Why is the earth's core hot?

As the outer core is fluid and presumably convecting (and with an additional correction for the presence of impurities in the outer core), we can extrapolate this range of temperatures to a temperature at the base of Earth's mantle (the top of the outer core) of roughly 3,500 to 5,500 kelvins (5,800 to 9,400 degrees F) at the base of the earth's mantle. read more

The collisions when it formed made it hot, to start with. Now the heat must go somewhere, but it take along time for something as large as a planet to cool down, especially in space where there’s no heat convection, only radiation. read more

Marc: One thing is that Earth's solid center is surrounded by an even larger layer of molten rock. So we have an inner core that is solid and an outer core that is liquid. Together they are over 2000 miles in radius, or around half the size of the entire planet. read more