How do scientists know what the inside of the earth looks like?
Thats a good point. Geologists and the like didn’t, until recently have a good idea of what the structure inside the Earth was like. The main way of finding out whats inside is from energy waves which are fired through the ground and picked up by sensors across the Earth. P and S waves are good examples of this technique – Almost all the information available on the structure of the Earth’s deep interior is derived from observations of the travel times, reflections, refractions and phase transitions of seismic body waves, or normal modes. Body waves travel through the fluid layers of the Earth’s interior, but P-waves are refracted slightly when they pass through the transition between the semisolid mantle and the liquid outer core. As a result, there is a P-wave “shadow zone” between 104° and 140°, where the initial P-waves are not registered on seismometers. In contrast, S-waves do not travel through liquids, rather, they are attenuated. This last bit was taken from wikipedia – check
