[time-nuts] gravimeters

[Neville Michie]

The problem with helium is that it comes out of oil wells.
It does not cost much because they were digging up the oil anyway.
If what they say about peak oil is true, in 30 years or so there will  
be no
more helium and nowhere to get it, save tiny quantities from nuclear  
plants.
It seems to escape from earth's atmosphere to be lost for all time.
We should be doing all the research that needs helium now, because
we will not be able to do it in the future.
Every time my grand kids play with a helium balloon I feel guilty.
Neville mIchie


On 13/12/2008, at 9:15 AM, Lux, James P wrote:

>> -----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 I think it's out of date.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...
>
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