New, revised edition of the world's superbestseller, based on materials from one of the most famous popular science sites of all time. Randall Munroe - a NASA engineer, scientist, artist and creator of the incredibly popular Internet comic xkcd.com - is trying to find serious answers to the most incredible questions that visitors to his site send him. It turns out that the most serious scientific problems can be said easily, and the most difficult things can be explained clearly. If you love science, comics and the internet - this book is for you.