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In this weekly series, Life's Little Mysteries provides expert answers to challenging questions.
There are roughly 7 billion people on Earth, with a total weight of approximately 800 billion pounds (363 billion kg). What if we all jumped at once?
Because people are spread somewhat equally around the planet's spherical surface , if we all jumped in place, nothing much would happen — all our lift-offs and impacts would cancel each other out, resulting in zero net force on the Earth, according to work by physicist Rhett Allain.
So let's imagine that everyone could congregate together in one place. Doing so would probably make it easier to synchronize our jump anyway.
Using the laws of conservation of momentum and energy, Allain, a physicist at the University of Southeastern Louisiana and blogger at Dot Physics, calculated what would happen to the 6-trillion-trillion-kilogram Earth under these circumstances. For simplicity's sake, he assumed the average human could jump one foot (30 cm) high and that we'd all be jumping from exactly the same point.
To cut to the chase, Allain found that our jump would push on the Earth ever so slightly, giving it a recoil speed of 2.6 x 10^-13 m/s. That is, in one second, Earth would move about a hundredth of the radius of a single hydrogen atom .
It's not so much, but would the infinitesimally small recoil last forever? Would we have permanently changed the course of the Earth? Allain says no.
"After all the people jump they would 'fall' back down — move towards the Earth. During this time, the Earth would move back up. All would be as it once was," he told Life's Little Mysteries.
The situation is much like two objects of very different masses connected by a spring. If you pull the masses apart and then let go, the force of the spring pulls them back together. The smaller mass moves much more than the larger mass, but both move. The Earth and the people are much like these two masses, Allain explained, except that "in this case, the spring is like gravity."
The crowd ROARED, jumping in their seats with excitement.... It was at this moment that a University of Washington seismology lab, located approximately one block away from the stadium recorded a quake registering between 1 and 2 on the graphs.
reply to post by forall2see
It has happened before. It is just the mass of a lot of people jumping at the same place. Especially at festivals, concerts and dance events where peepz tend to jump in rhythm.
That is why moving dance events, with a lot of trucks like a parade try to skip bridges or put the music down on the bridge. For the same reason the army doesn't march on a bridge.
Its a lot of fun and makes people feel connected but its not special imoedit on 3-12-2013 by Dumbass because: (no reason given)
So you're saying fans screaming, roaring cause earthquakes?
I don't think loudness or decibels are recorded as seismic. Are they all stomping? Doubt that would do it either
reply to post by Dumbass
New Zealand as we know, is prone to quakes as well. The professer mentioned in the article, John Vidale is also a member here on ATS, or has been from what I recall. I'll look through some of Puterman and Westcoasts threads to find him and see if he can share his two bits for us here.
I wonder if these people quakes are more common atop ground that is prone to earthquake activity. Or, could that simply be due to the fact that there is potentially a larger concentration of the meters over these more active zones. What we know so far is that 70,000 to 100,000 people could in fact trigger a seismic event.