Beware of the Train

We've just moved house, which means that we're waiting for a new broadband connection to be set up. While we're waiting for reliable Internet we've been making our own entertainment, and by "entertainment" I of course mean "beer". It's our first attempt at homebrewing, so we decided to walk before we tried running and bought a beginner's homebrew kit. Which made me think, as one does, of Ninkasi, the Sumerian goddess of beer and brewing, who every day used to brew beer for the rest of the Sumerian pantheon. Beer was one of the crucial enabling technologies for the early urban civilisations in Egypt and Mesopotamia: as well as being fun to consume, it allows you to live in close proximity to other humans without dying of cholera from contaminated drinking water. Beer brewing tech has moved on a bit since Ninkasi's day, but the essentials of the process remain the same: germinate grains to turn the starches into sugars, soak in water to extract the sugars, drain off the resultant liquid (the "wort"), mix with flavourings, ferment in a large vat, drink, enjoy. And since today is National Poetry Day (with a theme of "water", no less), I thought it might be fun to update the Hymn to Ninkasi. Dating from around 1800BC, it's one of the oldest known recipes for beer. Here's an academic translation, and here's a discussion, and a looser but more poetic translation.

Given birth by the flowing water, tenderly cared for by Ninhursaja! Ninkasi, given birth by the flowing water, tenderly cared for by Ninhursaja!

Having founded your town upon wax, she completed its great walls for you. Ninkasi, having founded your town upon wax, she completed its great walls for you.

Your father is Enki, the lord Nudimmud, and your mother is Ninti, the queen of the abzu. Ninkasi, your father is Enki, the lord Nudimmud, and your mother is Ninti, the queen of the abzu.

It is you who watches the included instructional DVD, and is soothed by the presenter's reassuring Australian accent and self-deprecating humour. Ninkasi, it is you who watches the included instructional DVD, and is soothed by the presenter's reassuring Australian accent and self-deprecating humour.

It is you who puts a cupful of bleach in the plastic bucket, and fills it up with hot water. Ninkasi, it is you who puts a cupful of bleach in the plastic bucket, and fills it up with hot water.

It is you who leaves the bucket to sterilise for half an hour, and then rinses it down carefully in the shower. Ninkasi, it is you who leaves the bucket to sterilise for half an hour, and then rinses it down carefully in the shower.

It is you who carries the bucket through to the kitchen, and places it on the counter. Ninkasi, it is you who carries the bucket through to the kitchen, and places it on the counter.

It is you who peels the backing from the thermometer strip, and sticks it to the outside of the bucket. Ninkasi, it is you who peels the backing from the thermometer strip, and sticks it to the outside of the bucket.

It is you who upends the wort can into a saucepan of hot water so that it may flow more easily. Ninkasi, it is you who upends the wort can into a saucepan of hot water so that it may flow more easily.

It is you who opens the can of hopped wort, and guards it even from the noble cats. Ninkasi, it is you who opens the can of hopped wort, and guards it even from the noble cats.

It is you who dissolves the wort in two litres of boiling water, then adds the 1kg packet of fermentable and non-fermentable sugars and stirs vigorously. Ninkasi, it is you who dissolves the wort in two litres of boiling water, then adds the 1kg packet of fermentable and non-fermentable sugars and stirs vigorously.

It is you who wonders what the hell the non-fermentable sugars are there for anyway, and tries to tell your girlfriend about that Holsten Pils advert with Dennis Leary, and remembers that she's too young to remember it. Ninkasi, it is you who wonders what the hell the non-fermentable sugars are there for anyway, and tries to tell your girlfriend about that Holsten Pils advert with Dennis Leary, and remembers that she's too young to remember it.

It is you who tops up the bucket to twenty litres with cold water, stirs and checks the temperature. Ninkasi, it is you who tops up the bucket to twenty litres with cold water, stirs and checks the temperature.

It is you who adds another couple of litres of cold water to ensure the temperature is within the range 21C-27C. Ninkasi, it is you who adds another couple of litres of cold water to ensure the temperature is within the range 21C-27C.

It is you who takes the packet of yeast, tries to tear it open, realises there is no slit in the packet, and looks frantically for a pair of scissors. Ninkasi, it is you who takes the packet of yeast, tries to tear it open, realises there is no slit in the packet, and looks frantically for a pair of scissors.

It is you who cuts open the packet of yeast with a Swiss Army knife and pours it into the bucket. Ninkasi, it is you who cuts open the packet of yeast with a Swiss Army knife and pours it into the bucket.

It is you who curses when your girlfriend reminds you that you were meant to sprinkle the yeast evenly over the surface of the liquid. Ninkasi, it is you who curses when your girlfriend reminds you that you were meant to sprinkle the yeast evenly over the surface of the liquid.

It is you who accepts all the blame if this whole thing goes wrong. Ninkasi, it is you who accepts all the blame if this whole thing goes wrong.

It is you who slots the stupidly-named Krausen Kollar onto the bucket, and then fits the lid. Ninkasi, it is you who slots the stupidly-named Krausen Kollar onto the bucket, and then fits the lid.

It is you who wonders why this system doesn't use an airlock, Googles to find out, and emerges no wiser. Ninkasi, it is you who wonders why this system doesn't use an airlock, Googles to find out, and emerges no wiser.

It is you who hopes that you won't end up with partially-fermented beer all over your new kitchen floor. Ninkasi, it is you who hopes that you won't end up with partially-fermented beer all over your new kitchen floor.

It is you who half-fills the hydrometer tube with the diluted wort and drops in the weighted bulb, to determine the beer's original gravity. Ninkasi, it is you who half-fills the hydrometer tube with the diluted wort and drops in the weighted bulb, to determine the beer's original gravity.

It is you who attempts to read the specific gravity at the meniscus, but can't actually see the meniscus because beer is fizzy. Ninkasi, it is you who attempts to read the specific gravity at the meniscus, but can't actually see the meniscus because beer is fizzy.

It is you who decides that accuracy to +/- 0.001 is probably good enough, and writes down your best guess in the Brewer's Log. Ninkasi, it is you who decides that accuracy to +/- 0.001 is probably good enough, and writes down your best guess in the Brewer's Log.

[It is you who has only proceeded up to this point so far, and is copying the remaining steps out of the instruction booklet. Ninkasi, it is you who has only proceeded up to this point so far, and is copying the remaining steps out of the instruction booklet.]

It is you who waits for four days, periodically checking that the temperature is within the range 21-27C, and then draws off another tubeful of liquid and measures the specific gravity with the hydrometer. Ninkasi, it is you who waits for four days, periodically checking that the temperature is within the range 21-27C, and then draws off another tubeful of liquid and measures the specific gravity with the hydrometer.

It is you who checks the specific gravity daily until it has remained the same for 24 hours. Ninkasi, it is you who checks the specific gravity daily until it has remained the same for 24 hours.

It is you who nervously taste-tests the beer, hoping that it has avoided infection or other problems. Ninkasi, it is you who nervously taste-tests the beer, hoping that it has avoided infection or other problems.

It is you who sterilises the supplied heavy PET bottles, ready to receive the beer. Ninkasi, it is you who sterilises the supplied heavy PET bottles, ready to receive the beer.

It is you who fits the bottling valve to the tube, and opens the tap. Ninkasi, it is you who fits the bottling valve to the tube, and opens the tap.

It is you who fills the bottles with the beer. Ninkasi, it is you who fills the bottles with the beer.

It is you who puts one sugar tablet into each 500mL bottle so that the beer may undergo a second fermentation, then caps them and inverts each one several times. Ninkasi, it is you who puts one sugar tablet into each 500mL bottle so that the beer may undergo a second fermentation, then caps them and inverts each one several times.

It is you who wonders what was going on in that bit in 1984 where the old guy complained that half a litre of beer wasn't enough, seriously, you can barely tell the difference between half a litre and a pint. Ninkasi, it is you who wonders what was going on in that bit in 1984 where the old guy complained that half a litre of beer wasn't enough, seriously, you can barely tell the difference between half a litre and a pint.

It is you who stores the bottles upright at a temperature above 18C (in Scotland, in October) for two weeks while the beer undergoes carbonation. Ninkasi, it is you who stores the bottles upright at a temperature above 18C (in Scotland, in October) for two weeks while the beer undergoes carbonation.

It is you who invites your friends round to try the finished beer; it is like the onrush of the Tigris and the Euphrates. Ninkasi, it is you who invites your friends round to try the finished beer; it is like the onrush of the Tigris and the Euphrates.

Cheers!

Here's the current state of play with the Assyriology:

( Doom, gloom, failure, sheep and kurtosis )

So I was down in Cambridge last week, as part of an exercise in convincing mathematics Part 3 students that there are other universities in the UK, and that some of them are even worth doing PhDs at. I didn't manage to see everyone I'd have liked to, but I did get to see Antarctic Mike for the first time in nearly two years (as the name suggests, he spent most of that time Down South), and to spend a night on his new houseboat. I also went out to the pub with Mike and Ros (our musical director from The Matrix) and had a very nice lunch with scribeofnisaba, whence the rest of this entry.

scribeofnisaba is an Assyriologist (coolest job title ever, no?), which means that she studies the literature and languages of the ancient Near East - the languages spoken by the Assyrians, Sumerians, Babylonians and so on. Roughly speaking, the languages spoken in modern-day Iran and Iraq, in the period 4000-1000BC(ish). In other words, the study of the oldest literature in the world. She tells me that it's a very exciting field, and that now is a very exciting time to be working in it, as so little is known, and much of what we thought we knew has recently been shown to be wrong - for instance, it was always thought that Sumerian scribes were all male, but this is now thought increasingly suspect. One surprisingly basic thing we don't know (if I'm understanding her correctly) is whether or not Sumerian poetry was metric.

A brief word of explanation. Poetry in many languages is characterised by the use of a repetitive pattern of long and short syllables, called the "metre". Shakespeare, for instance, used the pattern

SLSLSLSLSL
SLSLSLSLSL
...

whereas Virgil used

LSSLSSLSSLSSLSSLL
LSSLSSLSSLSSLSSLL
...

Now, it seems to me that it might well be the kind of problem that reacts well to having a few billion processor cycles thrown at it, but there are a couple of things I'm not too clear on, and maybe you lot can help me out.

As I understand it, we don't know
0. whether the Sumerians wrote metric poetry at all,
1. if they did, what metre they used,
2. how individual Sumerian words were stressed.

Assuming 0, then if we know 1, we can work out 2, and vice-versa. But if we don't know either, we might be able to bootstrap a knowledge of both by considering their interaction. This could well turn into a lifetime's work if done by hand, but fortunately we now have wonderful machines for doing repetitive calculations very fast, and the Electronic Text Corpus of Sumerian Literature seems like it was designed for precisely this kind of automated search.

[scribeofnisaba: You mentioned that cuneiform was syllabic: is the same symbol typically used in many different words? Because if so, we might be able to assume that it's stressed the same way whenever it occurs. But then again, probably not. Also, do we know that the lines are metrical units?]

Anyway, here's my idea. We search the space of possible ways of stressing words, and looking at the metres they produce on the corpus of poetry, and search for the stress patterns that produce the most regular metres. The searching's not that difficult, or rather there are well-known ways of doing it (more on that in a minute). The tricky bit, actually, is finding an automated way of looking for "poetic" stress patterns - the problem is that the pattern "short short short short short..." is as regular as you like. We could (for instance) calculate the stress pattern of every poem in the corpus, given our current guess at word stresses, then compress the resulting bitstream and observe the compression ratio - but that would tend to produce "short short short short...". We could, er, apply a discrete Fourier transform to split it into a sum of periodic functions, and then, er, um. Just eyeballing it won't work - we'd probably have to go through several thousand (mutate, calculate metre, compare) cycles. Is there some kind of constraint on word stress patterns for Sumerian that we know about? Each word must have at least one long syllable, or something? Anyway, there's presumably some way of doing this that I'm either too stupid or ignorant to find right now :-)

As for the algorithm for the search: the most obvious thing to do would be to simply try every pattern, but with nearly a thousand nouns in the glossary (and many other words of other sorts), each containing several syllables which can be either short or long, we'd have a search space with around 2^2000 elements. This is, to say the least, computationally infeasible. Another approach might be via "hill-climbing": start somewhere random, change it a bit, see if the change improves matters, keep it if so, repeat until you can no longer improve your results by making small changes. The problem with this is that you can get stuck at a "local maximum", or a point better than everything nearby but still not the best overall. Every mountain-top is a local maximum for the height of the Earth above sea level, but not every mountain is Everest. One way of dealing with this problem is to introduce a bit more randomness: the following elegant algorithm (which is the one I was thinking of using) is due to Metropolis:

1. Start at a random point in the search space.
2. Make a small change to your position.
3. See if this has improved things. If it has, keep your change. If not, toss a (weighted) coin, and keep the change if it comes up heads. The coin should be weighted proportionally to how much worse the change has made your results: a very deleterious change has a very low chance of being kept.
4. Repeat several hundred or thousand times until your position stabilises.

I attended a series of lectures by the mathematician and magician (mathemagician?) Persi Diaconis on (among other things) this algorithm about a year ago, and it's really surprisingly effective.