From: Kieran Mullen <kieran@phyast.nhn.ou.edu>
Subject: (urth) Re:  Digest urth.v028.n055
Date: Sun, 17 Oct 1999 11:18:38 

>From: "Jim Henley" <jlhenley@erols.com>
>Subject: Aw Hell (Giants)
>Date: Fri, 15 Oct 1999 23:29:38 -0400

>I was talking giants and the Square-Cube Law last night with my Amber (RPG)
>group and offered the oh-so-clever observation that one could get around it
>by living, giant-sized in the water, oh yes I did. But one of my pals said
>the real problem with the SCL is in the lungs - you pass a point where the
>surface area of your enlarged lungs can't absorb enough oxygen for all the
>cells in your enlarged body.

>Well darn! But I wonder; we didn't get into the math - I mean, Bill's from
>art school - but can anyone put a number on the size where lung limitations
>come into play?

   One data point would be the size of whales.  They don't seem to be
working on the evolutionary edge of lung capacity, since they can stay
submerged for long periods of time.  (That is, they seem to have enough
O2 marginal capacity to be able to hold their breath for long periods.)
If they were too close to the break point of the square cube law, I don't
think that would be easy for them.

   Our lungs are a fairly small fraction of our volume.  Anyone know 
what fraction of a whale's volume their lungs are?  Or an elephants?
If we have these few data points, I can fit the power law for you.
(I am pretty sure that the scale isn't linear.  Our legs, for example,
are proportionally thicker than an insects, as dictated by the SC law.)

           Kieran Mullen


 Kieran Mullen                         email: kieran@ou.edu
 Dept. of Physics and Astronomy        phone: (405) 325-3961
 The University of Oklahoma            FAX: (405) 325-7557
 Norman, OK 73019, USA                 http://www.nhn.ou.edu/~kieran/

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