Fetching details from the dictionary...

sky; the air; the heavens
weather
far-off place; distant place
state of mind; feeling
(from) memory; (by) heart
falsehood; lie
somehow; vaguely
fake
「空」 has other readings with different meanings.
今日の空はきれいだ。
Today's sky is beautiful.
空が崩れて雨になった。
The weather broke and it started raining.
故郷の空が時々恋しくなる。
Sometimes I miss the skies of my hometown.