Re: Re: Bio-Forces

On Wed, 5 Nov 1997 Cachalot@aol.com wrote:

Status: RO

> 
> In a message dated 11/4/97 6:39:35 PM, you wrote:
> 
> <<Sounds interesting except for one thing: Haven't you forgotten the
problem
> of relative scale? Eg if you made an elephant-sized mouse, it'd
collapse
> because it's legs would be too skinny to hold it up...that's why
> elephants/brontosaur etc have such thick legs in proportion to body
size
> vs. a mouse's body/leg ratio.
> 
> To drag this kicking and screaming back on topic: the scaling problem
is
> one that bugs me about giant alien bugs/bio-freak animals...especially
> bugs. A house-sized ant would break it's own legs when it fell on
them, in
> all but the lightest gravity...but no-one wants to look at an 'ant'
with
> elephant-like proportions, so mini- and movie-makers ignore the
> problem...see the teasers/ads for the new Starship Troopers movie...>>
> 
 <SNIP>

Actually the problem with insects is that their repiratoy systems are
designed to be scaled up.  In actuallity their exo skeletons are
incredibly strong and even if you scaled them up to a few tons it would
still provide sufficient support.  Just look at the fact that an ant can
lift 100 times its weight in its jaws and usually has to lift this to a
high angle with it's neck muscles.  The muscles are not the problem, the
methods of getting enough oxygen are.

In insects there is no need for an internal framwork since everything is
attached to the exoskeleton.  Insects don't have lungs per se but a
series of tubes that run the length of their body.  As you increase the
scaling factor, the rate that oxygen can diffuse from these tubes into
the
tissues decreases as a percentage.  Insects would have to be designed
with
respirators to work if you just scaled them up.

David Drake has taken this into account when he wrote The Jungle.  It
mentions that the giant grashopper had a symbiotic relationship with an
algae that produced hemoglobin.  The algae lived in the grasshopper's
tubes and fed it oxygen and in return got to be protected and carried by
the giant grasshopper.

Designing giant creatures should probably be done from scratch since
there
is a lot of size specific biology involved in most creatures.

Just some comments,

--Binhan