The gravitational binding energy of the Earth is $2×10^{32} J $, so the same amount of energy must have been released during the Earth's history.

According to this and this, the current internal energy of the Earth is ~ $1.5×10^{31} J$, and according to this source, the amount of heat loss due to outward radiation by the Earth during the entire lifetime of the planet is about $0.45×10^{31} J $.

So, by adding those two numbers we get the Earth internal energy + energy radiated = ~ $2×10^{31} J $, which is an order of magnitude less than what we should expect. We are also ignoring the fact that 50-90% of the current internal energy of the Earth is due to radioactive decay. So where did the rest of the energy go ?

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    $\begingroup$ Cross posted and answered here physics.stackexchange.com/questions/152979/… $\endgroup$
    – user889
    Dec 26, 2014 at 0:11
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    $\begingroup$ Please do not cross-post questions. Your question on physics.se already has answers. Closing for cross-posting. $\endgroup$
    – casey
    Dec 26, 2014 at 0:25