Now, the VOA Learning English program Words and Their Stories.On this program we explain common expressions that we use in everyday life.The world celebrates Earth Day every year on April 22.It is a day to think seriously about how our lifestyles and daily habits affect the earth.Well, today we celebrate our shared Mother Earth with a show about earth expressions.To which, you might say, "What on earth took you so long?!"Well, we think every day should be earth day!So, let's start with the simple yet common expression on earth.We use "on earth" to make strong feelings like surprise, shock, anger, disgust even stronger. And we use it a lot.Here are some examples.How on earth am I supposed to read this entire book in one night?What on earth are you cooking? It smells awful!Why on earth didn't you come to the party? It was awesome!I did not know what on earth she was talking about.