Prague Castle and not realising it's a castle. Not so at Vysehrad, whose massive ramparts are... err, well, they're very large. I think I've run out of metaphors for the day. Still, they provide a very nice walk through the extensive park grounds. I had lunch in what was an unremarkable café until I realised that the walls were four feet thick. Well, I suppose it was important to protect the tourists back in medieval times*.
* Another, much less likely possibility is that it wasn't originally built as a café.

Also, the bar was literally ship-shape and had a demon head hanging at the front.

Vysehrad, though almost deserted, does not lack for places to eat. I can only assume the place is busier in the summer. It also has one or two exhibitions, though I did not pay them a visit. Having spent several hours wandering around, and with the need for laundry becoming ever more pressing, it was time to return. For, as the poet Homer would say :

"But despite my grief, let me do laundry, since there is nothing more shameful than the wretched washing machine that demands a man’s attention however deep his distress, or heavy his heart, and my heart is heavy now, yet my laundry goes on insisting I wash it at 40 degrees with a 1200rpm spin cycle, making me forget what I suffered, demanding the washing machine its fill. "

Why An Imaginary Monkey Is Helping Me Measure Hydrogen

I once photographed a potato for NASA. This is going to be difficult to top, but I'll give it a damn good try.

Galaxies, by and large, are fairly simple shapes. Generally speaking they're either pretty spiral discs or tremendously boring yellow blobs (a.k.a. ellipticals). You can make analysing them as complicated and tedious as you like, but measuring how bright they are is pretty simple. Put a circle around them and have a program add up all the flux (energy) within the circle. Easy-peasy.

Images from the SDSS.

Of course, things get more complicated most of the time. Usually spiral galaxies are tilted away from us, so they're not neat circles. Sometimes there are stars in our own galaxy lined up directly in front of the distant galaxy, in which case there's little option but to break down and cry. Or find another galaxy to measure.

There are also galaxies whose shapes are just downright freakin' weird. Like this one, discovered by a Puerto Rican student this very summer. I can't resist re-posting this, because... NESSIE !

There are even galaxies which aren't so much exotic as they are... erotic. Well, erotic corporate logos at any rate, which is even weirder. I kid you not.

With galaxies shaped like Nessie or...ahem... rabbits, you could still slap a circle around them and get a reasonable answer. But in these cases you might suspect that the galaxy is made of several separate parts, so possibly you would choose to fit more complicated shapes.

With neutral hydrogen the observations give you 3D data cubes, and the gas can be all kinds of wonderfully complicated shapes. And pretty too. Did I mention it was pretty ? Because it is.

Gas clouds of the Milky Way, from the GALFA-HI survey.

NGC 628 from the THINGS survey.

The above GIFs were produced with FRELLED, my own script that imports FITS files into 3D art software Blender. That lets you freely rotate the view around the 3D images in realtime, which is nice because it makes the animations a lot easier to produce. And do all kinds of science, etc. etc. Anyway, it's pretty obvious in these cases that just drawing a circle wouldn't help much, unless it was accompanied by some arcane symbols and ritual chanting. This - unless you're a dyslexic astrologer who chose the wrong career path - is generally frowned upon as a method of data analysis.

So I was asked to give FRELLED the ability to measure the gas content within spherical or spheroidal regions (it only did cubes*, which are trivial). Well, spheres are easy, because you can very easily find all the pixels in the file which are inside the sphere and add them all up. Deformed spheres (ellipsoids) aren't much harder.
* Most of our observations have much worse resolution than the above examples, so cubes work just fine.

But the heck with that. I can see where this is going - today a sphere, tomorrow an ellipsoid, the day after... well, let's just go for broke and let it do arbitrary shapes. Like, say, a monkey. That's about as arbitrary as you can get.

This is Suzanne, beloved icon of Blender. Over the years she's been subjected to all kinds of deranged shenanigans, though not, I suspect, ever quite as pointlessly technical as this. What I needed was a way to check if any particular point was inside or outside of Suzanne (more generally any closed surface). And I found one on the internet, making life twenty times easier or more.

It's very simple to define the smallest possible cube which contains all of Suzanne. All I have to do is check all the points within this cube to see if they're inside Suzanne or not (I could check the entire data set, of course, but this is huge and would take a lot longer).

At that point I could make a leap of faith and have the program just spit the measurement of how much hydrogen is present. This is a terrible and boring idea. I'd rather have it first show me what the data it thinks is inside Suzanne looks like. That way I get to check if it's working correctly or not.* More importantly, I can now present you with a monkey head made out of hydrogen gas from the Milky Way. You saw it here first.
* Actually this was really important, because several early tests were giving ghastly results - and there isn't some "monkey parameter" to check if this is working. The only way is to look at the data and see if it looks like a monkey**.
**This is not a phrase used much in astronomy.

OK, this is pretty specialist stuff. It boils down to a short algorithm to let you measure hydrogen within an arbitrary volume. This is quite useful, but it isn't going to revolutionize astronomy. Not unless that depends on measuring the gas content of a monkey-shaped galaxy, at any rate.

Happy Birthday Arecibo !

Few would deny that Arecibo Observatory is home to the world's most iconic radio telescope, star of Goldeneye and Contact (Pierce Brosnan... ? Jodie Foster ? Who ?). Even fewer would deny that Arecibo is 50 years old, because this is a fact. This magnificent facility suffers, however, from a surfeit of names, being variously described as "Arecibo Observatory"*, "El radar"**, and, just to annoy the heck out of everyone, the "National Astronomy and Ionosphere Center"***.

* What nearly everyone calls it.
** The local name. Would a letter sent (from within Puerto Rico) to the address "El radar" get there ? "Yes" was the unhesitating and unflinching response from a senior staff member.
*** The name the lawyers use, and the website too.

These days the telescope itself is known as the William E. Gordon telescope, after its designer. Who, incidentally, made an almighty factor-of-ten slip in his calculations, and that's why a small island in the Caribbean ended up with a 300m telescope and not just another forgettable 30m antenna.

I'm not even going to attempt to do justice to either William Gordon or the telescope. About the telescope I will only saw that its list of accomplishments is by anyone's standards impressive. It measured the rotation rate of Mercury, discovered the first binary pulsar, the first exoplanets, has sent messages to aliens, measured the distance to numerous potentially hazardous Earth-crossing asteroids, and done a bunch of atmospheric work I don't understand but I assume is important.

About William E Gordon, I will only point out that (I'm told) he was more usually known as Bill, so really we should be calling it Bill's Big Dish. My suggestion that honour the Observatory's instigator by painting some suitable tribute in big letters on the dish somehow never got taken up. Can't imagine why.

It would be a talking point if nothing else.

Anyway, Arecibo is, as I mentioned, 50 years old - the same age as Dr Who (coincidence ?). I was asked to create a short animation to be shown in the background for the resulting, "hooray, we're still here !" celebration. Fortunately, I already have my computer model (which was used to produce a laser-etched glass cube you can buy in the visitor center for $80). What I really wanted to do was include something like this...

Thanks, NRAO !

... which is a wonderful image of the NRAO Green Bank facility with the sky shown as if the viewer could somehow see at 4.85 GHz. So I wanted to do something similar for Arecibo, but using (obviously) Arecibo data.

For this I was graciously allowed to use data from the GALFACTS survey, which covers a huge chunk of the sky (the image I have spans about 85 x 17 degrees). Arecibo can't see all of the sky, because it's pretty hard to move a 300m dish. So it can only see a (still pretty respectable) swathe, but Bill's bloody big dish makes up for it by being ridiculously sensitive. Here's what it would look like if we could see GALFACTS data (after the experts corrected me for having it the wrong way round) :

The forest is looking decidedly deciduous for a tropical island.

But having a computer model means I can do a lot more than make a static image (though having moved from Arecibo to Prague recently does rather slow things down somewhat). I opted to ape the award-winning opening credits from one of the best shows on TV at the moment...

Game of Scopes

A Song of High Humidity Levels and the Occasional Hurricane

The fact that the inspiration for this image missed out Arecibo is a source of continuing disgust to me.

Anyway, here's the resulting final animation. Somewhat crude - no vegetation at all because it took too long to render - but quite serviceable, I think.

The Pillars of the Earth

... as Ken Follet would describe cathedrals. In the interests of brevity I'm going to lose the standard chronological narrative and describe Prague somewhat more haphazardly.

The Charles Bridge, which my guide book insists should be the first thing to visit, is completely pointless in the middle of the day. You'd be better off staying at home and Google searching "pictures of statues".  Fortunately, you don't have to go astonishingly early to beat the crowds - before 10 is sufficient. If you go before 9, it seems from the webcam, you'll have the place to yourself. And while under the right weather conditions I imagine it is probably a very impressive bridge indeed, there really isn't any good reason why the mass of the crowd at midday is enough to generate its own gravitational field.

About 9:30am.

Around 11am. Where did the bridge go ?

Petrin Tower was a much more rewarding visit. The funicular was out of service so I took a pleasant walk straight up the hill through some extensive, well-kept and almost empty gardens. The tower itself is described as a miniature version of the Eiffel Tower, which it isn't, but it does give a very good view of the city indeed.

A more unexpected find in Petrin gardens was an observatory. Arecibo may win the title of most iconic telescope, while the Sphinx may claim the most exotic location, but Štefánik is probably in the running for having the best-kept grounds. It's in a freakin' rose garden, for goodness sake.

Petrin hill also offers a very good view of St Vitus cathedral, the heart of Prague Castle. The Castle is also the thing I should visit first, according to my ever reliable and self-consistent guide book (well, it was free). Although there are a few elements of fortification, it's really a disparate collection of historic buildings. And it's none the worse for that.

The castle area has been in continuous use in one form or another since around 870 AD. The exhibition hall gives an excellent and thorough description of the full history of the site, from pottery dated to around 5,000 B.C. (the fact that something as simple as a pot can survive for seven thousand years should be more than a little overawing) right up until the modern era.

The centerpiece, St Vitus, is truly resplendent. Begun in 1344, no-one seems to have gotten around to consecrating the place until 1929. At that point - one assumes - its use as a brothel and a opium den finally had to stop. Construction work is an ongoing project, so in that sense it's been in the making for over 650 years. It's survived fires, wars, and countless regime changes. Yet it turned out alright in the end. Here's to another 650 years, St Vitus.

So far I've climbed Petrin hill with its observation tower, the Astronomical Clock tower, and of course the hill to Prague Castle itself. I couldn't very well not also climb the south tower of St Vitus. This was definitely the most taxing of the viewing towers, partly because it's taller than the others (96m compared to 60m for Petrin tower and the Astronomical Clock) but also because the stairwell is a classic medieval spiral staircase. There are a few small windows into the tower interior, but generally you're stuck in a very narrow stone enclosure until you reach the top.

There are no passing places, but fortunately - and very surprisingly indeed - there were hardly any other tourists. Maybe half a dozen, not more. In contrast, the Astronomical Clock was heaving (the queue took half an hour before I could even go up; at the top itself things are verging on shoulder-to-shoulder), though Petrin tower was somewhat more pleasant. In terms of the best all-round experience solely for viewing the city, Petrin tower is probably the best, in my opinion. But for God's sake don't let that stop you from visiting the other towers too.

Prague Castle does have a few places I would more normally expect from a castle. One is the Powder Tower. This offers somewhat uninteresting exhibits about the Prague Castle Guard, though the history panels are more engaging. More fun is Golden Lane, which has a huge collection of medieval armour and a torture chamber. I also got to shoot a crossbow (for the rather obnoxious price of £1.50), though I only managed to hit the board once. Oops.

Finally there's the Prison Tower, which has all the mod-cons you'd expect from a medieval dungeon. Prisoner cage and rack as standard, with a special offer on solitary confinement... lower your prisoners through a tiny hole to a pitch-dark cellar by means of a metal harness. History is not for the squeamish.

Upgrades

After a week spent battling against a cold and addressing such vital necessities as, "where is my next meal coming from ?", "do I need any more toilet paper ?" and, "how can I ride dragons in Skyrim ?" I finally ventured out into the big wide world to see my latest adopted home.

Whenever possible I prefer to explore on foot and without any kind of set plan. I grabbed my free map from the airport taxi, hopped on to the Metro and for no particular reason, got off 20 minutes later at Wenceslas Square. The guide book doesn't have much good to say about it :

"Wenceslas Square should be the central and main attraction of the capital. Instead it is quite dilapidated and noisy, and after dusk it is better not to venture there at all."

What the frak ?? This is categorically NOT TRUE. If you want a dilapidated town square, see Arecibo, where the buildings are full of trees.

Whereas in Wenceslas Square, you'll find this :

The particularly grand building is the National Museum, sadly closed for renovation until 2016. But dilapidated ? Utter nonsense. Nor is it noisy or or a bad idea to visit it "after dusk". I was there after 8pm on a Saturday and it seemed little different to how it was in the morning, except that it was dark, and if anything less busy.

I decided to head up to the Astronomical Clock since this entailed a walk through the really rather nice square and looked easy to find on the map. And it was - just follow the crowds. The narrow, labyrinthine streets are crowded, no getting away from that (the wide open squares, however, are not - Wenceslas Square "can and has comfortably held 400,000 people", says my guide book).  But the crowds don't really matter, because the atmosphere is very pleasant. I mean this literally as well as figuratively. I don't know what it is about Czech food, but the smell of cooking from the vendors at the end of the square is particularly intoxicating. In the end I opted for a sausage in a baggette*, which, unlike most other street food, tasted as good as it smelled.

* This is the basic unit of street food. You can probably find it on distant planets where the atmosphere is mostly methane and the inhabitants have seventeen different words for "marmalade".

The Astronomical Clock was more impressive than I was expecting. For a start, it's almost at eye level, so it's easy to see. Parts of the mechanism are original and date back to 1410 (perhaps even earlier - no-one's really sure), but over the centuries it's suffered many disasters and reconstructions. Nonetheless, it's an ornate and beautiful feature.

What really won me over was the fact you can can go up to the top of the tower for a proper look at Prague. Here's where not reading the guide book pays off, because that way everything's a surprise bonus. £3 is well worth it for the view alone, though I maxed it out by walking up (instead of taking the lift) and reading the information panels.

Just as the clock itself isn't too far above ground level, so it is with the tower also. It's low enough that you not only get a good view of the nearby buildings, but you also hear everything happening at street level, like the street musicians. Prague, in short, seems to have a convivial atmosphere not found in other cities except at Christmas.

From the tower I decided to make for the Charles Bridge, which in this case is something I did actually plan to visit. Built in 1357, it's lined with gothic statues and is a major tourist attraction, so it seemed like a safe bet. Unfortunately it's a victim of its own success, because by 11am there's really no point going. It's simply rammed, verging on impassable. Why this should be I'm not sure. It certainly is a very nice old bridge, but it doesn't let you see into the future or turn base metals into gold.

There's a bridge behind the crowds.

The bridge is also lined with street vendors, mostly artists selling pictures, and also entertainers. In this case a string quartet playing.... Britney Spear's Toxic. I did a double-take when I walked past. Though I'm not sure how I recognize the song at all, because all I remember is that the video is one definitely best enjoyed with the mute button on (Britney may have the musical abilities of a dead duck that's just been sat on by an irate hippo, but she did have other... talents).

From Charles Bridge I walked up to Prague Castle, sipping a hot mulled wine from a polystyrene cup as I went. There needs to be a word meaning complete and total contentment, because that's what walking through Prague on a crisp October afternoon sipping hot wine is like.

I only wanted to have a look at the castle, because the guide book says that visiting every part of it can take at least 4 hours. It's not really a castle in the traditional sense (maybe it was once, I don't know), more a collection of historic buildings. Like this one - St Vitus cathedral, which has been an unsightly blot on the landscape since 1344. Honestly, I don't know why the locals put up with it.

St Vitus is practically youthful compared to St George's basilica next door, which was founded in AD 920. I mean that's just silly. Later, after I went back to the institute for a short while, I went there for a concert featuring Vivaldi's Four Seasons. Suffice to say that I now only wish to hear music if it's played in an 8th-century stone resonance chamber.

After that I went back, buying some trdelnik from one of the many street vendors in Wenceslas Square. This is something I thoroughly recommend, and I hope it becomes popular worldwide (but gets a better name). Charles Bridge remained crowded, but nowhere near to the extent it was earlier in the day. Possibly this was because there were now two huge eyes keeping watch on everyone at either end of the bridge.

The waterfront also featured a bizarre yet undeniably interesting art sculpture :

This is a mass of illuminated plastic spheres arranged - I suppose - to look like a cloud. The tendrils hanging down are pull-cords so that passers-by can turn the lights on and off. Wonderful - even if it does look like something that's about to attack the Enterprise.