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Comment by sharkster711 | Hacker News Reader

From https://www.renewableenergyworld.com/baseload/can-geothermal...

Some 42 million megawatts of energy reach the surface continually and are radiated into space as the earth cools from its initial molten state more than 4 billion years ago. No feasible amount of geothermal development could make even a small dent in this process. Furthermore, the earth’s heat budget is continually replenished by the radioactive decay of naturally occurring elements, and almost all of the energy associated with each decay event is converted to heat. Plus, the heat content of the geothermal reservoir rocks is continually replenished by conduction of heat from the earth’s deeper interior.

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I see. 42 million megawatts is 42,000 gigawatts. A quick google search tells me that typical power output of a nuclear power plant is around 1 gigawatt.

So a single nuclear power plant would be roughly equivalent to 0.002% of earths geothermal energy radiation. It doesn't sound like much, but for something as crucial as the earth's magnetic field, I wouldn't want to reduce it one bit.

I guess if the heat is radiated into space anyways and we simply capture that it doesn't speed up the core's energy loss, but if we start digging into the core and allowing energy to escape faster, we would effectively speed it up, right?

If only all problems were as trivially ignorable as this one.

The radius of the Earth is 4000 miles. A 10-mile hole is thus 1/400 of the way to the center. You may as well worry that scratching the skin of an apple might damage the seeds.

Actually scratching the skin of an apple does negatively affect the apple - the part of the "mantle" under the scratch begins to rot right away.

Look at a graph of the temperature of the Earth as a function of depth. The temperature jumps tremendously below the crust, and is much more stable per depth below. The crust is the insulation of the Earth - and damaging that crust might affect the mantle is ways we cannot yet imagine.

The answer remains "we don't know".

Hint: the mantle is not made out of apple flesh, it starts much, much deeper than 10 miles most places, and nothing exists that can eat it.

It could also leak out, loose heat, and drilling down to it could trigger earthquakes and eruptions.

The argument "it's big, we can't affect it" has been proven wrong in the case of the atmosphere, and again in the case of the ocean. It is no longer a sound argument.

"It's big, we can't drill more than a negligible fraction of the way to it" remains as true as ever. So, no, we cannot make it leak out, lose heat, or trigger earthquakes or eruptions. It will still be almost as hot in a half-billion years when the sun engulfs and vaporizes it, whatever we do.

Eruptions in Siberia, and later in India, not long ago geologically, released more heat in a (geologically) short time than we could use up in a million years, with no effect on the Earth's magnetic field.

Just because we haven't discovered giant planet-eating space aliens yet doesn't mean they don't exist.

> if we start digging into the core and allowing energy to escape faster, we would effectively speed it up, right?

I don't think we're even digging through the crust - there'd still be the mantle (~100x thicker) before we got to the core.

In numbers, I believe the deepest borehole is ~12km deep... and the Earth has a radius of >6000km. We're barely scratching the surface.

My concern is fundamentally whether or not we are siphoning energy out of the core faster than it would otherwise escape.

Since the layers are directly connected, it doesn't sound like to me that you'd have to dig into the very core for that to happen.

Of course at the current state of affairs the effects are miniscule, but it doesn't sound like a very good investment as something to potentially scale up in the future to where it will actually matter.

If it turns out to be a problem, how hard would it be to insert fuel back into the earth's core to sustain the magnetic field?

It is very, very, very unlikely to make any noticeable difference even on geological scales.

Literally impossible to do. And, also, absolutely pointless to worry about.

In another century, if we don't blast ourselves back to the stone age first (increasingly likely), energy from hydrogen-boron fusion will dominate wherever solar is impractical, and the geothermal wells will become too expensive to continue operating. So, either way, the whole process is an imperceptible blip.

OK, good. But yeah the high likelihood of returning to the stone age repeatedly makes it even more important for the magnetic field to sustain for as long as possible.

We will never have any way to interfere with the planetary magnetic field, in any circumstance.

Blasting our way back to the stone age will succeed in chopping off CO2 output suddenly, though. The climate could then return to normal in only a century or three, if the sudden change did not instead trigger an ice age or something.

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