[HN Gopher] U-Bahn station in Berlin is decorated with radioacti...
       ___________________________________________________________________
        
       U-Bahn station in Berlin is decorated with radioactive uranium
       glazed tiles
        
       Author : dewey
       Score  : 298 points
       Date   : 2023-02-07 11:45 UTC (11 hours ago)
        
 (HTM) web link (chaos.social)
 (TXT) w3m dump (chaos.social)
        
       | dTal wrote:
       | "No loitering"
        
       | [deleted]
        
       | Koshkin wrote:
       | U-238 must be pretty safe, given its long half-life?
        
         | russianGuy83829 wrote:
         | Didn't know they had so many Ubahn lines in Berlin, though it
         | went from U1 to U9 ;)
        
           | mpetrovich wrote:
           | No, he's talking about the movie. You know, the one with the
           | sub.
        
           | hef19898 wrote:
           | Because I felt like it:
           | 
           | https://en.m.wikipedia.org/wiki/German_submarine_U-239
        
       | LazyMans wrote:
       | There is a guy on youtube called "Radioactive Drew". He has some
       | interesting episodes exploring former/current uranium mines and
       | other things related to radioactive substances. He has a video
       | about a postoffice in Burbank California with similar radioactive
       | tiles on the walls. https://www.youtube.com/watch?v=tuZzOVxreK4
        
       | scrlk wrote:
       | For those wondering, the units on the dosimeter might be
       | milliroentgen/h. One of the replies mentions that it's a RKS
       | 20.03 "Pripyat" dosimeter.
       | 
       | 11.37 mR/h? Not great, not terrible.
        
         | H8crilA wrote:
         | If I'm not mistaken that's 0.1137 milisievert / hour. Meaning
         | you have to stand glued to the tiles for about 4 years to get
         | the LD50 lethal dose of about 4000 Sievert. Also, the lethality
         | of the dose only really applies when the exposure is short.
         | 
         | Or, alternatively, the average yearly background radiation of
         | about 2 milisievert takes about 18 hours of being glued to
         | those tiles.
        
           | neffo wrote:
           | An idea for Berlin police looking to move on those pesky
           | loitering youths in the station, charge them with triggering
           | an INES incident. (Giving themselves a dose of radiation
           | exceeding annual limits by leaning against the wall.)
        
           | Nitrolo wrote:
           | EDIT: Someone linked to the Wikipedia article for uranium
           | tiles, which says that the majority of the radiation comes
           | from the decay products and is beta radiation[1]. Beta
           | radiation has a weighing factor of 1, which makes your
           | calculation pretty much correct!
           | 
           | ==========
           | 
           | EDIT 2: Looking more closely it appears that the dosimeter in
           | the video is switched to uSv/h, so it's reading 0.1 mSv/h
           | anyway and the whole discussion below can be skipped if
           | you're not interested in the difference between Gy and Sv.
           | 
           | ==========
           | 
           | If I remember my lectures correctly (Wikipedia did help me
           | here), the conversion is 1 Roentgen ~ 00.1 Gray (Gy), which
           | is a slightly different unit from Sievert (Sv).
           | 
           | 1 Gy is 1 J/kg of absorbed energy, however the biological
           | effects change depending on the type of radiation. Sv is Gy
           | adjusted by a weighing factor. It's 1 for gamma rays, where 1
           | Gy = 1 Sv, but for alpha particles it's 20 [0].
           | 
           | Uranium-238 emits alpha particles, which get stopped by a few
           | cm of air or even dead skin. So the effective dose you are
           | receiving from the decay of U-238 is probably closer to 0
           | mSv/h.
           | 
           | Or, if you eat it and it's inside you, 2 mSv/h, at which
           | point you should probably be quite worried.
           | 
           | The decay products of U-238 however are beta emitters, which
           | changes the calculation again. The beta particles can
           | penetrate the skin, but the weighing factor for beta
           | radiation is 1, so it can reach you but is also less
           | dangerous. So what's the actual final value? I honestly don't
           | know, radiation can be complicated, and I just wanted to
           | share the difference between Gy and Sv!
           | 
           | [0]: https://en.wikipedia.org/wiki/Sievert [1]:
           | https://en.wikipedia.org/wiki/Uranium_tile
        
           | bioemerl wrote:
           | The real danger is the tiles, it's that throws something
           | hard, shatters one of the tiles, releases dust, and someone
           | breathes the dust in.
           | 
           | I'm actually astounded this is allowed to be there in a
           | public place, because at home you can reasonably expect
           | protect against someone shattering a tile, but in public? One
           | drunk guy is all you need.
        
             | tomxor wrote:
             | That's most likely the reason they are still there, because
             | of how much more hazardous it would be to attempt to remove
             | them.
             | 
             | Then again there are well practiced methods for removing
             | sources of similarly hazardous air-bourn particulates such
             | as asbestos, i'm not sure how much difference there is
             | between the two beyond the low risk of pure exposure
             | (inhalation being the serious risk here).
        
               | sofixa wrote:
               | > Then again there are well practiced methods for
               | removing sources of similarly hazardous air-bourn
               | particulates such as asbestos, i'm not sure how much
               | difference there is between the two beyond the low risk
               | of pure exposure (inhalation being the serious risk
               | here).
               | 
               | There's also the difference that this is a U-Bahn station
               | in use, in the rough middle of a line. Closing it down
               | for a prolonged period of time, _and_ fully sealing it
               | from the rest of the line to avoid the spread of dust
               | through the metro tunnels would be a significant and
               | disruptive undertaking.
        
               | tomxor wrote:
               | Good point. Even attempting to seal it off from the
               | tunnel seems futile considering how much disturbance to
               | air pressure a passing train will cause.
        
             | saiya-jin wrote:
             | I imagine some drilling would create quite a nasty cloud.
             | Of course this would require being oblivious of composition
             | by magistrate and allowing it, which I don't think is the
             | case here. Still, at least put on it some hard transparent
             | protective paint, I am sure there are things for that.
        
             | littlestymaar wrote:
             | Even if it happens from time to time, the amount of dusk is
             | going to be ridiculously small (you don't release that much
             | _dust_ from damaging a rock, let alone glazing, unless you
             | grind it).
             | 
             | And keep in mind that this is a subway station, places
             | where the pm2.5 levels are routinely extremely high because
             | of the dust released by train breaks, so a microscopic
             | amount of uranium dust is really negligible in such an
             | environment.
        
           | xattt wrote:
           | The LD50 would apply to effects of acute radiation sickness.
           | However, given the long duration exposure, it would increase
           | your relative risk of stochastic effects, like cancer.
        
           | kris_wayton wrote:
           | > 0.1137 milisievert / hour
           | 
           | I saw 11.37 on the display, wouldn't that be 0.01137 ?
        
             | tomxor wrote:
             | They are using different and not directly convertible
             | units.
             | 
             | Roentgen (R) used by the instrument only measures exposure,
             | but this is not the same as absorption which depends on the
             | type of radiation, the type of biological tissue exposed,
             | the duration of exposure etc. The parent is using Sv which
             | measures absorption for the purpose of more usefully
             | assessing biological risk. I'm not sure how the parent is
             | converting them, there are probably some good rules of
             | thumb.
        
               | kris_wayton wrote:
               | Here's a screenshot of the highest reading I saw (11.37)
               | and an english overlay of possible units it can display.
               | It's hard to see the button positions.
               | 
               | https://imgur.com/a/gl8NLqB
        
               | Jeema101 wrote:
               | They're switches, and it looks like it's set to mSv/h
               | based on your English overlay. So 11.37 mSv/h, or .01137
               | Sv/h - about 4 1/2 times the level of the typical
               | background radiation.
        
               | mrb wrote:
               | Background radiation is less than 3.5 mSv/year, or less
               | than 0.0004 mSv/hour. So if these tiles radiate 11.37
               | mSv/hour that would be 28 000 times more than background
               | radiation !
        
               | tomxor wrote:
               | Hmm, 3 mSv is supposed to be the average annual
               | _background_ radiation absorption for humans [0], that 's
               | roughly 0.000342 mSv/h. Which would make 11.37 mSv/h
               | 33245 times greater.
               | 
               | At the other end of the scale the minimum annual dose
               | with a clear link to increased risk of cancer is
               | supposedly 100 mSv [1]. But the risk is different
               | depending on the distribution over time, so if we make it
               | hourly for comparison that is 0.0114 mSv/h making this
               | reading about 1000 times higher than that risk threshold
               | (but the risk is over a year is effectively assuming
               | continuous exposure).
               | 
               | Seconds or minutes isn't going to be terrible, but in
               | only 9 hours leaning against it you would get a years
               | worth of high risk cancer dose!... I'd stay away from the
               | wall. happy to be corrected, this stuff is hard to
               | interpret if you are not an expert. The falloff is really
               | fast though, so it's basically harmless if you are just
               | walking through... maybe the original intent was to stop
               | people touching the walls :D like an electric fence
               | without the need for power.
               | 
               | [0] https://en.wikipedia.org/wiki/Background_radiation
               | 
               | [1] https://upload.wikimedia.org/wikipedia/commons/9/9f/E
               | xposure...
               | 
               | [edit]
               | 
               | Fixed various calculations.
        
               | inejge wrote:
               | The overlay gets that position wrong -- it's uSv/h
               | (microsieverts, the transliterated legend is "mkZv/ch".)
               | 11.37 mSv/h would be a radiological incident. The
               | Australian lost density gauge capsule from a couple of
               | days ago was 2-5 mSv/h.
        
               | mrb wrote:
               | Ah, that makes sense ! 11.37 uSv/hour is only about 28
               | times higher than background radiation.
        
           | retrac wrote:
           | The average, of course, is just that, an average. There are
           | some places that are naturally around 100 mSv dose annually,
           | or some 50x higher, and places that are much lower than
           | average. Under truly non-ideal conditions, like having a
           | poorly-ventilated basement made out of uranium-rich
           | limestone, it could probably get even higher than 100 mSv a
           | year just from the radon.
           | 
           | Speaking of which, radon gas is the main way in which uranium
           | affects the health of people. Depending where you live and
           | the construction methods, it may be worth getting your
           | basement checked, and ventilated properly if necessary.
           | 
           | Even the extreme scenario there is still far short of causing
           | acute radiation sickness. People who live in such regions are
           | sometimes exposed to such levels their whole lives, which can
           | still be long and healthy. But not quite as long and healthy
           | as those without such exposure, on average.
        
           | pera wrote:
           | Let's say you work in the station and your desk is right next
           | to one of these uranium oxide glazed tiles:
           | 
           | - You work about 2k hours per year in the orange office
           | 
           | - That would then be about 200 mSv per year
           | 
           | - "Exposure to 100 mSv a year is the lowest level at which
           | any increase in cancer risk is clearly evident"
           | (https://www.reuters.com/article/us-japan-quake-radiation-
           | idU...)
           | 
           | I guess then that maybe we could (barely) observe a higher
           | incidence of cancer for those who spend a lot of time next to
           | the walls?
        
             | marcosdumay wrote:
             | The "glued" on the GP is to be taken almost literally. I
             | bet your desk doesn't put your back supported by the wall.
             | 
             | Besides, Uranium radiation is mostly absorbed by the skin,
             | and your skill will be replaced many times on that
             | timeframe.
        
       | wkat4242 wrote:
       | Not great, not terrible.
        
       | albertzeyer wrote:
       | https://xkcd.com/radiation/ https://en.wikipedia.org/wiki/Sievert
       | https://en.wikipedia.org/wiki/Banana_equivalent_dose
       | 
       | I'm not really sure about the unit of the measure here. So how
       | does it compare really?
       | 
       | You need to realize, we are exposed to radiation all the time.
        
         | stefantalpalaru wrote:
         | > https://xkcd.com/radiation/
         | https://en.wikipedia.org/wiki/Sievert
         | https://en.wikipedia.org/wiki/Banana_equivalent_dose
         | 
         | The "banana equivalent dose" is an error that refuses to die.
         | Based on tables that estimate the effect of various radioactive
         | isotopes acting for 50 years, people ignoring physiology
         | decided that the average K40 in a banana will produce 0.078
         | microsievert of damage (rounded to 0.1 because it's close
         | enough for jazz and comics).
         | 
         | The reality is that, due to homoeostasis, the excess potassium
         | you ingest is eliminated the next time you piss, so there's no
         | accumulation inside the organism. Those 50 years become
         | something like 12 hours and the radiation exposure is more in
         | the ballpark of 0.00000213 microsievert.
         | 
         | But that value is now too small to use it in science fanboyism,
         | isn't it?
         | 
         | https://www.epa.gov/sites/default/files/2015-05/documents/52...
         | - page 156. That's where these people took the effective dose
         | equivalent for K^40 from, but those values are for 50 years of
         | exposure.
         | 
         | "For radioisotopes of elements that are under tight homeostatic
         | control by the human body, the inhalation or ingestion risk
         | coefficients given in this document may not be appropriate for
         | application to some exposure scenarios. For example, the
         | ingestion risk coefficient for ^(40)K would not be appropriate
         | for application to ingestion of ^(40)K in conjunction with an
         | elevated intake of natural potassium. This is because the
         | biokinetic model for potassium used in this document represents
         | the relatively slow removal of potassium (biological half-time
         | of 30 d) that is estimated to occur for typical intakes of
         | potassium, whereas an elevated intake of potassium would result
         | in excretion of a nearly equal mass of natural potassium, and
         | hence of ^(40)K, over a short period." - ["Federal Guidance
         | Report No. 13: Cancer Risk Coefficients for Environmental
         | Exposure to Radionuclides"](https://www.epa.gov/sites/default/f
         | iles/2015-05/documents/40...) - page 16
         | 
         | So, if you accept that the duration of exposure from eating a
         | banana is 12 hours instead of 50 years, a dental x-ray is the
         | equivalent of eating 2,347,417 bananas.
        
           | the_af wrote:
           | > _But that value is now too small to use it in science
           | fanboyism, isn 't it?_
           | 
           | I don't understand, what is "science fanboyism"?
        
             | stefantalpalaru wrote:
             | [dead]
        
         | Nitrolo wrote:
         | EDIT: Someone linked to the Wikipedia article for uranium
         | tiles, which says that the majority of the radiation comes from
         | the decay products and is beta radiation[1]. Beta radiation has
         | a weighing factor of 1, which means it's about 0.1 mSv/h. For
         | comparison Wikipedia says:
         | 
         | "90 mSv/h: Natural radiation on a monazite beach near
         | Guarapari, Brazil."
         | 
         | ================
         | 
         | EDIT 2: Looking more closely it appears that the dosimeter in
         | the video is switched to uSv/h, so it's reading 0.1 mSv/h
         | anyway and the whole discussion below can be skipped if you're
         | not interested in the difference between Gy and Sv.
         | 
         | ==========
         | 
         | Seems to be milliroentgen/h according to another commenter,
         | which is an older unit. Today you'd use Gray (Gy), which is 1
         | J/kg of energy deposited in material, and Sievert (Sv), which
         | is Gy adjusted by a factor to account for different radiation
         | types and body parts to get comparable biological effects.
         | 
         | For soft tissue (~= humans) 1 R = 0.01 Gy, so the dose would be
         | ~0.1 mGy/h. Converting that to Sievert is more complicated.
         | Uranium is an alpha emitter, for which you'd use a weighing
         | factor of 20 [0], getting 2mSv/h.
         | 
         | 1 mSv/h = "NRC definition of a high radiation area in a nuclear
         | power plant, warranting a chain-link fence." [0]
         | 
         | However alpha radiation also gets blocked by very flimsy
         | barriers, such as a few cm of air, or the layer of dead skin
         | cells on your skin. So the effective dose might be closer to 0!
         | 
         | You also have to consider that the decay products or Uranium
         | are beta emitters. Beta rays have a weighing factor of 1, but
         | they do penetrate deeper (stopped by a few feet of air, can
         | penetrate the skin).
         | 
         | The real effective dose in Sv depends on the exact ratio of
         | decay products to U-238, and how deeply the beta rays of those
         | products penetrate your body (there's different weighing
         | factors for different body parts!).
         | 
         | In conclusion: probably not too much, but radiation and
         | radiation shielding is a complicated subject we managed to
         | spend a whole semester on.
         | 
         | [0]: https://en.wikipedia.org/wiki/Sievert [1]:
         | https://en.wikipedia.org/wiki/Uranium_tile
        
         | funnym0nk3y wrote:
         | I'm very surprised that radiation workers are allowed half the
         | dose which is directly linked to cancer. Especially because you
         | get that dose in two years, imagine how much you get over a 40
         | year career.
        
           | retrac wrote:
           | Generally kept lower than that. Exceeding the human exposure
           | threshold for a worker amounts to an international nuclear
           | incident. Literally. Must be reported and the IAEA will do a
           | full investigation and eventually assign it an International
           | Nuclear Event Scale number. (7 = Chernobyl. 2 = Worker
           | dropped a small vial of tritium gas and breathed it in.)
        
       | vinaypai wrote:
       | Given the level of radioactivity, it's safe to say you should not
       | eat an excessive number of these tiles.
        
         | ChuckNorris89 wrote:
         | What if I were to scrape those tiles and snort it?
        
           | Tuna-Fish wrote:
           | It would be very bad for you.
           | 
           | You know, because of all the silicates in your lungs. The
           | radioactivity would probably not be very significant.
        
           | grishka wrote:
           | Other people at the station will start taking pictures of you
        
             | mousetree wrote:
             | Unlikely at U Rosenthaler Platz
        
         | Symmetry wrote:
         | I don't think I'd worry about that from a radiation standpoint.
         | Natural uranium is only around 1000 times more radioactive than
         | natural potassium, it's really not very bad in that sense and
         | it wouldn't have survived from the birth of the solar system to
         | the present day if it was.
         | 
         | On the other hand, it is a toxic heavy metal so please, please
         | don't eat it.
        
           | LorenPechtel wrote:
           | And you'll get a lot more of that potassium into your body
           | than uranium. So long as you don't eat such low-level things
           | they're not a threat. (And, personally, I'm not convinced
           | there's any threat. All of our estimates of the threat of
           | radioactivity are based on high level exposures. IIRC it's
           | about 100 Sieverts = 1 death. We project that linearly into
           | the lose dose realms that are effectively impossible to test,
           | but we have some data points that suggest the linear
           | projection is not accurate and low level exposure is of much
           | lower or possibly even negative threat--that the body's
           | reaction to the low level radioactivity actually is
           | protective. There is no relationship between cancer and
           | background radioactivity. The threat of radon noted in
           | uranium miners only shows up if they're also smokers--huh??)
        
             | chmod775 wrote:
             | > And you'll get a lot more of that potassium into your
             | body than uranium.
             | 
             | And your body needs potassium. In fact most humans don't
             | get _enough_.
        
           | papito wrote:
           | Oh, that's right. Sometimes containers full of bananas will
           | set off radiation alarms at shipping ports.
        
         | mc32 wrote:
         | People will leave them alone, as long as they're not filled
         | with jelly.
        
           | chrisweekly wrote:
           | hahahaha
           | 
           | For those not in the know, JFK immortalized the pastry from
           | Berlin in his famous "Ich bin ein Berliner" speech.
           | 
           | "Ich bin Berliner" -> I'm a citizen of Berlin
           | 
           | "Ich bin ein Berliner" -> I'm a jelly donut.
        
             | tannhaeuser wrote:
             | Actually, the traditional stuffed donut-shaped fried pastry
             | without hole is called pancake (Pfannkuchen) in Berlin
             | whereas at other places of Germany a Pfannkuchen is the
             | sweet souffle-like thing you make yourself in the pan
             | called Eierkuchen in Berlin and elsewhere. Just saying, as
             | native Berliners won't understand or take orders for
             | "Berliners".
             | 
             | Edit: what chiki said
        
             | socksy wrote:
             | This isn't true.[0] The difference between "Ich bin
             | Berliner" and "Ich bin ein Berliner" is that the former
             | says that you literally are from/living in Berlin, and the
             | latter means you are figuratively speaking as like a
             | Berliner. "Ich bin Clown" means that your job is to
             | entertain people with face-paint on, whereas "Ich bin ein
             | Clown" means that you sometimes behave clownishly.[1]
             | 
             | [0] https://en.wikipedia.org/wiki/Ich_bin_ein_Berliner#%22I
             | _am_a...
             | 
             | [1] https://language.mki.wisc.edu/essays/ich-bin-ein-
             | berliner/
        
               | hesk wrote:
               | The source [1] is misleading to the point of being wrong.
               | It is perfectly valid German to say "Ich bin ein Student"
               | meaning that one is indeed a student. "Ich bin Clown" is
               | not grammatical at all.
        
               | loevborg wrote:
               | It's funny how (presumably) native speakers make
               | judgments about their own language.
               | 
               | Of course you can say "Ich bin Clown" just as you can say
               | "Ich bin Kaminfeger" or "Ich bin Physiotherapeut"
        
             | chrisweekly wrote:
             | OP here.
             | 
             | FWIW, I'm not a native speaker but I did study German in
             | high school and college, and used my moderate proficiency
             | extensively while traveling in Germany (including Berlin in
             | 1990), and Austria, and living in Prague. I've laughed with
             | native Germans about the JFK speech (which story was first
             | related to me by my hs German teacher), and regardless of
             | its provenance / veracity, it makes for an interesting
             | discussion. :)
             | 
             | There's also a European liquor, bright blue in color, aptly
             | named "Blau" (which word, "blau", is slang for drunk or
             | intoxicated).
             | 
             | As for varieties of sausage, "wieners" (Wien/Vienna), and
             | Frankfurters (Frankfurt) were referred to as "hot dogs" by
             | Parisian college students jokingly(?) describing their
             | mysterious ingredients... (citation needed, but I did read
             | that in a seemingly-reputable magazine.)
        
             | fortran77 wrote:
             | Du liegst falsch.
        
             | nkozyra wrote:
             | > There is a widespread misconception that Kennedy
             | accidentally said a malapropism that he was a Berliner, a
             | German doughnut specialty. This is an urban legend which
             | emerged several decades after the speech, and it is not
             | true that residents of Berlin in 1963 would have mainly
             | understood the word "Berliner" to refer to a jelly doughnut
             | or that the audience laughed at Kennedy's use of this
             | expression.[2]
        
               | Loic wrote:
               | Especially because in Berlin they are known as _"
               | Krapfen"_ and not as Berliner.
        
               | fileeditview wrote:
               | Buying a Berliner in Germany can be very challenging if
               | you travel a lot. There are so many words for it
               | depending on the region. At least: "Berliner", "Krapfen",
               | "Pfannkuchen", "Krappel", "Kuchli" and probably others I
               | don't know..
        
               | saalweachter wrote:
               | Has anyone made a map, like they do for eg soda/pop in
               | the US?
        
               | cratermoon wrote:
               | Try buying a hogie, sub, hero, Italian, grinder, wedge,
               | or spuckie in the US.
        
               | throwanem wrote:
               | _Spuckie?_
        
               | superhuzza wrote:
               | Apparently from spucadella, an italian-american word for
               | a type of bread.
        
               | cratermoon wrote:
               | I've never heard anyone use it myself, but then I've
               | never tried to order the sandwich otherwise known as a
               | sub in the parts of the country where that name is used.
        
               | grogenaut wrote:
               | Wedge will get you a salad most places in the us. Hero
               | might get you a gyro or ask for clarification. Grinders
               | seem specities in much of the us.
        
               | wcarron wrote:
               | A 'hero' is just a gyro with bastardized spelling.
        
               | mc32 wrote:
               | The terms are unrelated [a sandwich named hero predates
               | the appearance of the Greek item]; though they may sound
               | the same depending on how they are pronounced. A hero is
               | just a submarine sandwich by another name. A gyro is a
               | pita-wrap --mostly pronounced like the 'gyro' in
               | gyroscope but also like /yirou/ or /hirou/
        
               | grogenaut wrote:
               | I have seen Heroes that are much more like hoagies and I
               | am seeing Heroes like the Greek rap depending on where
               | you are in the countrymy point overall is there doesn't
               | seem to be definitive things or just a lot of regional
               | uses and spellings of these differentfood types by region
               | so if you're cleaning that there's only one it probably
               | means you haven't traveled enough
        
               | soiler wrote:
               | For all its faults, we can thank Subway for partially
               | solving this problem.
        
               | nkozyra wrote:
               | Ich bin ein Hoagie
        
               | licebmi__at__ wrote:
               | Weird, I always have seen them in my nearest Rewe
               | advertised as "Berliner". Never thought it was a problem
               | in other stores.
        
               | zorked wrote:
               | Pfannkuchen in Berlin not Krapfen, I think?
        
               | senand wrote:
               | Indeed, Pfannkuchen in Berlin
        
               | ben_w wrote:
               | I've seen them sold here in Berlin under the names
               | "Pfannkuchen" (not to be confused with pancakes),
               | "Krapfen" (not as rude as it sounds in English),
               | "Amerikaner" (not to be confused with an oversized iced
               | soft cookie), and "Berliner" (not to be confused with the
               | alcohol).
               | 
               | Sometimes they're even sold as "Donut".
        
               | ff10 wrote:
               | Yes, Pfannkuchen is the name used in Berlin.
        
               | culturestate wrote:
               | That's what someone who grew up in Berlin would probably
               | say, but the city being what it is it genuinely depends
               | on which shop you're standing in. I've seen it every
               | which way.
        
             | chki wrote:
             | Interesting. I have heard about this famous speech many
             | times but I have never made the connection to the pastry
             | "Berliner" (or heard anyone mention this association).
             | 
             | Also, as a native German speaker, saying "Ich bin ein
             | Berliner" is not unusual if you are talking about being a
             | citizen of Berlin.
             | 
             | I don't think that was a common association at the time as
             | well. Especially since (pastry) "Berliners" are not called
             | "Berliners" in Berlin but "Pfannkuchen" instead.
        
               | verst wrote:
               | Berliner and Pfannkuchen are very different pastries (at
               | least in the Northwest of Germany). Pfannkuchen literally
               | implies it is made in a pan, whereas a Berliner is
               | typically deep fried. It often has a fruit jelly filling,
               | but you will also find those without a filling.
               | 
               | I agree that no native speaker would think of the pastry
               | when hearing "Ich bin ein Berliner." Just like I wouldn't
               | think of a sausage if someone were to say "Ich bin ein
               | Frankfurter."
        
               | locallost wrote:
               | It's just an urban legend. Most people don't speak German
               | so you can tell them anything you want :-).
               | 
               | Speaking of which, good thing Kennedy never visited
               | Hamburg.
        
               | HPsquared wrote:
               | I suppose that raises the question, if people from Berlin
               | do indeed call themselves Berliners - do people from
               | Hamburg call themselves Hamburgers? (genuine question)
        
               | tasuki wrote:
               | I don't see why not. Hamburger means "of Hamburg". If
               | you're thinking about the food item, it isn't a funny
               | coincidence or anything, its name is derived from
               | Hamburg.
               | 
               | I'm not German nor a linguist, YMMV.
        
               | Symbiote wrote:
               | Yes.
               | 
               | Compare "Danish" as an American term for a Viennese
               | pastry, "he's Danish" doesn't sound odd.
               | 
               | We don't generally abbreviate foods named after places,
               | but:
               | 
               | "Cheddar is 200 miles from both Sandwich and Stilton."
               | 
               | These are all places in England.
        
               | triceratops wrote:
               | Yes. Hence also the names Frankfurter and Wiener (Wien is
               | Vienna, in German).
        
               | mc32 wrote:
               | Well, you're in luck, he did visit Frankfurt.
        
               | dmichulke wrote:
               | And Wien... (Vienna)
        
               | mc32 wrote:
               | Oh, if he'd only made it to Denmark, it'd be deliciously
               | confusing.
        
               | weard_beard wrote:
               | Or Frankfurt!
        
             | luoc wrote:
             | Dit heest Pfannkuchen
        
             | pigbearpig wrote:
             | Can you not propagate urban legends please.
        
         | odiroot wrote:
         | That station is quite filthy, the glazing is the least of your
         | problems.
        
         | DJBunnies wrote:
         | Hello there, fellow collector-but-not-eater!
        
         | mhd wrote:
         | I think that type of glazing was once somewhat popular for
         | dinnerware. Gladly that got solved by the colors becoming quite
         | unpopular after the 70s.
         | 
         | (I'm aware that I'm writing this on "the orange site"...)
        
           | Bedon292 wrote:
           | Yes, Fiestaware. Where the most popular color was red, which
           | originally used natural uranium oxide as the pigment in the
           | glaze. It was actually WWII that saw the US government
           | confiscate their stock of uranium in 1943. They used depleted
           | uranium from 1959 to 1973 when the finally discontinued the
           | red color. And an estimated 2 million pieces sold between
           | 1959 and 1969. [1]
           | 
           | And people collect them. I remember being a kid and looking
           | at my grandmother's display of plates and being told they
           | were radioactive. But only a little. You can also still find
           | them on eBay easy enough.
           | 
           | [1] https://www.orau.org/health-physics-
           | museum/collection/consum...
        
             | cafard wrote:
             | A family I knew in Montgomery County, Maryland, dumped the
             | pepper out of its Fiestaware shaker and took it to a fire
             | station's test-your-stuff day. My recollection is that the
             | pepper was not hazardous.
        
               | dgfitz wrote:
               | [flagged]
        
               | cafard wrote:
               | I don't know why. Perhaps because I never heard of
               | hazardous substance days at firehouses elsewhere. Perhaps
               | because it sounds less as if I made up the story.
        
               | ender341341 wrote:
               | Not necessarily a day, but I know that it's not uncommon
               | for fire departments to do similar things for testing
               | items for lead.
        
               | renewiltord wrote:
               | [flagged]
        
               | [deleted]
        
               | baking wrote:
               | Is test-your-stuff day common where you are from?
               | 
               | https://en.wikipedia.org/wiki/List_of_highest-
               | income_countie...
        
           | pastor_bob wrote:
           | Vaseline Glass[0] is pretty common to find in antique stores
           | if you want your own uraniumware
           | 
           | [0]https://www.orau.org/health-physics-
           | museum/collection/consum...
        
           | superzamp wrote:
           | _chuckles_
           | 
           | glancing at my living room and seeing second-hand 70s orange
           | antiques, glasses and dinnerware everywhere
        
           | yanellena wrote:
           | A lot of glassware had uranium and other radioactive
           | materials in too.
           | 
           | Here's a good subreddit for it in the wild:
           | https://www.reddit.com/r/uraniumglass/
        
       | exo-cortex wrote:
       | Hm.... I've spent a lot of waiting time in this station
       | (Rosenthaler Platz) over the years. And these tiles (in different
       | colors though) are in a considerable amount of Berlin subway
       | stations. Are they all radioactive like these here? Or is it only
       | caused by the orange pigment?
        
         | rcme wrote:
         | The orange pigment was made with uranium.
        
           | gilleain wrote:
           | Specifically, Uranium Oxide (UO2, I guess? Or maybe the
           | trioxide?):
           | 
           | https://blog.colornavigator.net/dangerous-colors
           | 
           | https://en.wikipedia.org/wiki/Uranium_trioxide
        
       | stavros wrote:
       | How many bananas is that like being exposed to?
        
         | throw_a_grenade wrote:
         | For completeness, can we also get the measurement in
         | dishwashers and american football fields?
        
           | st_goliath wrote:
           | Statute or nautical football fields?
        
           | stavros wrote:
           | Wait, are American football fields particularly radioactive?
        
             | throw_a_grenade wrote:
             | Serious answer would be, it depends on the underlying soil.
             | Granite is particularly radioactive, to the point that
             | yearly exposure to background radiation in Scandinavia (a
             | granite penninsula) would be considered as crossing
             | threshold of general population exposure to artificial
             | sources (i.e. over background) in my country.
             | 
             | Also, famously, the dose of radiation in one of the long
             | term storage facilities nearby (measured on the floor,
             | outside containers) is lower than in the main church in
             | that town, which, you've guessed it, is built from granite
             | blocks.
        
               | fghorow wrote:
               | It's not just granites or other igneous rocks.
               | 
               | A major rock-forming mineral is Potassium Feldspar
               | (K-spar to geologists). The weathering products of K-spar
               | include many varieties of clay. Those, in turn, wind up
               | incorporated in sedimentary rocks
               | 
               | When logging a well for permeability -- an activity that
               | occurs for both hydrocarbon and geothermal projects --
               | detection of radio-emissions due to K is an indicator of
               | sedimentary strata that are unlikely to have much
               | permeability because the clays clog up the fluid-flow
               | pathways.
               | 
               | This has been today's lesson in geoscience. :D
               | 
               | (Edit: typo.)
        
         | yenda wrote:
         | I would say a truckload, because bananas radiations are making
         | just a bit more crack noises than the background, here the
         | Geiger counter go crazy. But without the background reading and
         | units it's hard to tell
        
       | I_am_tiberius wrote:
       | Does this concern stations in the eastern part of Berlin only
       | (former DDR part)?
        
         | smcl wrote:
         | The station was built in 1930, so the concept of DDR/BRD didn't
         | exist yet
        
       | tilsammans wrote:
       | This is great, nice find. I grew up with Uranium-based Fiestaware
       | in the house, and I am looking at a radioactive red vase right
       | now. My dad was a ceramics engineer and researcher. He wrote the
       | book on red ceramic glazes (The Defiant Red), and there is a
       | whole chapter on Uranium.
        
       | louthy wrote:
       | I assume this is what Kraftwerk were banging on about
        
         | janlukacs wrote:
         | Trans-Europe Express!
        
         | boomboomsubban wrote:
         | Kraftwerk famously sing about above ground trains, with "Trans-
         | Europe Express," the freeway, with "Autobahn," and
         | radioactivity, with "Radioactivity," but nothing I know of
         | about the subway.
        
       | xroche wrote:
       | Everything is radioactive.
       | https://www.discovermagazine.com/health/everything-emits-rad...
        
         | SnowHill9902 wrote:
         | All things are radioactive but some things are more radioactive
         | than others.
        
       | kreldjarn wrote:
       | There are also radioactive tiles decorating the Caltech campus:
       | https://www.flickr.com/photos/lapie/3340318920/
       | 
       | Apparently there was a brief period in the 20th century when this
       | was a popular way of making yellow glazing.
        
         | cultofmetatron wrote:
         | google "radium girls"
        
           | cultofmetatron wrote:
           | not sure why I was downloaded. the radium girls painted
           | radium on dials which glowed
        
       | PaulHoule wrote:
       | I was at an antique store where they had numerous pieces of
       | Uranium glass glowing under a UV light last weekend.
       | 
       | I think it's funny that Uranium has this connotation of "glowing
       | in the dark" which has nothing to do with the nuclear properties
       | at all but rather very interesting optical phenomena that happen
       | when you have an atom with a huge number of electrons like the
       | way Thorium Oxide is good for gas lamps because it emits
       | thermally in the visible range but not so much in the infrared.
        
         | the8472 wrote:
         | Some isotopes do glow in the dark if sufficiently enriched, due
         | to their decay heat.
         | 
         | https://en.wikipedia.org/wiki/File:Plutonium_pellet.jpg
        
           | PaulHoule wrote:
           | That Pu238 pellet is surrounded by ash, I think they buried
           | it in ash to hold the heat in and then uncovered it so you
           | could see the glow. In this case it is driven by heat
           | transport so the bigger of a mass you have the more the ratio
           | of volume to area and the more it heats up.
           | 
           | That's very different scaling from this kind of thing
           | 
           | https://inis.iaea.org/search/search.aspx?orig_q=RN:36003591
        
       | idiocrat wrote:
       | Many (or most) of the natural marble kitchen countertops are
       | radioactive, especially the dark spots. Perhaps not hazardous, if
       | epoxy glazed.
       | 
       | If I were to build a house, I would walk all materials with a
       | geiger counter, especially alpha particles. Sometimes difficult
       | to replace material, if it is already worked into the structure.
        
       | jonty wrote:
       | This is my toot, but the credit (and possibly the link) should be
       | to @gigabecquerel:
       | https://chaos.social/@gigabecquerel/109818433760462038
       | 
       | There are other stations on the U-Bahn with uranium tiles too,
       | you can find them with the crowdsourced Safecast radiation map:
       | https://map.safecast.org/?y=52.5002&x=13.4852&z=13&l=0&m=9
        
         | dewey wrote:
         | Thanks! I parsed that toot wrongly, should've submitted the
         | other URL. Maybe dang can update it.
         | 
         | (Wish we had quote-posts on Mastodon, would make it more
         | obvious)
        
           | jordigh wrote:
           | I don't like the idea of Twitter-like quoting. Linking to the
           | original toot is fine, it's clear that there's a link.
           | 
           | The Twitter-like quoting was used way too much for abuse. It
           | had legitimate uses, but the abuse it generates does not
           | warrant the legitimate uses.
           | 
           | Plus, it always made things so weird to read.
           | 2. The reply                 1. The original             3.
           | The replies to the reply
           | 
           | You say you find linking confusing right now, but it's just a
           | matter of getting used again to the idea that links exist and
           | can be followed, without always having a link preview. I find
           | Twitter-quoting confusing because it messes up the order of
           | the conversation.
        
             | mlindner wrote:
             | Can we just call them "posts" instead of "toot"?
        
               | jordigh wrote:
               | No! :)
               | 
               | https://news.ycombinator.com/item?id=34696041
        
               | TaylorAlexander wrote:
               | You can! I love calling them toots but it's perfectly
               | fine to call them posts.
               | 
               | For anyone unfamiliar, "toot" is the sound an elephant
               | makes and a mastodon is a prehistoric elephant. Just like
               | a bird tweets, a mastodon toots.
        
             | TaylorAlexander wrote:
             | This has been discussed to death on mastodon already.
             | However recently the mastodon devs added this feature to
             | their short list of what they are working on. (I think they
             | said they are "exploring" it.)
             | 
             | Quote toots offer a functionality not offered by other
             | functions, which is the ability to show two toots at once
             | as well as notify the original toot owner of this activity.
             | Linking another toot has a pretty horrible UX in
             | comparison. Last time I clicked on a linked toot, it opened
             | a new tab to view it, and then in order to click like on
             | that toot I was instructed by the UI to copy the toot
             | address to yet another mastodon window in to the search
             | bar. An absolute mess.
             | 
             | Quote toots allow side discussions while allowing everyone
             | to see what is being discussed. And they're great when
             | someone has a long thread and you want to pull out one
             | piece to share with your followers and add context like
             | "this piece of the puzzle is particularly important."
             | 
             | The fact that it changes the order of the conversation is
             | the point. Conversations fork in ways not always conducive
             | to a reply-only view.
             | 
             | I primarily want quote toots so I can quote myself to start
             | fresh threads that build on old ones. I did this all the
             | time on Twitter where I posted a thread of updates for
             | every evening that I worked on a project, with a new thread
             | quoting the last one for each new evening. Since replies
             | and links don't show the other posts, it's not as clear
             | what I'm talking about when I link to an old toot and say
             | "I made progress on this project tonight" given the awful
             | UX on link toots.
        
               | jordigh wrote:
               | The recent wave of Twitter immigration has reignited the
               | quote-toot discussion. People mostly want a silly copy of
               | a half-baked Twitter feature. If we get something like it
               | in Mastodon, I hope it's better thought-out. For example,
               | editing toots was done in an entirely sane way: it's just
               | plain possible to edit toots, and if someone edits a toot
               | you boosted, you get notified, so people can't fool you
               | initially and then insert a completely different idea in
               | your timeline.
        
             | dewey wrote:
             | Don't want to start a side discussion here, but what I like
             | about quote tweets is that I can see the quoted content
             | without having to click out to another tab and go back and
             | forth. Could probably handled with some auto-expanding by
             | clients though.
        
         | 4gotunameagain wrote:
         | Any idea why is Kaskelstrasse so high ? Could it be the
         | cobblestone ?
        
         | Krasnol wrote:
         | > you can find them with the crowdsourced Safecast radiation
         | map: https://map.safecast.org/?y=52.5002&x=13.4852&z=13&l=0&m=9
         | 
         | Oooh that's nice. I wish they'd have those kits in sale again.
         | Would buy one instantly but no time for fiddling myself this
         | year unfortunately...
        
         | secondcoming wrote:
         | First I've heard of a 'toot'!
         | 
         | It's pretty funny due to it's usage in UK slang. It can mean
         | everything from smoking a cigarette, to snorting cocaine, to
         | oral sex.
        
           | gnfargbl wrote:
           | That's true, but those uses of the word are pretty obscure. I
           | would say the most common meaning of "toot" in the UK is the
           | noise a horn makes, especially a bicycle/car/train horn.
           | 
           | It's much more of a friendly word for toddlers than it is a
           | slang word for debauchery. (Example: "Toot! Toot! Packed full
           | of fun and games, it's the Thomas & Friends Annual 2022!",
           | https://www.amazon.co.uk/Thomas-Friends-Annual-Packed-
           | games/...)
        
           | jordigh wrote:
           | Some of us who have been on Mastodon for a few years now
           | insist on calling them toots, despite the official renaming
           | in the original Mastodon repo. A toot is the sound elephant
           | friend (our mascot) makes with their trunk.
           | 
           | Also it's silly and all of the other silly associations you
           | have with it are a plus. "Twitter", "tweet", "google",
           | "facebook", "amazon", "apple", "mac", "tumblr", "kindle" are
           | all also pretty stupid names we've just gotten used to, but
           | "toot" is OUR stupid name, and we made it ours, and if its
           | silliness delays the corporate takeover of Mastodon, that's a
           | huge plus.
        
           | jwx48 wrote:
           | In my particular American-English dialect, it means
           | flatulence.
        
             | cratermoon wrote:
             | Thus the school-boy doggerel, "Beans, beans, the wonderful
             | fruit..."
        
               | jwineinger wrote:
               | I learned it as "the musical fruit" or "good for the
               | heart"
        
           | dewey wrote:
           | https://github.com/mastodon/mastodon/pull/16080
           | 
           | They officially switched from "toot" to "post" a few months
           | ago.
        
             | omoikane wrote:
             | Mastodon Renaming "Toots" to "Posts"
             | 
             | https://news.ycombinator.com/item?id=26882318
        
           | Nursie wrote:
           | Or "fart", don't forget that one!
        
         | sbst32 wrote:
         | Can you tell me how to find other stations with the Safecast
         | map? Rosenthaler Platz station is just blue all-around on that
         | map - maybe I'm doing something wrong?
        
         | [deleted]
        
         | dewey wrote:
         | Looking at this Safecast map, do you know how these values are
         | collected? From the path it looks like it's some kind of mobile
         | collection where user submit data? Are there people walking
         | around with Geiger counters every day?
        
           | cptcobalt wrote:
           | Safecast is the most interesting part of this.
        
       | azubinski wrote:
       | "Uranium tiles" are well known.
       | https://en.wikipedia.org/wiki/Uranium_tile
       | 
       | Personal radiation doses are well known.
       | https://www.nrc.gov/about-nrc/radiation/around-us/calculator...
       | 
       | Social. Chaos. OK.
        
         | SideburnsOfDoom wrote:
         | > Social. Chaos. OK
         | 
         | "Chaos" likely relates to "Chaos Computer Club"
         | https://en.wikipedia.org/wiki/Chaos_Computer_Club and related
         | activities in that part of the world.
         | 
         | A person running around Berlin with a Geiger counter (not on
         | official business) is a CCC kind of hacker.
         | 
         | Of course this comes to us via Jonty Wareing
         | (@jonty@chaos.social ), who is involved with the related EMF (
         | https://www.emfcamp.org/ ) event in the UK.
         | 
         | The Suffix "social" means "this is the social media (mastodon)
         | host".
         | 
         | In fact it says here https://chaos.social "chaos.social - a
         | Fediverse instance for & by the Chaos community"
        
       | jillesvangurp wrote:
       | Ah that's actually my local ubahn station. I assume the risk is
       | pretty minimal. Unless you spend a lot of time in close proximity
       | to those tiles. Like some homeless people seem to be doing.
        
       | ff10 wrote:
       | Apparently the amount of radiation is safe:
       | 
       | > Auch an einem eher ungewohnlichen Ort haben die Mitarbeiter der
       | Behorde schon Messungen durchgefuhrt. Der U-Bahnhof Rosenthaler
       | Platz ruckte wegen seiner vielen orangefarbenen Kacheln ins
       | Visier der Behorde. ,,Die Farbe wird mit dem Schwermetall Uran
       | hergestellt, weil es beim Brennvorgang sehr hitzebestandig ist",
       | sagt Leps. Die Strahlung ist laut dem Experten jedoch belanglos.
       | Auch fur Menschen, die sich langer auf dem U-Bahnhof aufhalten,
       | besteht keine Gefahr.
       | 
       | In short: "According to experts the radiation is trivial."
       | 
       | Source (from the toot thread):
       | https://www.tagesspiegel.de/berlin/bleibende-werte-1545553.h...
        
         | al2o3cr wrote:
         | I agree: if somebody goes around licking the walls in subway
         | stations, a few extra beta particles are the LEAST of their
         | worries :P
        
       | gus_massa wrote:
       | It's strange that the count increase too much near the wall.
       | 
       | If you have a 1/r^2 decreasement from a point source, the if you
       | have an infinite wall it becomes a constant value that does not
       | decrease with the distance.
       | 
       | Clearly the wall is not infinite, but when the distance from the
       | wall is much smaller (1/5?) than the distance to the border of
       | the wall, the approximation is good enough. The wall is like 8
       | tiles tall , so I expect the radioactivity at 1/2 tile (15cm,
       | 5in) to be almost equal to the radioactivity when the counter is
       | touching the wall.
        
         | gnramires wrote:
         | Good question. Another intuitive way to view (no pun intended)
         | 1/r^2 law is that the solid angle visible from an isotropic
         | emitter (like supposedly this wall) gives the exact decay
         | coefficient. So near the surface the solid angle is like 1/2
         | sphere (1/2 4pi), and doesn't change much with distance. Only
         | when you get a bit further away it starts to decrease.
         | 
         | Eventually at large distances, any finite object will have the
         | apparent radius decay as 1/r and solid angle as 1/r^2.
         | 
         | I think in this case it could be atmospheric absorption or just
         | getting near a peak point of emission.
        
           | penteract wrote:
           | Does that apply if the emitter is neither coherent nor
           | opaque? If we were interested in gamma radiation, is the sum
           | from each part of an infinite wall infinite (if we pretend
           | the wall and the air are perfectly transparent to gamma
           | rays)?
        
         | hanslub42 wrote:
         | Uranium (both U238 and U235) is an alpha-emitter. Alpha
         | particles travel at most a few centimeters in air.
        
           | gus_massa wrote:
           | That's a good explanation!
           | 
           | I made a mistake and assumed it was Beta or Gamma radiation
           | that travel easier in air.
        
           | addandsubtract wrote:
           | This is U8, though.
        
             | snovv_crash wrote:
             | (that's the name of the subway line for any non-Berliners
             | who might be confused)
        
         | perihelions wrote:
         | Yes, I noticed that too. I think it's mainly beta radiation
         | close to the wall. It would be attenuated by air absorption
         | further away.
        
         | tomxor wrote:
         | > If you have a 1/r^2 decreasement from a point source, the if
         | you have an infinite wall it becomes a constant value that does
         | not decrease with the distance.
         | 
         | It will still decrease with distance. If you represent the wall
         | as a collection of point sources distributed over a plane, as
         | the distance to the plane diminishes, the distance to
         | individual points do not diminish to and from the same distance
         | as each other, and do not diminish at the same rate. However
         | they still _all_ diminish, and thus the sum intensity must
         | diminish. Though the appropriate function describing the sum of
         | the contributions from each point is no longer 1 /d^2.
         | 
         | There will be some continuous equation to describe this...
         | someone more familiar with radiance feel free to chime in!
        
           | thehappypm wrote:
           | They're referencing a classic Electricity & Magnetism proof.
           | Given an infinite sheet of uniform charge density, the
           | electric field is constant at all distances from the sheet,
           | which is deeply unintuitive.
        
             | tomxor wrote:
             | That is unintuitive, but then is my mistake only in
             | representing the wall as an infinite plane? Would my parent
             | comment still be true for a finite plane, or is that merely
             | technically true but missing the point of the function
             | shape being _almost_ constant up to some threshold
             | (depending on the limits of the finite plane).
             | 
             | I feel like I want to plot this now to build an intuition.
        
               | penteract wrote:
               | If you're looking down at an infinite plane, then the
               | plane occupies half your field of view (assuming you have
               | a 360 degree field of view) no matter how far you are
               | from it. Given a 2d object of uniform density, the
               | component of the gravitational force towards that object
               | in the direction perpendicular to the plane it lies in is
               | proportional to the solid angle of your field of view it
               | occupies. For an infinite plane, the components in other
               | directions cancel out. I think this is related to how a
               | sphere acts equivalently to a point at its center - an
               | infinite plane is just a sphere of infinite radius.
               | 
               | The situation is similar for an opaque light source
               | (apart from the lack of atmosphere in the way, I don't
               | think the sun would be much brighter if you were much
               | closer to it and looking through a pinhole), but I'm not
               | sure it applies to gamma radiation which is emitted
               | uniformly in all directions from each point and treats
               | most stuff as pretty transparent - unless there's some
               | weird interference you don't get to cancel out the parts
               | coming from different directions.
        
               | tomxor wrote:
               | Yes, I actually kind of get the infinite part, but thanks
               | for the explanation it's interesting. I was wondering
               | what the intensity looks like for a distance field around
               | a _finite_ plane and how that relates. This might be
               | harder to describe.
               | 
               | What I'm suspecting is that under a certain distance for
               | a given finite plane it's almost constant similar to the
               | infinite version, but outside of that distance there must
               | be some non uniform falloff function.
        
               | penteract wrote:
               | For a finite circle, where you're on a line perpendicular
               | to it going through its center, the gravitational force
               | you experience towards it is exactly proportional to the
               | amount of your field of view it occupies - if I'm right,
               | that should be proportional to `1-cos(atan(r/d))` where r
               | is the radius of the circle and d is the distance between
               | you and the center of the circle.
        
               | gus_massa wrote:
               | You are correct. For a short distance it's a almost a
               | constant 1 like an infinite wall with the same charge
               | density. For a long distance is almost 1/r^2 like
               | punctual source. For an intermediate distance, it's a
               | mess and you hope nobody ask for an exact solution.
               | 
               | A rectangle is a mess. It's easier with a circle. The
               | approximations at short and long distance are the same,
               | but a circle has an "easy" formula in between.
               | http://hyperphysics.phy-
               | astr.gsu.edu/hbase/electric/elelin.h... 1-x/sqrt(x^2+R^2)
               | where R is the radio of the circle. Let's use R=10 to
               | keep it simple.
               | 
               | For a short distance 0<x<R/10, then it's almost a
               | constant https://www.wolframalpha.com/input?i=1-x%2Fsqr%2
               | 8x%5E2%2B10%...
               | 
               | For a long distance, x>4R it's almost like R^2/(2*x^2) ht
               | tps://www.wolframalpha.com/input?i=1-x%2Fsqr%28x%5E2%2B10
               | %...
               | 
               | There are some trick to add more term to the
               | approximations to reduce the middle part where both
               | approximations are bad, like using A+Bx or A+Bx+Cx^3 for
               | short distance and D/x^2+E/x^4 or D/x^2+E/x^4+F/x^4 for
               | long distance. It depends on how much you care about the
               | precision and how many calculations you want to do.
               | 
               | In some particular cases like a circle or the shell of a
               | sphere there are closed formulas for the intermediate
               | distances. In other cases there is no nice formula.
        
               | AdamN wrote:
               | The problem is that this wall does not exist in a vacuum
               | - the OPs comment is otherwise valid. The air is
               | absorbing the radiation (very effectively).
        
               | tomxor wrote:
               | Yes, I understand that. I'm wondering separately (in a
               | vacuum if you will), what the falloff looks like with a
               | finite plane, and how that relates to the infinite
               | version. Obviously we cannot actually represent the wall
               | as an infinite plane, from my current location it's
               | accurate enough to represent it as a point source... so
               | there is some threshold for a particular finite plane
               | after which the "constant" nature is clearly not true.
        
             | rubberpoliceman wrote:
             | I don't think that's unintuitive. What goes into a source-
             | free volume element has to go out of that volume element
             | (radiation or field).
        
       | Traubenfuchs wrote:
       | We have a long tradition of uran-containing glass and ceramic
       | objects/tiles/decoration/tableware.
       | 
       | https://en.wikipedia.org/wiki/Uranium_tile
       | 
       | https://en.wikipedia.org/wiki/Uranium_glass
        
       | ChrisMarshallNY wrote:
       | Old watches used radium dials.
       | 
       | This reminds me of cloisonne paint.
       | 
       | Many antique pendants, earrings, etc., used Uranium Oxide orange
       | paint.
       | 
       | Orange is actually a difficult color to make. Another dangerous
       | orange is Cadmium Orange (I used to be an artist, and probably
       | breathed in the paint, as I used it in an airbrush).
        
         | matheweis wrote:
         | > Old watches used radium dials.
         | 
         | Some new watches have luminescent dials that contain tritium,
         | also a radioisotope.
        
       | bookofjoe wrote:
       | Uranium ore: https://www.amazon.com/Images-SI-Uranium-
       | Ore/dp/B000796XXM
        
       | [deleted]
        
       | LarryMullins wrote:
       | U238-Bahn
        
       | snshn wrote:
       | A little bit of radiation is probably good for you.
        
       | jesperwe wrote:
       | Make me worry more about conditions for the workers in the tile
       | factory than for the U-Bahn travellers...
        
         | mseepgood wrote:
         | They're long dead, even if they survived the war. This was
         | built more than 90 years ago.
        
         | [deleted]
        
         | mahathu wrote:
         | There are around half a dozen or so homeless people sleeping in
         | this particular station every night, way more now during
         | winter. I'm worried about them. Not like they didn't have
         | enough issues besides the walls they sleep next to being
         | radioactive.
        
           | rom-antics wrote:
           | This seems like a particularly evil example of hostile
           | architecture
           | 
           | https://en.wikipedia.org/wiki/Hostile_architecture
        
           | Raydovsky wrote:
           | I think in Germamy the danger of radiation is overblown. It's
           | really hard to get any radiation damage from low intensity
           | sources.
           | 
           | Hell, even chernobyl is projected to cause at most 4k
           | premature deaths over 50+ years.
        
         | durnygbur wrote:
         | You are about 80 years too late to worry about Polish and
         | Jewish slave labourers.
        
           | flohofwoe wrote:
           | The station was opened in April 1930, three years before the
           | the national-socialists took over.
        
           | heywhatupboys wrote:
           | not everything in Germany in the 1930's was built by slave
           | labour
        
             | durnygbur wrote:
             | some private houses probably weren't haha
        
       | junon wrote:
       | Welp. No idea how many times I've walked through there....
        
       | gpjanik wrote:
       | Quite a few homeless people stay around for the entire day in
       | this station, leaning against these tiles all the time. Would
       | anyone be able to tell if this is a health risk?
        
         | snitch182 wrote:
         | No it is not. The station would be locked otherwise.
        
           | gpjanik wrote:
           | That's poor reasoning.
        
         | wongarsu wrote:
         | If they are always sitting in front of the tiles, leaning on
         | them with their back, they might have higher skin cancer rates
         | on their back.
         | 
         | But generally, the effect of frequent low doses isn't very well
         | understood, and you could even find specific circumstances
         | where it might be beneficial.
        
           | kzrdude wrote:
           | It's likely a coat is enough to shield the alpha and beta
           | decays completely
        
         | nemo44x wrote:
         | Being homeless is probably a much greater health risk.
         | Especially the cigarettes everyone still smokes in Berlin.
        
           | crucialfelix wrote:
           | Smoking cigarettes is much rarer than it used to be here.
           | 
           | But I've seen homeless guys openly smoking Heroin in the
           | U-Bahn stations. And many of them drink a lot of alcohol.
        
       | aaron695 wrote:
       | [dead]
        
       | supernova87a wrote:
       | I wonder if this gives the tiles any kind of antiseptic (or even
       | other) property to them, unintentionally.
        
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