Book excerpt: An inquiry into the limits of the possible. Our problems on Jupiter, Mercury, Venus - conquering Time - transport in the future - overcoming gravity - communications across space - benevolent electronic brains. The range of this enthralling book is immense: from the re-making of the human mind to the vast reaches of the universe. Newly revised, even the remarkable events of the last decade have affected few of the exciting speculations by Arthur C. Clarke - a scientist whose expert and wide knowledge is matched only by his brilliant imagination.