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 Problems The Public and its Problems is a 1927 book by American philosopher John Dewey. In his first major work on political philosophy, Dewey explores the viability and creation of a genuinely democratic society in the face of the major technological and social changes of the 20th century, and seeks to better define what both the 'public' and the 'state' constitutes, how they are created, and their major weaknesses in understanding and propagating its own interests and the public good. Dewey rejects a then popular notion of political technocracy as an alternative system of governing an