Every child goes through a phase of asking embarrassingly simple questions. Why is the sky blue? Why do we dream? Where did the Moon come from? Even the most educated adult can be stumped by such inquiries. But the curiosity behind them - and the urge to satisfy it - lies at the heart of science. This compendium of questions and answers is based on a weekly column first launched in The Independent more than 15 years ago under the rubric "Technoquest."