Suppose this is the original meaning, not strictly in the context of ambient occlusion though in general. Compare "edge case".
Ironically though, with division by zero for example, it's more of a center case.
Not to ruin a joke, but I wonder how far back this figure of speach goes. "extremum" is rooted in Lt. "exter", superfixially "ex-" + "-ter", with "ex-" derived from (reconstructed) PIE h1eǵhs or eḱs (out) [1] and "-ter" comparable to "inter". The derivation of "-ter" is uncertain and the whole reconstruction effort is a bit like reading tea leaves (oracles may follow strikt rules, too, you know). I'm going to go all out on a limp and suppose eks is related to h₂eḱ- (sharp), whence "edge" and Ger. "Ecke" (corner); And to h₂eḱs- (axis, axle), proabably related to h₂eǵ- (to drive) [to go out?]. IMHO it's most likely sound immitative of cutting, hence sec, ex, hack, axe, adze and so on. Suppose initially the problem was really a corner where it shouldn't be. Then what are you supposed to be doing? Cutting corners!
h1eǵhs can't be related to h2eǵ-, since the laryngeals and plosive phonations are different. The plosive phonation distinction isn't as relevant here as the laryngeals - for one thing, the reconstruction h1eǵhs isn't certain, even by the Greek evidence - but the numbered laryngeals were entirely different consonants, which only form a class insofar as they all disappear in non-Anatolian IE. (Well, probably. Word-initial h1 may have been preserved in some cases in Albanian, and word-initial h2 may have been preserved in some cases in Iranian. HC- -CHC- can be reconstructed by the Greek and Armenian triple reflex (e.g. *h2ster on the evidence of Greek ἀστήρ and Armenian astł), but laryngeal loss probably occurred in the late IE period, after the beginning of the development of dialectal innovations like that and, if you buy it, Cowgill's Law in Germanic.)
If it helps, you can use Kortlandt's values for the laryngeals: ʔeǵhs, χeǵ.
The -ter suffix in "inter" and "exter" (of which "extra" is an ablative form) could be from the comparative suffix -teros. Wiktionary thinks this is true of "exter" but not "inter", I guess because cognates of "inter" are more widespread (although it could be a loan in Albanian, but probably not Indo-Iranian) - so it could've spread from there to "exter" by analogy, or influenced the comparative form.
There are competing laryngeal theories but the truth is, currently, the symbols are just placeholders. -ter is interesting, but doesn't matter much.
> can't be related to h2eǵ-, since the laryngeals and plosive phonations are different.
I didn't wanna mention it, because there's no end to it, and leaning on the alternative reconstruction, I chose to ignore the difference. But you are welcome to tell me more about it--Running down the list of confirmed sound laws for PIE should be real quick. There are none, as far as I know. You can't deduce from this alone that the language was stable. So I wonder on what you base your assumption.
Well, there are rules concerning composition, and no Consonant the same in CVC except perhaps in one rare exception (ses - sleep). But that's far from exhaustive.
There's really too little known to say anything definite. Semantic speculation could help a huge deal, but of course linguists are biased towards phonetics, to the degree that comparing axe and ex could be humoured to sound nothing alike. Often times they are right. That makes them narrow minded. Of course I would need to know that better to argue with it.
> If it helps, you can use Kortlandt's values
There are competing theories. Although I used to ignore laryngeals, German dialects know so many different realisations of "ch", that I think I'm good, thank you (ach echt, kiek ma, ick dachte du brochst noch en Beispiel: woher kommt "auf dem Spiel stehen"? Vielleicht von Spiegel [Notenspiegel, Tagesspiegel, etc.] > Spieyel, Spie'l; Spiggel, spick, spec- peck pickel picture). It's very similar, ch after a, o, au or u it's rough, after e, ei, eu or i it's soft, but this varies with dialect (it's all rather rough in swiss, ch or not); g can be velar (geben or yeben, fällig or fällich; some dialect even says elektrich, but elektrisch is standard) etc etc.
I have Pacht pächter down for *pHter (father), that would be a surviving laryngeal ... Acht, ächten? So yeah, pinch of salt and all.
Are there any probable cases of laryngeal alternation? I'm not aware of any. Radical consonants (which the PIE laryngeals probably were) can be stable under certain conditions and unstable under others - they seem to be less stable in Germanic than in Semitic or Northwest Caucasian, although Germanic /k/ is stable... but Polynesian /k/ isn't. IMO the best guess at this point is that the PIE laryngeals were stable until they disappeared
Confirmation in historical linguistics is probabilistic. Sound laws can't be demonstrated the way "the sun is up" can be, but there's a great deal of evidence for Grimm's and Verner's Laws, less evidence for Cowgill's, and even less for things like the "pibati rule" or h1 preservation in Albanian. (I'm skeptical of the pibati rule - the root is irregular in some branches anyway, and it could be dissimilation or an exception to the loss of b or something.)
The root composition rules are a little more complicated than that - you can have TeT or DheDh, but not TeDh, DheT, or DeD.
Laryngeal preservation in Germanic is a pretty extraordinary claim. Are there other cases of this?
The big idea is tracing the roots of language to ancestors.
It's historical, comparative linguistics. At least for me, this is just an intensive hobby.
There's an intersection with CS in computational methods, which, is IMHO severly lacking, or better to say, rather promissing, because semantics was intractable, so far. There's a lot of exiting development in NLP, of course. Categorical Semantics gives it an algeabric underpinning ... so the whole thing ties back in with the featured article.
Most of the computational methods stuff I see in historical linguistics is about trying to put a computational gloss over lexicostatistics, which I don't think is a very promising field. Preliminary surveys of probable family groupings are one thing, but unless sound correspondence identification can be automated, I don't think the later stages of classification can be aided much by computational methods. You still want regular phonological and morphological correspondences and, ideally, shared irregularities (good/better ~ gut/besser, that sort of thing), and I'm not sure what computational methods could do for that.
But there's really a lot to do in the preliminary stage, although it isn't always obvious. I'm still seeing classifications of Papuan languages that go entirely by their pronouns, the historical map of Africa is being redrawn (to clear out the overly enthusiastically lumping Greenberg classifications), and there are probably a few more chunks to be torn off Sino-Tibetan, which could... maybe be identified by throwing computers at word lists?
It's too bad language family proposals don't come with epistemic status markers.
