Why is the earth's core so hot?

Question

Someone please explain to me WHY. Thanks.

Answer 1

It is due to several reasons.

1- it is the heat left over from the Earth's formation, due to the energy of the planetoids that aggregated to form our planet.

2- it is the heat due to tidal effect, as the Earth spins, the gradient of gravity caused by the Sun and the Moon knead the planet, causing some heat to develop (and it does have a side effect of progressively making the spin to get slower, energy is thus transferred from kinetic to thermal)

3- it is the heat due to the nuclear disintegration of radio-active elements, like uranium, that is present in greater percentage in the Earth's core than it is in the Earth's crust, due the those elements having a higher density than most, which makes them have a tendency to "sink". The Earth's core is a giant nuclear reactor.

Most other planets do have hot cores as well.

Answer 2

I don't know why everyone thinks its due to radioactive decay because the heat is caused by something really simple to understand, its called PRESSURE when you have thousands of miles of rock on top of it and billions of tons of rock the pressure is pretty extreme. And hopefully everyone knows that where ever there is extreme pressure there is heat.

Answer 3

There is original heat.  Although rock isn't the greatest insulator, it is extremely thick (thousands of miles) so it tends to hold the original heat of the earth.  In  addition, radioactive decay provides heat.  The liquid outer core is molten iron and nickel.  It retains this heat much as water does until loses it in crystal formation.   This process takes a long long time.  As the inner core cools, energy is slowly released.  Hmmm.  difficult concept and not easily explained in a short paragraph.  Hopefully that helped.

Answer 4

First, when the Earth was formed, all of the material was hot and then a combination of pressure and radioactive decay keeps the temperature hot with molten rock and metals.

The surface of the earth keeps the interior somewhat insulated, retaining the heat.

Answer 5

"The internal heat of the planet is probably produced by the radioactive decay of potassium-40, uranium-238 and thorium-232 isotopes. All three have half-life decay periods of more than a billion years.[42] At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa.[43] A portion of the core's thermal energy is transported toward the crust by Mantle plumes; a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce hotspots and flood basalts.[44]"

Answer 6

just to answer the pressure issue, heat is only generated with pressure at the time of the pressure change.  This heat, which was generated at the time of earth's formation, has had 4.5 billion years to radiate outward into space.  It is no longer a factor-there is no net change in the pressure gradient and thus no net heat generation from this source.  

The good answer is the one that discusses radioactive decay and tidal friction as the primary sources of heat generation in the interior of the earth.

Answer 7

Gravity acts such that all of an object's mass is "focused" into one point, its 'centre of gravity'. The earth has a mass of 5.9736×10^(24) kg. This means a LOT of pressure is at the core, which heats it up.

Answer 8

It could be due to the :

(1) insulated residual heat from the time of origin of earth.

(2) Thermo-nuclear reactions taking place within the core and mantle of earth.

thnks