Protective shield :Magnetic field of Earth
Our planet's magnetic flux is believed to be generated at its heart, within the Earth's core. Nobody has ever journeyed to the centre of the world, but by studying shockwaves from earthquakes, physicists are ready to compute its likely structure. In the guts of the world may be a solid inner core, two thirds of the dimensions of the moon, made mainly of iron. At 5,700 °C, this iron is as hot as the sun's surface, but the crushing pressure caused by gravity prevents it from becoming liquid. Surrounding this is often the outer core, which consists of a 1,242 mile (2,000 km) thick layer of iron, nickel, and small quantities of other metals. Due to the lower pressure than the inner core, the metal here is fluid. Differences in temperature, pressure, and composition within the outer...