Re: Dinosaur weights

[SarahAnne Hazlewood <sash@teleport.com>]

At 09:15 PM 8/21/97 +0100, you wrote:
>Sadly, the chemistry lab at the University of Bath was not the best
>place to conduct this and I could'nt get a suitably marked beaker or get
>the horrid models to sink properly.  And, they kept falling off the
>cotton.  The water kept wicking down the side of the jar and it was all
>a complete disaster.  We all went off to the pub for lunch and I have
>never gotten around to doing it again.  Anyone with access to proper
>equipment could certainly try it and check dino weights in the process. 
>I'd be really interested to hear the results.
>
>Helen

This type of experiment would be quite useful to determine the "volume" of a
creature - ie how much space does it occupy.  You simply immerse the model
completely.  If it's the right size and shape, the volume will be correct
regardless of the composition of the model - helium balloons or concrete.
(Remember this method from measuring shortening in Home-Economics?)

To determine the mass of an object, the internal structure and density of
the scale would have to duplicate that of the original creature.  (were they
big-boned or just fluffy?).  The model would then be allowed to free float
in the water, and the amount of water displaced would equal in weight the
model itself.  Just having the size right won't give you the mass.  Those
air sacs really do matter.  As for not getting the model to "sink right",
that would actually be the point.  A lighter creature wouldn't sink as far,
displacing less water.  A heavier creature would sink more, displacing more
water.  (I think there's a density at which this breaks down - a shot put,
for instance, couldn't displace enough water.  There must be some bouyancy
for the whole mess to work)

The obvious question is, once you have a full-scale, innards-all-correct-
density, sort of model, why mess with the water?  Just weigh the thing!  The
experiment usually works the other way around - how heavy can I make this
thing and still have it float.  That's when calculating the water
displacement is useful.  So, if we had a fully constructed creature and
wanted to know if it could have been aquatic, toss the model in the tank and
EUREKA!

        In  Peace  -  SarahAnne