This wouldn't work because they don't take into account the gravitational force everyone exerts on the Earth itself. For example, if you weigh 185 lbs (or 400 if you're Grav), you would pull that much combined force on the entire Earth itself. Even if everyone were to collectively push the Earth by jumping at the same time, the total gravitational pull of everyone in midair would nudge it back to where it was before.
The only way it would work (and my preferred method) is to blast everyone off into space at high speeds. It would be like a rocket except the fuel would be people! I win.
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