With his popular Getting Started in Electronics, and Engineer's Mini-Notebook series and a number of different electronics kits sold at Radio Shack, Forrest Mims inspired countless scientists and engineers. Even though he received no formal academic training in science, Forrest has appeared in 70 magazines and scientific journals. He has worked as a consultant for the National Geographic Society, the National Science Teachers Association, and NASA’s Goddard Space Flight Center. Today, Mims works on many scientific projects including climate change research. He's agreed to answer all your questions about science and engineering. As usual, ask as many as you'd like, but please, one question per post.