"Richard S. Norman" wrote:
>> On Mon, 09 Dec 2002 20:01:57 -0500, Jerry Avins <jya at ieee.org> wrote:
>> >Gary Bergstrom wrote:
> >>
> >> > > jmdrake wrote:
> >>
> >> > http://www.americanantigravity.com/> >> >
> >> > While on the surface it may seem "cranky" the fact is that their
> >> > flyer actually works. Now if it works by true "antigravity" or
> >> > by some other force is a big question. But the plans are pretty
> >> > simple and the results have been reproduced many times over.
> >> > However someone might mislabel them "cranks" just because they
> >> > have the word "antigravity" in their URL.
> >> >
> >> > Regards,
> >> >
> >> > John M. Drake
> >>
> >> The first time I saw this was on the cover of a Popular Science (I
> >> think) in the '60s. Not antigravity, just propulsion by moving air.
> >> The models are so light, because it's hard to move much air without
> >> arcing. (That old model on the cover was square rather than
> >> triangular, but otherwise looked the same!)
> >>
> >> And yes, I would label (NOT mislabel) them cranks because of the word
> >> antigravity.
> >>
> >> Gary
> >
> >Waddya mean, "cranks"? Antigravity devices are all around us. I'm typing
> >right now on a keyboard a little higher than my lap. You can bet that
> >gravity would pull it down pretty quick it there weren't something
> >preventing that. The same goes for what's holding me up. Those things
> >must expend energy continuously to do what they do. If you think that
> >there can be no work without motion, just hold a full gallon jug still
> >with an extended arm and tell me that it's only hard to do if it moves.
> >
>> Yes, I will tell you: there is no work without motion (or the
> equivalent for non-mechanical forms of work). Your muscles can get
> very tired without doing external work. You can push against a stone
> wall all day, even a metaphorical stone wall, and exhaust yourself
> without doing one erg of external work.
>> "Hard to do" does not require work in the technical physics sense!
>> Technical terms have technical meanings, whether you like them or not.
> Antigravity has a specific meaning. It means it eliminates or reduces
> gravity, not simply supports an object or elevates it against an
> unchanged gravitational force. And anyone who claims to work with
> antigravity is deserving the label "crank".
Excuse me please. I hadn't realized that the message was cross posted.
Those who know me realized that I was attempting humor. I'm sorry to
have failed. (I got As in all my physics courses, going back to 1948 in
high school.)
Jerry
--
Engineering is the art of making what you want from things you can get.
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