flat rotation curves and 'foam' large scale struct

Hmmm. It occurs to me that readers not familiar with nanotechnology might be misled by the title of the book I referenced above. It has nothing to do with religion.

LB

(Wow. Did we ever go off on a tangent here. All of us, including yours truely, need to make an effort to stay closer to the subject of any thread where we post. Start a new thread, with an appropriate subject line.

There is a really good practicle reason for this.

Suppose, in a year or two, you want to find that "strange post about building a virus in the lab". A thread about galactic rotation curves is probably not the first place you would look ...)

To help steer this thread back on course:

I'm not sure if the "conjecture that the value of 'G' depends on the proximity of surrounding matter" is saying the gravity of an object is greater or lesser in proximity to other matter. If they're saying, "greater", that sounds like possibly another way of saying that the range of gravity is limited.

According to TVF, the range of gravity is roughly 6 [thousand] light-years. [Thanks LB, that's what I meant to write; I just got careless.] I think he means that, compared to the standard model, gravity diminishes by an extra factor of two every 6 [thousand] lightyears. That makes gravity at great distances proportional to the inverse cube of distance. (I read somewhere that it is inverse linear, which sounds like a big misunderstanding to me.) If MM is correct, then spiral galaxies are held together, not by the gravity of the whole galaxy, but only by the gravity of neighboring stars, continuously distributed within the spiral arms. Each little bunch of stars hangs onto the next little bunch, all the way along the spiral arm to the center of the spiral. If a piece of a spiral arm became disconnected, it would drift away into intergalactic space.

To give you an idea how drastically the inverse cube differs from the inverse square, consider this. The Milkyway Galaxy is about 100 ly across. With gravity decreasing by an extra factor of half every 6 ly, that's a factor 10^-6 at 120 ly. At 240 ly, MM gravity is 10^-12 of what the standard model says it should be.

Does anyone know if that "conjecture" makes gravity out to be an inverse cube force at great distances?

Thanks Phil, for steering the topic back on course.

The conjecture described at the start of this thread, in www.gravity.uk.com , is that the value of 'G' is less in the proximity of more matter.

i.e. if a lot of matter is packed close together the value of G reduces - the formula is G(effective) = c^2/(c^2/G + m/r)

so if m/r is small G has the 'normal' value. If m/r is large then G can reduce significantly compared to its 'normal value'.

The advantages of this approach are that singularity problems can be avoided. Also the 'Big Bang' (or Bangs, if they occur on the scale of superclusters) are due to a reduction of 'G' for a collapsing region of matter, which then 'bounces'.

There is also a natural solution of the flatness problem and a possible explanation of the flat shape of the rotation curves.

J. Hunter (would the biology people please stay off this thread!)

[PhilJ] "According to TVF, the range of gravity is roughly 6 light-years."

Make that 6 *thousand* light years (1 to 2 KILOparsecs). And this is not actually the range of gravity. It is the average distance that gravitons travel before hitting another graviton and scattering. So at this distance the force of gravity will begin to decline noticeably. It is not a sharp edge.


LB

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Larry Burford</i>
<br />... Make that 6 *thousand* light years (1 to 2 KILOparsecs).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I knew that; just getting sloppy; correction made to the original post.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Larry Burford</i>
<br />... And this is not actually the range of gravity. It is the average distance that gravitons travel before hitting another graviton and scattering. So at this distance the force of gravity will begin to decline noticeably. It is not a sharp edge.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I believe I have correctly characterized it as such. If the mean distance between CG collisions is 6,000 ly, that will halve the force of gravity every 6,000 ly. Since gravity already decreases as the inverse square at short range, it becomes the inverse cube at long range.

Can anyone think of any evidence, for or against the conjecture that G depends on the proximity of other matter?

G(effective) = c^2/(c^2/G + m/r)

Where G(effective ) is the attractive gravitational mass for a body approaching another mass m, r being the distance apart?

John Hunter.