Book excerpt: From ancient times, people have wanted to learn about the sky. The stars, planets, and other heavenly bodies have been observed for centuries, and theories have changed as the equipment used has improved. Though we now know that the Sun is the center of our solar system, and planets and other objects move around it, we still have a lot to learn. What is a comet made of? Why is Pluto now called a dwarf planet? What causes a solar eclipse? A lunar eclipse? This book will help you answer these questions and more. Whether you try the experiments and activities in this book for fun or for a school project, you’ll discover why so many people are fascinated by our solar system.