[time-nuts] gravimeters

[Lux, James P]

> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Björn Gabrielsson
> Sent: Friday, December 12, 2008 1:55 PM
> To: brooke at pacific.net; Discussion of precise time and
> frequency measurement
> Subject: Re: [time-nuts] time-nuts Digest, Vol 53, Issue 46
>
>
> On Thu, 2008-12-11 at 14:38 -0800, Brooke Clarke wrote:
> > Hi Mark:
> >
> > I think it's out of date.
> >
> > The current method is to drop an optical corner cube
> (retro-reflector)
> > in a vacuum and using a laser measure the distance it moves (which
> > requires a reasonably good source of time.
> > http://www.ngs.noaa.gov/GRD/GRAVITY/ABSG.html
> >
> > Have Fun,
> >
> > Brooke Clarke
> > http://www.prc68.com
> >
> > Mark Sims wrote:
> > > The quintessential gravity meter (Worden Gravity Meter by
> Texas Instruments)...  still being made after 60 years or so:
> > > http://www.mssu.edu/seg-vm/pict0246.html
>
> Spring based (relative) gravimeters are NOT yet dead...
>
>    http://large.stanford.edu/courses/ph210/lee1/
>

See, there *is* a need for garage Liquid Helium plants...