Editing Internal structure of Earth (section)

== Seismology ==
{{Main|Seismology}}
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 increase in seismic velocity and are similar to light reflecting from a mirror.