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xkcd #2882: Net Rotations
(imgs.xkcd.com)
Alt text:
For decades I've been working off the accumulated rotation from one long afternoon on a merry-go-round when I was eight.
If every human on the planet just started running in the same direction, could we collectively affect the rotation of the planet like running on a ball? 🤔
Yes, we would affect the Earth's rotation. It's just by a ridiculously small amount that nobody would ever be able to measure.
Now I am wondering how many humans would it take to be measurable and significant?
The mass of the Earth is 5.972 × 10^24^, so you would need 5.972 × 10^20^ humans of 100 Kg each all turning in the same direction to make the Earth rotate 1% the other way (so about 597,200,000 trillion humans).
PS: I might be slightly wrong here as rotations have to do with angular momentum which is a bit more complicated than the linear kind because rotational inertia doesn't depende on mass alone, but the law of conservation of angular momentum does apply.
how fast do you spin them?
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Whatever amount of people it'd take, the effect we'd make, would cancel at break.
I was going to say a similar thing, how are you going to get gone without canceling it out.
But also if you walked away from the equator then walked until you were directly north/ south of your home before walking home, some effect would remain.
I don't believe that to be correct, but I'm to stupid to refute you. So I'll take it as facts. Thank you for enlightening me.
It's because your return journey is closer to the axis of the earth so your action has less torque.