If Earth spin decreased, how can I get it spinning faster?
The question Could we still live if Earth's spin speed slowed down by 90% assumed Earth's spin speed slowed down by undefined human activities (as if climate change was not bad enough). One answer suggested that Earth spinning slower will have weaker magnetic field, which is Not GoodTM
My question is: If that happened, what would be a plausible way to get to Earth spin faster, to get back the protection provided by Earth's magnetic field? Back to normal 24 hour days? Without destroying Earth in the process, so please no asteroid bombardment if we can avoid it.
We should increase spin slowly: even if it takes a century or two, it is OK. Because of huge energy necessary, any quick solution might melt Earth crust in the process.
And even though a slower spinning Earth was not so deadly, long nights are certainly annoying. And adding leap second every month (as we will have to in a few centuries' time) gets old soon too. We want to get Earth spinning because we want to, not because we have to. How?
XKCD cannot find an answer - maybe it is really tough.
I am not concerned about the bad effects this slow spin would have on Earth (you can add your answer to the question which inspired mine, follow the link). And "undefined human activities" cannot be reversed for whatever reason, we need to invent something new and interesting.
This post was sourced from https://worldbuilding.stackexchange.com/q/8425. It is licensed under CC BY-SA 3.0.
1 answer
Remove much of the Earth's mass.
The giant impact hypothesis states that about 4 billion years ago, when Earth was but a wee protoplanet, a Mars-sized object dubbed "Theia" hit it at an angle of 45 degrees, moving at 4 kilometers per second. This
- Destroyed Theia and knocked a bunch of material from Earth off the protoplanet; some of the remnants formed the Moon.
- Earth started spinning slower.
Previously, the Earth had a day of about 5 hours. Today, the day is about 24 hours (though the Moon is also changing the Earth's rotation as it recedes). The reason? Conservation of angular momentum. More mass put onto an object means that it will rotate slower. Conversely, take away mass from an object and it will spin faster.
So an asteroid impact would actually slow down the Earth's spin. To speed it up, simply remove most of it.
I think that violates the request to not destroy Earth, though, so even though that's your best option - because it would actually work - we have to consider alternatives. These are - to say the least - wacky, and would almost certainly not work. But, given the alternative (death!), I suppose we have to try.
To change the spin speed, we need angular acceleration. To have angular acceleration, we need torque. To have torque, we need to apply a force. So here are some ideas:
- Attach an incredible amount of rockets to one side of the planet and fire them until the Earth's spin has gotten back to what you want. This has a few downsides: It assumes the rockets won't just bury themselves in the ground, it's likely to fail, and will probably succumb to the Not In My BackYard problem.
- Push the moon in closer. The moon interacts with the Earth via tidal forces, which slows down the Earth's rotation, and makes the Moon recede. In theory, if you reverse the process (i.e. push the Moon inward), the Earth's rotation might - and this is a speculative "might" - speed up. If you can reverse those tidal forces - which I doubt you can - you're on the right track.
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