短语 to ask for the moon 直译是要天上的月亮，实质意思是说某人提出过分的需要，想要得不到的东西或是想做办不到的事儿。
例句
Bobs wife is always asking for the moon. He works hard 12 hours a day for poor pay, but she still expects expensive holidays and clothes.
Dont ask for the moon, Mr Jones. Be reasonable, please.
请注意
短语 to promise the moon to someone 的意思是向某人答应做不到的事儿，也就是汉语里常说的空口许愿。
例句
My husband promised me the moon when we got married: a big mansion1, a flashy car and all the diamonds I could wear. But none of it happened!
今日小知识
The Apollo missions between 1969 and 1972 returned over 380kg of rocks from the Moon, which have been used to help us understand its origins and structure.
从1961年到1927年，美国的阿波罗计划从月球上取回了380多公斤的岩石标本。这类带回来的标本对研究月球的由来和架构有非常大帮助。