"Nothing is happening."
Translation:Er gebeurt niets.
I wouldn't use it in written form, but this is used when speaking, with a clear emphasis on niets.
It was rejected. I will report it, in case you want to add it as an alternative.
It's an indefinite subject, thus you require the Er. An indefinite subject just means it is not specific, so iets and niets are both in this category. Additionally, as to why at the beginning of the sentence, when you have an indefinite subject, you put the Er at the beginning of the sentence.
Why can't niets be the subject? Is er absolutely necessary in this sentence?
I think "niets" is the subject here. As to "er", think of "There is nothing happening". In English, "there" is optional. In Dutch, it isn't.
Except that niets is in the predicate both in the Dutch sentence and "There is nothing happening", and the subject can't be in the predicate. (In your example "nothing" is a predicate nominative, which refers back to the subject, but is not the subject.)
Don't understand "predicate". You must be a grammarian. I'll take your word for it.
It is still the case that "er" is required.
"Predicate" is simply everything that comes after the subject (hence why it can't include the subject).
I've done a google search for "niets gebeurt" and nearly all the hits seem to have "er" in the clause. I understand that niets can't be the subject, but my question is still why it can't be the subject.