Why is the Earth magnetic?
• –Why does the magnetism of the Earth slowly change–unlike that of a bar magnet? • –Why are sunspots intensely magnetic–when their temperature is so high that they must consist of hot gas? • –Does the faint magnetization of volcanic lavas faithfuly record the magnetic field at the time they cooled? And if so, what about lavas which seemed to tell that the north and south magnetic poles were once reversed? • –Is it just a coincidence that South America and Africa fit together, like jigsaw puzzle pieces? How can magnetism help find the answer? And some questions you will find on the web site, but won’t be discussed here: • –How do satellites measure magnetic fields–even ones 100,000 weaker than those observed on the ground? • –Are any other planets of the solar system magnetic? Here only some ideas can be outlines, but you will find much more material on the web site, and many more stories. Why is the Earth magnetic? Gilbert thought magnetism was an inherent property of the Ear
