Re: Confirmation of Relativity

["William J. Larson" <bill_larson@CSI.COM>]

==>Which effect do you suppose is dominant?
OK, I'll bite. Compared to c, the satellites are moving very slowly.
but compared to the G field at the surface of a neutron star,
g is really small, so I *guess* the SR effect is bigger.

Is the a penalty for guessing on your MC tests?  :-)

Cheers,
Bill Larson
Geneva, Switzerland


----- Original Message -----
From: Leigh Palmer <palmer@SFU.CA>
To: <PHYS-L@lists.nau.edu>
Sent: 2000 May 04 2:34 AM
Subject: Re: Confirmation of Relativity


> > Rather than an actual experimental result, would a "thought experiment"
> > result do?  I show my students the section of COSMOS (Carl Sagan) that
> > he did on relativity, and the addenda he attached to the tape series.
>
> Shame on you! Gedanken experiments don't test any theory. I can make
> a Gedanken experiment which will reveal that all green objects have
> negative gravitational mass. What would that demonstrate? What is
> sought here (by the student) is *evidence*. He should not be happy
> with what you propose.
>
> > It shows a nice view of forshortening and curvature.
> >
> > Couldn't gravitational lensing be included here as an indirect
> > measurement?  It changes the path length of the light.
>
> Those are not special relativistic effects; they are examples from
> general relativity. Time is also dilated in a gravitational potential
> well. Time runs more slowly on Earth than it does on the Moon, and
> more slowly on an artificial satellite than on Earth's surface. As a
> timely example, since selective availability has just been turned
> off (hooray!), there are two effects observable on GPS satellites:
> their clocks run more slowly due to an SR effect, and faster due to
> a GR effect. Which effect do you suppose is dominant? GPS is the only
> consumer product I know that depends upon GR for its function.
>
> Leigh