It's funny that I can't even accomplish an emoticon in these comments while some people manage to draw complete scenes or algebraic formulas interleaved with the text.

I must admit that, unlike a lot of HN'ers, I'm using a virtual keyboard on a heldheld device to type comments; I never took the effort of looking up how it is done though it must have to do with extended char sets.

most emoji are banned, as are nonstandard space symbols like thin space and some other things. emoticons (things like :-) and XD) are allowed. generally alphabetic characters and digits are allowed, and some other things, but i think unknown unicode is forbidden by default. https://news.ycombinator.com/item?id=23440551 has some investigation and results which are probably still accurate

i do most of my algebraic formulas with the compose key and a custom compose map mostly written by mark shoulson https://github.com/kragen/xcompose

for the above, after a false start picking random unicode characters, i realized that maybe i shouldn't use a modern language because someone who actually uses the language might feel like i was calling them an extraterrestrial, so i switched to googling archaic scripts. i pasted part of the old permic table from wikipedia

    >>> s = '''𐍐‎    𐍑‎       𐍒‎       𐍓‎       𐍔‎       𐍕‎       𐍖‎       𐍗‎       𐍘‎       𐍙‎       𐍚‎       𐍛‎       𐍜‎       𐍝‎       𐍞‎       𐍟‎
    ... U+1036x     𐍠‎       𐍡‎       𐍢‎       𐍣‎       𐍤‎       𐍥‎       𐍦‎       𐍧‎       𐍨‎       𐍩‎       𐍪‎       𐍫‎       𐍬‎       𐍭‎       𐍮‎       𐍯‎
    ... U+1037x     𐍰‎       𐍱‎       𐍲‎       𐍳‎       𐍴‎       𐍵‎'''
    >>> print(''.join(c for c in s if ord(c) >= 0x10350))
    𐍐𐍑𐍒𐍓𐍔𐍕𐍖𐍗𐍘𐍙𐍚𐍛𐍜𐍝𐍞𐍟𐍠𐍡𐍢𐍣𐍤𐍥𐍦𐍧𐍨𐍩𐍪𐍫𐍬𐍭𐍮𐍯𐍰𐍱𐍲𐍳𐍴𐍵
    >>> len(''.join(c for c in s if ord(c) >= 0x10350))
    38
    >>> permic = (''.join(c for c in s if ord(c) >= 0x10350))
    >>> ''.join(random.choice(permic) for i in range(5))
    '𐍨𐍓𐍰𐍚𐍠'

and then i tried out the hieroglyphs range

    >>> print(''.join(chr(i) for i in range(0x13000, 0x14000)))
    𓀀𓀁𓀂𓀃𓀄𓀅𓀆𓀇𓀈𓀉𓀊𓀋𓀌𓀍𓀎𓀏𓀐𓀑𓀒𓀓𓀔𓀕𓀖𓀗𓀘𓀙𓀚𓀛𓀜𓀝𓀞𓀟𓀠𓀡𓀢𓀣𓀤𓀥𓀦𓀧𓀨𓀩𓀪𓀫𓀬𓀭...
    𓿦𓿧𓿨𓿩𓿪𓿫𓿬𓿭𓿮𓿯𓿰𓿱𓿲𓿳𓿴𓿵𓿶𓿷𓿸𓿹𓿺𓿻𓿼𓿽𓿾𓿿

but realized that most of them were unassigned, at least in my font and probably in the current unicode standard (in case someone discovers a new hieroglyph), so i just did this

    >>> hiero = (''.join(chr(i) for i in range(0x13000, 0x13100)))
    >>> ''.join(random.choice(hiero) for i in range(4))
    '𓃾𓂃𓂌𓀩'

you can do all this in python in termux on your phone too (you'll probably have to install it from f-droid) but it's a bit clumsier

it's funny how this conversation has swung from the extreme of universal constants of the universe to the opposite extreme of completely arbitrary and historically contingent things like which ideograms (themselves completely arbitrary) are prevented from being posted by implementation bugs in hacker news

Exactly a good reason why I love HN comments so much. The off-topic reply is frowned upon.

Thanks so much for this, let's see if copy paste works on this unix derived os. 𓀝𓀞𓀟𓀠𓀡𓀢𓀣𓀤𓀥

i'm glad you liked it!

Oh, they were just random hieroglyphs? I thought you made a tiny cartoon of a man flipping a table.

hahaha, that's awesome! i hadn't even noticed that it sort of looks like that

That’s why we picked water, but water exists everywhere. Earth, the kings foot, 1atm, are specific to the human experience.

most of the non-dark-matter non-dark-energy mass of the universe finds itself in conditions that prevent the existence of water: black holes, degenerate-matter stars, conventional plasma stars, things like that. almost all of the rest is hydrogen and helium, so water exists there in the same sense that uranium exists here. but, although almost all of the universe is cold enough to freeze hydrogen, its vapor pressure is high enough at the cbr that most of it is vapor, so basically none of that is solid. solid objects do have a substantial amount of water in them, although if our solar system is typical, many of them don't

but sure, if it turns out that there are electron-degenerate-gas vortex intelligences on the surface of white-dwarf stars, they could very likely work out some way to launch robotic probes out of the star into places where water could exist, so that they could measure its triple point. and the folks on 𐍨𐍓𐍰𐍚𐍠 use trace amounts of water in their biology (it's a reasonably powerful base) and have isolated it in liquid form in their cryogenic laboratories. it's accessible in a way that the artifact kilogram and artifact meter and the circumference of the earth aren't

> triple point of the ammonia-methane eutectic

Which is a shame that the temperature scale is still anchored in that arbitrary mix, picked by a lazy apprentice. It's also historically base-10, not like the modern systematic base-8 units.

(Can ammonia actually alloy with methane? Their crystalline lattices don't seem to be compatible, and they don't react together.)

i don't actually know. however, the same considerations would suggest that methane clathrates in water are impossible, which turns out not to be true. methane freezes at 90 kelvin, so if there's a eutectic, it would be lower than that.

Clathrates are different, they are not eutectics. If you try to freeze them, they separate into methane gas and water ice.

Metals can alloy with each other because the shared electron layer "glues" small imperfections in crystals where different metals meet. Can frozen ammonia behave similarly? Liquid ammonia can solvate free electrons, so perhaps frozen ammonia also can?

It'd be interesting to actually try experiments with frozen ammonia.

that's a fascinating idea! frozen electrides! it's a lot freezier than methane (195 kelvin, a difference large enough to make a methane eutectic much less likely) to the point where you might even be able to freeze it with convenient and safe dry ice rather than liquid nitrogen. and, i don't know, maybe if dry ice by itself won't do the trick, maybe dry ice mixed with liquid ammonia will. trying to buy anhydrous ammonia around here gets you put on a list, though, so i'm gonna opt out of this one

there are a lot of solvated ionic eutectics with atmospheric-pressure water ice, despite the absence of metallic bonding