Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Can Earth's rotation generate power? Physicists divided over controversial claim

nature.com

Post reply on HN
Print view View original

131–140 of 231 posts

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#131

Post by peer2pay »

Nifty3929 wrote: post #62
deepfriedchokes wrote: post #51

Earlier quoted context omitted.

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

I haven't seen any data that backs that up based on general principals. Most of the cost is in artificially-imposed operational requirements - however well founded. Also, remember that nuclear, unlike solar, has a lot of room for improvement still, both in how it's done, and how it's regulated. Solar has already been tremendously optimized, while nuclear has not. The cost argument seems to be advances by the same peo…

Calling Chernobyl a minor accident is insane. We are lucky it wasn’t worse but even then most of Europes forests are still polluted from the fallout. People directly killed during the incident is not a great indicator of incident severity when we're talking about environmental pollutants.

Nobody died from installing asbestos insulation yet here we are.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#132

Post by Certhas »

SecretDreams wrote: post #55
deepfriedchokes wrote: post #51

Earlier quoted context omitted.

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

> things like solar and batteries. Magnets too - let's just go magnets everywhere. Reality is solar isn't viable everywhere. And it's not optimal to put it in places where you use the sun to grow food. We should follow a holistic approach. * Wind where it's windy. * Solar where it's sunny - ideally on buildings/away from farms. * Hydro where possible. * Nuclear where it makes sense, i.e. stable geography, low occuren…

What do you base all these claims on? Plenty of papers show Solar + wind + storage is viable practically everywhere.

Also there is a ton of research on planning energy systems and what technology mixes make sense. This stuff has to be economical. Energy costs are measured in percentage of GDP. Simply liking nuclear doesn't make it viable. Especially in a world with PV meaning you can't sell energy during the day.

There really is only one macro fact that will shape the energy system of the future: The price of PV modules is now effectively zero in rich countries. Everything else has to be judged by how well it complements/makes use of free energy during daylight hours. The geopolitical implications of this haven't even begun to be explored.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#133

Post by golol »

ziofill wrote: post #25

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)

Where does the angular momentum go?

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#134

Post by rokkamokka »

peterashford wrote: post #120
sroussey wrote: post #86

The Earths rotation already generates power for us: wind. It’s why the jet stream only goes one direction.

Wind power is mostly due to solar energy. Earth's rotation contributes a very small amount and even that smaller effect is more located in the upper atmosphere where we don't collect wind power versus solar caused pressure gradients

While true, if the earth stopped rotating the sun would also stop being "evenly" distributed around the globe, which would affect wind patterns a lot

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#135

Post by [deleted] »

Certhas wrote: post #119
api wrote: post #84

Earlier quoted context omitted.

I was about 99.99999% sure that one was bogus because it was violating bedrock conservation laws. I'm not sure that this does. AFAIK there is no conservation law that says a spinning mass can't extract power from that. Still... it would have been hilarious of the EmDrive had worked. "Well, they've progressed! Last time we checked in on the third planet in this star system its inhabitants were still using warp drives…

For the EmDrive it also was that the claimed theoretical mechanism was mathematically impossible, because it was based on equations that (like all known equations and everything ever observed) satisfy the conservation laws. That's a good question actually. Supposedly this is extracting energy from the rotational kinetic energy of the earth. I haven't looked at the paper but you'd need to worry about conservation of a…

[deleted]

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#136

Post by walleeee »

grepfru_it wrote: post #63
EncomLab wrote: post #45

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.

Solve the waste problem and you solve nuclear. Waste is still the giant elephant in the room and a lot of people have a fifth grade solution to the problem (we will bury it under ground! We will fly it to the sun! We will resuse it until it is no longer radioactive!) I used to have a neighbor who worked for the DOE, all of the viable solutions are blocked by people who don’t want it in their backyard. Can’t really mo…

Some MSRs can consume spent nuclear fuel, that's a 7th grade solution at least

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#137

Post by qnleigh »

drewolbrich wrote: post #104
bmacho wrote: post #71

Imagine a massive planet spinning in empty vacuum. Can the inhabitants slow down their planet, and generate electricity? I suspect that they can generate electricity with angular momentum with it, that can be only used to do work with the equivalent angular momentum.

The Moon's tidal forces are already slowing down the rotation period of the Earth, which was apparently only 5 hours long about 4.5 billion years ago.

Yes, but when you consider the combined system of the earth and everything that affects its orbit, angular momentum is conserved.

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#138

Post by qnleigh »

fpoling wrote: post #38
qnleigh wrote: post #16

Earlier quoted context omitted.

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.

That would make so much more sense. So then the comments about only slowing down Earth's rotation by a few ms/century. It would deplete Earth's magnetic field, and likely on a much faster timescale.

This would not be good...

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#139

Post by qnleigh »

nyc111 wrote: post #44

Why does the earth have a magnetic field?

This is a great question, and it's not as simple many comments here make it seem to be. This Veritasium video has a great explanation (and an enormous ball of molten sodium).

Re: Can Earth's rotation generate power? Physicists divided over controversial claim

#140

Post by bee_rider »

nopelynopington wrote: post #23
ChrisNorstrom wrote: post #3

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?

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

Fundamentally, yes, right? For some definition of “enough.”

Actually, after some quick googling (so, maybe someone actually knows better) it seems like this is an issue where there’s an active discussion? Maybe somebody actually involved in the field knows more.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2004JD00...

https://esd.copernicus.org/articles/3/79/2012/esd-3-79-2012....

But that came out in 2012. I bet you could find some other article citing it, as rebuttals.

It seems a bit implausible to think we could somehow pull enough energy from the wind to really matter, but then again carbon based climate change also seemed a bit implausible so, I guess, who knows?

Post reply on HN