Structure of the Earth the crust, upper mantle, lower mantle, outer core, and inner core. The geologic component layers of Earth are at the following depths below the surface: The layering of Earth has been inferred indirectly using the time of travel of refracted and reflected seismic waves created by earthquakes. The core does not allow shear waves to pass through it, while the speed of travel (seismic velocity) is different in other layers. The changes in seismic velocity between different layers causes refraction owing to Snell's law, like light bending as it passes through a prism. Likewise, reflections are caused by a large
The Public and its Problems the public and its potential. Dewey did not call for an abandonment of the public; rather, he hoped the public would regain a sense of self. The solution to this, he writes, is improved communication. Only then, with communication, will the public find itself and become a cohesive group. In addition to Dewey's proposition that the public cannot find itself because there are too many publics, he also blames the distractions of modern society. He points out that even in the past, the public has had other concerns than politics: "Political concerns have, of course, always had strong rivals". In