Translation:The sky is big.
I think hiroi is actually wide. So far I've only seen it used with features at ground level.
It sounds like a colloquialism. I've seen references to a large sky before, so that may be either the normal Japanese usage or at least a poetic expression.
Agree. I assumed it was the kind of reference one makes when we might say "you don't say" when someone has stated something very obvious. Not sure but assume that unless I learn otherwise.
I thought of it as more of a statement on the weather type of thing. Like saying, "It's a beautiful day!" Well, yes, and the other person already knows that it's a nice day. But we say it anyway because it's part of the social lubrication that moves society along.
The exercise where you just get to listen, and have to write by yourself (you don't get the english translation, but just have to go by sound), kanji isn't accepted for some reason. Have to use hiragana for my whole solution. Can't report for "My solution should be accepted either".
Montana is also called "Big Sky Country." It's uncommon, but the phrase is also known in American English.
With respect adjectives are not tied to specific nouns. The sky is huge, large, vast, immense, enormous, big etc. All are correct according to speaker preference.
There are, however, certain collocations that are more natural than others.
It's only what you are used to yourself which makes other sentence constructions sound odd or unnatural. Even within England, a small country we can see this differ sometimes from one county to another.
Now to figure out how to say "space is bigger"
Or maybe it's worded as "more big" in Japanese. (I'll find out one day)