Why Gravity is the only explanation for the Cosmic Acceleration
Universal scenarios
Scenario 1
You are in a singular universe that is accelerating apart, kinetic energy increasing and density of mass(energy) per unit volume decreasing, such that the overall energy per unit volume seems to be steady, or a constant. Very neat!
However, two big problems, one, that you can’t explain why the universe appears to be accelerating apart and two, when you take gravity into account, everything moving apart is increasing the gravitational potential energy of the whole system, so there is no longer a constant overall energy, and the system seems to be breaking the conservation of energy principle.
This then is the basic reason no one ever thought the universe could be accelerating apart (before that was observed).
Scenario 2
You are in an infinite eternal universe of which your own universe is only a sub-universe and surrounded by infinite others, coming and going like fireworks, always there and before your own universe came into being. These other ‘universes’ are sprinkled stochastically through infinite space and don’t move apart relative to each other but do each accelerate apart/explode like fireworks that may eventually overlap each other, such that the overall density of mass energy per unit volume is a constant (if the emergence of new universes/bangs is balanced by the disappearance/collapse of old /amalgamated universes, or matter generally, into black holes).
In this scenario, since the accelerating expansion of the mass in each sub-universe, is, in the bigger picture, an acceleration of mass towards other mass (of the other sub-universes) then it can be explained as an effect of Gravity. And as an effect of gravity, the increasing kinetic energy of the accelerating expansion is afforded by a decrease of gravitational potential energy, so there is no overall breach of the conservation of energy principle.
The following questions arise…
Q1 How can these sub-universes pop out of, or disappear into, points in space?
A1 Infinite space has infinite background zero point energy, to either release or engulf energy in a point.
Q2 How does this immeasurable zero point energy exist in space?
A2 The collective Gravity (cyclically) converts the infinite radiation from the infinite sources into a zero wavelength/ infinite frequency (immeasurable) infinite energy that permeates all space (and all things)(according to an interpretation of the equation for the gravitational red/blackshift of light (Einstein’s))
Q3 Such energy, everywhere, all the time, must allow the eruption of new sub-universes everywhere all the time, so how come they are not happening here, but only in the farthest reaches of space beyond our sub-universe?
A3 Two reasons (that are in agreement). i) Given the background context of infinite formless energy that could give rise to any reality, the emergence of anything of form or order is against probability (the reason why in the infinite universe there should only be a very low instance of matter (ordered energy) – but the slight probablity does allow a certain steady overall density of matter per unit space. And ii) Any new sub-universe/reality is attended by a strict set of constants (that are of its own origin as the background infinite energy is common to all possible realities). Unless another sub-universe happens to share exactly the same constants then it is not real relative to your own universe and is thus only in the realm of the infinite background energy. The very slight probability that a newly emergent sub-universe can have exactly the same constants is accommodated by the vastness of infinite space and time, therefore there can be infinite other real-to-us sub-universes (that we connect to through gravity) across space.
Q4 Why are those other gravitationally real –to-us sub-universes generally not moving relative to ours, if space has no fixed absolute static background? Why are they not accelerating apart from us like the galaxies in our sub-universe?
A4 There may be (infinite other) sub-universes that are doing that, but, for reasons of Special (and General) relativity, if their point of origins are moving faster than the speed of light relative to ours then again they would not be real relative to ours. So that means only those sub-universes that are relatively static to ours will share the same strand of (physical) reality with us