"What if there was no star in the sky?" does not sound particularly weird, and we can find instances of people using that exact phrase. If we focus on the key aspect of that statement, "no star in the sky" appears to be commonly used.
But if someone says “There was no star in the sky,” I parse that as something like: An astonishingly dark night, I searched the sky quite carefully and found not even one star.
Meanwhile I parse “no stars in the sky” as: a very dark night, I didn’t see any stars.
Of course really, it is always a matter of degree technically, right? The stars are always there. They are just sometimes attenuated to the point where your eye doesn’t detect them.
If I said "There is no star in the sky", are you going to be unclear about what I am trying to say, yet understand me perfectly if I said "There are no stars in the sky"?
I disagree: The most-charitable scenario I can think of is that someone has context-shifted from regular "stars" to "our sun, Sol, which is technically a star even though we typically consider it separate from the rest."
In other words, it involves a situation where someone is assuming the amount is capped at 1. (Yes, I know binary stars exist.)
Compare:
* "What if there was no star for Earth to orbit?" [Works because =1 is the normal assumption in this context]
* "What if there was no star in the night sky?" [This is weird.]
* "What if there was no constellation?" [This is also weird.]
With what? English is defined by use, and we can find untold examples of "No star in the sky."
"All birds have eyes" != "All things that have eyes are birds."
My hypothesis is that wherever we speak about "zero" and some quantity, it seems like we can substitute "no", and the pluralization rules we'd use for "no" are being inherited.
In contrast, it sounds like you're going the opposite direction, starting with sentences that contain "no" where we cannot drop-in "zero". For example, "No star in the sky is green" cannot become "Zero star in the sky is green."
Without a full understanding of the intent and background behind that statement that is not clear. It might be disprovable under some circumstances. If we take it to the logical extreme, the words absolutely could be defined such that it is disprovable, so it obviously could be.
Is that likely? In this case, probably not, but it becomes more likely when there is more fractured use. Consider tech jargon. The marjory of the discussions on HN are parties talking past each other because they came with different understandings of what words/phrases mean.
> "No star in the sky is green"
I wrote "No star in the sky<period>" to try and steer us away from different contexts. While I acknowledge that such usage also exists, that is outside of what I was trying to refer to and I think you will agree that in your interpretation that usage is not in line with what we are talking about.
Such is the downfall of languages made up on the spot as they are used. All you can do is try and convey something to the recipient, and sometimes you'll fail. This ended up being a great example of exactly what we're talking about!
While English is defined by use, that doesn’t mean that all forms of slang automatically become grammatically correct.
For example: “no star in the sky” might be common vernacular in some regions but it wouldn’t be appropriate to use in formal writing. It’s also not a phrasing I’ve encountered before.
But the original example was "What if there was no star in the sky?" so your example is irrelevant. The original example sounds weird (to me, a native speaker). But "No star in the sky is a triangle" sounds OK and contains your example phrase.
"What if there were no stars in the sky?"
Note that not all native speakers of English use or prefer this type of construction. Also, this use of "were" instead of "was" is sometimes now called irrealis and considered separate from the subjunctive (which is then used to refer only to constructions like "it's important that you be here early tomorrow").
At the end of the day there is accepted grammar and there is actual usage.
If you ask people for the accepted grammar they will give you something most people accept. Which is not "What if there were no star in the sky?"
The Three Wise Men are back. But this time, there's no star in the sky to guide them.