In order to explain the acceleration of galaxies, scientists have invoked the existence of a mysterious 'dark energy'. This is because their thinking is constrained by their belief in an expanding universe caused by the 'Big Bang'.
A more open minded observer might conclude that the galaxies are under the influence of the only known force of nature that could cause such acceleration - gravity. This would require the existence of a supermassive non-luminous body in space (possibly a black hole) towards which all the galaxies in the observable universe were being drawn.
If such a body existed, it does not seem likely that it would be the only such body in the universe, just as the Milky Way is not the only galaxy. There might well be billions of such supermassive bodies, each drawing billions of galaxies towards them. This would mean that that which we call the 'observable universe' is merely a finite system of galaxies among many such finite systems in the universe at large.
If such a model could explain other observations such as the fact that the galaxies were all moving away from each other, then would it not deserve to replace the increasingly baroque and untenable Big Bang theory which requires us to believe so many unorthodox and unproven assumptions about the universe? I believe it should.
A simple 'thought experiment' reveals how the 'Gravity Model' would result in almost all the observable galaxies being redshifted. In 1994, comet Shoemaker-Levy was broken up by Jupiter's gravity into 22 discernible fragments up to 2km in diameter. The fragments were described as being like a 'string of pearls'. Imagine five of these 'pearls' in a line numbered 1 to 5, with 1 closest to Jupiter and 5 farthest away, with equal spacing between them. You, as the observer, are on number 3, the middle fragment. You have at your disposal the most exquisitely sensitive scientific instruments capable of detecting minute differences in redshift, velocity and acceleration. You would see that the other 4 fragments were all redshifted. Fragments 2 and 4 would have the same value. Fragments 1 and 5 would also have the same value, but the value would be higher than that for 2 and 4. In other words, the farther away a fragment is, the greater its redshift. This is not because the space between them is expanding, but because of the differential influence of Jupiter's gravitational pull with regard to the proximity of the fragments. This increasing redshift with increasing distance is exactly what we see when we look at the galaxies. Your instruments would also tell you that the fragments were accelerating.
It could be argued that the galaxies are not a two dimensional string of pearls. This is true. But, in whatever direction you look, the galaxy you view will either be closer to or farther away from the 'Great Body' than the observer, and so will be redshifted. Nevertheless, this presents the Gravity Model with its most serious challenge. Big Bang theorists claim that the universe is isotropic. This means that galaxies at a given distance from the observer will be moving at the same velocity away from him in every direction. However, this idea that the universe is isotropic is simply not true. Various research groups have found that the recessional velocity of galaxies with similar intrinsic luminosities varies according to the direction in which the galaxy is to be found. One study adjudged minimum values to be around two thirds of the maximum. One might have expected a greater discrepancy. It may be that galaxies which lie in the direction of the Milky Way's galactic plane, and are therefore not seen, may provide more extreme values.
Another observation which Big Bang theory cannot explain is the'peculiar' motion of galaxies. In the Gravity Model, the galaxies will not simply be travelling towards the Great Body in a straight line. They will be spiralling towards it and the 'peculiar' motion is the transverse component of their spiral path.
The CMBR. I have read that the 2.7K temperature of the Cosmic Microwave Background Radiation could be caused by hydrogen clouds, but that astronomers have not been able to detect enough clouds to account for it. If the observable universe is a finite system, as it must be in the Gravity Model, then the question arises as to what lies beyond it. The answer must be that it is a hydrogen field, since galaxies cannot condense out of nothingness. This hydrogen field envelopes the observable universe and presumably radiates at 2.7K. It is the source of galaxies and astronomers have observed huge, highly flattened 'pancakes' of hydrogen containing up to 10 to the power of 14 solar masses. These are believed to be the precursors of large clusters of galaxies.
Hope that clears things up.