> The density in the observed universe is used to extrapolate the number of galaxies in the non-observed universe.
As has already been pointed out, our best current model of our universe is that it is spatially infinite. That means an infinite number of galaxies.
The finite galaxy numbers that astronomers give are for the observable universe.
> The size and shape of the observable universe also changes.
Not the way you are describing, no. The observable universe does increase in size as time goes on, because there is more time for light to travel so the light we see can come from objects further distant. Its shape, however, does not change.
A good reference is Davis & Lineweaver's 2003 paper:
> A moving observer, say someone doing 30% of lightspeed, will see further in one direction than another.
I don't know where you're getting this from. What part of the universe you can observe from a given point does not depend on your state of motion.
> Accelerate quickly enough and the "dark" side of your custom observable universe might catch up with you, causing all sorts of havoc.
This is nonsense. The Unruh effect is (a) nothing like what you are describing, and (b) irrelevant to this discussion anyway, since the Unruh effect only applies to objects which have nonzero proper acceleration, which is not the case for any galaxies, stars, or planets in the universe.
As has already been pointed out, our best current model of our universe is that it is spatially infinite. That means an infinite number of galaxies.
The finite galaxy numbers that astronomers give are for the observable universe.
> The size and shape of the observable universe also changes.
Not the way you are describing, no. The observable universe does increase in size as time goes on, because there is more time for light to travel so the light we see can come from objects further distant. Its shape, however, does not change.
A good reference is Davis & Lineweaver's 2003 paper:
https://arxiv.org/abs/astro-ph/0310808
> A moving observer, say someone doing 30% of lightspeed, will see further in one direction than another.
I don't know where you're getting this from. What part of the universe you can observe from a given point does not depend on your state of motion.
> Accelerate quickly enough and the "dark" side of your custom observable universe might catch up with you, causing all sorts of havoc.
This is nonsense. The Unruh effect is (a) nothing like what you are describing, and (b) irrelevant to this discussion anyway, since the Unruh effect only applies to objects which have nonzero proper acceleration, which is not the case for any galaxies, stars, or planets in the universe.