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From: pmk@prometheus.UUCP (Paul M Koloc)
Newsgroups: sci.physics
Subject: Re: A Question
Message-ID: <301@prometheus.UUCP>
Date: Thu, 30-Oct-86 17:46:24 EST
Article-I.D.: promethe.301
Posted: Thu Oct 30 17:46:24 1986
Date-Received: Fri, 31-Oct-86 02:20:13 EST
References: <230@sri-arpa.ARPA> <572@epimass.UUCP> <1529@oddjob.UUCP>
Reply-To: pmk@prometheus.UUCP (Paul M Koloc)
Organization: Prometheus II, Ltd., College Park, MD 20740-0222
Lines: 44

>Joe Buck sez:
>>In article <230@sri-arpa.ARPA> JDM%SMVL%rca.com@CSNET-RELAY.ARPA writes:
>>>    o  Given the old "accellerating-elevator-in-space" experiment,
>>>       how can one within the elevator tell the whether he is
>>>       accellerating or under the influence of gravity?
>>
>>You can't tell the difference.  This is the heart of general
>>relativity.
>
In article <1529@oddjob.UUCP> matt@oddjob.UUCP (Matt Crawford) writes:
>Actually you can tell the difference, as I am sure Joe knows.
>Sufficiently sensitive instruments will detect the slight
>variations from place to place in a gravitational field.  If the
>accuracy of the instrument is known in advance, the elevator can
>be made small enough that the variation will be undetectable.
>Example: a device which can detect variations of one part in a
>million, used inside an "elevator" 3 meters across, will not be
>able to distinguish between a 1 g acceleration and the earth the
>gravitational field at the earth's surface.

I didn't know the General R. had a heart, although perhaps Dr. Who 
makes up for it!

I think in one case as time went on time dilation would begin
setting in as well as increasing contraction (spatial) along the
line of acceleration. Also in the "static" case the vertical height
of the elevator is important since the "Mossbauer effect" could 
reveal a "time rate (field) gradient", if it were present.  By
checking the "frequency" spectroscopy of sharp line emmissions 
in the "horizontal" plane of the elevator using a grating spectro-
meter and comparing it with the standard (reference on a known 
platform), perhaps the time dilation due to increasing velocity 
would become apparent although the spacing of the grating rulings 
should not be effected, unless rotated.

Then again may be we could open the door and look out!

        For those really long term acceleration experiments,
          Use PLASMAK(TM) fusion astro propulsion drive. 
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