Re: Apparent weight

[Tim Folkerts <Tim.Folkerts@valpo.edu>]

On Wed, 18 Feb 1998 20:32:23 -0600 (CST) "A. R. Marlow" 
<marlow@loyno.edu> wrote:

 
> In GR gravitation is very real:  it is the effect of living in and moving
> through curved spacetime.  The real geometric curvature of spacetime
> cannot be transformed away by any coordinate transformations, say to
> accelerated reference frames, so it is about as real as you can get.  

How do other forces, like E&M fit in to GR?  Imagine the earth having a 
net charge, and a person having enough charge that electrostatics 
exactly counterbalance gravity (and ignore rotation).  Is the "inertial 
frame" still the one accelerating downward at -9.8 m/s due to curved 
space time, or is it the one with no acceleration.  

If you choose the first, it would seem you need to talk about THREE 
fundamental forces, and a "fundamental curver of spacetime."

If you choose the second, then all four force are on an even status: 
either as "forces" or as "curvers of spacetime."  

If we want to interpret gravity as "curving spacetime" instead of as a 
"force", that would be fine.   Both give the same motion, which 
is the ultimate test.  It is just a question of a MODEL not a 
question of the PHYSICS.  But then why not choose a model so that the 
other three forces "curve spacetime" as well?   

Or put another way, why is the "intertial frame" the one where only 
GRAVITY is acting?  Why not the one where only E&M is acting, or only 
the strong force is acting?

To me, putting all four forces on the same level is simpler and more 
appealing. Of course, experiment, not "appeal" is the final arbitrator. 
Can experiment point to a fundamental difference between gravity and 
other forces that justifies giving it this special status?

 

---   Tim Folkerts


********************************************************
Timothy J. Folkerts               Tim.Folkerts@valpo.edu
Dept. of Physics & Astronomy      219-464-6634
Valparaiso University
Valparaiso, IN  46383