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happened such a long time ago . . . Maybe someone picked up a piece of “magnesian” rock on an Aegean coast and noticed the piece of lodestone was peculiar. It attracted a piece of iron, and could change the properties of the iron when the iron was rubbed with the rock. Thales—who lived in Greece about 600 B.C.—studied attractive forces associated with magnets, and a resin called "amber." That started the long history of magnetism and electricity that is still being added to today. It may have been that some Chinese used magnetic stones which pointed northward to find their way through the Gobi desert many centuries ago. The use of a magnetized needle floated on a cork, that has developed into the compass we know today, was a great boon to explorers and markedly changed our world. More recently, the discoveries of new materials—such as ferrites and rare earth magnets—are likely to change our world again. Have you ever wondered about: How magnets work? Why some elements are magnetic and other aren't? How a magnet manages to change things without touching them? This book may suggest at least partial answers to some of these questions. But most likely there will still be more questions than answers, for there are still many things to be discovered about magnets. More work needs to be done. Maybe YOU will do it if you get interested in magnets. That's one of the reasons for this book. Way back in 1734, a Swedish scientist named Swedenborg showed the difference between magnetized iron and unmagnetized iron. And since then, we've discovered a lot of new materials and new techniques. Today there are better sensors for making measurements, and there are computers to help in recording, analyzing, and displaying them. Another reason for this book is to tell you about these new materials and techniques and to show you some magnetic patterns that no one else has ever seen. |