Pilot Wave Theory

Aug. 15th, 2017 07:45 pm
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[personal profile] jack
Does anyone understand pilot wave theory even a little bit?

Prodded by several recent articles, I've been trying to follow what it says, and am still quite unsure of the realities.

The analogy usually presented is, if you have a small oil drop on the surface of water, and the water container is subject to a regular pattern of vibration, the water forms standing waves in shapes affected by the edges of the container and any obstructions in the surface of the water. And the oil drop tends to move across the surface of the water following the paths in those waves.

If you look solely at the oil drop, you can't tell which of two equal paths it would follow, but you can predict it will take one of them with equal probability, and predict its motion probabilistically. And if you couldn't see the standing water waves, you could deduce something in that shape exists.

You can even get some analogies for weird quantum behaviour like the an electron passing through two parallel slits and experiencing interference with itself: the water waves form possible channels for the oil drop, and the oil drop goes through one slit or the other, but ends up only at certain places on the far side.

However, the analogy to actual quantum physics is still unclear to me. Not whether it's true, but even what people are suggesting might happen.

Are people suggesting there's some underlying medium like the water? In that case, isn't there some propagation speed? The water waves exist in a steady state once all the obstructions are set up, but they don't respond to changes instantly. If the water trough were miles long, the oil drop would set off following water wave paths that existed at the point it passes through, not the paths corresponding to the obstructions that are going to be in place when the oil drop passes through them.

And yet, as I understand it, no-one expects a propagation delay in quantum experiments. People keep checking it out, but there never is: it always acts like an electron propagates just like it is itself a wave.

I agree, if there WERE some delay, if you changed the slits at this time, and got one result, and changed them at another time, and got another result, that would be massive, massive, evidence of something, possibly of something like pilot wave theory. But AFAIK proponents of pilot wave theory aren't advocating looking for such delays, and don't expect to find any.

Contrariwise, if this is just an analogy, and the quantum equivalent of the water waves (equivalent to the wave function in other interpretations of quantum mechanics) propagates at "infinite" speed, then... that is undetectable, indistinguishable from other interpretations of quantum mechanics. But it raises red-flag philosophical questions about what "infinite speed" means when all the intuition from special (or general) relativity indicates that all physical phenomena are local, and are influenced only by physics of nearby things, and "the same time" is a human illusion like the earth being stationary. Even if you don't expect to detect the pilot wave, can you write down what it should be in a universe where physics is local? Does that in fact provide a way to make QM deterministic and independent of observers, even if you change the reference frame? Because it doesn't sound like it will work.

FWIW, those are very superficial objections, I don't understand what it's saying enough to actually evaluate in depth. But I don't understand why these don't show up on lists of "common objections and rebuttals". Common objections have confident rebuttals in several places, and I've *seen* articles about them, but not understood well enough. Can anyone explain better?

Digression

I do agree, the idea that QM equations are an emergent property of something else, ideally a statistical interpretation of a deterministic underlying reality, would be very nice in clearing up a lot of confusion. But AFAIK, the closest candidate to that is Many Worlds, which doesn't appeal to many people who want to get away from QM unpleasantness.

(no subject)

Aug. 14th, 2017 10:29 pm
raven: white text on green and yellow background: "ten points from Gryffindor for destroying my soul" (sbp - destroying my soul)
[personal profile] raven
I am tired and wound up about my book, which seems to be my default state of being at present. (The book is now necessarily modified, "the stupid book", "the thrice-damned book", "the bloody book", "the book that I HATE and is DREADFUL and the BANE OF MY LIFE" etc.) Part of it is that my confidence as a writer has been significantly dented as everything else in my life has been, recently: I also don't think much of self as lawyer, friend, etc., and I'm working on it. (I am doing much, much better than I was. I'm very grateful. But piecing one's life back together turns out to take time.)

I'm also not doing well with reasonable self-care related to the book, which I should, because finishing the version that went on agent submission - in a several-month, every-spare-minute sprint - was what precipitated my last visit to the bottom of the well. (Perfectly nice as wells go, but not one to revisit.) But I keep wanting to just finish it and get it over and winding myself up in the process. And of course I'm aware that I have read it approx fourteen thousand times over the last two and a half years and naturally I'm seeing nothing but flaws? And perhaps other people might not think it is the worst thing ever committed to paper? In my more rational moments I think this. And yet, oh my god, I hate this book. I want to bundle it up and throw it into aforesaid well and write SOMETHING ELSE. It never gets less ridiculous. I spent four days trying to think of a 1940s-appropriate preferably-funny insult? And it had to be two syllables because otherwise the sentence wouldn't scan? And then [personal profile] tau_sigma suggested "strumpet", because she's a perfect human? And all of that hungama was about literally one word? etc.

Etc. Two months ago I was about as a far from a clean, well-lighted place as I could be. And now I'm not, but nothing terrible will happen if I don't finish this book soon. (Or ever? Like, it would be sub-optimal after two and half years, but I'm not writing Hamlet here.) And nothing terrible will happen if it's not as good as I wanted it to be. And nothing terrible will happen if I do it in ten-minute, 100-word chunks. This is quite a rubbish pep talk but there you are, it's what I've got, and it's better than the alternative.

In other news: I'm enjoying being back out in the world. I'm enjoying seeing friends and going for walks and learning to love this city again. I miss my legal practice and my Gaelic. I'm looking forward to returning to both in the autumn; I'm ready for the new terms and the start of the year.

What I saw at Worldcon 75

Aug. 14th, 2017 06:05 pm
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[personal profile] ewx
 

Things I attended included...

  • Appeal of the Bland Protagonist. I remember only that Robert Silverberg was fairly entertaining.
  • The Long Term Future of the Universe & How to Avoid It. I don’t think we got as far as proton decay. Entertaining but I don’t think I learned much.
  • Polyamorous Relationships in Fiction. I think a fair few examples given but I don’t really remember much about this.
  • What Science Can Tell Us About Alien Minds. This was largely a very well-pitched survey of what we know about minds and brains and their development here, with the implications for the alien underlined. Excellent.
  • New, More Diverse Superheroes. Something that’s been improving lately. Many of the examples were familiar. Slightly surprised that Vimanarama wasn’t mentioned, it can’t be that obscure?
  • How to Tell the Ducks from the Rabbits. This covered some unpublished research modelling some perceptual effects we find in human vision. Ian Stewart is a good speaker.
  • Cyberpunk and the Future. Fairly rambling but quite entertaining and IIRC avoided the trap of falling into a laundry list of recommendations which can sometimes happen.
  • New Publishing. A couple of models I didn’t know about (though ‘run publisher as a co-operative’ doesn’t seem conceptually new) but I didn’t get a sense that any particular model was about to set the world on fire. Apparently ebook sales are declining as a proportion of the total, which surprised me.
  • Supermassive Black Holes. A quick survey of how black holes work (which didn’t contain many surprises) followed by some new stuff: the GR-aware visualization of a black hole made for Interstellar, corrections to it involving red/blue shifting and the spin of the black hole, a further visualization of what you’d see as you flew into one (assuming you destroyed by any of the many hazards) and a project to radio image out galaxy’s central black hole. Another excellent science talk.
  • Hugo Awards. Very glad to see Monstress winning Best Graphic Story.
  • Beyond the Goldilocks Zone. Panel about the possibilities for exoplanets that sustain life. One point I’d not previously been aware of was that although Europa-style bodies might (hypothetically) have life in sub-ice oceans, there’s no realistic way of detecting this from a distance, meaning that more earth-like planets are a better bet for analysis. (The “goldilocks zone” is the range of distances from a given star in which planets can support liquid water on their surface, making them a good bet for life.)
  • Gender and “Realistic History”. The panel largely surveyed past examples of groups and behaviors sometimes thought to have been absent or rare in the past. Interesting listening.
  • Exoplanetary Zoo and The Search for Earth 2.0. Another excellent science talk, this time on the detection strategies for exoplanets and the results they’ve had so far. There are a lot of exoplanet discoveries awaiting confirmation.
  • Language Creation. David Peterson (famous for the conlangs from Game Of Thrones) described the basics of making a convincing sketch conlang. A very entertaining speaker.
  • The Singularity: Transhuman Intelligence in Fiction and Futurism. An opportunity for Charlie Stross to steal the show. Fun.
  • Bullets in Space. Basic orbital mechanics, done fairly well. The basic proposition is that ballistic projectiles are a terrible idea when fighting in an orbit; if they miss the target they are probably going to hit something you didn’t want them to.
  • Tomorrow’s Cool SF Physics. Enjoyed it but don’t remember anything else about it.
  • Designing Life. Fun discussion of biotechnological possibilities for modifying and creating life.
  • Ideas Crossing the World: Japanese Adaptations of Western Fantasy. In practice I think this mostly amounted to an opportunity for the panellists to entertain with their encyclopaedic knowledge of manga and anime.

...there were other things but I can’t remember enough to say anything about them.

Oh hey, there it is

Aug. 11th, 2017 09:40 am
rmc28: Rachel smiling against background of trees, with newly-cut short hair (Default)
[personal profile] rmc28
I was commenting last night to a couple of friends that I was not as fatigued by the holiday as I had expected.  And then as I got back to our apartment in the early hours this morning, I felt that familiar drag set in.  Spoke too soon!   So Tony is getting the 'night passes' for the rest of the con and I'm going to be pulling bedtime cover with the children.

(This holiday so far is being an excellent illustration of just how much we have life-at-home optimised for everyone's needs and just how much work it is to cope without those optimisations.  I'd thought my physical stamina was going to be the limiting factor on what we got done; instead it's the family's collective emotional comfort level with being in new places and Doing Stuff.)

Before staying up too late talking to lovely people, last night I danced my legs off at the Clipping concert.  Clipping's hip-hop Afrofuturist dystopian concept album is up for the Hugo award for Best Dramatic Presentation: Short Form, and the con managed to persuade them to come over and play a gig to a bunch of geeks.  The queue for entry was long, and the room was set up with seating, but the band basically said "ok, we're not allowed to get rid of the chairs - we asked - but there's a lot of space here at the front", which was enough to get [personal profile] ceb up and dancing, and I followed.  It was ace.  I think that about 90% of the population right in front of the stage was female-presenting (and within that, mostly white, and mostly around mid-thirties or older).  I am not sure this is Clipping's usual audience demographic? I had a moment of looking around and realising I was dancing in the vicinity of a number of amazing women who I admire greatly and just feeling overwhelmed and joyous and incredibly lucky to be there at that time.  (Speaking of,[personal profile] mizkit also liked the gig.)

So I not only danced at a Clipping gig a few metres away from Daveed Diggs, I had a short appreciative conversation with him in the bar afterwards, and my internal squee may not stop for days.

Totally worth being shattered today.

marnanel: (Default)
[personal profile] marnanel
[CW sexual assault]

I met a a guy yesterday who was fired from his delivery job because someone had been raped and he sat with them for half an hour. Gross misconduct, apparently. But he says he's better off not having a job at all than working for that company. I told him he did the right thing. I admire him for that.

Keep them busy and poor

Aug. 8th, 2017 06:53 pm
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[personal profile] marnanel

There was a protest against austerity in Piccadilly Gardens, in the centre of Manchester, last year. A friend of mine was on a bus and heard someone say, “I wish these people didn’t keep protesting all the time, I need to get to work!”

Keep them busy and poor, and they won’t have time to think about revolution.

When I was a small kid, I was always hearing about politically active students. But that was when students routinely got grants, and before college tuition fees. Most students didn’t have to work. Now I don’t know any students with spare time to speak of.

Keep them busy and poor, and they won’t have time to think about revolution.

Every time the railway workers go on strike, I hear people saying “I get paid less than them for longer hours. They’re so selfish, asking for better conditions.” They never seem to figure out the cause and effect, but they’re too desperate to keep their jobs to even think about strike action.

Keep them busy and poor, and they won’t have time to think about revolution.

(no subject)

Aug. 7th, 2017 04:28 pm
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[personal profile] naath
20.A song that has many meanings for you

I'm totally blocked on this. I'm not sure any songs have 'many meanings' to me really.

I am Curie House, yellow

Aug. 6th, 2017 10:00 am
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[personal profile] sparrowsion
I was going to reply to this, then realised what I had to say was another level up, so decided it deserved its own post.

So each year at our state comprehensive was divided in three (orthogonal) ways.

There was the traditional red, yellow, green and blue houses, called Wedgewood, Scott, Curie and, er something else. I was in Curie, which was yellow. When you got points, the teacher would fill in a little ticket in your house colour (ideally) with your name and form (more on which in moment) and you'd post it in a house-coloured box in reception. And your tie was the colour of your house. And that was the sum total of the impact of houses on school life. In fact, it was so pointless(!) they abolished the entire system when I was in the fourth year or so (I think that's Year 10 in new money) and (optionally for existing pupils) introduced a single design of tie.

All intra-school competition, registration and pastoral care was done in forms, which were class-sized units with a variable number per year depending on intake (there were seven in my year, which was typical, but there were also years with six or eight). These were designated by your year, followed by two letters, the first of which was A, B or C and the second was J, K or L. If there was ever any reason for this, it had been long forgotten. I was in xAJ— as you changed year, obviously so did the number in your form changed, but also so usually did your form teacher (and therefore where your form room was). These forms were a mix of all houses and all sets—what you were actually taught in.

Each year was split into two streams by academic ability. Each stream was then further subdivided into sets by ability in maths, English (also used for history and French in the first year) and "mixed ability" (which was really only mixed within the stream). This got more in later years where there were more subjects, some of which weren't taught to all sets in a stream (for instance, only the top two English sets got a second foreign language), and some of which had additional restrictions on facilities (eg home economics).

I don't really remember much about assemblies. You couldn't fit in the entire school in the hall (which was also dining hall, theatre and three-badminton-courts worth of extra gym space) so they would be divided up by year. Except at some point they were dropped completely (and sod the law)—possibly because at that time the main teaching unions were working to rule and someone considered assembly to be the kind of extra-curricular activity they wouldn't do. CW violence )

Media log

Aug. 6th, 2017 09:40 am
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[personal profile] naraht
Reading

After a long stretch of not reading very much at all, I've picked up several books to prepare for my trip to Russia in three weeks....

Russia and the Russians by Geoffrey Hosking is a decent one-volume history, although it has very little good to say about the orthodox church.

The Whisperers: Private Life in Stalin's Russia by Orlando Figes is a monumental work of social history. Difficult to follow because there are so many stories included as part of it, but a page-turning account of the worldview of ordinary Russians under Stalinism. Humans will go through so many mental contortions to make their lives livable, understandable or justifiable for themselves.

Second-Hand Time by Svetlana Alexievich is a collective oral history of the transition from Soviet to post-Soviet Russia. She won the Nobel prize for literature despite writing non-fiction; this is an amazing collection of stories. Impressionistic and vivid. One of the most emotionally difficult books I've read, ever, but this is not a dis-recommendation. Just be prepared.

And on top of this I'm trying to get back into my Icelandic. Another go at Pálssaga by Ólafur Jóhann Sigurðsson, which tells the story of Iceland in the World War II era from the point of view of a young journalist.

Watching

In the wake of the Tour de France, there have been so many different cycling races on simultaneously. I picked the Vuelta a Burgos partly because of the start list but mostly because of the commentating team of Matt Stephens and Brian Smith. They're not as tactically oriented as David Millar but they offer great insights on the riders. OK, they did spend about five minutes talking about one rider before remembering he wasn't in the race, but that was endearing.

I've been hearing here and there about Comrade Detective, the new Amazon comedy whose shtick is that it's a 'rediscovered' cop show from '80s Romania intended to glorify Communism. Reviews are mixed. The Guardian liked it a lot. Neither Variety nor Vulture think it's actually meant to be funny. Vanity Fair focuses on the idea that it's meant to be a statement about propaganda.

But I would like to hear more thoughts from Romanians. There's some unsurprisingly unamused commentary from vrabia on Tumblr, which has only whetted my appetite for a detailed deconstruction.

Anyway I've watched the first episode and... I wouldn't call it good, but it's intriguing? The setting, the visuals seem really well done, and I'm half willing to watch it just for its evocation of '80s Bucharest. The fact that they hired Romanian actors and then dubbed the whole thing as a star vehicle for American actors probably tells you all you need to know. Very literally talked over. The characters and plot are formulaic but that's the point... it's an evocation and celebration of the (Western) genre. The Communist ideology seems notably off-kilter and I say that as someone who's not an expert in Communist ideology. And yet there's something fascinating about how mixed and meta and just weird the whole thing is. In cultural appropriation terms it obviously gets a 9.9 out of 10, but I may keep watching because I'm curious. I wonder whether it will be a Yuletide fandom, and if so, what people will do with it.

(This also makes me want to watch more films/TV that were actually made behind the Iron Curtain. Someone seems to have uploaded a selection of Russian classics to Daily Motion... The Irony of Fate, Office Romance, Moscow Does Not Believe In Tears...)

I keep trying to decide whether or not I actually want to go and see Dunkirk. By the time I decide it won't be in the cinemas any longer.

And finally I really want to see Icarus, a new documentary about drug testing in cycling that accidentally revealed exactly how much the head of Moscow's Anti-Doping Centre knew about how to beat the system.

Thomas Thurman CWR

Aug. 5th, 2017 12:33 pm
marnanel: (Default)
[personal profile] marnanel

How was/is your school organised? Mine wasn’t, very.

My school (state comprehensive) had houses called Anglia, Mercia, Northumbria, and Wessex. Northumbria was red, Anglia was yellow, Mercia was blue, and Wessex was green. I was in Wessex.

There was a system called “tutor groups” that applied to everyone except the sixth form, where you had to report to a particular teacher (in whatever room they taught in) at the beginning and the end of each day. The teachers were organised into houses and you were in the same house as your tutor. Despite the name your tutor wasn’t responsible for teaching you anything.

The school had 1200 kids and had outgrown the rather small hall, so assemblies alternated between Mercia+Anglia and Northumbria+Wessex. If you weren’t in assembly you just sat around in your tutor group doing homework (i.e. playing Top Trumps).

The school secretary was really really keen on coding everything. Each of the teachers, each of the rooms, and each subject had a three-letter code, and you were expected to memorise all the ones which applied to you. You wrote your tutor’s three-letter code after your name on everything– my tutor was Mr Crowther who taught chemistry, so my name was “Thomas Thurman CWR”. His room, where we went every morning and evening, was L05 (laboratory zero-five).

We had house points in the first two years, but they weren’t tallied up per house and they only applied to you. (This made no bloody sense even at the time.) You were given a card where the teachers initialled squares.

You got a badge if you made 100 or 200 house points. I finally reached 200 at the end of the last term of my second year. I’ve still got the badge somewhere. [edit: found it!]

 

It's actually happening

Aug. 5th, 2017 06:16 am
rmc28: Rachel smiling against background of trees, with newly-cut short hair (Default)
[personal profile] rmc28
A bit less than two years ago, I was in a hospital bed creating a googledoc named Helsinki, with https://www.seat61.com/Finland.htm open in another tab, starting to build up the shape of the holiday we could have using Worldcon as an anchor.

Now I'm in an airport hotel room, about to wake up the children and go get our flight to Helsinki.

"He drew", part 1

Aug. 5th, 2017 12:30 am
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[personal profile] marnanel

I've been drawing illustrations for the anonymous poem He Drew. I read the poem when I was about seven, and it's stuck with me ever since. Many people have told me I'm not alone.

"He always wanted to say things, but no-one understood.
He always wanted to explain things, but no-one cared."

"So he drew."

"Sometimes he would just draw and it wasn't anything. He wanted to carve it in stone or write it in the sky."

Again, my illustrations but not my poem. More pictures in a few days; you can find the whole poem online if you go looking.

[This post was supported by my Patreon sponsors, who saw it three days before everyone else. Join us! https://www.patreon.com/tjathurman ]

A thing

Aug. 4th, 2017 02:30 pm
sparrowsion: male house sparrow (male house sparrow)
[personal profile] sparrowsion
So it looks like tiny trains really are going to be part of my life. Specifically, tiny little trains:
Image, and many more words ).

Doctor Who - A Chat for Heroes!

Aug. 3rd, 2017 11:55 pm
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[personal profile] sir_guinglain
Thoughts from the Oxford Doctor Who Society on the most recent series, condensed from several weeks of discussion on Facebook Messenger, are now available in one document downloadable from The Tides of Time blog.

Deoptimisation can be a virtue

Aug. 3rd, 2017 11:43 am
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[personal profile] simont

There's a well-known saying in computing: premature optimisation is the root of all evil. The rationale is more or less that tweaking code to make it run faster tends to make it less desirable in various other ways – less easy to read and understand, less flexible in the face of changing future requirements, more complicated and bug-prone – and therefore one should get into the habit of not habitually optimising everything proactively, but instead, wait until it becomes clear that some particular piece of your code really is too slow and is causing a problem. And then optimise just that part.

I have no problem in principle with this adage. I broadly agree with what it's trying to say. (Although I must admit to an underlying uneasiness at the idea of most code being written with more or less no thought for performance. I feel as if that general state of affairs probably contributes to a Parkinson's Law phenomenon, in which software slows down to fill the CPU time available, so that the main effect of computers getting faster is not that software actually delivers its results more quickly but merely that programmers can afford to be lazier without falling below the ‘just about fast enough’ threshold.)

But I have one big problem with applying it in practice, which is that often when I think of the solution to a problem, the first version of it that I am even conscious of is already somewhat optimised. And sometimes it's optimised to the point of already being incomprehensible.

For example, ages ago I put up a web page about mergesorting linked lists; [personal profile] fanf critiqued my presentation of the algorithm as resembling ‘pre-optimised assembler translated into prose’, and presented a logical derivation of the same idea from simple first principles. But that derivation had not gone through my head at any point – the first version of the algorithm that even worked for me at all was more or less the version I published.

Another example of this came up this week, in an algorithmic sort of maths proof – I had proved something to be possible at all by presenting an example procedure that actually did it, and it turned out that the procedure I'd presented was too optimised to be easily understood, because in the process of thinking it up in the first place, I'd spotted that one of the steps in the procedure would do two of the necessary jobs at once, and then I devoted more complicated verbiage to explaining that fact than it would have taken to present a much simpler procedure that did the two jobs separately. The simpler procedure would have taken more steps, but when all you're trying to prove is that some procedure will work, that doesn't matter at all.

I think the problem I have is that although I recognise in principle that optimisation and legibility often pull in opposite directions, and I can (usually) resist the urge to optimise when it's clear that legibility would suffer, one thing I'm very resistant to is deliberate de-optimisation: once I've got something that has been optimised (whether on purpose or by accident), it basically doesn't even occur to me in the first place to make it slower on purpose. And if it did occur to me, I'd still feel very reluctant to actually do it.

This is probably a bias I should try to get under control. The real meaning of ‘premature optimisation is bad’ is that the right tradeoff between performance and clarity is often further towards clarity than you think it is – and a corollary is that sometimes it's further towards clarity than wherever you started, in which case, deoptimisation can be a virtue.

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