Magnetic rotatory dispersion in transparent liquids

So how much do we know about whatБЂ™s inside the Earth? Very little. Scientists are generally agreed that the world beneath us is composed of four layers-rocky outer crust, a mantle of hot, viscous rock, a liquid outer core, and a solid inner core.[28] We know that the surface is dominated by silicates, which are relatively light and not heavy enough to account for the planetБЂ™s overall density. Therefore there must be heavier stuff inside. We know that to generate our magnetic field somewhere in the interior there must be a concentrated belt of metallic elements in a liquid state. That much is universally agreed upon. Almost everything beyond that-how the layers interact, what causes them to behave in the way they do, what they will do at any time in the future-is a matter of at least some uncertainty, and generally quite a lot of uncertainty. Even the one part of it we can see, the crust, is a matter of some fairly strident debate. Nearly all geology texts tell you that continental crust is three to six miles thick under the oceans, about twenty-five miles thick under the continents, and forty to sixty miles thick under big mountain chains, but there are many puzzling variabilities within these generalizations ...»