Based on this information, scientists have created a model , or a physical representation, of an atom that explains the evidence that exists about atoms. A model is a best explanation of the facts. Because it is an explanation that scientists have created based on evidence, as new evidence is collected, the model may change. Scientists have also created a model of the interior of the Earth. The majority of the information used to construct this model has been based on data gathered through seismic waves.
Seismic waves are the energy impulses that are released during earthquakes.
The energy from this release travels at different speeds and directions depending on the type of material that surrounds it. Just as a vibrations move differently through water and through a pan of Jell-o, seismic waves move at different speeds through different densities of materials. The pressure from the outer layers keeps the inner core solid even though the temperature at the core is thought to be approximately 6000 degrees Celsius. The width of the core is measured by its radius, which is about 2100 km. The outer core is also made up of nickel and iron, but is liquid because of its high temperature and the decreased pressure exerted on it by the remaining outside layers.