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Sheogorath's Blog


Depending on the time of the day a friend, a colleague, a wise guy. The beauty of the world is its sense of humor to show humans their way by letting them search their own.


  1. Water hammer

    Today I learned about “water hammers” also known as hydraulic shocks. This is a phenomenon one can witness every day when opening and closing a tab in any water pipe system. It’s a shock wave that travels through a liquid backwards, when the liquid’s flow was stopped. Most liquids, like water, are incompressible, which means they are unable to adjust their density to absorb a shock wave. Instead the shock wave travels through the liquid with the entire momentum of the mass of the liquid was moving before. Pipe systems have to account for those shock waves by being able to adjust the system pressure to those shock waves which increase the system pressure by magnitudes for a very short period of time only to drop it below the regular pressure directly afterwards. The Joukowsky equation is used to calculate the shock wave of a hydraulic shock and mainly provides 3 parameters to adjust, which are the speed of the shock wave, the speed of the liquid and the time that is taken to stop the flow. The easiest to adjust for you as a person and therefore reducing the amount of “water hammers” in the pipes you handle every day, is the time that you take to stop the liquid, i.e. closing the tab. Do it slow and the waves will be small, even when the design of your pipe system should already have taken care of them. …


  2. Tally marks around the world

    Today I learned that people around the world use very different tally marks but the majority of them represents 5. While in Europe it’s quite common to use the 4 straight lines (||||) and put the firths across, in Brazil, France and Spain it also happens that people instead of putting 4 lines side-by-side, they draw a box with it line by line with a final line crossing it. In East Asian countries people found an even easier way to represent a group of 5. The Chinese character for 5 is made up of 5 strokes “正”. Therefore in China an other East Asian countries people simply write the character and add one stroke for each time they increase the count. Finally in 1898 a man called “Carl Schenck” came up with the so-called “Tukey Tallying”, which is a counting technique where you first make a dot in the 4 corners of the square, then connect those dots for each further number and finally add 2 additional strokes crossing the box, making it 10 instead of 5. Funnily enough, it wasn’t called after Mr. Schenck but after “John Tukey” and this way of counting is mostly used around forestry. …


  3. Pocket watches

    Today I learned that pocket watches exist since ~1430, meaning the late dark ages, and had the form of a small can. The “modern”, flat form of pocket watches was developed in the 17th century, when they got traction and became a status symbol. Shortly after, in the mid of the 17th century, the first minute hands were added to the watches. The original ones weren’t precise enough to bother with a minute hand, instead they only showed the (rough) hour. …


  4. Friends of dorothy

    Today I learned that American gay men were referring to themselves as “friends of Dorothy” starting from the times of the second world war. Back then homosexuality was illegal and therefore this phrase was used to cover it. While this sounds harmless, according to Wikipedia1 in the 1980s it actually triggered an investigation by the National Investigative Service (NIS) to find said “Dorothy” as the “friends of Dorothy” were spreading across the US military. Obviously this wasn’t successful as it was a made up code word with possible relations to books like the Wizard of Oz. And a book source I didn’t verify ↩ …


  5. Half-mast is not for the Queen of England

    Today I learned that the flag of the British monarchy, the royal standard, is never put on half-mast because it’s considered the fall of the monarchy itself. Following the famous statement “The king is dead, long live the king!” the king or queen can’t die as long as there is an immediate monarch to step into the position of their predecessor. Means when the king or queen didn’t die, then there is no reason to wear mourning and therefore no reason for half-mast on a state level. Other flags like the Union Jack can and are put on half-mast in case of such an event. …


  6. Earwax around the world

    Today I learned that earwax differs depending where on the world you are from. There are multiple types of earwax, and the basics of how your earwax looks is determined by your genetics. Around European people yellowish to slightly brownish earwax is quite common, while in eastern Asian areas whiter and dryer earwax is a thing. Generally speaking the main purpose of earwax is to keep your ears clean and healthy. It collects all dust and dirt that might flies around and bind it before it can get too deep into your ear, it also has an anti-bacterial function and unironically not less important: It prevents insects from checking your ear out as it has a very bad smell. …


  7. Operation Paperclip

    Today I learned about “Operation Paperclip”, which was a US operation at the end of the second world war that took successful engineers and scientist from Germany and brought them to the US in order to develop (mainly) in the rocket and weapon industry over there. All of them were spared facing any justice system for what they did in their time under the Nazi regime including those who were very high up in the ranks, basically leading parts of the NSDAP, the German Nazi party at the time. Instead they became “assets” of the US development strategy and got high ranks over there as well. Noteworthy is that the US are not alone with such programs. Basically all of the victorious parties of the 2nd world war had such operations. …


  8. lost+found

    Today I learned that one can’t recreate a functional lost+found directory using mkdir but has to use mklost+found1. The lost+found directory is a special purpose directory that is used as part of file recoveries by fsck. Everything that looks like a file but has no inode will be created as file in the lost+found directory of the partition. This allows to recover all possible data, which otherwise wouldn’t be accessible. As this is not how regular directories work, it can’t be recreated like a normal directory. Yes, this command has a + sign in it. ↩ …


  9. Juice vs Smoothie

    Today I learned that the essential difference between a Juice and a Smoothie is the way it’s produced. While juice is produced by extracting the liquid from the fruit, leaving behind dried pulp. A smoothie intentionally leaves the entire fruit together but cuts it small enough to so it no longer bothers your teeth when “drinking” it. A noted difference is that while juice usually results in almost pure liquid, smoothies often require some additional water to make them easier to drink. …


  10. Adaptive DNS discovery

    Today I learned about Adaptive DNS Discovery, short ADD, which is an upcoming DNS standard to discover and configure DoH and DoT clients. The idea is that the client learns about a local DoH or DoT server either by Router Advertisement (PvD), well-known entry, an HTTPSSVC or SVCB DNS entry, or a regular alt-svc header for HTTPS. …