If it were physically possible to fold a piece of paper forty-two times, its thickness would reach from the Earth to the Moon.
Why it is true
Each fold doubles the paper's thickness. This exponential growth means forty-two folds would result in a stack over three hundred and eighty thousand kilometers high.
Source: Mathematics Physics
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.