robryk @robryk@qoto.org

The Book of All Skies (https://www.gregegan.net/ALLSKIES/AllSkies.html) seems to be a novel about, a.o., fundamental groups.

TIL that the United Kingdom has the notion of an appeal in a criminal case that will not affect the outcome of _this_ case.

> Where a person tried on indictment has been acquitted on all or part of an indictment, the Attorney General has the discretion to seek the opinion of the Court of Appeal on a point of law which has arisen in the case. The procedure is to clarify the law. It is not a means to change the outcome of the individual case.
-- https://www.cps.gov.uk/legal-guidance/criminal-justice-act-1972-attorney-generals-reference-point-law-under-section-36#principle

@welshpixie The case of Spanish flu again...

https://en.wikipedia.org/wiki/Spanish_flu says:
> The pandemic broke out near the end of World War I, when wartime censors suppressed bad news in the belligerent countries to maintain morale, but newspapers freely reported the outbreak in neutral Spain. These stories created a false impression of Spain as the epicenter, so press outside Spain adopted the name "Spanish" flu. Limited historical epidemiological data make the pandemic's geographic origin indeterminate, with competing hypotheses on the initial spread.

@Paradox @timorl

Also, electricity does _not_ flow readily. A battery is essentially an charge pump with a chemical power source.

@Paradox

> I can't imagine there are very many people, even on fedi, that have experimented with this, so I'm kinda impressed you found this. (unless you follow wizz or chjara and I don't know)

Blame @timorl :)

> My ultimate concept is going primitive technology with a computer, as close to a modern one as possible. If time was no object, I could certainly replicate one, even given I only barely have a Master's in CS. However I would likely only have enough time to make something much simpler.

There are some computer architectures that are extremely simple on the hardware side and annoying but possible to program for. I have misplaced a description of one such, might find it later.

> I don't like the idea of using gravity because I'd eventually need to pump it back up to restore energy.

Your computing device will be losing energy to heat. You will need to supply energy to it. I have no experience with the free-air gates, which operate at ~atmospheric pressure (because gate outputs are at atmospheric pressure at the height of the gate: water is pushed into them purely by gravity), so in their case having a bucket that you need to keep filled just above the machine seems like the easiest solution. In setups where gates are fully enclosed you are much more free to choose supply pressure and it's generally useful to use higher supply pressures (you can make the device smaller, esp. all the connecting hoses/pipes can be thinner because you can tolerate higher pressure drop along them). While whatever you construct will have a _range_ of operating pressures, the pressure that matters is the difference between source and outflow, and you can increase outflow pressure by clamping the outflow hose a bit if need be. So, I just made a shower barb adapter and used water at our supply pressure (~4ata).

@Paradox @wizzwizz4 @chjara@mk.absturztau.be

There are multiple ways. Note that to build a computing machine you need both logical operators *and* an amplification setup (usually double negation can serve as an amplifier), because you need deep logical expressions. You also obviously need to have a way to pass signals with a well-defined symbols (usually just two). If you want to have an actual computer, you also need to have memory; usually that can be arranged by doing the same feedback loops that SRAM uses (e.g. https://commons.wikimedia.org/wiki/File:SR_Flip-flop_Diagram.svg), so usually gates are sufficient to construct that.

One approach is to define flow of water/fluid as one symbol and lack of flow as another. Then you can have free-air gates like https://en.wikipedia.org/wiki/Fluidics#/media/File:Fluidic_AND_XOR.svg.

In the same setup, you can use constructions such as a modified version of https://en.wikipedia.org/wiki/Fluidics#/media/File:Fluidicamplifier.svg to get logical gates without relying on free-air streams and on gravity. This allows you to have a wider range of pressures, which helps if you are forced to have long or thin pipes.

Another setup (that I know very little about) is to have constant flow of water and distinguish symbols by overlaying a vibration on top. The advantage is that the total flow is roughly constant over time, which makes "water supply" simpler.

Yet another setup that can work at very low scales, is to have constant flow of fluid and indicate symbols by different patterns of bubbles in the liquid stream. There are very ingenious ways to combat desynchronization, and to make a memory cell that keeps its state across a water flow outage. See http://cba.mit.edu/docs/theses/08.09.Prakash.pdf for lots of details.

The search term for all this is "fluidics". You'll find not only digital logic, but also (maybe even predominantly) analog logic. There are for example very simple purely-fluidic angular rotation rate sensors (that rely on Coriolis effect), and many effectors are anyway actuated hydraulically. That, a.o., once made fluidics very attractive for closed loop control systems in aircraft (at the time when electronics were less reliable).

Note that fluidics includes systems that work with other fluids, in particular with air. For example, https://www.technologyreview.com/1997/02/01/41630/kosher-sound/ is a (very abstruse) example of a fluidic system that uses just air.

I've tried reproducing fluidic amplifiers (or rather, generators) in water. I've managed to get oscillations of frequencies that I did not expect and put the project on hold because I didn't really have a good way to measure the resulting signal (I wanted to target low acoustic frequencies, both because I wanted the device to make sound that can be heard and because this is the range which is practical to design oscillators for while keeping all the pipe lengths shorter than 10m).

@kmic Czemu to dziwne? Jest dużo substancji, które w dużej koncentracji są szkodliwe, ale w mniejszych są bardzo powszechne w przyrodzie. Jeśli np. wylejesz popłuczyny z popiołu drzewnego (uważając, żeby się nie sparzyć), to być może zabijesz trochę roślin naokoło, ale nie spowodujesz żadnej długoterminowej szkody -- w końcu to jest coś co się naturalnie pojawia podczas deszczu po pożarze lasu.

@kmic

https://en.wikipedia.org/wiki/History_of_cancer_chemotherapy#Beginnings

@schlink "correct horse batttery staple no really" is a password one gets from that list. If one gets that password, does that not mean that they get 0 entropy?

@freemo

The book you mentioned (https://www.worldcat.org/title/on-looking-eleven-walks-with-expert-eyes/oclc/820149011) has a very interesting premise: let's see what people with different expertise see in places that we usually see every day. I've only started reading it, so don't have an opinion on execution yet, but I love the premise.

@timorl who might also find it interesting.

TIL that in an ideal gas speed of sound does not depend on pressure (for a fixed gas, it depends only on temperature).

@timorl

This is a weird bug:

https://en.wikipedia.org/wiki/Template_talk:Convert#Weird_behaviour_when_target_unit_is_specified_as_1

https://en.wikipedia.org/w/index.php?title=Vananui&diff=1057305451&oldid=986493280

@icedquinn @freemo @timorl It does help in ways in which code review doesn't, due to orders of magnitude shorter round trip time.

@izaya @stux @freemo

Hm~ I'll need to look up examples of materials used for high-temperature pipes. I had a baseless impression that they're always metal (well, not completely baseless -- they need to be flexible or to have very small thermal expansion coefficient).

What kind of rules you'd want to lawyer? My impression is that the temperature of the coolant is limited by the temperature the device being cooled can handle. Ah, we could try pumping heat from the device into the coolant, thus increasing the cooling power (because coolant's hotter), while paying some penalty in having generated some additional heat (because efficiency of heat pumps is thermodynamically limited)? Thanks, I'll need to think about it.

@izaya @stux @freemo

Sure, but you still need to pump it through the device you're cooling, so you still need pipes that can withstand the operating temperature of your coolant.

@freemo If you're looking for a solution, LibreOffice can handle docx files (both for reading and writing).

@izaya @stux @freemo

Wikipedia doesn't say anything about water droplet radiators behind able to handle higher temperatures. I also don't understand how would that be possible: the liquid, before being sprayed has to be pumped through pipes, so we need to have a material that can withstand that temperature (and I naively expect that adding the "has reasonably high thermal conductivity" requirement doesn't narrow things that much; does it?).

@freemo @stux

Actually I forgot one "spacecraft": Apollo portable life support backpack used a sublimator. I _think_ all the spacecraft I mentioned previously used evaporators, but am less sure than previously (esp. about the LM, which had to support very low power levels). Funnily enough, in some cases the evaporator (or the steam piping from it) actually had an electrical heater to prevent freezing.

Apollo CSM, late Gemini, and Shuttle had an overabundance of water (because they were powered by hydrogen-oxygen fuel cells), but that water had to be condensed from steam first, so the evaporator was essentially part of "negative heat storage" system. Apollo LM was constrained to a very short period of operation by many other constraints (e.g. the descent engine would become inoperable IIRC 72h after it was first used, and something like a week after launch).

@freemo @stux

You can also evaporate something (but only as long as you have something to evaporate). Surprisingly many spacecraft used evaporative cooling at least sometimes (Gemini had an evaporator that seemed to have been used at low flow continuously, Apollo LM was cooled purely by evaporation, Apollo CSM had an evaporator to allow higher heat rejection rates than by radiators alone and as the sole way to dispose of heat after the SM was gone, Shuttle had an evaporator to cover high heat load intervals and, I assume, to help in the case the payload doors won't open).