Is the passive or impersonal "se" being used in "Todavía no se sabe cuán grandes serán las pérdidas"?

Question

I'm struggling with the impersonal "se" vs the passive "se". In the following sentence:

Todavía no se sabe cuán grandes serán las pérdidas

is it the passive or impersonal "se" that's being used?

Answer 1

This is an ambiguous case.

We know it can be impersonal because of we replace se sabe with alguien sabe or unos saben the sentence makes sense.

We also know it could be passive because we can replace se sabe with es sabido and it still makes sense.

Since both mean, in effect, the same thing, I wouldn't stress over the difference.

Answer 2

As I point out in a comment, the key is "try to rephrase it" as a paassive. If you can do it, then stick to it.

My old teachers warned me that impersonal "se"'s are quite rare, while passives are actually the most common ones. In fact, the passive structure is more commonly used with "se" rather than with the verb "ser".

Answer 3

It is an impersonal se, no specific person is refered on the sentence.

Look how the verb sabe is used as third-person singular of saber. No se sabe: Who? People in general. Nadie lo sabe (Nobody knows it)