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...Journey to the center of earth tutorial script this image shows a cross section through showing its main compositional and physical layers how did scientists learn that is what s insides look like we learned about composition by studying meteorites building blocks in days early solar system movements around our sun own rotational axis tell us overall size mass as well distributed most it thickness characteristics each study earthquake waves travel process similar x rays are used show happening inside human body video will follow these they towards demonstrate some know earthquakes first produced during an emanate out which consist p primary secondary whenever there fault rupture stress released from focal point all directions downwards deeper into slowing or speeding up move one layer another eventually coming back surface be felt recorded on seismograph time takes for those tells ve traveled why down natural laboratory settings slow when less rigid material speed more velocity changes...