# Urban myth

Peter Pan
Help me disspell this urban myth(sorry to waste all of your time)

If everyone in china jumped off a ladder at the same time, would it be enough to knock the earth out of orbit or mess up how it(the earth) rotates on its axis?

a few things to concider

1) how far everyone is spaced apart
2) how tall the latter is
3) average weight of the 2 billion people in china

sorry, i didnt see that this question was just posted

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Staff Emeritus
Gold Member
Dearly Missed
A few other things to consider
1) The mass of the earth
2) The momentum of the earth in its orbit
3) The conservation of momentum

Homework Helper
Conservation of momentum implies that if one chinaman climbs a ladder and then jumps back down, then the net movement of the CG of the system is 0. Not close to zero -- but actually zero. So the sum of any number of people jumping off of ladders is not going to cause the earth to go off kilter either. Unless something actually reaches escape velocity, it can't have a long-term effect on the earth's path.

Now. let's say that there are N chinese, with average weight m, jumping from height h. Then the total energy is about
Nmgh
Let's use some conservative numbers here:
Let's say that there are 10 billion chinamen
Let's say that they weigh 100 kg each
Let's approximage the acceleration of gravity with 10m/s/s
Then we have
10,000,000,000*100*10=10,000,000,000,000
1*1012 joules of energy.

The earthquake chart at http://www.geop.itu.edu.tr/~onur/seis/energy.html [Broken]
gives that as equivalent to a magnitude 5.5 earthquake, or about a fifth of a Nagasaki bomb.

A magnitude 5.5 earthquake in San Francisco probably wouldn't even be noticed outside California without special detection equipment.

I would guess that you would see a larger earthquake every week or two.

It certainly pales in comparison to the Castle/Bravo nuclear test which was thousands of times larger.

Based on the results from nuclear testing and earthquakes, some of the people in nearby countries might notice.

Regarding spacing and synchronization -- the Nuclear Bombs typically have all of the energy within just a few cubic meteres, and effectively instananeously.

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