Re: Center of Mass of the Universe?

From: Mark Cavin (Mcavin_at_wi.rr.com)
Date: 11/16/04 

Date: 16 Nov 2004 12:10:53 -0800

hemetis@hotmail.com (EL) wrote in message news:<7563cb80.0411160310.4893916@posting.google.com>...
> Mcavin@wi.rr.com (Mark Cavin) wrote in message news:<241521ff.0411151425.6485e224@posting.google.com>...
> > hemetis@hotmail.com (EL) wrote in message news:<7563cb80.0411150036.6c4ad3d9@posting.google.com>...
> > > Mcavin@wi.rr.com (Mark Cavin) wrote in message
> > > news:<241521ff.0411141151.4f029aaa@posting.google.com>...
> >
> > HiYa El,
> >
> > [EL]
> > "It must be more difficult to demonstrate a 3D wave as a surface
> > propagating within a volume, but I do have some ideas."
> >
> > [Mark]
> > Exactly, it would be very interesting to "see" a representation of
> > wave propagation within the whole of a volume. I wonder if a
> > combination of H.O.E arranged in a multiplexed hologram could provide
> > some volumetric and animated example of such a view; one that gives
> > the impression of a volumetric propagation when the viewer scanned
> > back and forth across the image plane. About 1/4 down this page is an
> > interesting drawing of a 3d cross section of wave interference
> > http://agamemnon.cord.org/step_online/st1-10/st110eii.htm. And then
> > there is Rudie Berkhout to study on, he is a master of integrating
> > H.O.E in display holography.
> > http://rudieberkhout.home.mindspring.com/SPIE-UsingHOEs-tomakeholograms.htm
> > IM convincing myself as I write this that it might just be possible.
> > L8r,
> > Mark
>
> [EL]
> Indeed, all combinations of art-physics / art-optics are greatly
> appreciated.
> Computer generated graphical representations too are very helpful, but
> that is not what we may call a visible experiment.
> The true problem is that while things may be out there in 3D or 4D
> each human eye interacts with light through the array of elements on
> the retina.
> The retina is basically a surface (a Gaussian Curved Surface).
> Although the curvature elements are 3D elements in a 3D coordinate
> system, the surface is essentially a 2D entity.
> Our visual perception of 3D bodies and the depth element set comes
> from the mental comparison between the left-eye right-eye images of
> the same scene composition.
>
> A temporal image superposition gives the 3D impression while a
> temporal image sequence gives the state of motion.
> Let me elaborate a bit, but before I do that I need to recall your
> line:
>
> "one that gives the impression of a volumetric propagation when the
> viewer scanned back and forth across the image plane."
> In that line you wrote, it was clear to me that you are quite aware of
> the two functions of binocular vision.
> The word volumetric as you have used successfully between the words
> "impression " and "propagation " have summarized the whole issue. :-)
>
> Nevertheless, I do have an objection on the "viewer" being able to
> "scan" across the image plane.
> That concept is an artificial concept by definition and is most
> suitable for computer graphics art, representations and
> demonstrations.
>
> In an empirical experiment (Laboratory set-up), the scientist must be
> aware that what can be exposed to seated audience is the "outer"
> surface of the wave-fronts (impression) and the progress of the
> interference contour lines (propagation/motion).
>
> The problem is that for any number of concentric spheres there is only
> one sphere that we may call the outer sphere, which is the one exposed
> to the viewers. Such a perspective is hardly interesting to watch.
> What is interesting would be any perception of patterns.
>
> The solution to the problem is in having each spherical wave be
> semitransparent (Perhaps 90% transparency) such that a side view would
> reveal a succession of decreasing transparency as the number of layers
> increase. That transparency may be controlled by controlling the
> particle density of the medium in which the wave is set.
>
> Historically, smoke in air and micronic-air-bubbles in water were used
> successfully to demonstrate the Helmholtz rings.
>
> From:
> <http://www.phys.virginia.edu/classes/252/more_atoms.html>
> {
> It is fascinating to note that the most exciting theory of fundamental
> particles at the present time, string theory, has a definite
> resemblance to Thomson's vortex atoms. One of the basic entities is
> the closed string, a little loop, which has fields flowing around it
> reminiscent of the swirl of ethereal fluid in Thomson's atom. And it's
> a very beautiful theory - Kirchhoff would have been enthusiastic!
> }
>
> Also, please read about Peter Guthrie Tait at:
> <http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Tait.html>
>
> Air bubbles in water dissipate soon due to the effect of buoyancy,
> while smoke particles in motion cannot overcome friction indefinitely.
>
> In search for better representation media a semitransparent "Gel" that
> is sensitive to pressure and reacts optically is estimated to be the
> best medium.
>
> Sound waves pressure shells set in an optical-gel can demonstrate
> those patterns and be recorded on video.
>
> The mathematically expected visual images shall not be more than a set
> of hyperbolic contours resulting from two identical waves
> interference.
>
> The vibration sources can be as simple as a rubber bubble inside which
> incompressible transmission fluid is injected and sucked under the
> effect of a vibrating pin. This should periodically change the volume
> by expanding and contracting the bubble periodically causing spherical
> waves to be generated.
>
> There are already on the market some surface coating materials that
> are sensitive to stress and change colour accordingly. Such materials
> can be diffused into a silicon based transparent gel to form the ideal
> medium for exposing spherical sound waves for demonstration.
>
>
> Kindest regards.
>
> EL

Thank you kindly for the links. Sooooo, you want a real time view of
propagating waves made visible by some reactive medium. I was
thinking more of a static model, but the appearance of index
modulation back into the hologram could be animated with multi slit
exposures combined into a final rainbow copy that straddles the image
plane; then the effect of this semi transparent plane waves propagate
outwards towards the viewer if the reference beam moves or the viewer
moves. But, I like your idea better. Take two, scene one; Hang
vertically a field of many white strands of some light weight
material. Make a transmission hologram of the field, develop and
superimpose the virtual image over the real objects. Play your tuba
and as the real material oscillates you might see a volume of fringes
thru the hologram. I wonder then if two coherent sound sources are
phase varied then the hologram will show the interference at that
level too.
Mark

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