Re: [Phys-l] Weightless

[John Mallinckrodt <ajm@csupomona.edu>]

Anthony Lapinski wrote:

> People in their everyday experience think a bathroom scale measures  
> their
> downward weight.

I don't think the average person would think to consciously qualify  
their weight as "downward."  What they think (correctly in my-- 
mainstream, I think--opinion) is that the scale measures their weight.

> And so when the scale reads zero for the astronauts, they
> think g = 0!

I'm even more skeptical that the average person would consciously  
think something like that.  (On the other hand, if they did, they  
would also be correct in my opinion!  Here I'm prepared to concede  
that my opinion may not be mainstream or even pedagogically sound  
even if it is in agreement with our current best theory of gravitation.)

> Lots of confusion and misconceptions with this with ALL
> people.

I'm still not convinced.

> I guess one could never have a true weight equal to zero unless you  
> are
> "very far" from all objects (so that g = 0).

By "true weight" I assume you mean the same thing as "gravitational  
force" so why not just call it that?  And at the risk of sounding  
like a broken record (a train that left the station long ago!), I  
will point out once again that, according to the current best theory  
of gravitation, there is no less and no more "gravity" (in the sense  
of gravitational force or gravitational force field) in deep space  
than there is here on Earth or any where else in the universe.   
According to the principle of equivalence, that aspect of gravity IS  
inertia and vice versa.  We make our own gravity.

Standard disclaimer:  I'm not promoting the idea that we teach  
students general relativity.  I just think there's room within our  
professional ranks for a little more appreciation of the deep and  
beautiful message conveyed by the principle of equivalence.

John Mallinckrodt

Professor of Physics, Cal Poly Pomona
<http://www.csupomona.edu/~ajm>

and

Lead Guitarist, Out-Laws of Physics
<http://outlawsofphysics.com>