[net.origins] Those amazing 250 pound birds.

dmcanzi@watdcsu.UUCP (David Canzi) (08/13/85)

Ted Holden has used the pteratorn, a 250 pound bird with a 30 foot wing
span, as evidence that the force of gravity was once less than it is
now.  Birds existing today that fly weigh less than 30 pounds, and the
largest can barely take off.

I'll give Ted the benefit of the doubt, and assume for the sake of
argument, that the pteratorn existed, would not be able to fly today,
and that the force of gravity was weaker before the flood.  If all this
is so, then, even in lower gravity, the pteratorn would *still* not be
able to fly.

Sure, the bird would weigh less, but so would the air.  The lighter air
would, as a result have lower pressure, and as a direct result lower
density.  Even though the bird would be lighter, the thinner air still
wouldn't be able to support it.

The flood waters above the surface of the earth couldn't add any weight
to the atmosphere to increase it's density to a point where it could
support the bird, because, as Ted has said, the water was *orbiting*.

I'm rather curious to know whether the Velikovskians have ever thought of
this problem, and if so, what their answer to it is.

-- 
David Canzi

Ultimate tabloid headline: "Crazed by UFO radiation, pregnant man bites dog."

stro@ur-univax.UUCP (08/16/85)

I do not know much about these 250 birds, so perhaps someone can enlighten
me: How do we know these birds flew, anyway.  Just because they had wings?
Peguins have wings, ostriches have wings, so does our hospital - but
none of them fly.



						- Steve Robiner
						  University of Rochester

       {allegra|seismo|decvax}!rochester!ur-univax!stro

peter@baylor.UUCP (Peter da Silva) (08/16/85)

> Sure, the bird would weigh less, but so would the air.  The lighter air
> would, as a result have lower pressure, and as a direct result lower
> density.  Even though the bird would be lighter, the thinner air still
> wouldn't be able to support it.

Wrong.

The limiting factor in bird growth isn't wing size, it's muscle power. A
bird of indefinit seize can glide. The problem is moving the wings: pushing
a mass of air around.

Even if the gravity and air pressure are less, the bird can still generate
the same amount of power & would be able to fly.

Of course there are still many problems with the "low gravity" thesis. Here's
one:

	If skylab came crashing down in a couple of years, how long
	would the aqueous firmament stay up?
-- 
	Peter da Silva (the mad Australian werewolf)
		UUCP: ...!shell!neuro1!{hyd-ptd,baylor,datafac}!peter
		MCI: PDASILVA; CIS: 70216,1076

dmcanzi@watdcsu.UUCP (David Canzi) (08/23/85)

In article <417@baylor.UUCP> peter@baylor.UUCP (Peter da Silva) writes:
>> Sure, the bird would weigh less, but so would the air.  The lighter air
>> would, as a result have lower pressure, and as a direct result lower
>> density.  Even though the bird would be lighter, the thinner air still
>> wouldn't be able to support it.
>
>The limiting factor in bird growth isn't wing size, it's muscle power. A
>bird of indefinit seize can glide. The problem is moving the wings: pushing
>a mass of air around.
>
>Even if the gravity and air pressure are less, the bird can still generate
>the same amount of power & would be able to fly.

If the bird simply glided, it would have the same glide slope under
heavy gravity as it would under light gravity (since the density of the
air will be proportional to the strength of gravity).  I expect a bird
with 15 foot wings would tend to avoid flapping them.  It could search
out updrafts and circle in them to gain altitude, as needed.

If it's too far to the nearest updraft, the bird may *have* to flap its
wings.  Under lighter gravity, the bird has less energy because it's
breathing thinner air.  It maintains altitude by accelerating some mass
of air downwards, but under lighter gravity, less mass must be
accelerated downwards, so less energy is required.  So far, the
advantages and disadvantages of lighter gravity balance.

In order to accelerate this smaller mass of air downwards, the bird
must flap its wings at the same rate as it would in heavier gravity,
because the air is thinner.  The effort required to flap its wings, ie.
to accelerate the mass of its wings upward at the end of the downstroke
and downward at the end of the upstroke, remains the same for our poor
oxygen-starved bird.  This means (if I've managed to take everything
into account -- I doubt it) that under lighter gravity, it would
actually be harder for the bird to fly.

So, if the pteratorn couldn't fly today, it would have had to walk
back then too.

>Of course there are still many problems with the "low gravity" thesis. Here's
>one:
>
>	If skylab came crashing down in a couple of years, how long
>	would the aqueous firmament stay up?

If the orbiting water is far enough above the atmosphere, this would
not be a problem.  The water would have to be orbiting either as a ring
around the earth, or as a spherical body like the moon (held together
against tidal forces by surface tension, perhaps?)  I'd be interested
(and probably amused) to find out what shape Velikovsky thought the
mass of water took.

We shouldn't be arguing... we're on the same side... I think...
-- 
David Canzi