From: prl@csis.dit.csiro.au (Peter Lamb)
Subject: Re: Muscle tissue from mouse to sauropod
Organization: CSIRO Division of Information Technology
Date: Mon, 25 Jan 1993 02:19:27 GMT

news@fedfil.UUCP (news) writes:

>Adrien Desmond (HOT BLOODED DINOSAURS) that thorough calculations indicate
>that fifty lbs or thereabouts is the absolute maximum size for any flying
>creature in our world, and that beyond that, even simply holding wings in
>a turn, much less flapping them, would break bones.


Unfortunately for Ted, the "thorough calculations" are neither given nor
cited by Desmond, so we are unable to examine their assumptions.
Desmond says:
	"calculations [ no mention of their thoroughness - prl ]
	bearing on weight and power suggest [ not absolutely define -
	prl ] that the maximum weight that a flying vertebrate could
	attain is about 50lbs."[1], p182.

Desmond cites L. B. Halstead to defend this statement, but this is also
to a popularisation, and doesn't contain any sort of calculation. In
fact, Desmond is not much more than a paraphrase of Halstead:
	"In any flying machine, the larger it becomes the more power it
	requires, and the power needed increases at a higher rate than
	the linear increase in size, if the general proportions ramain
	the same. ...  There comes a point beyond which the system will
	no longer function. The maximum weight of a flying vertebrate
	is calculated to be about 50lbs. Were this not the case, as
	Haldane noted, `eagles might be as large as tigers and as
	formidible to man as hostile aeroplanes.'"[2] p142.

Halstead goes on with Haldane's calculation of the size of sternum
needed to support flapping-wing flight in man.  While Halstead appears
to be using a figure of 50lbs calculated by Haldane, he never
explicitly says this, and also neglects to mention Haldane at all in
his bibliography.

Halstead at least gives us some hint of where his problem
might lie: "... if the general proportions remain the same ..."
The remainder of Halstead's discussion refers to birds; and if this
conclusion is based on living bird data, then it is easy to see where
the argument breaks down, unless Ted can point us to a bird that
scales linearly into a large pterosaur.

I have seen these quotes by Haldane in other places (from Ted
himself?); can anyone provide us a reference, and preferably also a
summary of Haldane's assumptions?

Anyway, Ted's continual assertion that Desmond somehow provides an
authoritative upper limit on the weight of vertebrates using
flapping-wing flight is simply not true. The calculations are not
merely lacking in thoroughness, they are completely absent, both in
Desmond and in the source he cites for support.

Of course, it has already been pointed out in t.o that human muscle
powered, sustained flight greatly in excess of 50lbs has already been
achieved, by using suitable unpowered prostheses and the more powerful
leg muscles, rather than the rather weaker chest and arm muscles.


Another entertaining possibility is that Ted's reduced felt effect of
gravity may not have helped flying animals all that much. Assuming a
constant mass, composition and depth of atmosphere, atmospheric
pressure would be halved by halved gravity. This would lead to a halved
atmospheric density (mass/vol), and so reduced lift at a constant
flight velocity.

Anyone have aerodynamic equations for sinking rate which include
atmospheric density?

Note that all animals would have to survive in a halved oxygen partial
pressure, too. Maybe that's why the dinosaurs were so dumb :-) See Huxley, A,
"Brave New World" for how this might be applied to humans :-( .

Of course, a reduced effect of gravity caused by tidal effects would
not have a constant atmospheric depth, but it has already been pointed
out that the tidal effects and land surface distribution proposed by
Rose & Ted in this "model" are incompatible with the known distribution
of large sauropod fossil finds.

-- 
Peter Lamb (prl@csis.dit.csiro.au)
Newsgroups: talk.origins