Given that the majority of the Earth’s interior is over 1000 degrees Celsius, how does the planet maintain a relatively cool surface temperature, considering it has a thick atmosphere?
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The atmosphere of the earth is not that thick. The result is enough heat is radiated out to keep the average surface of 15C.
An a lot thicker atmosphere like Venus results in a warmer atmosphere at around 475C
Think of the Earth’s atmosphere like a cozy blanket that wraps around the planet. This blanket is made up of different layers of gases, like oxygen and nitrogen, that surround the Earth. These gases help regulate the temperature and protect us.
When sunlight reaches the Earth’s surface, it warms it up. But the Earth doesn’t keep getting hotter and hotter because the atmosphere acts like a shield. Some of the sunlight is reflected back into space, and some of it is absorbed by the atmosphere.
The atmosphere also has something called greenhouse gases, like carbon dioxide and methane. These gases trap some of the heat from the Sun, just like a greenhouse traps heat to help plants grow. This is called the greenhouse effect. It keeps the Earth warm enough for life to exist.
But if the greenhouse effect was too strong, the Earth would become too hot. So, the Earth has a natural balance. The atmosphere allows some of the heat to escape back into space, which prevents the planet from becoming too hot.
Another important factor is the Earth’s surface itself. The land, water, and ice on the surface can absorb and store heat. They act like sponges, soaking up some of the Sun’s energy during the day and releasing it slowly at night. This helps regulate the overall temperature.
In addition, the Earth has something called convection currents. These are like invisible currents that move heat around. Just like when you stir a pot of soup and the heat spreads, the Earth’s interior heat is also circulated by these currents. They help distribute the heat from the hot interior to the cooler surface.
The atmosphere is sort of thick. There’s a dozen or so pounds of air above every inch of ground.
The ground is *very* thick. By my math less than 20 feet of ground is as heavy as all of the air above it. As much as the atmosphere may insulate the surface, the ground itself insulates the core *way* more.
For the same reason a baked potato left out for a few minutes can feel cool on the outside, but still burn you when you bite into it. An object’s surface radiates heat into its surroundings. If the object’s material conducts heat poorly, then heat radiates faster from the surface that it is replenished internally.
Rock is not a particularly good heat conductor, which is why Earth has a nice crispy outer layer.
Don’t think of anything as “maintaining” cool temperatures – the core is just holding onto its remaining heat.
When a pie comes out of the oven, and is left to cool, the outside cools first, but you can cut into it and find that the inside is still too hot to eat. That’s the Earth
The atmosphere has as much mass as a layer of rock with a height of just ~5 meters.
As seen from the point where you reach 1000 C (~50 km deep), 99.9% of the mass are between the 1000 C rocks and us and only 0.01% are above us.
Our surface temperature is mainly determined by the amount of sunlight that reaches us and how easily that gets radiated away again. Heat from Earth’s interior is a very small contribution.
Space is very cold. The interior of Earth is very hot. Somewhere in between, it’s going to be room temperature. For Earth, that is roughly at the surface.
You can be more precise if you want with a simple model like the heat equation, but that’s probably going beyond ELI5.
[The answer](https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget)
Heat from below (core): ~47 TW. About 0.1 W / m2 (not much)
Energy from above (sun): 173,000 TW (1361 W/m2, top of atmosphere)
The Earth is a very thick blanket.
The atmosphere is a fairly thin blanket.
Your oven can reach a few hundred degrees, but you can usually touch the outside of it because it has good insulation. Now, add a few MILES of insulation between the earths core and us, and it makes it much easier to prevent heat from reaching the surface.
it’s that hot *because* the heat isn’t escaping.
turns out that having a much much thicker silicate mantle and a thin skin of dirt and basalt on top of that makes for some pretty good insulation.
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