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Re: [Phys-l] feeling gravity, or not



I'd read that most senses are in the 3% region, especially if trained, e.g. 1.03# in one hand 1.0 in tother is just detectable. Since it's unlikely we'll ever, well not this cent., get that close to a black hole ... so if one is that close to a black hole, will the rocket have sufficient thrust to escape?

bc, too lazy to do the calc.

p.s. an exception: two tones heard at the same time.

John Denker wrote:

BC opined:


... one is unlikely to ever feel gravity and survive.


Oh, I wouldn't have said that. It's sorta like Archimedes and his
lever. If you give me a place to stand, and a robust connection
to places on the far side of the earth, I can easily feel the
nonuniformities in the gravitational field by making a very
nonlocal comparison, comparing the field “here” to the field
“there”.

This is discussed in detail at
http://av8n.com/physics/rotating-frame.htm#sec-feel-gravity
including a much-improved diagram.


====================================

On 10/30/2006 12:02 AM, carmelo@pacific.net.sg wrote:

John Denker wrote:


Whether we can feel gravity depends on three things -- the degree of inhomogeneity
-- the size-scale of our measurements
-- the sensitivity of our measurements

That is incredible!


Incredible or not, what I said remains true.


Sound like Obi-Wan Kenobi asking Anakin Skywalker to "feel the force". May
the Force be with you then...


That is a poor substitute for logical argument. If there is any
equation or principle of physics that is casts doubt on what I
said, please let us know.


I prefer to recall Einstein's thought experiment, "the happiest thought of my life. I was sitting
in a chair when all of a sudden a thought occurred to me: if a person falls freely he or she will
not feel their own weight. I was startled. This simple thought made a deep impression on me."


That seems to support what I'm saying.

BTW, note that Galileo used essentially the same argument in 1638.


Besides, in the movie, "The hunt for Red October", an officer on the bridge shouted "gravity
anomaly values in milligals". This was a breach of U.S. security when the movie was made because
it was a classified secret that gravity measurements were used to navigate. (The technology which
can "see" the terrain.) Let's not talk about how we feel, but operational measurement! Better
still, how gravity anomaly values can be measured. Anyway, this technology is already
*de-classifed*.


I don't see how that has any relevance to this discussion.

The device carried on real submarines is a very sensitive gravity
gradiometer. It measures the _gradient_ i.e. the inhomogeneity,
which supports the first point I made. It is an exquisitely
sensitive and delicate instrument, which supports the third
point I made.

And BTW, gravity gradiometers have been in unclassified use for
a long time. There is a picture of one in Misner, Thorne & Wheeler
_Gravitation_ (1973). This considerably predates the 1990 movie.

Finally, I say again that the /feeling/ of "gravity" when walking
around on the earth is a highly nonlocal effect. The nonlocality
is mediated by forces transmitted through the earth, on a planet-wide
scale, as I discussed the other day. An improved version of that
discussion, including a much nicer diagram, can be found at
http://av8n.com/physics/rotating-frame.htm#sec-feel-gravity

Note: That document is still a work in progress. Beware of typos.
Comments welcome.

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