Re: inertial frame: state of the art

["Bernard G. Cleyet & Nancy Ann Seese" <georgeann@REDSHIFT.COM>]

I've lost a number of posts due to a Netscape failure, so this may be redundant:

This is a BTW --  Squires (Practical Physics)  describes an experiment to measure g.  It is the forerunner of the measurement of G JD refers. (One author is common, Faller).  It uses a falling mass in
a falling chamber, a retro-prism for position measurement, and, of course, the chamber in a vacuum chamber.

In preparation for the revision of the Cavendish exp.. in the advanced lab. (UCSC), I read (~ '95) that the best measurement of G was a variation of Cavendishe's expt. where in the variation in the
period of the torsion pendulum was measured due to the presence of tungsten cylinders.  The Leybold apparatus is sensitive enuff to show this variation.  (as the amplitude decreases the period
changes.)

Panzers to JD for this "update."

bc

P.s. Squires description includes the servo system to keep the test object and the falling chamber "in sync."
P.p.s. A sign of the US's imperial power is that the british author (Fellow of Trinity College) has abandoned british spelling.


John Denker wrote:

> At 02:25 PM 9/14/00 -0400, Carl E. Mungan wrote:
> > I'll settle for an experiment which can tell me to within a
> > specified accuracy that a frame is inertial. And I'll now allow you
> > to use the full arsenal of physics, not just N1. What
> > state-of-the-art experiment can I do
>
> I quote from
>   http://www.ngs.noaa.gov/PUBS_LIB/BigG/bigg.html
>
> > > The test mass falls within a cylindrical aluminum vacuum chamber
> > > customized for this G experiment to allow us to place the source mass
> > > closer to the drop (small diameter). This increases our gravitational
> > > signal. The chamber is made of aluminum (rather than the stainless steel
> > > commonly used in vacuum systems) to reduce thermal gradients. It forms an
> > > unbroken conducting shell around the drop region, thereby shielding it
> > > from electrostatic fields. A co-falling ``elevator'' shields the falling
> > > test mass from residual gas forces.
>
> The description of the apparatus continues in considerable detail, but you
> get the idea:  They deal with gravity by using a free-falling object.  They
> screen out known stray forces like electromagnetism and stray gas.  In
> particular, I like the co-falling "elevator", because it is a pretty direct
> implementation of the usual textbook Gedanken experiment.
>
> >  and what accuracy will it give me?
>
> Schwarz et all report a sensitivity of 1 part in 10^9 of earth's gravity.