So last Saturday I found myself with a good 450g of rhubarb in need of cooking. I also had some almond meal left in the cupboard from previous baking, and figured that there must be something nice I could make with almond meal and rhubarb. A bit of googling turned up this recipe which looked interesting, but I didn’t have all the ingredients.

I’d heard about ratio baking, and that what really matters when making a cake is the ratio of flour : eggs : fat : sugar. After a bit of googling, I pulled down *On Food and Cooking*, a book given to me by a friend, and which, to my shame, I have not read anywhere enough of. Of course, it has an excellent description of cakes and various ratios.

So I decided to bake a rhubarb cake somewhat inspired by the recipe and somewhat by the ratios. I back of the enveloped the ratios in the recipe above, and ended up using

- 6 eggs, or 282g without the shells, 47g each – surprisingly uniform
- 70g butter
- 280g caster sugar
- 190g almond meal
- 50g flour
- 35 g brown sugar
- 2 tbsp rice bran oil
- 2 tbsp lemon juice
- 2 tsp baking powder
- some lemon rind and fresh ginger

I tossed the rhubarb (cut into half inch lengths and washed) with the brown sugar, and layered this in the bottom of a 20cm x 20cm square pan which was about 8cm deep. It was mostly one bit of rhubarb deep.

I used a hand mixer on the butter and sugar. This left me with lots of little lumps of sugar rather than the creamy mix I was expecting. I think this was because the cake was very low on fat according to the ratios in the book. On a whim I chucked in the rice bran oil at this point to up the fat a bit and get a workable mix.

I beat the egg yolks in one at a time with the hand mixer – all except the last, of which I’d managed to break the yolk of when cracking them. After this went in the almond meal. I kind of got a bit worried about the low quantity of meal, and it’s lack of gluten, compared to the sugar and egg and the notional ratio, and added a bit of plain flour to boost this up a bit. After this I chucked in the broken egg.

I hand whipped the egg whites to pretty foamy, and folder them through the mix, followed by the lemon juice, rind, and some fresh grated ginger. At this point the mixture was looking more liquid than i expected, and i was fretting a bit about it all. Possibly due to this stress, and being somewhat off road, i decided to go heavy on the baking powder and mixed in two teaspoons.

I poured the batter over the rhubarb, maybe half filling the pan depth, and chucked it in the oven. Of course I had forgotten to preheat it until the final stages, so it probably wasn’t as hot as I’d dialled up, namely 175°C, so I just tested it every 20 minutes or so. After 40 minutes the top was a bit brown, so at Megan’s suggestion i covered it in foil. After 60 minutes a skewer was coming out pretty clean.

I took it out and let it rest for a good 15 minutes before turning it out. I was pretty nervous it would still be a bit liquid. It was quite moist, but structurally sound. It tasted good – the rhubarb was almost over done but still good, and the lemon flavour in the cake was pronounced. The ginger was too muted, and next time I’ll add a couple of teaspoons of ginger powder with the dry ingredients. Distribution of the giner might also be a problem, so I’ll probably add the rind and ginger before the egg whites next time.

Here’s a couple of pictures of the final product:

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Apart from poking gentle fun at date ordering, i do have mathematical reasons to like 22/7 more. As i mentioned in a follow up tweet, 22/7 is a better approximation to π than 3.14 in an absolute sense – 22/7 is within 0.0013 of π, whereas 3.14 differs from π by just under 0.0016. I am swimming against the tide though – even Wikipedia calls 22/7 Pi Approximation Day, reserving Pi Day for the less accurate 3.14.

However, it was a reply from a friend pointing me at All Rational Approximations of Pi Are Useless which spurred me to action, in as much as blogging is action. Apart from the fact the provocative title is demonstrably false – i use a rational approximation of π (typically 3) all the time to estimate the volume of cake tins amongst other things, that article really deserves critiquing. The claim is that rational approximations are useless because they are no better than remembering decimal digits. Already we can see this depends on what you mean by better – 22/7 is better than 3.14 for the same number of digits, if by better you mean “closer in absolute value”. Ah, but his version of better is “correct digits when expanded in base 10” – in other words – a definition skewed towards base 10!

Let’s think it through a bit more – in base 10, we have 3.14 = 3 + 1/10 + 4/100, whereas π = 3 + 1/10 + 4/100 + 1/1000 + 5/10000 + …

So what is a fair comparison for 22/7 ? Surely its base 7! Here, 22/7 = 3 + 1/7, whereas π = 3 + 1/7 + 0/49 + 0/343 – 3/2041 + … . The denominators here are the powers of 7, and i’ll allowed myself “negative digits” to make clear how close the value is. So in fact, 22/7 gets three fractional base 7 digits right, for only one fractional part (1/7). The approximation 3.14 needed two fractional parts (1/10 and 4/100) to get, umm, 2 digits right … hopeless!

Another way to think about how good a rational approximation *p/q* is to an irrational *a* is to look at the absolute difference between *p/q* and *a* as a power of *q*. In symbols, find *k* so that |*p/q – a*| < 1/

Back to the article – the author finds 355/106 by brute force, and then searches to 10,000 to no avail. There’s a good reason for that – the next great rational approximation of π is 103993/33102. Of course, the way to find these is not brute force, but by thinking. That is to say, by doing maths – specifically the theory of continued fractions. His brute force technique finds 99/70 as an approximation to √2 – again, this value is predicted by the theory of continued fractions – it takes about under 60 seconds of *hand* computation to find it once you have the theory – no need to throw the massive computation engine of Mathematica against a problem which has an elegant and well understood theory behind it.

A mathematician and friend who will remain nameless for now once suggested to me that Kepler would not have made his ground breaking work in planetary motion if he had had access to Mathematica. At the time, planetary motion was predicted via epicycles, an approximation technique. The claim is that it was the difficulty in getting better approximations via epicycles – the calculation just gets too hard – that drove Kepler to look for, and find, a correct theoretical solution that was also elegant and practical for computation. Had humanity had a computation engine capable of computing epicycles, it might have been generations before his inventions were made in the absence of their mother necessity.

*Postscript*

I want to leave it there, but feel i must observe that i’m not against machine computation – far from it – computers have enabled fantastic progress and contributed significantly to human wellbeing. However, i do have a sympathy for the point of view that being required to find a theoretical solution in order to make practical progress can lead to discoveries that you miss if you’re overly focused on answers because you can find them easily. It’s the journey, not the destination.

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I drifted away from reading somewhat in the last decade – busy with work, homemaking, and later a baby / toddler / preschooler. I still consumed my favourite (Banks) greedily, but was reading less new fiction. First podcasts, and then twitter filled my commute time where once i’d’ve read. More than this, i just lost track of making the time to read.

For my birthday, the wonderful @ms_miff gave me a kindle – the 6″ 3G+WiFi version. This was in consultation – i’d realised i wanted to read more again, and had started buying / borrowing / rediscovering some books, as well as trying reading on my iPhone screen, which i found hard on the eyes. I decided on a small, fit for purpose e-reader rather than the obvious tablet.

Why ?

That’s hard to answer. So, instead, i’ll say what i think of the kindle after reading my first full e-book on it. Some of this I expected to be true, and answers the why, and some may be helpful if you’re asking the same question. And some will just be post-hoc justification.

Firstly, the screen is amazing. If you’ve not looked at an e-ink reader, do so before thinking you want to read off a backlit screen. When i unwrapped it on my birthday morning, i saw the screen had a lovely greyscale design on it. I promptly tried to remove the overlay – assuming it was one of those “stuck on for shipping” stickers. It wasn’t – it was the screen showing a static image. As i understand it, the resolution isn’t that much greater than a 3G/3GS era iPhone, but the high contrast reflective screen makes it look immensely better. The refresh is odd at first (a kind of inverted video flash), but it’s fast enough (at least on the newest model) that it doesn’t interfere with reading (at my speed anyway).

The small size still fits enough text to make reading pleasant (it’s a bit like a smallish paperback) even at the slightly enlarged font size i use. It’s light enough to carry one handed easily, which means i can read it while walking – my morning commute often involves a 30-40 minute walk. It also means it can be always in my bag, which assists in having it when i have a spare moment to read. This last point is actually critical to displacing the iPhone as my time sink of choice. I’m not sure how a larger kindle, or tablet, would fare here. Battery life also matters on this point – i’ve had the kindle for a week now and read a book, and it’s used about one third of the first battery charge. This means its always ready to go when i have spare moments to dive into a book, without me needing to remember to charge it daily.

I’ve not yet got a case – i stick it in a $1.10 Australia Post Pb2 padded bag for protection in my backpack. It fits nicely in this, but this does go to one of my concerns – i’m not really sure how hardy it is, and obviously don’t want to find out through catastrophic failure! Ergonomically, it’s hard to “grab”. It’s nice to hold when you’re reading, but when you’re trying to fish it out of a bag or grasp it while shouldering a back pack, its not clear where you can apply pressure. I’ve taken to grabbing it by the keyboard.

Which brings me to my only negative – the keyboard. In a post iPhone world, i thought i would want a touchscreen. I don’t miss that at all – the page turn buttons work fine, and on the rare occasion i use the joypad to navigate a menu it’s not a big deal. I actually try to avoid touching the screen so i don’t have to clean it – i want to read off it after all! No, the keyboard is a negative because, for my usage, the device doesn’t need one. i’d rather have more screen, or a smaller device. So far, i have used it twice – to enter my amazon credentials and my home WiFi key. I’d happily have done both of these via a USB connection. I don’t search for books on it, i do that on a PC and wishlist them, at which point they’re only a few clicks away on the kindle. Or, i expect, i’ll buy amazon recommendations – again, a few clicks away. Maybe i’ll change my tune on this, but for now, it’s the only minus i’ve found in the kindle experience. In an ideal world, my WiFi capable iPhone could act as a keyboard for the Kindle, but that’s a level of integration that is, unfortunately, probably a pipe dream.

In summary, after one book, i love it. I bought a book i’d never heard of via links from a favourite author and checking half a dozen reviews. The book was in my hands a few minutes later, and i read it over the next week. I’ve now queued nine items on my wishlist, and look forward to reading them the same way. Reading on the kindle is, in almost all respects, at least as, if not more, pleasant than reading a physical book. It’s smaller and lighter than most paperbacks, the screen is like paper, but resizable for my below average eyesight. I can carry it everywhere and read when i please. It’s not as robust or cheap as paper – but you can’t have everything.

On a final note, i received a second kindle related birthday present – a kindle book from my oldest friend. This was a real “welcome to the future moment” – while chatting with him online, an email arrived, and a few clicks later my present arrived on my kindle. I’ve yet to start that book, but, in fact, i’m going to go start it now …

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However, of late, i’ve been afflicted by a mild professional ennui – it happens from time to time – and found myself getting more interested in matters of the hearth. This post is not the place to go into a lot of detail on the reasons, although i will say that reading Stephanie Alexander‘s Kitchen Garden Companion played a large part in kindling an interest in gardening and the raw materials used when i cook.

So, it was on this fertile soil that the seeds sown by various people on twitter landed. My few attempts to garden in our small terrace courtyard have met with mixed success. Growing a sour dough leaven tickled a similar nerve, but seemed easier, and not to mention quicker. I also came across SourDom’s instructions for making a starter, which, for whatever reason, sounded accessible in a way others hadn’t. So, at the end of March, i began following the instructions. On Easter Sunday evening it staged an escape attempt, and by the end of that week it was rising well when fed, and i figured it was time to cook.

The recipe i settled on was Norwich Sourdough. Why ? Firstly, it used a 100% hydration starter, which is what i had to hand. Secondly, it could be done in a day once i had ripe starter. Finally, the instructions were quite precise in quantities and times – when i start cooking, i like this until i get the feel of what it’s supposed to look and feel like. Of course, there are probably hundreds of recipes with these three properties, this is just the one i found. I made a half quantity, as that neatly matched one ripe load of leaven, and varied the times a bit because my loaves seemed a bit bigger – i think i ended up with 15 minutes of steam and 20 minutes without.

I was very happy with the result – straight from the oven, and when cut. Megan and Griffin also approved – in fact we ate the smaller loaf in its entirety yesterday, and the larger one is pretty much down to just a couple of ends now. I’m very keen to try again – i’d like to do the same recipe a few times in a row to learn the variation, but we’ve got some busy weekends coming up which will preclude a day spent cooking for a while. However, i’m also interested trying @tammois‘ overnight recipe, but i’m not sure about my judgement for the quantities.

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Finally, i’ve decided to do something about it. Expect to find sundry rants here, on the varying topics which occupy my time and energy.

That could mean a lot of things:

- food and cooking, including a recent interest in sourdough
- photography, a hobby i’ve been neglecting of late
- my lovely wife and wonderful son, as well as my family and friends
- mathematics, including NMSS
- technology, the field in which i work and sometimes rant about

You can also find me on twitter.

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