There is a problem in assessing the total mass of a galaxy cluster by estimating stellar output plus counting galaxies and using the Virial theorem, the latter giving around ten times as much mass as the first. Also, rotation curves for galaxies flatten off rather than following the expected Keplerian curve. This is explained by assuming that there must be a lot more missing mass in the Universe, which is hidden (dark matter).
It could be argued that there should be a background gravitational field, which should be everywhere, uniform and constant. This would be so small that it would be negligible in our own region of space. However, in the outer regions of galaxies and in intergalactic space it would become more important. An analogy would be the background radiation. If we calculated the electromagnetic radiation flowing past our planet, we would not dream of adding in the background radiation, because it is totally swamped out by the sun’s radiation. However, in the outer reaches of galaxies or in intergalactic space it is more relevant.
If there were a background gravitational field, gravity waves would form it by the same speculated quantum processes that have been outlined with electromagnetic radiation. Its value may be of the same order of magnitude as the gravitational pull of the entire observable Universe.
If you ask yourself what the gravitational force would be due to the entire contents of the universe if you were situated at he edge of the observable universe in a non-expanding situation. Then using the formula:
Force = GM/r
and using accepted values for the radius of the observable universe and its mass,
around 1054
kg, then M/r2 cancels
leaving a gravitational force of the same numerical value of the gravitational
constant.
Therefore, if for any two points in the universe Newton's gravitational attraction law was rewritten as
Force = GM/r2 + |G|
Then rotation curves become flat naturally without the need for missing mass and galaxies behave normally. Just as we speculated that the background radiation was created from all electromagnetic radiation by quantum effects, then the same thing should happen to gravitational waves creating a background gravitational force, which is extremely small, and of no significance until in the outer reaches of galaxies or in intergalactic space. Then you add in that tiny constant and that makes the difference.
Here we see the the effect of adding in a universal constant the magnitude of G to every standard Newtonian calculation. The lower line is the normal expected Keplerian curve which we do not find with galaxies. Click here to see the spreadsheet calculation for the chart.