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Re: Fw: Dinosaurs and birds



On Wed, Apr 11, 2007 at 06:58:56AM -0700, don ohmes scripsit:
> Why then, do track records set on windy days not enter the record
> books? Ignorance on the part of the AAU, or empirical evidence? 

But wind is a _field_ effect, equally producing thrust to the whole
windward side of the runner.

That rule is also being applied to an artificially flat and smooth
surface inside artificial shelter (stadium walls), and whatever benefit
definitely breaks down at higher wind speeds.  (No one goes out jogging
in a hurricane so they can run at sixty miles an hour.)

In the case of wings, they're not generating a thrust field to the whole
animal; they're generating thrust that feeds through the shoulder girdle
and does not directly affect the legs.

> No one argues that the upper body out-accelerating the lower body (the
> thrust-parallel-to-ground case) will eventually cause "problems" (=
> falling over). Small amounts of acceleration don't cause _instant_
> failure however, and what happens in the interim is important in the
> evolutionary context. 

Isn't that the gust-utilization that's been given as a probable
important use of wing precursors?

-- Graydon