MadSci Network: Other
Query:

Re: Why can china withstand more underwater pressure than humans in ocean depth

Date: Tue Jan 5 11:17:22 1999
Posted By: Tye Morancy, MadSci Admin
Area of science: Other
ID: 915501470.Ot
Message:


   That's an interesting question.  There is a simple reason for this 
"apparent" contrast.  The delicate artifacts at the Titanic resting site, such 
as the fine bone china and crystal, survive the crushing forces due to some 
fundamental differences between them and the human undersea explorers.

   A human is a complex machine composed of solids, liquids, and, most 
importantly, gases.  When exposed to the environment without a pressurized 
environment to protect, the human body would suffer an instantly fatal 
implosion event.  The china, on the other hand, in and around the wreckage sits 
apparently unaffected since it is solid.  The forces from the environment 
surrounding it are pushing on all its sides and cancelling out.  Since it is an 
"incompressible solid", nothing happens to it.  The human body is very 
compressible though, so a compressing environment will do its worst and make 
short work of our explorers.

   If a sealed china vase, let's say, was able to survive the violent jarring 
motions of the ship all the way to the bottom, the pressure would surely 
implode it and rupture it, because of the compressible gases within. Therefore, 
the forces on the exterior would've been far greater than inside and the vase 
would break.  An open vase, though, fills with the surrounding water and is 
very incompressible to the outside forces.  The forces also equalize and it 
helps that china is incompressible like some other pure solids.  Its easy to 
assume it would crush because we think of china as delicate in the sense of 
other types of forces such as the jarring or impacting kinds.  
  
   A human has a body with lots of dissolved gases within it, such as oxygen 
and nitrogen, which can be compressed and expanded.  These gases and such make 
the human body compressible under the conditions present in the environment.
This is also the reason why deep sea divers need to undergo compression and de-
compression before and after dives.  

   Thanks for the question...I hope my answer helped...


Tye Morancy


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