The Earth’s inside is sort of totally inaccessible to humanity, so how do we all know what it consists of? As defined on this video, our information of the planet’s inside relies on measuring waves despatched out by earthquakes and nuclear blasts. Each produce two sorts of waves — strain waves (P-waves) and shear waves (S-waves) that journey via the earth and get picked up by seismometers. Scientists seen that strain waves journey via the middle of the planet whereas shear waves — which get dissipated in liquids — don’t. This led them to conclude that a part of Earth’s inside is a liquid. The thought of a strong internal core got here from observations of strain waves scattering in a manner that solely made sense in the event that they’d hit one thing strong. (Video and picture credit score: Science)