The core of earth is made out of iron and nickel. the outer cores tempeh is so hot that it melts the metal the inner core is solid mental. What causes these different

It’s commonly accepted that the earth’s core is solid, due to the fact that scientist believe that an extremely hot nugget of iron began to have crystallization around it. Now we have a 4,200 mile of metal at the center of our planet. Also due to pressure and high temperatures. However all of these are theories since we have not been able to actually drill to the center of the earth.