It's important to note that the core is made up of two parts:

* Inner core: A solid ball of mostly iron with a radius of about 1,220 kilometers (758 miles). It's incredibly hot, with temperatures estimated to be around 5,200° Celsius (9,392° Fahrenheit).

* Outer core: A liquid layer of iron and nickel surrounding the inner core, extending out to a radius of about 3,485 kilometers (2,167 miles). The outer core is also very hot, with temperatures estimated to be around 4,500° Celsius (8,132° Fahrenheit).

While we can't physically reach the Earth's core, scientists have learned a lot about it through studying seismic waves from earthquakes.