Galactic Dark Matter Distribution

There are only three basic possibilities that answer the dark matter problem. These are:

1) Unseen matter (normal-exotic w/ odd distribution) is <i><b>pulling</b></i> in the outer stars of elliptical galaxies.
2) The theory of gravitation needs an overhaul with respect ot the inverse square law.
3) The undiscussed possibility of something <i><b>pushing</b></i> galaxies together from outside.
... Like Petit's ( www.jp-petit.com/science/f200/a204.htm )
... or my own guess (a surface tension analog, i.e. matter would "clump up" even without gravity)
... or a variation on a "pushing gravity" scheme.

Number one is steadily being ruled out by "non-observation". Number two requires an ad hoc assumption for which even its adherents agree is difficult to justify physically. That leaves <i>mwah</i>. I eagerly await future professional debates about such possibilities ;o)

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by EBTX</i>
<br />2) The theory of gravitation needs an overhaul with respect ot the inverse square law. ...
Number two requires an ad hoc assumption for which even its adherents agree is difficult to justify physically.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

You must be thinking of MOND. However, <i>Pushing Gravity</i> explains why the inverse square law must change character at some range. In brief, when a graviton has traveled its mean free path between collisions with other gravitons, it will become scattered and no longer carry its inverse square message. That has been known since the mid-18th century, so there is nothing ad hoc about it. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">when a graviton has traveled its mean free path between collisions with other gravitons, it will become scattered and no longer carry its inverse square message.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

If it no longer carries inverse square message, how do we account for the orbits of galaxies around one another while at the same time accounting for the odd velocities within one of the orbiting galaxies?

Can the inverse square message be turned off at some distance, then on again at a greater distance and presumably off again at yet another distance ... all from the same free path process?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by EBTX</i>
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If it no longer carries inverse square message, how do we account for the orbits of galaxies around one another while at the same time accounting for the odd velocities within one of the orbiting galaxies?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

We presently have no secure knowledge whatever about galaxy orbits. It is all theory. In any case, according to MM, other scale-appropriate forces, unobservable at our scale, would be acting at these very large scales because scale is infinite.

As for galaxy rotations, the predicted behavior is just what we observe. For example, the Sun feels no force from our Galactic center because it is too far away and all graviton shadows are filled with scattered gravitons. However, the Sun does feel force from stars within 1-2 kpc of the Sun, of which there are more interior to the Sun's distance from the Galaxy center than exterior to it. This results in a net force toward the center that keeps the Sun in orbit. This differential force, present at any distance from the center of any galaxy, is inverse linear with distance, consistent with observations. -|Tom|-

Tom,

One possibility I have not seen considered in the MOND camp (perhaps for good reason) is that perhaps gravitation at the scale of galaxies primarily propagates laterally through the disk and not in all directions as is assumed. Perhaps scale is indeed involved here. For instance, the phenomena of temperature gradually becomes ill-defined as one passes to a small enough scale. So it may be that we are observing a phenomena that requires a grouping of hundreds of thousands of stars to occur but does not occur at the scale of an individual solar system. The path of sound waves can be modified by the appropriate scattering of intervening bodies and light has been treated the same way with success. Why not gravity waves as well. Its only a thought.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jeremy</i>
<br />The path of sound waves can be modified by the appropriate scattering of intervening bodies and light has been treated the same way with success. Why not gravity waves as well.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Gravitational waves, assuming they exist, are not contributors to gravitational force. Most likely, they are very-long-wavelength members of the electromagnetic spectrum.

But the essence of your idea is good. -|Tom|-