The police as the modern priest-Levite

Last weekend, I was cycling home at around 1am and was going through the East Road–Newmarket Road–Elizabeth Way roundabout, when I went past a woman who looked like she was waiting for a lift. However, the side of a major road away from any houses seemed like an odd place to wait for a lift, and she seemed distressed, so I stopped and asked if she was okay.

She was not okay. She was not waiting for a lift. She had been walking around Cambridge, lost, for the last two and a half hours. She was from a different city, having been on a hen night, having split off from the rest of the group, and trying to find her way back to the Travelodge. Her phone battery had run out. She was dressed up for going out; her shoes were not suitable for that much walking, and the cold weather was becoming increasingly unpleasant. (As it happened, the Travelodge was just down the road, about two minutes’ walk away.)

She was grateful, and told me that she had tried to stop and ask multiple people for directions, eliciting only ‘I don’t know, sorry’, rudeness, or abuse. Most horrifyingly, she had approached police officers for help and directions, but the police refused to help her, on the grounds that she was not a victim of a crime and therefore not in trouble.

Is their job to uphold the Law and to stop crime, or to serve the public and keep them safe?

Reporting biases in Genesis and Andrew Lloyd Webber

It’s always bugged me how in Joseph and the Amazing Technicolor Dreamcoat Pharaoh hires Joseph rather arbitrarily to be his Vizier responsible for Egypt’s economic policies over the next fourteen years, based solely on Joseph’s (as yet unproven) ability to explain his dreams. Even if Joseph’s forecasting was accurate, as a lowly foreign-born slave-turn-prisoner would he have had the administrative skills to oversee such huge reforms?

Then, I realised: Assuming that Egypt had existed for centuries before the time of Joseph, then successive Pharaohs might have appointed lots of people to be Viziers in this way, based solely on their abilities to make predictions based on individual dreams. Those who turned out to be wrong, or who were unable to enact the appropriate policies, were disposed of and their stories were not recorded and have not been passed down to us.

Chinese proverbs

I’ve noticed an annoying and persistent tendency for people to inaccurately claim that certain sayings are Chinese proverbs. ‘Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime’ is one example of such. ‘A picture is worth a thousand words’ is another.

These are admittedly only a couple of examples, so I may be going a bit far, but nonetheless, I claim that the following proverbs are true:

  • C0: For any proverb P, ‘P is a Chinese proverb’ is a proverb.
  • C1: For any proverb P, P is not a Chinese proverb if and only if P is claimed to be a Chinese proverb.

Since it is unnecessary for the Chinese to claim that a statement is a Chinese proverb (we need merely claim it to be a proverb), I make also the following claim:

  • C2: For any proverb P, ‘P is a Chinese proverb’ is not a Chinese proverb.

Can these claims be consistent, and which (if any) can I consistently claim to be Chinese proverbs?

Addendum: Oftentimes, the claim that a proverb is Chinese is used by orientalist woo-peddlers to create credence for their claims. Allow me therefore to go so far as to claim:

  • C3: For any proverb P, if P is claimed to be a Chinese proverb then P is false.

Is this consistent?

Using Matrix instant messaging

Following my recent rant on decentralising our communications, I’ve started trying out the Matrix communication protocol on the suggestion of a friend. It’s a wonderful idea, and it’s great that the network can be connected to by various different clients. And it seems to be very easy to add people to the network: you just need to give their email address(*) to invite them. The Riot.im is quite easy to use for basic usage, although there are some nuances that I haven’t got used to yet.

One thing that’s not immediately obvious is how you refer to things. On Twitter, you can refer to people as @jftsang and to groups as #example. On IRC networks, channels are usually called #channel or ##unofficialchannel.

Well, on Matrix, user IDs take the form @username:server, such as @jftsang:matrix.org. The latter part tells you about the homeserver of the user, which is needed because Matrix is a distributed network and different users might be accessing through different servers. Rooms take the form #room:server, and communities take the form +room:server. I’m not yet sure what the relationship between rooms and communities is.

(*) Ten years of relying almost exclusively on Facebook means that we tend not to have many of our friends’ email addresses. The situation was particularly bad when Facebook tried pushing their @facebook.com email addresses, which fortunately didn’t catch on.

I would recommend anyone interested in a free-as-in-speech-and-as-in-beer IM service to try this out; send me a message on @jftsang:matrix.org on Matrix, or giving me your email address so that I may invite you.

Explaining my PhD using the ten hundred most used words

You can try this yourself at http://splasho.com/upgoer5/.

In my work I look at cups full of hundreds of hundreds of hundreds of hundreds of tiny little bits, such as little glass balls, or the hard white stuff that you can put on your food. When you try to move these bodies made up of little bits, such as when you move them from one cup to another, they act a little bit like water but not quite in the same way. We understand how water moves from one cup to another quite well, but it’s much harder when you have these little bits because they can do a lot of different things that water can’t do. It’s also harder to learn about how these little bits move because they are usually not see-through, so that you can’t look inside the body and see how it’s moving under the top.

I want to understand how these bodies made up of tiny little bits move when you make them go over things. It’s hard to try it out in real life because the bits are not see-through, so instead I use a computer where I can play with pretend tiny little bits. This lets me look at how each little bit moves. It’s also much cleaner to do it on the computer and I can try many different set-ups at the same time, but you have to make sure that the pretend little bits are like real ones.

It’s important to study how stuff made up of tiny little bits go over things, because sometimes too much of this stuff can move at the same time, very quickly, over houses. This happens quite often and a lot of people get hurt. It’s also interesting because people also use a lot of this stuff to build things and we need to know what’s the best way of moving it.

The LaTeX psalm chant

LaTeX’s output, showing its hyphenation algorithms at work, makes me want to set my bibliography to plainchant:


[19] [20] [21] (./blasius.bbl
Underfull \hbox (badness 1210) in paragraph at lines 13--15
[]\OT1/cmr/m/sc/9 Andreotti, Bruno, Forterre, Yo[]el & Pouliquen, Oliver \OT1/c
mr/m/n/9 2013 \OT1/cmr/m/it/9 Gran-u-lar Me-dia\OT1/cmr/m/n/9 .
[22]
Underfull \hbox (badness 6396) in paragraph at lines 156--158
[]\OT1/cmr/m/sc/9 Peregrine, D. H. \OT1/cmr/m/n/9 1967 Long waves on a beach. \
OT1/cmr/m/it/9 Jour-nal of Fluid Me-chan-ics

Underfull \hbox (badness 5954) in paragraph at lines 180--184
[]\OT1/cmr/m/sc/9 Rajchenbach, Jean \OT1/cmr/m/n/9 2005 Rhe-ol-ogy of dense gra
n-u-lar ma-te-ri-als: steady, uni-form

Underfull \hbox (badness 10000) in paragraph at lines 180--184
\OT1/cmr/m/n/9 flow and the avalanche regime. \OT1/cmr/m/it/9 Jour-nal of Physi
cs: Con-densed Mat-ter
[23]) [24] (./blasius.aux)

Free speech and free beer

Facebook is in the news in both the UK and the USA for its dealings with Cambridge Analytica, in which Facebook users’ personal information was handed over to the political consultancy firm. There are a couple of problems with the way this is being reported in the media.

  • We, as mere users of Facebook, are not Facebook’s customers. We are its products. We refer to Facebook as a ‘service’ because we tend to think of it in much the same way as we think of the fire service, the armed forces or the NHS. But of these four things, only one of them is privately owned and largely unregulated.
  • This was not a data breach, it was a data leak if not a data transfer.
  • I haven’t read Facebook’s terms of use in any detail recently, but its almost certain that they permit this sort of data transfer to third parties (or at least does not specifically forbid them). It’s not a secret.
  • Even if it were a secret, it should be unsurprising. The selling of personal information is Facebook’s business model, which should be surprising to nobody. What do you think is paying for the upkeep costs of a website serving billions of people each day, doing so at zero price?
  • Although the #deletefacebook and #boycottfacebook campaigns are currently enjoying a surge in popularity and have the backing of prominent figures, they won’t result in immediate or significant change: I have said before that Facebook holds a monopoly on communication. This is exemplified by the fact that these campaigns are taking place, to a large extent, on Facebook.
  • Moreover, if we all migrate to a new social network (just as we have all left MySpace and Bebo), then the new company would be just as abusive towards its users. In any case, there is currently no centralised, zero-priced website that offers all of the things that Facebook offers its users: a soapbox, an address book, a calendar and an instant messaging service. Nor is there likely to be such a website in the future. This is a matter of economics; the ‘market’ for social networking websites admits natural monopolies.
  • As much as Brexit and Trump are regrettable, the fact that Cambridge Analytica was behind the two campaigns, helping to spread fake news and influencing the two votes to a strong degree, is a distraction. The real danger is our willingness to sign up to such a website in the first place.

For users of social networks, the only long-lasting solution is to break away from the centralised model and start using decentralised models, such as diaspora*. For instant messaging, using something like IRC would be a good first step towards decentralisation. As for having a soapbox, I run my own website (which you are reading now), because I want to have ownership and control over what I write. I have the freedom to amend or retract my content without the information being held in perpetuity by another party. I can make content accessible to a select group of friends without it also being accessible to any third parties (provided that I trust my friends, which by definition I do). Setting up one’s own website is not technically challenging, if one is happy to pay a monthly fee in exchange.

In summary,

‘Free as in beer’ implies ‘not free as in speech’.

That means you can’t expect to have a social network (or any other ‘service’) that does not charge you and yet entirely respects your digital rights.

Confucianism in Harry Potter

I didn’t notice this at first, but one of my friends pointed out that most of the wizarding labour in the Harry Potter universe seemed to be employed by one of two employers. As a graduate of Hogwarts, you could respectably become a teacher at Hogwarts, or a civil servant of some description in the Ministry of Magic. Or you could leave the wizarding world and live a low-key existence amongst the Muggles. Appointments to either Hogwarts or the Ministry of Magic are conditional on you performing exceptionally well in a number of exams.

It then hit me that the Harry Potter world is actually an implementation of Confucius’ vision of society, complete with all the flaws in such a system!

The bureaucracy of the Ministry of Magic is sprawling and has an almost totalitarian (but not necessarily adversarial) influence over wizarding life. The same people constitute the executive, legislative and judiciary branches, with no separation of powers. There is only a very small private sector, and the state does not practise outsourcing.

Entry into the wizarding world is in theory open to all that display magical abilities, but in practice such abilities run mostly down bloodlines and there are relatively few Muggle-borns. While Muggle-borns are no less talented than their pure-blood colleagues, they nonetheless face either explicit hostility, or subtle prejudice. Such prejudice is common within the pure-blood aristocracy, with dissenting voices being rare and limited to liberals such as the Weasley House, who have some, but not much, political influence.

The Ministry of Magic is mostly concerned with policing the activities of wizards, and is uninterested in the Muggle world, for the most part desiring neither to improve nor oppress the latter. Like the Party in Nineteen Eighty-Four, the Ministry is concerned with staying in power and focuses its efforts on fighting potential rivals such as Albus Dumbledore, rather than effectively addressing the evils of society.

Retinal detachment and Bayes’ theorem

I had my eyes tested yesterday, having put it off for several years. Happily, my vision seems not to have deteriorated in the last couple of years.

After the test, the optometrist told me that my short-sightedness meant that I was at risk of retinal detachment (RD). I asked if this was something to be worried about on a day-to-day basis. They said no, it was just something to be aware of: retinal detachment affects about 1 in 10,000 people, but 40% of cases happen in people with severe myopia.

I didn’t feel very comforted by this, since this information doesn’t directly tell you about my personal risk of retinal detachment given that I have severe myopia. To make sense of that figure, you need to know the prevalence of severe myopia.

According to Haimann et al. (1982) and Larkin (2006), the figure of 1 in 10,000 is actually an annual incidence: in a population of 10,000 healthy people, on average one new case of RD will develop after a year; the lifetime risk is therefore about 1 in 300. The prevalence of severe myopia (beyond −5 diopters) amongst Western Europeans aged 40 or over is about 4.6% (Kempen et al. 2004).

A calculation using Bayes’ theorem would predict that RD has an incidence, amongst people (Western Europeans aged 40 or over) with severe myopia, of about 1 in 1,000 per year, which corresponds to a lifetime risk of about 1 in 30.

This lifetime risk is surprisingly high, and not nearly as comforting as ‘1 in 10,000’. It is so much higher than the base incidence because severe myopia is fairly uncommon, and also because people live quite long lives; the exact relationship between lifetime risk and annual incidence depends on one’s lifespan, and the incidence is not uniform with age. Fortunately, the annual incidence of 1 in 1,000 is still quite small, so no, it’s not something to worry about every day.

This is an extremely simplified calculation using figures drawn from across different populations; the Haimann study was for Iowans of all ages. Myopia is much more common in China, but it’s unlikely that there’s any data out there specifically on Chinese ethnicity people living in Western Europe (both genetics and environment affect myopia). I’ve been unable to find any more detailed information on the prevalence of retinal detachment as a function of myopia strength.

Gariano and Kim (2004) describe the mechanism by which severe myopia might cause retinal detachment.

TL;DR: Opticians don’t understand conditional probabilities, causing me to stay up late browsing optometry and epidemiology papers.