This puts the pesky quantum fluctuations originating in a universe that is so tiny it can communicate all the way across with light and it evens out as the universe expands during inflation.
So, what does that assumption say about the
apparent speed of light in the early universe? For an observer
inside the universe? The observer would have to "see" that the universe is tiny, so that light goes across it in a short time. But, that observer then stays "
uninflated" as the universe inflates, so that, later in the life of the universe, the observer is measuring a larger universe and light cannot get across it at all, because its "edges" are going apart faster than light can catch up. In effect, such an non-inflating observer is looking at the inflating universe from the "outside". Otherwise, the observer would be a tiny thing with a tiny "meter stick" that makes the universe still look huge, and, if light only went 3 x 10^8 of those tiny meters per second, it would
not get across the tiny universe in a short period. So, if the tiny observer in the very early universe still sees the speed of light as 3 x 10^8 m/s, there is still a "horizon problem" with explaining the size of the fluctuations in the CMBR to make it fit the BBT.
That is the frame of reference problem that I am trying to get across to you. An observer inside the inflating universe and the meter stick he is using for measurements, should be inflating with the universe, not maintaining a steady length as viewed from "outside". We have had this discussion in other threads. It is not even clear that an observer inside an inflating/expanding universe can measure the expansion with a (extremely precise) meter stick, if that meter stick is expanding at the same rate as the space around it. Yes, some people argue that only the space between galaxies expands, and matter stays the same size during expansion/inflation of space. But, that is an assumption with no basic proof available - it is just a convenient position to use to defend the BBT. It is hard to argue that space did not expand matter at all, because all matter was supposedly once all within a tiny volume compared to a sub-atomic particle. And, to me, it seems unlikely that space "inflation" could expand matter up to some point and then stop, given that the inflation is diluting the other forces by increasing the distances.
This whole "scale" of "inflation" seems to be applied inconsistently and without regard to anything other than making the BBT
seem to "work".
There are similar issues with the rate of time passage. GRT says that time passes more slowly near matter. But, from the "inside" of an inflating universe, could an observer detect that the decreasing density of the universe was changing the rate of time passage - if it was doing so?
In another thread, I proposed an experiment to look at the amount of time dilation as a function of depth into a mass, such as the Earth. I think that experiment could be done, but it is tricky to avoid confounding variables for the measuring apparatus. But, it would tell us if time varies with the local acceleration rate or with the escape velocity from the mass (which are the same outside of the mass, itself). I think that would be a good thing to know as we try to figure out the evolution of our universe.