It's the biggest thing in the night sky, so it's no surprise the moon appears in many English expressions. Here are a few examples. If someone says they "love you to the moon and back," it means they love you very much, because their love is as large as the distance between the Earth and the moon – an average of 384,000 kilometers. This expression is used in Guess How Much I Love You, a 2008 children's book by Sam McBratney. It's usually said to romantic partners or people in your family. If someone is talking "moonshine" it means they're talking about something that isn't real or is foolish. But more often someone will offer you a drink of "moonshine," which is a word used in the US for illegal liquor. If something doesn't happen very often, it can be said to only happen "once in a blue moon." A "blue moon" isn't really blue – it's either when a second full moon is seen in the same month, or the third full moon when four full moons are seen in the same season. Both types of blue moon don't happen very often, only about once every 2.7 years.