The sun. Electromagnetic forces of our nearest massive fusion generation body are very strong and affect all kinds of things in our planet including earthquakes, weather, and... Rotation speed.

Thank you.

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thanks. i must have mis-read recent news articles that stated that the core had reversed its spin and was now spinning in the opposite direction. this implied to me that the field reversal must have already happened in short order and so we would have seen the effects of that weakening here on the surface.

Yes, and yes. The magnetic field has flipped before, and during the transition the magnetic field is very weak.

However IIRC it takes on the order of hundred to thousands of years, so probably not something we'll have to worry about. Although the timeline in the article OP is referring to seems to state it's happening faster than we previously thought. (IIRC, In the 90's the core was spinning faster than the planet, by 2009 it was spinning slower)

So if the oceans boil away, will the earth just become a smooth marble of rock with a bunch of fog over it?

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By far the two major sources of heat are primordial heat and radioactive decay. Changes in pressure can cause changes in temperature, but largely static pressure with depth does not generate heat. Tidal heating is not relevant for the Earth (though it's important for other planetary bodies in the solar system).

This seems to ignore the literature stream suggesting that there is a fundamental hemispheric anisotropy of the inner core and that this may relate (in part) to the super-rotation of the inner core (e.g., Dumberry & Mound, 2011, Wazek et al., 2011, Deuss, 2014, Lythgoe et al., 2014, Yu et al., 2017, etc). Is that no longer valid?

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The moon is tidally locked so it always faces the earth, but the earth doesn't always face the moon. It rotates unequally to how the moon orbits. There is also drift between the number of orbits and the ultimate position the moon ends up in a year. One month is roughly equal to a lunar month, but not exactly.

Earth and the moon are tidally locked aren't they? Interesting answers here and I actually had some keywords to use too lol thank you.

Like, human extraction of oil? No, we don’t dig up anything that isn’t sitting in the crust of the earth. The mantle, sitting between the crust and the outer core, is something around 75x thicker than the crust. We have no impact on what happens to the core.

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Does the extraction of oil take the lubricant out of the equation?

Nuclear reactions happening in the Earth are all radioactive decays. These produce heat, and it's in fact the main contribution (I've written another comment here with a bit more detail) but most of it happens in the continental Crust and in the Mantle.

This nuclear process is not generally dependent on pressure, in fact it mainly happens in the external layers of our planet. The distribution of radiogenic heat depends on where the element that may undergo beta-decay are located. If you are curious, the main elements responsible for this on Earth are Uranium, Thorium and Potassium.

Despite there being large uncertainty, geochemical studies show that these element are not much soluable in the liquid core. Radioactive decay contributes to the heat production in the core for 0.2 TW, while the the total amount of heat produced by the core is around 10-15 TW.

EDIT: well, not all nuclear reactions in the earth are decays. A few occurrences of natural fission reactions have been found, where particular conditions, like more abundance of a certain uranium isotope and different amount of oxygen in the atmosphere, made the fission reactions possible. The only few occurrences known happened in the far geological past in Oklo (region of Gabon).

Heat retained from the formation of the earth, and compressive forces.

Insulation from the thick layers above.

Tidal heating - Continual squeezing and squashing of earths core by the moon orbiting around the earth. Though note that this doesn't occur with moons that are tidally locked.

Having a relatively warm surface from heating by the sun and thick atmosphere, though this is of lesser effect than say Venus. By having a warmer surface, the temperature differential is lessened, so less thermal energy moves across the gradient.

Definitely heard of it. I haven’t had as much time as I like to respond to comments but the most efficient way to say this is that we have not been selecting for characteristics that will create conditions for more dangerous or difficult births in such a concentrated way.

We are selecting for babies and moms who will survive the process of gestation and birth, which has changed in a way more nuanced way (ie we have lost some ways of moving and feeding ourselves which create more dangerous birth conditions, and we have gained a lot of tools that have increased survival of pregnancy and birth). That won’t change the mortality rates of pregnancy and birth in a huge way within a few generations of c sections and other more modern interventions.

Not caused by the pressure (that's what stars do and the Earth isn't one) but rather the heat of radioactive decay. It's also believed that tidal forces from the Moon create some heat.

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Aren't there continuous nuclear reactions also that help keep the heat going? Likely caused by the pressure.

Core is molten for two reasons:

Initial formation of Earth generated a lot of thermal energy, because a lot of stuff smashed together

Continued decay of radioisotopes has contributed additional thermal energy-- without this, the core would have cooled by now

Thermal energy is lost from the core through heat transfer to the mantle, which brings it to the crust by way of convection; this is what ultimately causes plate movement, earthquakes, volcanism, subduction, etc. on Earth. Once the core is cool enough that mantle convection stops, tectonic forces will subside and uplift processes will cease. From that point, weathering and erosion will gradually erase all land above sea level, giving us an ocean planet. I think the Sun will be hot enough to boil our oceans well before that happens, though (solar brightening over geologic time).

Sure, I agree with all of that.

>Gravity causes the pressure. It’s the weight of everything above pressing down, which naturally increases the deeper you go which really isn't the case as no work is being done.

I just read the above as suggesting that a static pressure will result in an increase in temp.

> the pressurised can analogy kind of works if you scale it up?

It did 4 billion years ago when the debris in our Sun's accretion disk coalesced to form our planet, and again when whatever planet sized object hit us to form our Moon, but since then we've been cooling off like a pot of old coffee. Fortunately there's a lot of mass left to cool off, and it's stored in the best Thermos ever created...