this post was submitted on 18 Jan 2024
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xkcd

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For decades I've been working off the accumulated rotation from one long afternoon on a merry-go-round when I was eight.

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[–] marcos 14 points 10 months ago (1 children)

Yes, we would affect the Earth's rotation. It's just by a ridiculously small amount that nobody would ever be able to measure.

[–] [email protected] 5 points 10 months ago* (last edited 10 months ago) (4 children)

Now I am wondering how many humans would it take to be measurable and significant?

[–] Aceticon 5 points 10 months ago* (last edited 10 months ago)

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.

[–] [email protected] 3 points 10 months ago

how fast do you spin them?

[–] MySkinIsFallingOff 1 points 10 months ago (1 children)

Whatever amount of people it'd take, the effect we'd make, would cancel at break.

[–] [email protected] 1 points 10 months ago (1 children)

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.

[–] MySkinIsFallingOff 1 points 10 months ago (1 children)

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.

[–] [email protected] 1 points 10 months ago

It's because your return journey is closer to the axis of the earth so your action has less torque.

[–] Atlas_ 1 points 10 months ago