"To look at" and "to see" are distinct in English (and in Russian). If I say that I see something, that simply means it appears somewhere in my visual range. On the other hand, if I say that I'm looking at something, it implies intent on my part -- I'm actively tracking it if it's moving, or I'm focused on it if it's stationary.
I was thinking the same thing - but with a reversal of the connotations (or nuances of meaning) attached to the words. I can look at something - have it be in my view - but not actually see it. Seeing implies some sort of particular recognition or even comprehension of the thing being looked at.
Example (Husband and wife talking):
"Honey, I can't find my car keys."
"They are on the table next to the door."
"I'm looking there right now, and I just don't see them."
Spouse comes into the room, walks up to the table and picks up the keys, which were in plain view, saying, "You were looking right at the keys. Why couldn't you see them?"
In particular, you can ask (or order) someone to look at something or look in a particular place or in a particular direction, but you cannot ask/order that person to see something, because seeing requires some sort of mental connection, while looking is simply a physical act.
"Don't you see?" is sometimes synonymous with "Don't you understand?"
It really depends on context. In the case of looking for something, see and look at do have those connotations.
However, in the case of viewing a scene, they are as the previous poster mentioned. I can be looking out at the ocean and see - recognize - a certain boat on the edges of my view without directly looking at it - tracking it.
Is Что invariable? It seems like a special instance in the universe of grammar, occupying usually what one would call an "interrogative" rather than a "noun", hence is not subject to declension.
That makes natasha.jensen42's question more pertinent. I suppose the lesson about Accusative is that что doesn't change even if it appears to be used as if it were a direct object. I question whether it is actually a direct object, since it's more an interrogative here.
The conclusion I reached was that this sentence has almost zero connection to learning about Accusative. Any thoughts on that?