Did you know that Earth is zooming around the Sun at about 66,000 miles per hour (107,000 km/h)? Or that Earth's crust is made of giant pieces that fit together like a jigsaw puzzle? And did you know that there are huge mountains under the ocean, and enough salt in the oceans to cover the whole Earth with a salty layer as high as a 50-story building? These and dozens of other fascinating facts provide a perfect high-interest introduction to the...