Should Gravity be Complicated? (dark Matter vs. MOND)

Thinking of the resistance the physics community seems to have for MOND and the acceptance of "Dark Matter" as the explaination for higher observed object orbit speeds at the edges of galaxies... Given the well known nature of The Strong Force, varible from attractive to very strongly attractive to repulsive as a function of distance, why not suspect gravity also changes as a function of separation distance? Why not suspect the nature of gravity is to increase slightly over the attractive force predicted by inverse R squared when that attraction is at a nearly negligibly small value due to great separation, and then transition to a repulsive force at distances great enough, so as to explain expansion of the universe galaxy to galaxy ? Should not there be a naturally suspected similarity between The Strong Force and Gravity ( MOND ) ?
- Don Jones (age 62)
Panama City, FL, USA

Nice question.

I don't think gravity should show the complications that the strong force shows. The reason is that the strong force is not fundamental, but rather an effective force between complicated multi-part objects such as protons and neutrons. Those objects are bags of quarks and gluons, so it's no surprise that the force between them gets messy as they start to overlap.  The  source of the strong force is the more fundamental quantum chromodynamic force between quarks, which is actually much simpler.

Nothing about the form of gravity (General Relativity) suggests any room for such complications down to the scale where quantum gravity becomes important, far smaller than even those nuclei. Nature may surprise us, but it's not using the strong force to give us a hint of what to expect for gravity.

Mike W.

(published on 09/18/2015)