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)
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.
Isn't friction from the atmosphere already slowing the planet's spin? Many weather effects like hurricanes ultimately derive their energy from a combination of the earth's rotation and thermal/uneven heating effects so I don't see why this is contentions.
Like most things, nature is already doing it and has been for millions of years.
Why would angular momentum be conserved? Rotation within an atmosphere should cause friction would should convert angular momentum into thermal loss.
Interestingly, it looks like the upper atmosphere generally rotates faster than the planet, so it could be that the opposite effect actually dominates. IE the uneven heating causes a atmospheric bulge that actually pushes the atmosphere around slightly faster than the planet rotates, thereby slightly contributing to planetary angular momentum.
Because the system exhibits rotational symmetry. It follows from Noether's theorem that angular momentum is conserved. Only when you include the interactions with other stellar bodies you lose the symmetry and you have an opportunity to shed angular momentum.
Sure. I'm not going to perform the computation, but my physical intuition tells me that it's completely negligible. The amount of thermal energy the earth absorbs or emits per year must be dwarfed by several orders of magnitudes compared to the rotational energy or the energy lost via tidal friction.
It's actually driving north south that changes the rotation speed. Because your 'real' speed gets higher as you get closer to the equator, you 'steal' momentum from the earth as you get closer to the equator.
Its effectively the same principle as a figure skater pulling in their arms when spinning, to spin faster.
Reminds me of a glorious question from undergraduate physics:
Calculate the change in the length of the Earth's day if the UK were to switch to vehicles driving on the right-hand side of the road rather than the left..
It was indeed all about the roundabouts. I forget the details but I do know it took us quite a while to get there(!)
Those tutorials filled me with dread at the time, but with hindsight they were - how can I put this - a fairly formative experience.
Watching your tutor use paper and pencil - and estimation - to calculate something like that was actually quite inspiring. That was, once it stopped being terrifying.
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.
it's the angular momentum that gets transferred to the earth's spin, and all the other numbers, energy, power, are simply how the books are balanced. GP should have asked the question in terms of momentum in the first place.
with energy, you need to consider friction, losses, thermodynamics 3rd law, but with momentum it's pure.
