The paper is here: https://arxiv.org/abs/2503.15790

(via https://news.ycombinator.com/item?id=43520716, but we merged that thread hither)

It's incredible the lengths humanity is willing to go to avoid adopting nuclear energy - despite the US navy driving mobile reactors millions of miles over the last 70 years.

Many countries would have to buy nuclear fuel from other countries much like they do for gas and oil. On the other side very few countries can build their own solar panels so it seems the same sort of problem. However if you accept to depend from potential hostile countries at least solar panels don't do much harm when they fail and it takes very little effort to install the equivalent amount of power of a nuclear power plant. If we only could all get along and have a global power grid with always 12 hours of sunshine on it.

The Navy isn’t constrained by economics. Nuclear doesn’t make sense economically compared to things like solar and batteries.

I wonder how many wats of power we would be able to generate before earth slows down for i.e. 1 second longer day.

Current = 25.4 ± 1.5 nA, Voltage = 17.3 ± 1.5 µV.

Making total power for the 30cm shell = 0.44 picowatts.

No, it took far more electricity to make than it produces over any conceivable lifetime.

That's untrue

This is really cool. Question for EEs / Material Scientists reading the paper - they mention you could shrink the cylinders and get the same voltage provided a "suitable material" could be found. Any back of the envelope or explanation of materials needed to make these cylinders say 1/1000th their current size? That'd be an extremely useful amount of energy when put into say a 1000x parallel array.

It seems hard to imagine that this kind of shrink-down could go on forever, but on the other hand, the earth is just sort of hurtling us around with great energy while it rotates.

Wouldn't this eventually slow down Earth's rotation? The rotational kinetic energy of our planet is 1/5 M * R^2 * w^2 with (approximately) M = 6e34 kg, R = 6.3e6m, w = 7.4e-5 rad/s, which gives approximately 5e36 joules. Yearly we need roughly 3e16 Wh. Yeah ok there's plenty. Woah! (also, I may be off by some orders of magnitude)

The IERS will never stand for this!

This is addressed in the last paragraph of the article:

> Even if it works, the method will not generate energy from thin air. It would tap Earth’s kinetic energy and, in doing so, cause the planet’s spinning to slow over time — although only slightly. If the technique provided all of Earth’s electricity needs, which was around 11 trillion watts in 2022, this would slow the planet’s spin by 7 milliseconds over the next century, the authors calculate. This is similar to the change in speed caused by natural phenomena such as the Moon’s pull and changing dynamics inside the planet’s core.

Doesn’t driving west to east on a highway slow down the Earth’s rotation, via the power transferred into the ground?

0.44 picowatts = 4.4e-13 watts so not in a detectable fashion before the sun consumes the earth billions of years from now.

Well, the watts that come out of the rotational energy must match the ones we need, for energy conservation.

Sure, but there’s no “eventually” it happens instantly.

The only way you’ll care about what happens eventually is if you’re concerned about some detectable result. Meanwhile individual rocket launches to Mars extract like 10^18+ times as much energy as this will over it’s lifespan and those still aren’t detectable.

Why does the earth have a magnetic field?

The earths rotation creates it. Or was this rhetorical.

No, it was a serious question. Does anything that rotates create a magnetic field even if it is not an electrical material?

I had an idea somewhat related to this where we use the solar winds as a sort of road and the earth's magnetic field as a sort of rotor to convert kinetic energy from the sun into electricity.

Sounds like solar power with extra steps

My Stupid Question, please don't laugh:

If you did this on a massive enough scale, to generate serious amounts of power, would that accidentally slow the Earth's rotation down over time?

It isn't a stupid question, it is a good one. The answer would depend on how the field is generated in the first place.

Given a field generated by asymmetric rotation of the molten core at the center of the Earth, 'shorting it' (apply a load) would presumably affect the core's rotation. In terms of relative energy however, the poor coupling at the surface would suggest that this would be a very challenging way to divert any meaningful amount of power from the core itself. It would however have to deal with points in time where the core reverses its magnetic field. The papers on core reversals are fun to read.

I think more usefully, the presence of the voltage, might be an interesting way to localize one's location and orientation.

I remember brainstorming "off the wall" power generation ideas and one that has yet to be realized would be to inject dust ahead of a wind turbine with a collector in the back. Then using the Van DeGraf effect to generate power instead of lightning as it currently does.

If one needs location, then the magnetic field can be measured directly. It is already considered as a potential alternative for GPS, https://www.electronicdesign.com/markets/automation/article/...

The main problem is that locally measured Earth magnetic field varies on a daily basis and is strongly influenced by solar storms.

A better alternative is to use variations in Earth gravity to improve inertial navigation. That vastly more stable.

They are one step ahead of you. :-)

"We previously showed that even in an extreme scenario where our civilization somehow would obtain all its electrical energy from the effect described here, Earth’s rotation would slow by <1 ms per decade [2]."

Not stupid at all, especially if only one part of physics exists and not quantum physics.

fast forward a hundert years and there is a massive culture war between the "rotation slowdown deniers" and people religiously buying "rotation friendly" products.

The term "generate power from Earth's rotation" is basically saying "convert kinetic energy from Earth's angular momentum". If you extract energy, by conservation of energy that energy has to come from somewhere. So yes, we would normally expect Earth's rotation to slow.

But I think if you do the math, it would be absolutely miniscule.

I've often wondered about a similar issue with wind power. Would enough wind turbines dampen the force of wind?

On a local level they absolutely do, in a wind farm one turbine can shadow another and reduce its output significantly. It makes wind farm layout a tricky optimisation problem. On larger scales the impact is pretty minimal though, there’s so much energy spread over such a large area that significantly reducing it a global scale is not a concern.

If a politician talks in front of a wind turbine, does it make a sound?

Alternatively, we could speed up the Earth! Let's get rid of those pesky leap seconds!

I'm not saying that is why we left Mars.

Yeah, after making an oopsie with a runaway greenhouse effect in Venus. All this has happened before and it will happen again.

No because of conservation of angular momentum. Maybe it would cool the Earth's interior faster than otherwise though. It's heat flow from the inside to the outside that drives the fluid flows in the mantle and generates the magnetic field.

Earth's rotation has been slowing down despite principle of conservation of angular momentum, at about 2 mille-sec/century. Dinos had an hour shorter days than we do now.

I'm not an EE, but isn't this related to Tesla's last invention which bankrupted him - I believe he was working on electricity generation from thin air.

It's slowing down mostly because of drag induced by tides, which involve the sun and the moon. The total system including the earth, moon, sun and everything else does conserve angular momentum.

But this paper seems to imply that Earth, isolated from evening else in the solar system, could be made to slow down. This does seem like a violation of conservation of angular momentum...

This is poorly discussed in the article and AFAICS it reaches wrong conclusion.

I think the energy comes from weakening of the magnetic field and the energy stored within it, not from slowing down earth rotation. Earth as the result may rotate faster as the moment stored in the field will be transferred back to Earth as in the example with a sphere from the article.

Would this reduce the magnetic field stength allowing more cosmic rays to reach the surface.

I, for one, look forward to ground-level auroras.

Wouldn't this slowly slow the earths rotation down? Let's say everyone tried to build power plants using this.

Ah didn't see this comment and I asked the same. Yes, right? The energy has to come from somewhere...