You can use these expressions when you are not very happy with someone or with the situation.

Example conversations:

A. "Where on earth are my car keys?"
B. "I don't know?"
A. "I think I've lost my car keys. Are you sure you don't know where they are?"
B. "Sorry, but I have no idea where you put them!"

A. "Hello, Maria."
B. "Daniel? Is that you?"
A. "Yes it is, Maria."
B. "How on earth did you get my phone number?"
A. "I looked it up on the Internet!"

A. "What on earth are you doing?"
B. "Sorry Mom, I got hungry, I had to eat some of the birthday cake!"
A. "John, that birthday cake was for your birthday celebration."
B. "Yeah, I know. I just couldn't wait until tomorrow."

A. "Why on earth are those neighbors playing that crazy music again?"
B. "They like having parties."
A. "Well, it's 3:30am in the morning, I can't sleep with that loud music playing."
B. "I'm sure they will finish their party soon. Try to get some sleep."

By Christina

What on earth am I supposed to say here?