Breakdown of В этом музее нельзя фотографировать.
музей
museum
этот
this [f: эта, n: это]
в
in / to (direction)
нельзя
one must not
Questions & Answers about В этом музее нельзя фотографировать.
Why do we use the imperfective verb фотографировать with нельзя here instead of the perfective сфотографировать?
This ties into the core rule for нельзя. When you pair нельзя with an imperfective verb, it means the action is prohibited or against the rules (taking photos is forbidden). If you used a perfective verb, it would mean the action is physically impossible to achieve (for example, it is impossible to capture a photo because it is too dark).
Why is it В этом музее (Prepositional case) instead of В этот музей (Accusative case)?
We use the Prepositional case for static locations to answer the question "where?" (Where are photos forbidden? In the museum). You would use the Accusative case (в этот музей) if you were talking about motion or direction toward the museum, such as "We are going to this museum."
There is no "it" or "you" in the Russian sentence. How do we know who is forbidden from taking photos?
Нельзя is an impersonal word. Without a specific person attached, it applies to everyone in general, which is why it translates perfectly to "It is forbidden." If you wanted to specify that a particular person isn't allowed to take photos, you would add them in the Dative case (for example, Ему нельзя фотографировать means "He is not allowed to take photos").
Could we change the word order to Нельзя фотографировать в этом музее?