[time-nuts] time-nuts Digest, Vol 53, Issue 46

[Brooke Clarke]

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I think it's out of date.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
> 
> 
> ------------------------------------------
> Geologists measure gravity to get the density of of the underlying rocks.  I 
> saw a neat topo map of the San Francisco peninsula at one of the USGS open 
> houses.  The contours were rock density rather than elevation.
> 
> Of course, they had to correct for elevation.  When I asked how they got the 
> elevation, the guy smiled: "From the sewer people".
> 
> They had the instrument on display.  It wasn't very big, say a cubic foot.  
> Maybe they will have it out at the next open house so I can look closer.
> 
> 
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