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Extra Credit Blog

JUMP!
By: Lauren Kern

If everyone went to the same point on the Earth and jumped at the same time, what would happen?


This question is asked by many physics students (and some teachers) all around the world. Not only is it an interesting question, but it is a good question. What would happen? On this Earth, there are about 7 billion people, and the total weight of all these people is somewhere around 800 billion pounds (363 billion kg). The mass of the Earth is 6 x 10^24 kg. Clearly, something would happen.

This question was answered by a physicist at the University of Southeastern Louisiana named Allain. He did this by assuming that each human could jump about 1 foot (30 cm) high at the exact same location on the Earth.

Momentum Conservation Equation:

Energy Equation (for initial velocity of the people):

Equations Combined:

Velocity of the Earth:

With Allain's calculations, he found that everyone jumping at the same time at the same place would push the Earth slightly and give it a recoil speed of 2.6 x 10^-13 m/s. But, after the people jumped they would "fall back down" and during this time the earth would move back to its regular position.


This could be compared to two masses connected with a spring. When you pull them apart but then let go the string brings the two masses back together, with the smaller mast moving more than the larger mass.

In the end, nothing would really happen. Although it seems like something would happen considering there are so many people in the world, it the end, it will feel as if nothing has changed. And, realistically, this scenario is impossible because it would be impossible to get all 7 billion in this world in the same position and jumping the same height at the same time.

All of these people would make up about the size of Rhode Island or Los Angeles. If this "experiment" was tried it Rhode Island, this would be impossible at T.F. Green Airport in Warwick, Rhode Island because even if they could run at a 500% capacity for multiple years, the group of people would not even seem to have gotten smaller.


Links: https://www.wired.com/2010/08/what-if-everyone-jumped/
https://www.livescience.com/33383-everyone-on-earth-jumping-at-once.html
https://www.youtube.com/watch?v=jHbyQ_AQP8c&feature=youtu.be


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