Re: [Phys-l] Weightless

[John Denker <jsd@av8n.com>]

On 11/21/2006 05:14 PM, Richard Tarara wrote:

> YES...I think many of us would go along with Anthony, and the idea that the
> astronauts are apparently weightless, or experience a weightless condition.
> I use this, and believe I am consistent with my definition and usage.  I
> believe there are advantages to doing this for the level of student being
> taught. 

1) What level of student are we talking about?  I assume the students
 have enough background to have some chance of understanding *some*
 explanation of weightlessness;  oherwise this whole discussion is
 obviously a waste of time.  The only question is /which/ of the
 available explanations is most suitable.

2) How does "experiencing a weightless condition" differ from "being
 weightless"?

 Obviously I'm not understanding something here.  Are we really going
 to argue about what the meaning of "is" is?

3) I've been following this thread pretty closely, and I don't think
 anybody would disagree with the proposition that the astronauts
 "appear" weightless in the spacecraft frame.  The problem lies
 elsewhere.  There is one camp that says the astronauts appeare
 weightless because they _are_ weightless ... and for the life of
 me I can't figure out what the other camp is saying.  Apparently
 they say "the astronauts appear weightless but are not weightless
 (in the spacecraft frame)  because ......" and I have no idea how
 to finish that sentence in a way that is consistent with the ordinary
 definition of weight.

 I repeat:  The problem is not with zero "apparent" weight.  The problem
 has to do with contrasting "apparent" weight with some other kind of
 weight.  I have tried, but have been unable to figure out what this
 other kind of weight is.

4) Students (even the most naive students) start out with some rough
 concept of weight.  If you talk to them about "apparent" weight, they
 naturally assume that stands in contrast to some other kind of weight.
 If you use such a term but don't follow through with some sort of
 contrast, that will cause all sorts of confusion.  In the field of
 marketing and sales, this would be called overhanging the market,
 by which I mean ginning up demand for a product you're not prepared
 to sell.

Again:  If you're going to say that the astronauts have zero "apparent"
weight, why not just call it weight (in the spacecraft frame) and be
done with it?  If there's another part to the story, I'd like to hear
it.