The AFU and Urban Legend Archive
Science
 jumping chinese




From wilms@astro.uni-tuebingen.de Fri Dec 13 23:17:32 1996 Date: Fri, 1 Nov 1996 17:50:04 +0100 (MET)
From: Joern Wilms <wilms@astro.uni-tuebingen.de>
Subject: AFU FAQ

F.   If the entire population of China jumped up at the same time: a) the 
     Earth's orbit would be disturbed, b) the entire US would be swamped 
     by a tidal wave.

O.k., if everybody in China weighted 100kg (200 pounds) and jumped down from one meter height (about 3ft) the total energy released would be mgh=10^(12) joules. The total energy in an Earth quake or a huge tsunami is about 10^(20) J (that's the number for the San Fransisco 1906 Earth quake, see in Kuiper, G. P., ed., The Earth as a Planet, Chicago: Univ. Chicago Press, 1954), thus several orders of magnitude higher than the jumping of the people --> no effect would be felt in the U.S.

The question to a) is that you cannot disturb the Earth's orbit by just jumping up and down on Earth. This is because to change the orbit you need to change the momentum of the Earth and you cannot do that by just jumping up and down (no momentum gets transferred). Now, if all people in China would jump so high that they would reach the Earth's escape velocity, momentum WOULD be transferred and the Earth's orbit would be changed by a VERY minimal amount (that's nothing more than the rocket principle: to push yourself forward you need to push something backwards).

For the other question: 

T.   There was a natural nuclear reaction in Africa long ago [NOT an 
     explosion.]

This refers to the so-called Oklo phenomenon. This is the Francevillain Deposit of Uranium in Oklo (Gabon) where a difference in the abundances of two Uranium indicates that a natural nuclear reaction took place a few million years ago. A more popular reference to that is in Krane, Nuclear Physics (don't have the book on my desk). Also information can be found at

http://www.crpg.cnrs-nancy.fr/MODEL3D/oklo.html

and search on Oklo in AltaVista gives 7 pages of references.


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