Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watdcsu.UUCP Path: utzoo!watmath!watnot!watdcsu!dmcanzi From: dmcanzi@watdcsu.UUCP (David Canzi) Newsgroups: net.origins Subject: Re: Those amazing 250 pound birds. Message-ID: <1626@watdcsu.UUCP> Date: Thu, 22-Aug-85 22:34:12 EDT Article-I.D.: watdcsu.1626 Posted: Thu Aug 22 22:34:12 1985 Date-Received: Sat, 24-Aug-85 15:50:02 EDT References: <1600@watdcsu.UUCP> <417@baylor.UUCP> Reply-To: dmcanzi@watdcsu.UUCP (David Canzi) Distribution: net Organization: U of Waterloo, Ontario Lines: 54 Summary: 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