@robryk@qoto.org avatar

robryk

@robryk@qoto.org

I enjoy things around information theory (and data compression), complexity theory (and cryptography), read hard scifi, currently work in infosec, am somewhat literal minded and have approximate knowledge of random things. I like when statements have truth values, and when things can be described simply (which is not exactly the same as shortly) and yet have interesting properties.

I live in the largest city of Switzerland (and yet have cow and sheep pastures and a swimmable lake within a few hundred meters of my place :)). I speak Polish, English, German, and can understand simple Swiss German and French.

If in doubt, please err on the side of being direct with me. I very much appreciate when people tell me that I'm being inaccurate. I think that satisfying people's curiosity is the most important thing I could be doing (and usually enjoy doing it). I am normally terse in my writing and would appreciate requests to verbosify.

I appreciate it if my grammar or style is corrected (in any of the languages I use here).

This profile is from a federated server and may be incomplete. Browse more on the original instance.

robryk, to random
@robryk@qoto.org avatar

@freemo Since the update I get multiple end of voting notifications for each poll I have voted in (e.g. just got 10 notifications in a row for https://mastodon.nz/@pezmico/112028203100230568). It doesn't bother me so far, but I figure it might be a symptom of something with other annoying consequences.

robryk, to random
@robryk@qoto.org avatar

I'm really surprised that E27 lightbulb sockets are considered fine for multi-kV voltages (there are sodium vapor bulbs without an internal igniter that have that base and require upward from 1.5kV to ignite).

robryk, to physics
@robryk@qoto.org avatar

riddle

My parents have a garden ornament that contains a "vertical spiral thingy" that can freely[^] rotate. When wine blows, it sometimes rotates clockwise and sometimes counterclockwise. What gives? When it has rotated by 180 deg it should be in the same position as if the wind was blowing in the opposite direction (the cage around it nonwithstanding), so I'd expect it to always rotate in the same direction, or to oscillate.

Some videos: https://photos.app.goo.gl/CQWvBBggW4jXQPKZ9

[^] there might be some weird hysteresis there, because it's basically a wire that slips in a hole

robryk, to random
@robryk@qoto.org avatar

Why do pressurized cans warn against puncturing them "even if empty"?

robryk, to random
@robryk@qoto.org avatar

In what world is walking on a bike lane (instead of a pedestrian lane immediately to its side) a reasonable way to minimize the chance of collision with a bicycle?

robryk, to random
@robryk@qoto.org avatar

@ftdl Wasze obrazki są serwowane z niewłaściwym content type:

[robryk@howl:~]$ curl -s --head [https://pol.social/system/media_attachments/files/111/997/477/376/191/561/original/c95ac2fa43c76db5.jfif](https://pol.social/system/media_attachments/files/111/997/477/376/191/561/original/c95ac2fa43c76db5.jfif) | grep content-type  
content-type: text/plain  
x-content-type-options: nosniff

[robryk@howl:~]$ curl -s [https://pol.social/system/media_attachments/files/111/997/477/376/191/561/original/c95ac2fa43c76db5.jfif](https://pol.social/system/media_attachments/files/111/997/477/376/191/561/original/c95ac2fa43c76db5.jfif) | file -  
/dev/stdin: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 1080x1080, components 3
robryk, to NixOS
@robryk@qoto.org avatar

Why would one ever want to use nix-env on NixOS? It causes a lot of confusion for new people when they realize that what needs updating is not only channels of their user, and channels of root, but also nix-env-installed packages. Even once you resolve that confusion, you are still stuck with one more independently updated thing that you need to update in sync (due to graphics drivers), so the promise of easy rollbacks is a bit further away (because one needs to roll back one more thing and remember to do that).

robryk, to random Polish
@robryk@qoto.org avatar

@szczurtorebkowy @szczur

Ojej, właśnie się zorientowałem, że jesteście dwoma różnymi osobami ^^* (piszę, bo strzelam, że inni mogli też się podobnie mylić)

robryk, to random
@robryk@qoto.org avatar

Vibrating your head blurs your vision (try taking a metronome or substitute, striking it, and then touching your teeth with the stem while looking at something with a well defined edge or ridge: the picture will become slightly blurry).

I wonder what's the frequency dependence. I have two (nonlocking) forceps that, when measured with my phone's accelerometer, give similar amplitudes of ~50Hz+harmonics and resp. ~60Hz+harmonics. Maybe I'm placeboing myself, but it seems to me that the blur from 50Hz one is significantly larger.

whitequark, to random
@whitequark@mastodon.social avatar

what doesn't kill you makes risk-seeking behavior so rewarding you'll certainly discover other things that do not kill you

robryk,
@robryk@qoto.org avatar

@whitequark

Hm~ it's an interesting question how much willingness to go against fear gradients (regardless of the source of the fear) gets adjusted as opposed to a fear-specific knob being adjusted. (I would bet a lot on both getting adjusted, but the IMO interesting thing is by how much.)

robryk, to random
@robryk@qoto.org avatar

https://www.pcengines.ch/eol.htm

:(

robryk, to random
@robryk@qoto.org avatar

@freemo

Putting "https://mas.to/@TechConnectify/112328384373243115" in qoto's searchbar results in an error toast saying "500". When I look at network requests involved, I see a request to "https://qoto.org/api/v2/search?q=https:%2F%2Fmas.to%2F%40TechConnectify%2F112328384373243115&resolve=true&limit=5" returning an error page with status code 500.

robryk, to random Polish
@robryk@qoto.org avatar

MPK w Krakowie używa openstreetmap do pokazywania pozycji pojazdu w środku. Wszystko byłoby dobrze, tylko używają wersji sprzed budowy trasy łagiewnickiej, więc tramwaje radośnie jeżdżą poza torami.

robryk, to random Polish
@robryk@qoto.org avatar

Mam wrażenie, że bezrefleksyjna powszechność zwrotu "głosowanie za kimś" powoduje podobnie dużo szkód jak "aresztowanie za coś".

Powszechny jest pogląd, że głosowanie polega na wybraniu kandydata, którego najbardziej chcielibyśmy widzieć wybranego. Nawet w przypadku wybierania jednoosobowego organu nie jest to sposób, w który najlepiej możemy realizować nasze preferencje (nawet nie może, bo nie zależy od tego, których z pozostałych kandydatów wolimy bardziej). W przypadku organów wieloosobowych sytuacja jest jeszcze bardziej skomplikowana, bo przestrzeń możliwych preferencji jest większa.

IMO warto myśleć o głosowaniu nie jak o wyrażaniu poparcia dla konkretnego kandydata, ale jak o wyborze, który ma skutki. Jeśli mamy do dyspozycji rozsądnie dobre przewidywania wyników wyborów, możemy poszacować jak każdy możliwy wybór może wpłynąć na wyniki.

Eh, chyba powinienem po prostu napisać taką symulację i ją udostępnić.

robryk, to random Polish
@robryk@qoto.org avatar

@ftdl

Serwujecie na pol.social media z niewłaściwym Content-Type. Np takie https://pol.social/system/media_attachments/files/110/935/884/311/554/703/original/be66df9224d6be69.webp ma Content-Type: text/plain, a jest obrazkiem. To powoduje, że linki do nich (np. te w klientach innych instancji) otwierają stronę robaczków miast obrazek.

robryk, to random
@robryk@qoto.org avatar

The most recent (about chains) claims that the cooling bath for hardening is water (it's surely oil: water would visibly boil and Leidenfrost effect would make cooling insufficient).

I've used WDR's contact form to tell them that and we'll see what happens.

robryk, to random
@robryk@qoto.org avatar

Random thought: is there any fantasy novel that includes a strike (in the labor sense) of magical weapons?

robryk, to random
@robryk@qoto.org avatar

How can one estimate comparisons of human heat loss across different scenarios?

According to, a.o. https://sci-hub.se/https://pubmed.ncbi.nlm.nih.gov/4820331/, one can assume that a swimming person's skin temperature is between T_water and T_water+1degC. This seems to suggest that a swimming person at T_water=T will observe similar heat loss as a nude sweating person at T_wetbulb=T with significant relative wind. (Well, that's kinda reasonable even without that confirmation, and relies on similarly intuitive-but-uncited statement that the temperature of sweat film and skin under it will both be at not more than T_wetbulb+1degC, which is probably reasonable in the nontrivial wind assumption.)

Is there a rule of thumb how (thin) clothing should affect that? (I'm trying to figure out rough comparisons of heat loss between running and swimming.) I'm most curious about rules of thumb for (a) loose thin clothing (which I'd model as reducing wind speed and increasing humidity experienced by the film of sweat, but I can't guess by how much) (b) skintight hydrophilic clothing with high heat conductivity (which I'd model at first approximation as changing nothing from being nude).

robryk, to random
@robryk@qoto.org avatar

So, Swiss Post offers a "print and send a postcard with a photo of my choosing" service and gives everyone one such postcard free[1] per day. The canton of Zürich has an opt-out publicly readable mapping from license plate numbers to owners' names and addresses.

So, does anyone have some nice artwork for "please check your headlights", "thank you for being considerate", "please remember to use your turn signal", "please don't use a cell phone while driving", ...? :)

[1] well, ad-supported: they put an ad on the back next to the text

robryk, to random
@robryk@qoto.org avatar

TIL that the sequence of increasingly finegrained random walks that converges to Wiener process has walks that increase their speed as they get finer (speed grows with square root of scale). Post factum it seems kinda obvious: you'd otherwise converge to a constant function. I haven't yet figured out how this changes as one adjusts the exponent.

robryk, to random
@robryk@qoto.org avatar

Swiss law on prescriptions is weird.

There are categories of medicines (Abgabekategorien) with a clear demarcation between requiring a prescription (A-B) and not (D-E). Notably category C is missing, because it was eliminated in 2019 (it used to be "can be sold in pharmacies only but without prescription" IIUC). Some of the stuff from C went to D, some of it to B.

That would be clear. However, "this medicine was once in C" is an exception to the requirement for prescriptions for medicines in B! (See https://www.fedlex.admin.ch/eli/cc/2018/588/de#art_45) Thus, we effectively still have C, but it's way more confusing.

This story was brought to you by a pharmacy wanting a prescription for KCl from me. (Which I'm really amused ended up in B, given that it has a similar safety profile to table salt afaik: you can overdose on it, it can have bad interactions with your other medications or diseases, it's kinda hard to overdose without really trying.)

robryk, to random
@robryk@qoto.org avatar

I think I nearly collided with a bat today. I was riding a bike along Sihl just north of Sihlcity (the path is between a small forested hill and a river with a highway overpass over it; it's sparsely lit with streetlamps) and saw (~single frame only, because of timing wrt my blinking) a dark concave-sided diamond shape in front of me and felt a gust of wind.

It's not that surprising, given that a bit further north friends of mine would semi-regularly notice bats over the rive (and I did once or twice), but the near collision is surprising given my very predictable motion.

robryk, to nuclear
@robryk@qoto.org avatar

Why do PWR reactors use boric acid, as opposed to some random salt of boron? Apparently boron salts are often well soluble, from the nuclear POV we only care about boron being present, and I'd expect salts to cause fewer chemical problems due to their closer-to-neutral pH. In fact some random papers (https://inis.iaea.org/collection/NCLCollectionStore/_Public/28/034/28034575.pdf) describe tradeoffs involved in maintaining pH as boric acid concentration changes.

There clearly must be some reason why boric acid is preferred over any simple boron salt. What is it?

robryk, to random
@robryk@qoto.org avatar

First world problems: drying cat ears.

Also, surprisingly many people compliment them (not counting kids, 2 in a bit over an hour).

robryk, to random
@robryk@qoto.org avatar

Lymphatic flow in arms seems weird: the stain from failed venipuncture in the crook of my elbow appeared distal, nearly entirely on my forearm.

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