It’s about 3,700 miles (5,957 km) to the center of the earth.
The inner core of the Earth is believed to consist of an iron-nickel alloy, and may have a temperature similar to the Sun’s surface.
The existence of an inner core that is distinct from the liquid outer core was discovered in 1936 by seismologist Inge Lehmann using observations of earthquake-generated seismic waves that can be detected by sensitive seismographs on the surface of the earth.
The temperature of the inner core is estimated by using the melting temperature of impure iron at the pressure of the inner core boundary, which leads us to a figure of 5,700 K (5,430 °C; 9,800 °F).
