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 Dog and Its Reflection The Dog and Its Reflection The Dog and its Reflection (or 'Shadow' in several translations) is one of Aesop's Fables and is numbered 133 in the Perry Index. An indication of how old and well-known this story was is given by an allusion to it in the work of the philosopher Democritus from the 5th century BCE. Discussing the foolish desire for more, rather than being content with what one has, he describes it as being 'like the dog in Aesop's fable.' In the story, a dog that is carrying a stolen bone, or piece of meat or cheese, looks