[General] why on earth or what in the world.

[arjitsharma]

I would like to know the meaning of the following?
1. Why on earth did you accept his challenge?
2. What in the world did you say that?

 

[J&K Tutoring]

Your #2 is incorrect. It should be either:

a. What in the world did you say?

b. Why in the world did you say that?

 

[GoesStation]

On Earth and in the world are intensifiers in these phrases. Why did you do that? can be said more strongly by inserting either phrase after Why.

You can also use them to intensify a what question.

 

[Raymott]

I'll add that another common intensifer here is "Why the heck* did you do that?" or "What the heck did you do that for?"

*'Heck' is a bit old. It's used to avoid "What the hell" which offends some people, and 'What the f***", which I would advise everyone to avoid. But you probably should know what 'WTF' means, since you can't avoid seeing it on the 'net. By itself, this is used as an expression of surprise, outrage, etc. In a sentence, it means the same as above. I don't like any use of the 'f***' word, and am only writing this for comprehension purposes.