What would happen if you jumped into a tunnel that went straight through the center of the Earth? That's exactly what Worry is about to find out! Her sister Hope has been kidnapped by a dragon and Worry is determined to bring her home. To do so, she'll travel from the center of her planet to the surface of a nearby moon, learning about gravity with help from the echoes of Aristotle, Kepler, Galileo, Newton, and Einstein. A Fairy Tale is part of the Fairy-Tale Physics series. Each book begins with a story and includes explanations of the real-world physics for anyone who’s curious. With over 35,000 copies sold worldwide, the Fairy Tale Physics series weaves foundational physics concepts into whimsical fantasy adventures for ages 10-12. Written by a 20-year physics educator with degrees in physics and cognitive psychology. Topics Newton’s Law of Universal GravitationCircles and EllipsesHow Orbits WorkTides and Planetary MotionPendulumsLogical Reasoning and SyllogismsA Short History of Gravity, from Aristotle to Einstein