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I'm not an advanced physics person, so any explanations need to be reasonably low-level...

I was looking at oil/water bubbles (hydrophobic vs hydrophylic molecules) and it got me thinking about the way galaxies cluster, and how suns at the outer rim don't spin off into the void. Rather than needing a huge supply of "dark matter" is it possible that space repels mass?

I've heard gravity described as a "weak" force. This would need to be even weaker, to avoid detection in laboratory measurements of attraction between 2 masses. You need the significant distance between galaxies before you see enough force to prevent a sun spinning off.

Is there a [simple] explanation why this is not possible?

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  • $\begingroup$ Why would suns at the rim spin off into the void? They're gravitationally bound to their galaxy & galaxy cluster. But I guess you could interpret dark energy as space repelling space. $\endgroup$
    – PM 2Ring
    Sep 10 '18 at 5:41
  • $\begingroup$ The argument for dark matter goes: 1 - suns at the outer rim of galaxies are travelling so fast, they should spin off into the void. 2- this isn't happening, so something is holding them back. 3- Implying there is more mass (dark matter) in the galaxy, increasing the force on outlying suns. I'm suggesting the overall formula for gravitation attraction become: F = [G*M1*M2 /(r^2)] - K , where K is not yet defined. $\endgroup$ Sep 11 '18 at 5:21
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    $\begingroup$ You should use @ to notify users of your responses like this: @PM2Ring (no spaces). Also check this on the gravity law: en.m.wikipedia.org/wiki/Modified_Newtonian_dynamics $\endgroup$
    – safesphere
    Sep 11 '18 at 6:15
  • $\begingroup$ Ok. In that case, you sbould add that info to your question. $\endgroup$
    – PM 2Ring
    Sep 11 '18 at 6:27
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    $\begingroup$ Here is a popular description and a video of the author describing this theory: quantamagazine.org/… $\endgroup$
    – safesphere
    Sep 11 '18 at 7:04
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The existence of Dark Matter is still up for debate. I suspect a definitive answer is not yet possible.

The MOND theory (Modified Newtonian Dynamics) claims the force of attraction changes for low accelerations. I'm not sure how this would affect the original measurements of gravitational force, by Cavendish.

If space, of itself, repels mass, then the wooden box housing the experiment would have interfered with the measurements.

There are tests used in MOND vs. dark matter arguments. If I find them (and understand them) I will edit this response to include details.

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