Eli5: How does the core of the Earth (or any planets) not cool and still give off tons of heat energy? Where is this energy coming from?
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So the lie to cooking of anything is surface area. That’s why radiators have all those fins. Planets don’t have fins. They are round.
And the thing about round things is that as you add more stuff to them the increase in volume much faster than they increase in surface area. This is in math terms. The square/cube law. Square as in flat, cube as in thick, if you put it in simplest terms .
So all you got to really understand is that the bigger the thing the harder it is cool.
Now when the solar system was forming it was a bunch of radioactive dust more or less. And the biggest lump settled towards the center. And it’s oddly enough the lightest lump per cubic foot. That is, it’s all hydrogen pretty much. Then as you go out you get a heavy band and that’s where all us rocky planets are and then you got a little farther and you start getting light again. But big enough that it’s giant ice chunks that squeeze themselves down and become hot as well.
If you’ve ever done the science experiment where when you press stuff together it gets hotter. You can see where heavy means more squeeze which means more heat .
And then the dust was radioactive and radioactive stuff gives off heat as it becomes less radioactive .
So the inside of the earth is constantly losing some of its radioactivity and turning it into heat. But the earth is so big that it can’t really get rid of that heat quickly by any measure. Like no matter how many volcanoes you spew lava out of. That’s nothing compared to how just mind-boggling huge the earth is. So it can’t cool down fast enough to become cold. At least not until it runs out of a lot of that nuclear stuff.
And that leads us too. The fact that if you put enough heat into a small thing it will explode because the heat will push out so hard that the shape of the thing can’t hold together. I mean that’s basically how all bombs work. If you set off a bunch of gun powder in a pile it’ll go fizzz and no big deal. But if you wrap it up tight and paper all that escaping gas can’t get away fast enough in the paper. Explodes.
Which brings us to things like The earth is a grain of sand next to the giant spear. That is the sun. The sun is way too big to be healthy. So it’s constantly trying to crush itself and it’s also constantly trying to get rid of a lot of heat that it just can’t get rid of. Since it’s trying to crush itself that actually generates more heat, not just how much it does in this easy science lab, but because it’s actually mashing Adams together to make bigger atoms. So the sun should explode. But right now it won’t. That’s because there’s literally enough light to keep spreading the sun out. It takes thousands of years for a single photon to get from the center of the sun to the surface of the sun and out to shine down on us. And that bouncing photon and all of its brethren keep the inside of the sun from crunching down as much as it could be crunched down.
But as the sun uses up its fuel, turning all that hydrogen into helium, it’ll start making less and less light. With less light. It doesn’t have as much energy spreading itself apart and it can get smaller very quickly. And when that happens the sun or star gets small very fast by comparison and it gets too small to let out the heat it’s got and then it explodes. And that’s where we get Nova’s and supernovas from. They literally run out of light before they run out of heat. I mean they don’t actually run completely out of light but you know what I mean.
All this stuff basically forms a square if you put it down on graph paper hotter beans bigger bigger means cooler cooler means smaller. Smaller means hotter. This is basically the principle that you’re car engine runs on. It’s called a heat engine. Particularly a car, no heat engine. And amusingly enough. The version that uses gasoline and internal combustion is the Otto cycle, which is just coincidental compared to the word automobile, which is one of my favorite pieces of physics trivia.
TL;DR :: a hot plate will cool much faster than a hot rock of the same material.
Disclaimer: because of my screwed up hand, I had to dictate this with my phone, and it often makes the fascinating set of word substitutions. I’ll try to get back and edit this down later. So if a sentence doesn’t make sense just say it out loud instead of reading it.
P.S. All this stuff about cooling off is also true about heating up. That’s why the you can boil a smaller quantity of water faster. Cuz less stuff. Let’s heat in easier just like it. Lets heat out easier.
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