# gravity \[Why is the center of the Earth hot?\]
**URL:** https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033
**Category:** Factual Questions
**Created:** [October 19, 2016, 3:44pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033 "2016-10-19T15:44:16Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Vicsage](https://boards.straightdope.com/u/Vicsage)
#### Post date: [October 19, 2016, 3:44pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033/1 "2016-10-19T15:44:16Z")
From what I understand, the center of the Earth is hot because of the intense pressure. This pressure is a result of gravity trying to crush the stuff in the center. Since gravity is eternal and constant, will the center of the Earth always be hotter than the surface?
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [October 19, 2016, 4:08pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033/2 "2016-10-19T16:08:59Z")
The centre of the Earth isn’t hot because of the pressure. It is hot for two reasons. Initially when the dust cloud accreted to form the earth it was hot, and that heat takes a very long time to radiate away from a planet sized object. But the Earth has remained hot because it contains radioactive material, and this injects new energy into the Earth. The steady state is what we have now. Eventually the radioactivity will diminish and the Earth will cool.
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [October 19, 2016, 4:19pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033/3 "2016-10-19T16:19:40Z")
Thread title edited to indicate actual question.
Colibri
General Questions Moderator
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [October 19, 2016, 6:37pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033/4 "2016-10-19T18:37:01Z")
_Being_ pressurized doesn’t cause heat. _Becoming_ pressurized does. If an object is heated by collapsing into something compact, then it’ll eventually cool off.
As an aside, before the discovery of nuclear reactions, this was the best guess as to the Sun’s energy source. Which caused considerable confusion, because in that case the Sun couldn’t possibly be any more than a few million years old, in conflict with geological evidence which was already (correctly) saying that the age of the Earth was billions of years.
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### Author:  [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)
#### Post date: [October 19, 2016, 6:43pm UTC](https://boards.straightdope.com/t/gravity-why-is-the-center-of-the-earth-hot/769033/5 "2016-10-19T18:43:00Z")
> [@Chronos](#):
>
> _Being_ pressurized doesn’t cause heat. _Becoming_ pressurized does. If an object is heated by collapsing into something compact, then it’ll eventually cool off.
(This is how air conditioning works, if anyone needs a concrete example.)