what is the observed distance range of gravity?

Hmmm. Define. Explain. Describe.

Sometimes you really puzzle me, Jim. Why do you say things that are so easy to disprove? Every dictionary I've looked at has a definition for gravity.

Perhaps you meant explaining, rather than defining? But that is not impossible either. We have several explanations that seem at least a little plausible. Whether any of these explanations are a good match with physical reality remains to be seen, but we will get there.

We also have several really good mathematical descriptions of how gravitational force behaves. These are what allow us to predict ... but gravitational force is observed to behave differently than our predictions under some conditions. And these deviations are not always small, so it is presently not "for sure ... a predictable force".

LB

Hi LB, I could guess what you refer to that defys your best models but it would be clearer if you listed these items. I guess you are thinking of all the problems galatic disks display but you may be aware of things I am not where gravity defys your models. A humble statement might include some reference to the fact the models could have shortcomings rather than say gravity is unpredictable(don't you think?).

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">geistkiesel: Does anyone have information regarding any distance limitation for gravity forces?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Chinese Academy of Sciences conducted highly sensitive gravity measurements during last July's solar eclipse in an effort to detect whether the moon blocks a fraction of the sun's gravity. I'm still waiting to hear what they found.

If TVF is correct about the limited range of gravity, Newton's universal law of gravitation becomes
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I used to think that was an inverse cube law for large values of r; on second though it decreases much faster than the inverse cube. (I guess I better hunt down those erroneous posts and fix them.) That being the case, I would expect the outer arms of galaxies to orbit much more slowly than what the inverse square law predicts. Observations show them rotating faster, not slower. If dark energy is the answer, then a limited range of gravity would require more dark matter, not less.

I'm not enough of a mathematician to determine what effect the finite speed of gravity might have on galaxy rotation curves. My limited reasoning is, if the finite speed of gravity tends to move planets farther from the sun by pulling them forward, it should have a similar effect on galaxies. TVF used that postulate to set a lower bound on the speed of gravity. Has anyone applied that same reasoning to the rotation curves of galaxies?

My own Fractal Foam Model of Universes does not suggest a limited range of gravity. My gravitons are ethereal pressure waves (dark energy), not elastic particles. Pressure waves pass thru one another rather than bounce off one another. I do believe these pressure waves exchange momentum with ethereal shear waves, and matter consists of orbiting pairs of shear waves, so gravity blocking is not precluded by my model.

Fractal Foam Model of Universes: Creator

PhilJ, The rule used to estimate the speed of stars in a galatic structure is not designed to work on a disk because mass of a disk is not located anyway near the center of the disk. The simple fact is too simple for the advanced minds of astronomers to comprehend but the mass of a disk is scattered throughout the disk structure and every star within the structure adds some small fraction of the total force effecting the the structure. This simple fact also applies to more compact structures like stars and planets so when viewed from outside the rule works very well-it just doesn't work within the structure. Models have limits.

Why not estimate the limit of a gravity field by assuming it's force vanishes when it becomes equal to the gravity force of the universe in total? No one yet agrees on a concept of universal gravity but I see it as a force equal to ~1nm/s^2 that is observed and defined as a universal redshift of about that force. This would explain the cosmic redshift as a gravity effect.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />Why not estimate the limit of a gravity field by assuming it's force vanishes when it becomes equal to the gravity force of the universe in total? No one yet agrees on a concept of universal gravity but I see it as a force equal to ~1nm/s^2 that is observed and defined as a universal redshift of about that force. This would explain the cosmic redshift as a gravity effect.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I haven't done the math, but isn't the problem with galaxy rotation curves happening in a much stronger field than what you are referring to?

What is this "gravity force of the universe"? Are you referring to the acceleration of every point away from the origin. That acceleration does not exist in comoving coordinates . In non-comoving coordinats, it is equivalent to a parabolic gravity hill centered on the origin; its slope (rH0^2) is proportional to the distance from the origin (except when relativity turns it into a hyperbolic function). Perhaps the cosmic redshift is partly a gravity effect in non-comoving coordinates. We have to be very careful to specify the coordinate system in which we are arguing. Different coordinates systems define space, time, etc., differently. Disagreements often result from the fact that the same words have different meanings in different systems.

Fractal Foam Model of Universes: Creator