Philip Pullman's His Dark Materials trilogy is renowned for its mystery and magic. What's the truth behind it all? Is the golden compass actually based in science? How does the subtle knife cut through anything? Could there be a bomb like the one made with Lyra's hair? How do the Gallivespians' lodestone resonators really work? And, of course, what are the Dark Materials? Drawing on string theory and spacetime, quantum physics and chaos theory, award-winning science writers Mary and John Gribbin reveal the real science behind Philip Pullman's bestselling fantasy trilogy in entertaining and crystal-clear prose.