Stuff

[liv]

Various bitty things to record what I've been up to lately:

I actually took advantage of Cambridge being Cambridge and went with cjwatson to a lunchtime recital in John's, a young cellist called Ghislaine McMullin performing a Rachmaninov cello sonata. It was the kind of performance that held my attention for every note, really enjoyable. I didn't know the piece (Op 19 in G minor), and I rather fell in love with the transitions between movements, a sort of lovely anticipation, so I shall try to get hold of a sensible recording. There was a little bit of Ravel being silly and Orientalist for the encore, and it wasn't sublime like the Rachmaninov but even silly Orientalist Ravel is still a treat. Since we'd spent lunchtime listening to the concert we went for afternoon tea afterwards, choosing Brown's since it's central and easy even if a bit obvious. I got to point out that Cambridge contains surprisingly many gilded pineapples, which cjwatson hadn't noticed in spite of living there for many years.

You are welcome to kick me for it, but I did in fact end up celebrating Valentine's Day. jack and I decided to stay in being coupley rather than try to deal with the commercial version of VD on a Saturday night. We made this Mushroom stroganoff; I use tarragon instead of parsley, I think it matches the rest of the flavours better. Somebody, I can't remember who, linked to a rather breathless clickbaity article recently about how most people cook mushrooms "wrong", and personally I like sautéed mushrooms and the nice juice that they exude, but I thought it was worth a try searing the mushrooms on a high heat, separately from the onions and seasoning. That did work, though ideally I need a more interesting high temperature cooking oil than sunflower.

And we rented Fucking Åmål (its rather milquetoast English title is Show me love). I like this film a lot and wanted to show it to jack; it's a love story, but not a romantic comedy. It's that rare thing, a fairly realistic depiction of the sexuality of teenaged girls, not a just deniably short of soft-porn show for a presumed audience of 20-something men, but a character story where the girls are very much the subjects. Rebecka Liljeberg's acting is outstanding; she was only a year or so older than her 16-year-old character, in contrast to the Hollywood convention of having adult actresses play teenagers. But her utter devastation at social humiliation, her radiant joy when her love-life goes unexpectedly well, make this a much more romantic film than the kind that follow standard romantic tropes. Plus, you know, Agnes and Elin have a good reason for not talking to eachother about their feelings, given that they are teenaged lesbians in a homophobic school environment way out in the sticks in the 90s.

I was invited to a third birthday party. It was in a community hall and the children were more interested in playing with the toys, softplay including a ball pool, and playground outside than interacting with the adults, so I actually just sat around eating tasty food and chatting, which was easier than I'd expected it would be. Thank you for all your present suggestions; I ended up getting the Ahlbergs' Each peach pear plum, which was a childhood favourite. Reportedly the verdict is that it has really good letters in, which, yes it does, though I mainly chose it for the words and verses rather than the letters.

In other getting to know my friends' children news, this weekend I attempted to tell the story of Medusa to their six-year-old. I ended up reading the Nathaniel Hawthorne's Wonder Book version aloud to her. I remember my grandfather reading it to us when we were about that age; he had a beautifully illustrated edition we weren't allowed to touch, and I understood a fairly small proportion of what was going on. Hawthorne's a lovely story teller, but he tells selections from the myths and I couldn't find a good version of the rest of the story about what Perseus did with the Gorgon's head having acquired it. We also played a lot of OLO, which is, of all things, a smartphone app version of shove ha'penny. She's better than me at playing the game, and sort of interestingly picking up the meta-skill of playing in a sportsmanlike way, we've been experimenting with bits of friendly trash-talking without crossing the line into mean.

OTOH I completely failed to answer the three-year-old's question of why a slinky climbs down the stairs. Mainly because I don't actually know the answer, and "because physics" is hardly satisfying. So I'll try to crowd-source this one, can anyone explain why the slinky does that thing? I welcome either simple or mathsy explanations; I reckon if I understand it properly myself I can probably figure out how to explain it to a kid who hasn't yet got to formal physics.

My latest student, by my count the fifteenth I've coached since I started with my brother in 1993, celebrated his bar mitzvah at the weekend. I'd let myself get a bit nervous about it, but actually it was perfect. The young man did brilliantly, he read well, and I know he's worked hard to bring his Hebrew reading up to scratch, cos I was guiding him through the process. He didn't take any shortcuts with rote learning or using a crib, he just put his head down and learned to read. And it was good for the community as well, the first time we've celebrated a bar mitzvah in 15 years, and the service I think meant something to the regulars as well as to the bar mitzvah boy's family and friends (most of whom aren't Jewish). Anyway people were enthusiastic, and I feel pretty good about the whole thing.

I got to talk to darcydodo! She says that the best possible contemporary children's book of Greek myth is D'aulaires' book of Greek myths, so I shall seek that out, cos stuff that's old enough to be in the public domain tends to be a little obscure in language and not exactly what I'd want in attitudes and values.

And hatam_soferet asked me to learn some midrash with her, chevruta-style, which is the most wonderful thing! I mean, she's ridiculously more advanced than me these days, but we have been learning together since the turn of the millennium, and it works. I miss my friend and I miss proper intense text learning, so getting both together is just wonderful

Also, congratulations to randomling who correctly guessed that what I was thinking of in Pessimized Twenty Questions was Croatia. randomling, you're of course welcome to start a new round if you like, but perhaps a single game was enough, playing by comment discussion. Honourable mention goes to seekingferret who played with great cunning, coming up with informative guesses and not getting trapped in assumptions based on what had been discovered so far.

ETA: randomling started another round, do go and join in!

Comments

[seekingferret]

xkcd had some interesting stuff about slinkies here: https://what-if.xkcd.com/126/

[liv]

Oh, that's really cool. I'm a bit annoyed with the humour in What-if, but that link to the loose heavy spring paper that works through the equations governing the motion of the slinky is awesome.

[davidgillon]

Fascinating, though I wonder if there's an alternate model possible based on conservation of momentum, and good look reading the paper to the 3yo ;)

[(Anonymous)]

Liv is very good at explaining to small children. For example, over the weekend she was telling them Greek myths, and today said 3 year old busy told me he was a sea monster eating 'Andomda'. So I think a little physics should be much easier.

[(Anonymous)]

Not busy: just.

[liv]

He did? That's awesome, I wasn't even sure he was listening, it's so cool that he's being the sea monster. I am quite good at explaining stuff to small children (it's a very related skill to explaining things to doctorlings, in fact), but I am not very good at understanding how mechanical things work, and if I can't understand things myself I usually can't explain them either. Which is why I am pretty happy to have a slinky explanation with lots of equations in, I get equations.

[davidgillon]

Wonderful. I do think we sometimes underestimate small children. I'm reminded of a friend's 3yo (now 13yo, eek) making a comment as we drove past the church in a deserted French village (a really bizarre village of the damned scene), and finally working out that what he was saying was 'The bells aren't tolling, Mummy'. Which was absolutely true, just not something you expect a 3yo to say.

[liv]

The anon you're talking to most certainly doesn't underestimate small children, given that hers do things like teaching her astrophysics! But I agree a lot of people do. I also think I, like many adults, over-estimate my ability to actually understand how the world works in a way that makes it possible to explain to curious little ones. Like, however much I try to resist it, it's easy to fall into just taking it for granted that something is the way it is cos you've always experienced things that way, and not really understand why at all, until some three-year-old asks you (not having that bank of experience) and you realize you don't actually know.

[davidgillon]

Isn't there a Feynmann quote around the lines of 'if you can't teach it you don't understand it' (I think it's connected to his work on Quantum Chromo-Dynamics).

A quick google turned up 'If you can't explain it simply, you don't understand it well enough', but that's attributed to Einstein, while Feynmann's 'If I could explain it to the average person, I wouldn't have been worth the Nobel Prize' isn't at all the same moral.

Aha, this is it: "Feynman was once asked by a Caltech faculty member to explain why spin 1/2 particles obey Fermi-Dirac statistics. He gauged his audience perfectly and said "I'll prepare a freshman lecture on it." But a few days later he returned and said, "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it."

[liv]

That's a very Feynman anecdote, hee! I do think there are some things, particular the really fundamental bits of physics, that you just can't explain simply no matter how good a teacher you are, because the issue is in fact not simple, and also doesn't connect at all to our experience of how the world works. So in order to explain it, you can't get round the fact that you have to explain the underlying concepts first, and you probably could do that for an "average" person or a small child or whatever, but it would take longer than most people have patience for. Which is in fact why we have specialized university courses for people who want to understand these complex ideas.

[davidgillon]

I agree, it's possible the explanations of even the most esoteric corners of quantum theory are simple, it's the not having the doctorate in that particular esoteric corner that makes them look hard ;)

[liv]

My intuition for this kind of thing is really poor, but I feel like if it were about momentum the height of the stairs would affect how fast the slinky climbs down them? My not very mechanical mind feels a lot more comfortable with, it's a spring, it obeys Hooke's law, its motion is a factor of the relative tension in the different bits of the spring, than with thinking about it in terms of conservation of momentum. Can you explain more about what alternative model you're thinking of?

I need to remind myself of some of the maths – I can follow the algebra but not the partial differentiation. But I'm a lot closer to being able to explain the slinky to the kid than I was before I read the paper, and having a physical spring to play with should be fairly helpful in explaining that the stretched bits tend to return to a slack state, and how this causes waves to travel through the spring. That's kind of what a slinky is for, making those properties tangible.

[davidgillon]

I was wondering if it might be possible to model it as a rotating stick moving down a slope, which sort of considers it a wheel with only two possible points of contact. The point that sticks in my mind is the way that the base comes up, over, then down again, pulling the other base into a repeat of the cycle. Clearly the spring nature modifies it from the pure motion of the stick, but can you approximate it?

(And part of the reason I'm attracted to the rigid model is it's clearly far too long since I did Hooke's Law for me to be comfortable modelling the behaviour of springs!)

[liv]

A rigid rod rotating down a slope, yeah, maybe that gets you somewhere. I just feel like if there's no springiness involved it won't have any reason to somersault like that, it'll just fall flat – it's only the springiness that's pulling the top over the base, not the gravity. Also surely the stick will walk down a steeper slope faster, which is exactly what the slinky doesn't do?

[davidgillon]

I just feel like if there's no springiness involved it won't have any reason to somersault like that, it'll just fall flat

Conservation of angular momentum, there's both linear and rotational momentum at work, though you'll need to assume the frictional effects and acceleration down the slope exactly cancel each other out.

Also surely the stick will walk down a steeper slope faster, which is exactly what the slinky doesn't do?

That is a definite problem with the stick model.
ETA: It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.
Richard P. Feynman

[liv]

Ah, with you. Yes, it feels like I need to think about angular momentum, even if I start with a Hooke's law explanation. (And I do like the way that Longuet-Higgins and Binnie actually tested their mathematical proof about the slinky, empiricism FTW.)

[lovingboth]

Yes, conservation of momentum was my first thought. I wonder if the material of the stairs affects the result - if the stair absorbs impacts very well, does that make a difference?

[liv]

Good question. It seems like they tested stairs of different heights, but not really of different hardnesses. (And I am loving the image of these dons wandering about Trinity dropping slinkies downstairs and timing them with stopwatches.) But I don't think the slinky is exactly "bouncing" off the stairs when it climbs, so maybe hardness isn't so important.

[seekingferret]

Well, probably, but once you throw in frictional losses you're outside the Hooke's Law regime and the conservation of momentum regime, right? And you're looking at a much more complicated set of differential equations. And giving me flashbacks to my mechanical systems analysis coursework.

[liv]

:-) I kind of want to drop a slinky down some soft bouncy stairs now! But yeah, I think you pretty much have to assume negligible friction if you want any kind of feasible maths. I'm mildly envious you've studied this kind of thing properly, I got funnelled into dropping maths earlier than I really wanted to because the English education system involves specializing really young.

[davidgillon]

I got funnelled into dropping maths earlier than I really wanted to because the English education system involves specializing really young.

Ditto, in fact I look back and realise part of the reason I dropped it was it wasn't challenging me, which suggests it might sort have been something I really should have specialized in!

Lancaster made me do roughly the equivalent of A Level maths my first year at university (as they did anyone on a science course who didn't already have it), I went into the three hour exam having already passed on coursework, and after an hour was sat there thinking 'there's two hours to go, I must have done something wrong?' Nope, it really was possible to finish it that quickly if you were comfortable with maths. (I sat there for half an hour rechecking everything, then other people started to leave, so I did too). But even that's a looong time ago

[liv]

Yeah, I was fast and confident at maths when I was in education. I did double maths A Level and I was still fast and confident and finished exam papers quicker than I was supposed to. Which meant that at uni I got promoted to "maths for chemists" in first year (basically there was a hierarchy that went biology > biochemistry > chemistry > physics > computer science, and if you had less than A level ish maths you went down one level, and if you had more than A level ish maths you went up one level.) And I really enjoyed first year maths-for-chemists, that got me as far as the very beginnings of what proper mathematicians call analysis, and there was a point in my life when I could derive and manipulate the Schrödinger equation. But I got steered away from doing maths-for-chemists options in second year, because it was felt that would distract me from my actual degree subject, biochem.

So having not really done any maths since 1998, I have forgotten a lot of what I used to be able to handle fluently. And I never hit the wall in mathematical education, I never got as far as maths that I struggled to get my head round. I'm pretty sure I wouldn't have been happy actually doing a maths degree, just because I found maths easy, but I wish I could have, say, majored in biochem and done more maths alongside that.

[davidgillon]

I'm pretty sure I wouldn't have been happy actually doing a maths degree, just because I found maths easy, but I wish I could have, say, majored in biochem and done more maths alongside that.

I've found myself wondering in recent years if I really would have been better off doing a maths degree rather than CompSci, but I suspect that's at least in part a symptom of being burnt out on programming (or maybe just burnt out on the industry, programming may just have been caught in the collateral damage).

[seekingferret]

I'm a mechanical engineer by training, so this sort of thing is considered foundational or something, because it leads into useful things about automation? But as with most foundational engineering concepts, it's not actually very practical to do it by hand when there are computers around to do it for you, so the main import of my systems analysis coursework was learning the vocabulary and concepts. I no longer remember very much of the math. I have only had to solve a system of differential equations by hand once in the eight years since I graduated and became a practicing mechanical engineer. And the follow-on semester of basic control theory has been replaced, in practice, by a little black box with a microprocessor inside that does all the PID calculations for me.

[liv]

Right, if you're actually a mechanical engineer it makes sense that you took courses in this sort of thing! And yeah, most of the actual maths you rely on computers for, once you've grasped the concepts. On a much lower level it's the same with stats, I would never sit there and calculate any of it by hand IRL, but spending a bit of time doing that during my education helped me to decide what inputs to put into the computer and what to do with what it tells me.

[cjwatson]

I'm glad you came up with that, because when liv was considering this question the other day I was thinking "I'm sure I read something about this just recently", but associative memory entirely failed me.

[cremains]

Old havrutha partners are the best, and I find I get overly attached (intellectually, not emotionally); like you co-create a third mind between the two of you and IME it can be quite sad missing the experience of participating in that mind.

[liv]

Yes, I think that's a good description of long-established chevruta! There are two people I started learning with in college, hatam_soferet is one, and I think we do participate in a third mind even though her scholarship has long since surpassed mine. My other old chevruta isn't really interested in religion any more, but we have a kind of mental symbiosis going on anyway which grew out of many hours spent in the depths of the Oriental Studies Institute trying to get our heads round midrashic commentaries.

[seekingferret]

This is a placeholder to remind me to dig up a great quote from silly orientalist Ravel on his Kaddish.

[seekingferret]

Ravel, in a letter dated July 18, 1921, to conductor Ernest Ansermet, about the soprano Madeleine Grey:

She sang the première of my 2 Hebraic Songs in Hebrew- I couldn't vouch for the purity of her pronunciation, but I was assured that it was quite good.


(of course the other eyerolly part is that one of the 2 Hebraic Songs is in Aramaic and the other is in Yiddish)

[liv]

Wow. I did not realize Ravel had set the Kaddish. Having gone to listen to it, yes, it really is eyerolly Orientalism, isn't it? There's just a couple of phrases in there where you think he might have listened to some synagogue music at some point, but mostly it's just semitones.

[seekingferret]

Yeah, it's a lovely piece of music, and I think at minimum it's aware that it's about mourning, but it's pretty clear that that's about the level of research Ravel did before writing it, and to me the idea that he was unaware of the pronunciation of the words in a piece he wrote seems almost musical malpractice.

He also wrote Five Greek Songs, which at least some scholars think is as close as he came to coming out, so I tend to read the existence of Two Hebrew Songs as testimony to his internal conflict about his sexuality more than any statement of his perspective on Judaism or Jewish culture.

[cjwatson]

It's interesting that you were experimenting with friendly trash-talking, I entirely missed that. They do some of the same at J's football training: there are two coaches, and when they divide into teams for a short match at the end they huddle to talk about strategy and at the end of the huddle each team generally aims some kind of trash-talk at the other's coach, at the sort of level of "Coach James has smelly socks". I don't totally know what I think of it, but there's never a hint of actual enmity and it feels like probably useful channelling of something that might otherwise end up aimed at other players, so on the whole it seems OK.

[(Anonymous)]

Hm. The point of ‘trash talk’ is to gain a psychological advantage, often by making the opponent angry and therefore more likely to make mistakes while you keep your calm (I know of one guy where the key to winning is to keep him at bay until his frustration and patience builds to the point where he simply throws himself in flèche after flèche and can be picked off). How does insulting the coach help develop those psychological gaming skills?

(The most effective strategy actually, I’ve often found, is not to ‘trash talk’ but to figure out the exact insult that will press the opponent’s rage button, create the exact situation in which to deploy it, and then pointedly not do so. If they can keep their cool after that they probably deserve to win.)

[liv]

That's possibly a point of trash talk, but I'm personally not interested in playing games in a culture where that sort of thing is the norm. I'm most certainly not interested in teaching a really sweet-natured six-year-old to play like that.

[seekingferret]

Eh... For me, trash talk is far more often about building a rapport with my opponent than trying to make them angry. I don't think I would have very much fun trying to make an opponent so angry that they perform badly. That just seems mean.

At the moment, it's pretty widely agreed that the NFL's most effective trash talker is quarterback Andrew Luck, whose favorite move is sincerely and honestly complimenting tacklers who tackle him. It works because it minimizes the effect of the defenses' head games, and at the same time it builds a genuine respect between the players.

[liv]

I didn't set out to do so, I realized that J was mimicking the ways I was talking about the game, and started being more conscious about what sort of remarks I was making. It was mostly things like mock-threats, I'm getting you back for that! or, let's see if that messes things up for you! And a bit of pretend-cursing when I fluffed a shot or lost a game by a big margin, which isn't precisely trash-talking, I think. I also praised or congratulated when J did something well, and deflected her from directly calling me useless or rubbish, which she only tried a couple of times. Maybe that's already too much meanness, I was aiming for competitive but friendly.

I see what you mean about the football thing, it's probably ok but you have to stop and think about it. Especially given the ways football rivalries get used as a vehicle for sectarianism and racism. And it's like the thing with Ingress, you have to watch yourself not to fall into thinking of the opposite colour as the "enemy" just because you've been sorted into two completely arbitrary alliances.

[randomling]

Thank you for the invitation to start a new round! I was hesitating a bit, but I think I will, it looks really fun. :D

[liv]

Yay silly game, I'm so glad you're playing. I am racking my brains for where to go from Katniss, though.

[randomling]

It is such fun!

*evil grin*

[damerell]

Odd, my then partner and I saw that movie (as "Show me love") many years ago. I remember it being pretty good.

I think the slinky spring works by a combination of conservation of angular momentum and the spring making it very bad at transferring that momentum to the stairs - rather, the now top end of the spring gets most of the sideways and whips over to start the next stage.

[liv]

Yeah, I'm impressed with what Moodysson does with that film. I mean, in some ways it shouldn't be that rare, it's a fairly simple small town coming-of-age story, but it's so unusual for Queer girls to get that kind of narrative.

And yes, that sounds about right for the slinky, that's a level at which I can understand what's going on well enough to discuss it with a young child.