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Cake day: June 23rd, 2024

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  • Yes, in digital logic, ones and zeros are almost always represented as LOW (negative pole of power supply) and HIGH (positive pole of power supply), such as 0 V and 3.3 V, referenced to ground. This is based on properties of both bipolar and CMOS transistors, fundamental logic elements, where zero base-emitter current or zero gate-source voltage means they’re non-conductive (I hate using open/closed for obvious reasons). However, high-speed and/or long-distance communication pretty much requires differential signalling, which is pure AC measuring between the two conductors. (Just compare SCART (coaxial analog baseband signal, RGB+bidirectional composite SD A/V) and DP or HDMI (shielded twisted digital differential pairs, unidirectional 4k+ A/V) cables by thickness and bandwidth.) And much like sound, radio waves can only be AC.

    A piano/guitar string is plucked and then vibrates at its own natural frequency (plus in practice, higher modes aka harmonics/overtones defined by where it’s plucked and mechanical design). Wind instruments are designed to create continuous oscillation from constant flow of air by amplifying reflected waves with incoming air pressure energy (blowing straight into a cylinder won’t work, hence the weird pipe shapes, holes and reeds). Either way, they resonate at their design frequency. So do self-oscillating piezo buzzers. The speaker membrane, ideally, does not have a resonant frequency (responds equally to disturbances at any frequency between 20 Hz and 20 kHz) and needs to be pushed constantly to create sound. Like the membrane of a mechanical phonograph/turntable, the shape of the wave it should create is delivered to it in real time, except electromagnetically. That’s why player pianos need very little data (literal punch cards: one bit per beat and string (ignoring dynamics), so up to about 240 × 88 ≈ 2.6 kB per minute, uncompressed) to reproduce entire songs as opposed to audio recordings that require samples at decent precision (16 bits is generally good enough) at at least 2x the highest frequency to be reproduced (about 5 MB/min for one CD-quality channel, uncompressed).



  • I could add to this analogy. Yes, the wind passes from a high-pressure point to a low-pressure one but that’s just direct current. The weather can change, reversing the wind every few minutes (alternating current) and you can still harvest it with a turbine (for example, a lightbulb filament or heater lights up in either polarity) but it wouldn’t help a ship with a basic sail travel to a destination (much like DC motors, it would change direction when polarity is reversed). And then there’s sound, akin to very quick polarity changes where particles never travel very far. It doesn’t carry much energy but the waves travel faster than wind and can be modulated with a signal to carry information. Both wired and wireless electronic communication is kind of like that. (Except wireless is decoupled from the charged particles that create the waves, the disturbances in E and B fields propagate on their own without matter)


  • There’s a HUGE number of electrons in everything with a massive total negative electric charge but almost exactly balanced by protons. That’s why electrons move very slowly in a conductor but still transmit lots of current (electric charge over time).

    Accumulating charge in a place is what charging a capacitor or battery is, it creates voltage (potential difference). Charges in an electric field store energy but also their presence/absence can represent data (DRAM and flash memory) and the field has various effects we can use, such as deflecting the beam in a CRT oscilloscope or controlling a stronger flow of electrons in a vacuum tube (valve) or field-effect transistor.

    And the current also creates magnetic field with some similar effects (deflecting the beam in a TV CRT) and some different ones (attracting magnets in a motor, inducing current in a transformer’s secondary winding).

    Plus, both fields can oscillate at a vast range of freequencies and travel in waves, making radio, microwave ovens, vision, UV sterilization, X-ray machines etc. possible (although each of these applications uses the properties of EM waves at specific frequencies differently).


  • Which Czechoslovakia? The states over its history were quite different.

    • First Czechoslovak Republic (1918-1938)
      • Declared as Austria-Hungary fell apart at the end of WWI.
      • Industrial powerhouse dismantling Austro-Hungarian power structures, investment in modernizing rural Slovakia
      • Some people see the creation of this state as attempts of entitled Czechs to legitimize their country stretching far east but Slovaks were not organized as a nation before this point so joining Czechs was their best option (days before Czechoslovakia was declared in Prague, the few Slovak intellectuals who knew about their nation’s extent and situation reached this consensus and informed the Prague AH-separatists in a letter). Frankly, the inclusion of German-populated Sudentenland (establishing historic Bohemian, rather than ethnical borders), Transcarpathia and Upper Hungary were way more problematic, not to mention Trans-Olza, settled in a minor war with Poland over Cieszyn Silesia They do have a minor point: the prevalent push towards “Czechoslovak” national identity as opposed to accepting CSR as a country of Czech and Slovak (and Ruthenian, plus Hungarian and increasingly problematic German) nationals (some were even trying to classify Slovak as a Czech dialect) was ignoring many ethnical differences, and Slovakia only got represented on the flag as it changed from the not helpful Poland🇵🇱-with-slightly-more-contrast to still-controversially-used-today-🇨🇿 in 1920.
    • Second Czechoslovak Republic (1938-1939)
      • Beaten into submission by superpowers signing the Munich agreement that was supposed to appease Nazi Germany but nobody believed that would hold. Prior to the agreement, Czechoslovakia could likely defend itself long enough for Allies to come but didn’t want to start a war that Chamberlain insisted wasn’t inevitable.
    • Protectorate of Bohemia & Moravia + Slovak Staat (1939-1945)
      • Two Nazi puppet states, not actually called Czechoslovakia. Created after Czechoslovakia, weakened by the Sudetenland loss and other Munich Agreement consessions, plus flanked by the now-annexed Austria, surrendered to Nazi Germany in exchange for not being bombed.
      • The democratic government fled to London and helped organize dissent via radio & sent elite paratroopers to sabotage the arms industry and assasinate the Protector
    • Third Czechoslovak Republic (1945-1948)
      • Created after the Prague Uprising and liberation by Soviets (most territory) and Americans (West Bohemia)
      • Struggling to restore democracy with the Soviet-puppeted Communist Party’s influence
      • Controversial expulsion of Germans that was a humanitarian disaster and a massive brain drain
    • Czechoslovak Socialist Republic (1948-1989)
      • After Communists gained majority vote, they did a coup d’etat and Czechoslovakia became a Soviet puppet state.
      • Collectivization and Stalinist purges in the 50s, hopes of democratization in 1968 crushed by Soviet invasion (the only success was that Slovaks gained more independence and CSSR became a federation because the Soviets didn’t care), largely passive submission until Gorbachev (1988) but moderate living standards increase in the 70s and 80s
    • Czech and Slovak Federative Republic (1990-1992)
      • After the Berlin Wall fell, it was obvious the Soviet sphere of influence wouldn’t hold so on the next protest opportunity (legal marches on 1989-11-17, 50th anniversary of protests for a Nazi-assasinated student), dissent members spoke out and a general strike was announced; police beat some protesters but nobody died, hence “Velvet Revolution”
      • Democracy, unrestricted import of foreign goods & media and wild privatization started, people could get rich or poor overnight as the economy turned inside out
    • Czech Republic + Slovakia (1993-present)
      • Created after Slovak politicians wanted more independence and everybody was just trying to comprehend the market changes so nobody really complained and a no-fault divorce was scheduled on 1993-01-01
      • The countries have a brotherly relationship but went their own ways and it’s clear there will most likely never be a Czechoslovakia again





  • RNDr. Jiří Jarník, CSc. is basically a co-author with all these “(pozn. překl.)” and I think they greatly improved it. I don’t think there’s any other translation of the book, so I’d say the ultimate version is Czech. It’s on my bookshelf too, no need to find scans online.

    Here’s a fun question from the book, shortened and adapted for modern typesetting:

    Jméno kterého matematika se skrývá v rébusu?
    ^πr
    Řešení: https://cs.wikipedia.org/wiki/%4A%6F%68%6E%5F%4E%61%70%69%65%72





  • The photos are the contents of the “CV” and “Reports” (basically resume and qualifications) folders she brought.

    Per TV Tropes on Jucika:

    This strip references the comic’s change of ownership [trope page] from Érdekes Újság to Lúdas Matyi, presenting Jucika as a job-seeker trying to prove her qualifications to the titular Matyi and his goose [trope page].

    Looks true, except “change of ownership” is definitely not what happened, Wikipedia says it happened after

    in 1959, Érdekes Újság was merged with the Ország-Világ magazine

    so the party was doing media restructuring, and Lúdas Matyi became the only explicitly satirical periodical allowed (and very popular as a result). This is the first Lúdas Matyi Jucika strip, marking the transition to color. Don’t ask me what kind of contract Pál Pusztai signed or how much say he had, I’m neither Hungarian nor have lived before 2000. And Hungarian is Hungarian to me, the only bits I recognize are új = “new” and ország = “country”, plus Erde is “Earth” in German so perhaps Érdekes Újság is “World News”? (Edit: No, “Interesting Newspaper”) My qualifications are basically just knowing basic research techniques and the xkb Combine key for diacritics.

    See also Wikipedia: Mattie the Goose-boy


    I really like how the boy looks in the third image, reminds me of the 1973 Polish popular math book Przez rozrywkę do wiedzy: Rozmanitości matematyczne (“Science through Fun: Mathematical Curiosities”) by Stanisław Kowal (no illustrator credited so presumably also him), inspired by Martin Gardner, which I’m very nostalgic for as one of my first “nerdy” books.

    I’m sure this was a reasonably common style but I haven’t read that many books from that era that used this kind of printing press so this is the reference you get.

    The book’s not as good as Ian Stewart’s similarly-titled 2008-9 collections, there’s some tedious exercises (optional, obviously, but “here are factorials of 1 to 20, will you please fill out 21-25 if you’re good at calculating” feels like overly cheap content), but the translator did a great job, his notes are like 10% of the text.




  • It’s 18 MB because it’s GIFs, about 16 frames each… at least the palette of is optimized by panel. There is some charm to the dithering as opposed to DCT (JPG/WebP block) artifacts. Also, she only started using WebP in 2021, it wasn’t viable much earlier. Technically, the static background and low-color foreground could be separated (JPG + GIF with very small palette, maybe rotated to compress streaks horizontally (GIF uses basic lossless LZW compression of the palettized image that handles high run length very well); too early for APNG) and overlaid with CSS to achieve about the same signal-to-noise ratio at about one half to one third the size. However, the noise would be different…

    The falling drops that indicate loading of each image are very cool but I wonder if something similar, plus the fade-in of all images at once, could have been done with just HTML and CSS, broadening accessibility to noscript users.


  • There are actually two interpretations of N/A:

    • N/A (not available): There is lost media so it can’t be evaluated.
    • N/A (not applicable): The show is in sign language so evaluating that is outside the scope of this string-matching program.

    Meanwhile, undefined seems to mean the value has not yet been evaluated. Maybe null is really the best.