Re: inertial frame: state of the art

[John Denker <jsd@MONMOUTH.COM>]

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.