# Geothermal Energy 2

A great peculiarity is that radioactive decay seems utterly immune to influence. High magnetic fields, electric fields, movement, and spin don’t seem to change the rates of radioactive decay at all. Nothing does. Particle interactions, including some really high energy photons, can cause a radioactive particle to decay differently right now but that’s usually a different decay. There doesn’t seem to be any particular way of changing the halflife of some whatever.

In numbers, the halflife of U238 is 4.468 billion years. If one sample of U238 has a hundred nuclei, in 4.468 by that sample will have fifty nuclei. We can’t change that without seriously altering the decay path. If an experimentalist whacked those one hundred nuclei with high energy neutrons, one could get some other decay path and decay reaction, meaning in far less than 4.468 by the sample would have only fifty or less nuclei. But the natural decay path is more or less immutable. Exposing the sample to a high magnetic field doesn’t change it. Putting the sample in zero g doesn’t change it. Putting it at the center of the Earth doesn’t change it. Whacking the sample with high energy neutrons doesn’t change the characteristics of the existing natural decay path (ie decay reaction); whacking the sample with neutrons may shift the decay reaction to something else. So instead of decaying into Thorium 234, we could smack it until it decays into something else.

So what does this mean?

It means the radioactive elements in the Earth’s core are naturally decaying in some fashion, releasing heat at some fixed rate, and there’s not much we can do to change that. This energy and the process of harnessing it are both called geothermal energy, sort of like how football is the game, the physical ball, and the activity.

So how good an idea is taking this fixed supply of energy for our purposes?

There’s a finite amount of sunlight that hits the Earth, right about 1300w/m^2 at the top of the atmosphere, and about 1kw/m^2 at the surface of the Earth. It’s coming whether we use it or not. Solar and wind are both fundamentally solar energy, as wind is caused by temperature differentials in the air, caused by sunlight hitting the heterogeneous Earth.

There is no consequence on the Sun by us harnessing solar energy. It’s close to free. To be more accurate, the energy is free; building stuff to harness the energy has costs, and so when we talk about the cost of solar energy, we talk about the costs of building the stuff. And maintaining the stuff. And hiring someone to go out to the solar panel farm to clean away the bird crap, pull the squirrel nests out of the wiring box, replace the wiring the squirrels ate, and replace the broken solar panels, etc.

If we take energy out of the Earth, would we be cooling the Earth? Is it radiant free like sunlight, or could we cause serious negative consequences? What happens to plate tectonics if we cool some part of the crust by 200k in a localized area?

Probably nothing, but that same probably nothing that people thought about greenhouse gases.

Remember the source of the energy, radiant heat from radioactive decay, is (as far as we can tell, but I find this kinda sus) utterly invariant.