5 ms·
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 = 6.3e
by ziofill 2y ago
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)
- Retric 2y ago0.44 picowatts = 4.4e-13 watts so not in a detectable fashion before the sun consumes the earth billions of years from now.
- ziofill 2y agoWell, the watts that come out of the rotational energy must match the ones we need, for energy conservation.
- Retric 2y agoSure, 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.
- frozencooler 2y agoDoesn’t driving west to east on a highway slow down the Earth’s rotation, via the power transferred into the ground?
- BurningFrog 2y agoOnly while you're driving.
- amarant 2y agoYes, but that energy is returned when you break
- danillonunes 2y agoThings get interesting when you reverse.
- logifail 2y agoReminds 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..
- antod 2y agoIs that due to all the roundabouts switching direction relative to the Coriolis effect? Hence the relevance of the UK? Presumably without roundabouts it's all random directions and balanced? Or am I barking up the wrong tree?
- logifail 2y agoIt 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.
- rocqua 2y agoIt'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.
- thayne 2y agoThen when you stop the angular momentum of your car is transferred back to the earth.
- MathMonkeyMan 2y agoThis 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.
- api 2y ago> 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. Really puts how small we are on a cosmic scale into perspective. If we did it for a million years at current energy use scale it would shorten our day by about 1.1 seconds.
- OccamsMirror 2y agoWouldn't it extend our day?
- api 2y agoYes. Had it backwards.
- aeternum 2y agoIsn'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.
- mr_mitm 2y agoNo, that's not possible due to conservation of angular momentum. Only tidal effects can transfer some of it to the sun.
- foota 2y agoThe IERS will never stand for this!
- DriverDaily 2y agoCan we put energy in to speed it up? That way a day can be 24 hours exactly instead of 23 hours, 56 minutes, 4 seconds, etc...
- incognito124 2y agoI mean, solar day is 24h, it's the sidereal day that's 23.9344696h
- Detrytus 2y agoDon’t follow your logic: if the day is currently shorter than 24 hours we need to slow the Earth rotation down, not speed it up.
- DriverDaily 2y agoYou’re right, I had that backwards
- deleted 2y ago[deleted]
- golol 2y agoWhere does the angular momentum go?
- fsckboy 2y agoit'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.
- teamonkey 2y agoTorque is applied, the paper mentions a magnetic braking effect.