* Seismic waves travel differently through different materials. There are two main types of seismic waves:
* P-waves (primary waves): These are compressional waves that can travel through both solids and liquids.
* S-waves (secondary waves): These are shear waves that can only travel through solids.
* Earthquakes generate seismic waves. These waves travel through the Earth's interior and are detected by seismographs at the surface.
* S-waves are blocked by the liquid outer core. Scientists observed that S-waves do not pass through the Earth's core completely. Instead, there's a "shadow zone" where S-waves are absent. This indicates that the outer core is liquid, as S-waves cannot travel through liquids.
* P-waves are refracted at the core-mantle boundary. P-waves, however, do travel through the core, but their speed changes as they pass from the mantle to the core. This change in speed indicates a change in density and suggests a solid inner core.
In summary: The combination of S-wave blockage and P-wave refraction provides strong evidence that Earth's inner core is solid.
