Thanks for the answers,guys,you have answered everything but the question which was what is the word for questions which nobody can answer.
The chicken and egg question was just an exampleof the kind of question.Though personally I think the answer to that question depends on whether you take a creationist or evolutionary approach.
chickens have been coming out of eggs for a long time. But at some point it wasn't so much a chicken as some kind of dinosaur-type chicken ancestor, just as we had our own ancestors who hadn't yet developed into humans. But the egg was still the means of delivery, so the egg was first.
A chicken is only an egg's way of making another egg.
The answer is paradox, or even "catch 22"
Like the unemployed vagrant who could'nt get a job without accomodations, and could'nt get accomodation without a job.
Or even the flea in the centre of a circle, he jumps 1/2 way to the edge, and keeps jumping 1/2 the previous distance, always moving foreward... never reaches the edge.