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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.origins
Subject: Re: more on large animals and gravity
Message-ID: <692@psivax.UUCP>
Date: Thu, 29-Aug-85 15:48:56 EDT
Article-I.D.: psivax.692
Posted: Thu Aug 29 15:48:56 1985
Date-Received: Mon, 2-Sep-85 03:43:12 EDT
References: <382@imsvax.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 98
Summary: 

In article <382@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes:
>
>               Scientists studying dinosaurs around the turn of the century
>          concluded that  the big  sauropods lived  in water.  Calculations
>          they did  showed that  their legs  would not support them on land
>          and that water  bouyancy  would  have  been  their  only possible
>          hope.  Two observations:
>
>               1.   Those who  made these  calculations were not relying on
>                    any immature or incomplete body of knowledge as regards
>                    engineering or  math.  The  Brooklyn bridge had already
>                    been built by then and  the  first  really  large steel
>                    warships were being built.

	The basic fallacy in these calculations, as I understand them,
were failure to properly account for the bulk properties of bone, and
for the effects of the internal structure of bone. In short, an
analysis based on the physics of steel girders will not work for the
different reactive properties of bone.

>
>          RIGHT.  I admire a man with a sense of humor.  This was enough to
>          send me  back  to  the  Rockville  library  where,  amongst other
>          things, I learned about the breviparopus.
>
>               I went  back to  the library and spent several hours looking
>          at the more recent  dinosaur books.   Basically, the  newer books
>          indicate  that  scientists  have  decided that sauropods lived on
>          land, based upon the aforesaid lack of aquatic structures as well
>          as evidence  from newer sauropod tracks.  There was no mention of
>          anyone doing  calculations showing  that sauropods  could move on
>          land.  Like  I said, the basic principles of engineering have not
>          changed since the late 1800s....
>               No mention  of any precise math formulations in either these
>          two or any of the other  books  I  found.   The  enigma  is still
>          there.  Both  describe the many problems of weight for dinosaurs.
>
	Well, it sounds as if you are reading "popular" books, which
quite naturally leave out a lot of detail. The correct place to find
out about these things is in *journals* where the truely detailed
analyses can be found. If I can get to UCLA this weekend I will try to
find at least a few of the references I have mentioned.

>          The Avon Field Guide states that:
>
>               "The largest carnosaurs may  have managed  nore more  than a
>               rapid rolling  walk, using powerful muscles to keep the tail
>               held stiffly off the ground, so balancing the  mighty torso,
>               short, thick  neck, and  big, deep head....

>               So the best modern science can do for the mighty tyrannosaur
>          is to  make a  jackel out  of him.  It's almost too funny to deal
>          with.  

	I agree, if this analysis is correct it is quite absurd! But
many(perhaps most) palaeontologists disagree with this analysis.
Another journal article I read recently covered dinosaur gaits, and
it came to a quite different conclusion.  Or you might try the
"popular" book "Warm-blooded Dinosaurs", it is better than most, and
gives more in the way of calculations.
>
>               I have news for  Stanley Friesen,  the editors  at Avon, and
>          anyone else  interested in  dinosaurs.  Nothing  makes it in this
>          world by  wallowing,  shuffling,  floundering,  hobbling, gliding
>          without being  able to  flap your  wings and  FLY when needed, or
>          flying at 5 mph.
>          ...  Likewise, the pteratorn  had to  catch prey  to live.
>          Try catching  a deer or rabbit sometime with your governor set at
>          5 miles per hour.  Likewise, the picture science gives us  of the
>          pterasaurs  is  basically  ludicrous.   You get this picture of a
>          giant flying reptile, making it's home in cliffs, using its 5 mph
>          stall speed  to spread  its wings  into the wind and take off and
>          soar.  The problem with  all  this?   It's  wouldn't  be  able to
>          capture airborne  prey at  5mph;
>
	You do not seem to understand the significance of stall speed,
it is the *minimum* speed at which something can fly, not the maximum.
The optimal flying speed for Pteranodon(the genus for which the
calculations were done) was more like 30mph. The reason the low stall
speed is so important is that its wings were so large relative to its
body that it couldn't have flapped them while on the ground, so it
needed pre-existing wind speed to take off. It *didn't* need cliffs,
that was the assumption when we thougth it took more than 5mph to take
off.  This animal was in fact predominantly a glider, very similar in
build and proportion to am Albatros. It seems to have been a sort of
cross between an Albatross and a Pelican, catching fish by scooping
them out of the water with its large beak. If you have ever watched
them, fishing Pelicans do not even fly 30 mph!
	As far as other types of Pterosaurs are concerned, most of
them are quite small, and have more normally proportioned wings, so
there is no problem about *them* flying.

-- 

				Sarima (Stanley Friesen)

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