"Below zero degrees?"
Translation:מתחת לאפס מעלות?
Of course, but מתחת matches the English sentence perfectly so it should definitely remain the preferred answer.
Note, however, that פחות takes a different preposition to מתחת. The former takes מ and the latter takes ל. So the sentence would be פחות מאפס מעלות?
Probably in part because the value is represented by אפס and the intervals along the scale against which it is located or compared (as in talking a measurement) is represented by מעלות. Also, it's an entrenched, conventionalized pattern to ask for example how many degrees something is (on a given scale), so that might factor into using the same form or construction is used in communication specific measurements. Finally, like airlibre said, although we might say "one degree" the notions of אפס and zero are somewhat peculiar and unique (compared to other values). Many other things like mass nouns and mass noun construals can have interest exhibit interesting patterns as well.
I have no freaking idea. Zero is not a plural word so I would expect it to come with a singular noun. Do you say מעלות no matter if it's 0, 1 or 25.5 degrees?
Zero is not a singular word either. It's a funny customer, but in all the languages I know that have plurals, it uses the plural.
One degree = מעלה אחת same as in English.
This is really crazy, what you write seems to be true and I just can't find out why. Zero is of Arabic origin but it was originally an adjective. My only guess is that this is because it is allegedly an even number. Maybe this use found its way to most languages due to a strong lobby of mathematicians, who wanted this to be reflected.
I like how you think, but no: it has nothing to do with zero being even. The reason is that plural doesn't mean many, but not singular (or not any of the numbers the language already marks, like dual, trial or paucal). Most times, plural matches perfectly with the meaning of many, but it also marked fractions before the existence of the idea of zero.