It had an illustration that captivated him–a diagram showing Earth’s interior as it would look if you cut into it with a large knife and removed about a quarter of its bulk. The idea of lots of startled cars and people falling off the edge of that sudden cliff (and 4,000 miles is a pretty long way to fall) was what grabbed him in the beginning, but gradually his attention turned to what the picture was trying to teach him: namely that Earth’s interior is made up of several different layers of materials, and at the very centre is a glowing sphere of iron and nickel, as hot as the Sun’s surface, according to the caption. And he very clearly remembers thinking: “How do they know that?”Bill’s storytelling skill makes the “How?” and, just as importantly, the “Who?” of scientific discovery entertaining and accessible for all ages. He covers the wonder and mystery of time and space, the frequently bizarre and often obsessive scientists and the methods they used, and the mind-boggling fact that, somehow, the universe exists and against all odds, life came to be on this wondrous planet we call home.