I don't know if adiabatic processes are responsible for the temperatures in the core, but if it is, it would be more accurate to describe this in the past tense, rather than the present tense that the other commenter used:

>"High pressure makes made the core hot"

You made the same distinction:

>the earth was pressurised

That being said, I doubt adiabatic heating plays a significant role. Adiabatic processes operate through compression, not pressurization.

Suppose I have a sealed tank of water. I put a balloon inside it. Then I pressurize the water to double the pressure in the tank. The volume of the balloon shrinks.

Here's the important part: Even though the balloon is half the size now, it still has the same amount of heat: none has entered or exited yet. The same amount of heat in a smaller volume means the temperature has risen. That's adiabatic heating.

Replace the balloon with an iron or nickel ball. When you double the pressure, the volume of the ball doesn't change. Increase the pressure a hundred times, a thousand times, it doesn't matter: the volume of the ball stays the same. The heat within the ball is not concentrated. There is no adiabatic process involved.

With the core of the earth being primarily comprised of non-compressible materials, I don't think adiabatic heating explains the temperature of the core.

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> Otherwise something highly compressed would radiate heat indefinitely which ain't going to happen.

Sure, the earth is cooling down. The mantle however is a reasonably good insulating layer though (mostly because it's so damn thick). The heat loss is is estimated at 47±2 TW (or about 3 times to total energy usage by humans). Still, the Earth will be destroyed by the Sun before it cools down.

It really is brilliant

Woooh, Thanks for this. Going back to re-read it and try to better understand things

So if the core slows/stops/reverses course then shouldn’t the magnetic field lines of the earth also flip or change in accordance? And if so wouldn’t this transition allow solar wind particles to bombard us in the meantime?

Not really because Halo's don't orbit around things the same way a ringworld would. Not that that makes it any more feesable, its just not THAT particular reason it would be a problem.

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As far as I understand earth will inevitably become similar to mars: as the earths core cools down and solidifies our magnetic field begins to disintegrate, seismic and volcanic activities will disappear which ultimately will thin out our atmosphere to a point where life will be impossible. We talking billions of years ofc.

According to science only half of earths internal heat stems from radioactivity, the rest being primordial heat. This in turn means our planet is obviously much cooler than it used to be.

https://www.science.org/content/article/earth-still-retains-much-its-original-heat

Following the analogy... Isn't it so that the earth was pressurised to a tremendous amount of psi, and is now in that process of cooling down to ambient temperature?

Of course many other processes play a role, but the pressurised can analogy kind of works if you scale it up?

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The main heat sources in the core are secular cooling (i.e. losing primordial heat), latent heat due to the ongoing solidification of the inner region, compositional energy (essentially gravitational energy, the lighter elements in the core do not solidify and some fraction of the core solidify these elements rise up to the liquid part) and radioactive decay.

The estimates in Earth's Core (by Cormier et al., nice book) are around 0.3 TW for radioactive decay and a few TW (2 to 6) each for the others.

As an order of magnitude estimation, compositional changes, phase transition and original heat loss contributes equally, while radiogenic heat is only a minor contribution.

The heat balance we measure at the surface has obviously much more than this. We have to take into account the secular cooling of the mantle itself (16 TW), plus the heat production of continents (8TW) and again the mantle (11 TW), which are mainly radiogenic (data here from the Encyclopedia of Solid Earth Geophysics).
Note that every estimate, despite being in line with scientific consensus, is subject to high uncertainties, due to the very difficult nature of these kind of measures/models.

To close going slightly OT, this combination of heat production and heat loss is the driving force of hot spots and plate tectonics. Which means that the cooling dynamics of the earth is responsible for essentially the entirity of what we observe in the solid earth. Earthquakes, volcanic eruptions, tectonic movement, but also interactions with surface geomorphology are all byproducts of a ball of molten rock cooling.

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The relationship between temperature and pressure does not work the way you are describing. A substance is not at a given temperature just because it is at a given pressure. Pressurize one cylinder of nitrogen to 30PSI, and another cylinder of nitrogen to 3000PSI. Leave them alone in a room for awhile, and they will both become room temperature.

The temperature of a given mass is not dependent on its static pressure, but on changes to its pressure.

You are (effectively) arguing that adiabatic heating is responsible for the heat of the earth's core. To make this argument, you will have to show that the earth's volume is shrinking, or otherwise demonstrate that the pressure at the core is not just high, but increasing.

Without a pressure change, we need to look at the heat entering or exiting the system. The simple fact is that relative to the total amount of heat within them, very little heat actually leaves the core and mantle. At the current rate of dissipation, it will take billions of years to remove a significant amount of that heat.

You're confusing the Joule-Thomsom effect with a fundamental law.

It only applies to most gases at standard conditions, whereas liquids generally heat up as they are expanded.

https://en.m.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect

Yes, somewhat, there are fluctuations but mainly the earth is hot, it was heated by the pressure, and is now cooling down.

To what extent is it kept warm simply by heat retention from primordial times and the formation of the earth? As in, how does the thermal energy generated by the core/mantle over the past few billion years compare to the thermal energy lost and the thermal energy it started out with when the planet was a mostly molten blob?

I guess to simplify the question, I'm curious whether, in the absence of radioactive decay in the mantle, we'd be another Mars right now.

The actual regulation in a car is done by the ECU or some circuit inside the alternator that limits the output voltage to a certain amount.

The battery is mostly there so that when there is a load transient, the regulator mentioned above can have a relaxed response time--the battery takes up the slack when there's a sudden load increase or decrease.

If a control system has to react quickly, it's more liable to instability like oscillation and divergence. Better to keep it safe by making it slow to react, especially if you already have a big ass battery that can smooth things out that you need to start the car.

Capacitors are devices that store energy by moving charge carriers (usually electrons) in places it really doesn't want to be in--which means they have to be forced in that position--which takes energy that you can get back later, quite easily. Charge carriers like electrons can move around efficiently and quickly in conductors like metal, so capacitors generally can be charged and discharged rapidly.

Batteries are devices that store energy by making ions stay in energetically excited conditions that it doesn't really want to be in. Ions are generally floating charged particles in a liquid solution, so they take much longer to float around and do their chemistry to get your energy back. The upside is that you get to store a lot more energy into the structure, but the downside is that the rate at which you can charge and discharge is beholden to the chemistry and the speed at which ions move, so it's quite slow. They are also inefficient since ions aren't efficiently transported, as much as electrons are in metal.

But its a static pressure isn't it?

Otherwise something highly compressed would radiate heat indefinitely which ain't going to happen.

There's also one more fact that I think other commentators glanced over. One of the many approaches you can have towards gain and directivity of an antenna is the idea of an effective cross section of an antenna.

Think about a simple dipole. It basically has no cross sectional area, but yet it is still capable of capturing free air propagation and confining it to a conducted EM wave (into coax, for example).

This is because the presence of the dipole creates a disturbance in the way free air propagating EM waves (which can be approximated greatly since it's in free air), and creates more complex "near field" phenomena which essentially increases the cross sectional area of the antenna.

In this sense, all antennas disturb the free air propagation and create near field cross sectional areas that it will use to capture EM energy and send it through a conductor.

Indeed, there's actually a relationship between directivity/gain and this imaginary cross sectional area. I haven't done this in a while but I believe for parabolic antennas (or any antenna where the physical size >> wavelength) this cross sectional area is essentially the same as the physical size, and hence this is one way to think about the high gain of parabolic antennas like the ones used for radio astronomy.

In that sense, in certain degenerate scenarios, the flat plate might have a larger cross sectional area than an actual semi-spherical dish (hint: it has to do with physical size vs wavelength of the wave you're dealing with)