1. the study of the structure of the world. Scientists have been trying to find different ways to study the structure of the world, both directly and indirectly, by attempting to use the evidence can be found, as well as the main branch of the scientific theory and modern technology in order to answer these questions. At present, there are limitations to human technology for the study of the structure of the world directly and now learn from borehole survey to collect rock samples, which is boring a hole in deep drilling only in the current depth 12.3 km only. For the study of the internal structure of the Earth indirectly, from the study of seismic waves caused by the earthquake and from the human trial. The study of seismic waves at the world structure from moving through the world. The waves used in the analysis are the primary waves (Primary waves, P waves) and secondary waves (Secondary waves, S waves), a wave in a medium (Body wave) seismic waves, it has important properties. Is as follows: -P waves can pass through the middle of it all, there are more than speed and wave S. S-waves can move through the only medium that is solid only.
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