meaning of "What on earth"

[Sroth]

Dear Teacher,

Could you please explain to me as the following expressions:

(b) Are they on earth?
(c) Do they live on earth?
(d) Why on earth to?

Thanks

Savath

[Alan]

Hi Sroth,

(b) Are they on earth? This could mean: Have they landed? It would be better to know the context here.
(c) Do they live on earth? This asks the question about whether they live here on the earth or whether they live on another planet.
(d) Why on earth to? The expression: Why on earth? is an expression of surprise or disbelief as in: Why on earth did you paint your car bright pink?

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple

[Sroth]

Dear Alan,

Thanks you very much for your explanation.

regards
Savath

[Usher.fitz]

I'am so enthusiastic to learning this sentences .

thank you.

[Jordano]

I didn't understant the question and the answer.

what do they mean?

They went on strike last week.
why on earth for?

could you explain, please?

[Cleverbarbi]

Thank you so much for the explanation...

[Beeesneees]

[Shopgirl]

"what on earth for ?"
.It means 'why do they doing so?'....simply doesn't connect with the word 'EARTH'
......But many people use this .....well I think this is totally used in speaking CASUALLY . Because I have noticed this sentence used in many English movies.

Am I right Alan??

[Matian]

Means What but you use earth to emphasize,or to indicate your surprise
also
we have why on earth....why?
and where on earth :where?
englishbyidioms.com/american-idioms-expressions/american-idioms-expressions-lesson-4/