Maybe you are not yet familiar with how i see the cosmos, as re-stated yet again in post #26 of the "Bang/Crunch Revisited" thread, as follows:
Our cosmic event horizon is just a small bubble of visibility *within* the thickness of the "rubber" of the good old cosmic expanding balloon. This mini-cosmos within the maxi-cosmos, the Whole Balloon, is cycling through bangs and crunches even as the whole balloon keeps expanding.... *Yes*... out into the infinity of space.
Anyway, we can't even "see out of the rubber" (the visible cosmos) let alone see the *yes* empty space within or beyond the bubble.
Me thinks you're taking the analogy an order of magnitude or two too far. The rubber sheet (or the balloon) is not a description of the universe. It's an analogy for how distance behaves in the metric which describes the universe. Let me repeat that:
The balloon is an analogy for how distance behaves in the metric which describes the universe.
Our cosmic event horizon is just a small bubble of visibility *within* the thickness of the "rubber" of the good old cosmic expanding balloon.
The rubber sheet and the balloon have no thickness. They are both 2 dimensional otherwise the analogy breaks down. The balloon is a manifold, not a 2-sphere. If you care to represent our cosmological horizon on the manifold then it must be a circle. It can't be a "bubble".
This mini-cosmos within the maxi-cosmos, the Whole Balloon, is cycling through bangs and crunches even as the whole balloon keeps expanding.... *Yes*... out into the infinity of space.
The balloon in the analogy represents the infinity of space. Saying that the balloon expands into the infinity of space wouldn't make sense. It's best to understand that astronomers are answering physical questions. Astronomy is a physical science.
How far is RD1
from earth? How long did it take the light from RD1 to reach us? How fast is RD1 moving relative to us and in what direction? Those questions have physical answers that persist regardless of the semantics of the balloon analogy or how real or not real we consider space.
If you have 4 people each grab a corner of the sheet and stretch it apart then you have effectively modeled the manner in which galaxies move away from one another. One of those dots on the rubber sheet has every other dot moving away from it and the further the other dots are from it, the faster they move away. This is true for any dot.
The above is a two dimensional rubber sheet... a plane. My expanding balloon is a 3-D sphere... and the "rubber" is the "stuff" of cosmos... with a thickness containing the whole mini-sphere of visibility which is our cosmic event horizon.
So, naturally cosmos appears isotropic/homogeneous in all directions
as the whole balloon expands with our little visible cosmos as one tiny bubble in the rubber of the balloon.
Can you understand what I am saying?
Do I understand what you're saying? Yes. You're saying that the surface of a rubber balloon expands isotropically in 3 dimensions which is demonstrably false. The surface actually gets thinner as the balloon expands. Clearly our universe is not expanding in one direction and contracting in another.
The balloon analogy is meant to relate an aspect of cosmological theory... that there is no center to a two dimensional spherical manifold, and if the manifold expands, it's not expanding away from anything.
The expansion of the universe is very similar. Saying "space is expanding faster than the speed of light" means that the distance between two objects on the metric is increasing faster than c. This is an inevitable conclusion given two things:
- The further away one galaxy is from another the greater the rate at which their distance increases.
- The universe is infinite in size.
Space is infinite emptiness. Cosmic "stuff" exists in specific locations within unbounded space.... reference balloon cosmology above.
Nothing... none of this cosmic "stuff" travels faster than light, and space is lack of 'things', emptiness... no-thing-ness, the *volume* in which stuff exists, and "it", being nothing, does not 'travel" or expand at all.
It doesn't matter if you think of space as emptiness, nothingness, volume, or whatever. It doesn't matter how you interpret cosmological theories—you either agree with the physical answers or you don't. If you disagree then you'll need to provide a different theory which gives predictions that can be falsified. That's the way the scientific method works.
If nothing can recede faster than the speed of light then how old (from the last big bang) and how large (to what you call the "cosmic event horizon") is the observable universe? Big bang theory gives a comoving radius of 46 billion lightyears and an age of 13.7 billion years. Clearly 46 divided by 13.7 is greater than 1 so BBT does indeed give answers greater than the speed of light. If you disagree then you should give different specific answers and a theory for finding them. Otherwise, what is there to discuss?
To give one example, if an object is moving away from us *through space* then we expect it to exhibit a redshift which can be calculated with and is due to special relativistic Doppler shift. If, however, space is expanding SR doppler shift will not give the correct redshift results. Cosmological redshift must be used. Wiki summarizes the difference:
I may introduce a very important criticism of all assumptions surrounding the redshift paradigm, but this is not the "place or time."
I'm not sure what you mean by "redshift paradigm" or what your criticism of it could possibly be, but cosmic redshift is very-well handled by a scale factor in standard cosmology (aka "expansion"). Cosmic redshift as a measure of expanding space is verified by the Tolman surface brightness test, time dilation in Type Ia supernovae light curves, and the temperature of CMBR as a function of redshift. These things are a means of distinguishing expanding space from other models and extensive observation shows they are consistent with the former and rule out the latter.The Tolman Surface Brightness Test for the Reality of the Expansion.
So, again, unless you have a theory which explains that data...
I am not "wondering" at all "what difference it makes if we say something is moving through space or if we say space is expanding between things."
It is my most profound understanding that space is empty volume in which all *observable/detectable* phenomena exist and move.
Space is emptiness. It has no properties... being the *void* in which things with properties exist. Space does not expand. Things move away from other things in space... emptiness/volume.
You're missing the issue. When an astronomer says "expanding space" (such as the paper I just linked) they are characterizing the way things move—the way the universe evolves. It doesn't matter if you want to interpret space as "emptiness" or if you want to say it doesn't have properties. That's not what "the reality of the expansion" is referring to. It refers to something very specific: the Robertson Walker metric, and the fact that the kinematics of the universe on large scales is very well modeled by that metric.
Your objection to "expanding space" is semantics. It's like someone saying that a football field is 100 yards and you objecting that a yard isn't a real thing with physical properties... it just misses the issue.
I will study it at another time.... and get back to you on prevalent dissent on redshift as the basis for the "inevitable conclusions"... what you believe are indisputable "facts."
A fact is an honest observation. As such, redshift is a fact. I'm not sure you understand why I wrote "inevitable conclusion". If the speed of something increases with distance (Hubble's law) and distance can increase to infinity (open universes are spatially infinite) then an inevitable conclusion is that speed will increase beyond some finite value. An informed counter proposal to that logic would be the Milne model
Before you get into the "prevalent dissent on redshift" I'd be interested in hearing about the physics of redshift. How is it measured? What does the measurement refer to physically? What theory could I use to predict the sun's redshift? I think this is important because I have a hard time judging the relevance of something until I understand it.
I don't think "volume" is that bad of a word to substitute for "space" in the setting of astronomy and cosmology. We could say that the volume between galaxies increases over time rather than saying the space between them increases...
But the reason for more volume between objects over time is that they are simply moving away from each other as in the expanding balloon... not that "space itself" (as if it were an entity) is expanding.
Yes, like the balloon. Consider this as a mental exercise. Blow up a balloon half full of air. Draw latitude and longitude lines on it (a grid). This grid is what astronomers call comoving coordinates
. Mark a spot on the surface of the balloon and call it "Milky Way" and another spot a good distance away called "RD1".
Now we imagine 2 bugs which you're going to drop on RD1. These bugs are trained to crawl directly to the Milky Way spot from RD1. You start blowing up the balloon slowly and consistently and drop the first bug and it starts crawling with it's tiny little legs. A second or two later you drop the next bug and it starts crawling the same speed as the first. Now you have 2 bugs crawling along the surface of an expanding balloon. You use a ruler to measure the distance between the bugs and it's one centimeter.
The balloon continues to expand and the bugs continue moving toward the Milky Way. When they get there, how far apart do you suppose the bugs will be? Because the balloon expanded they will indeed be more than 1 cm. As I'm sure you've guessed, this is an analogy for light moving from one galaxy to another in an expanding universe. The bugs represent two crests in a wave of light. The wavelength is shorter when it is emitted versus when it is detected.
The physics model of the expanding universe is very much like this analogy except it is in 3 dimensions while the surface of the balloon is only 2 (there would be one more set of grid lines in addition to the latitude and longitude we drew). Also, space is very-nearly flat at large scales so the grid lines wouldn't be spherical. But, the point is, neither of these dots are moving relative to these grid lines. Every galaxy is at rest relative to the universe as a whole while the distance between points on the metric expands. This has very specific observational consequences which must be taken into account in order to correctly predict astronomical observations.
If you describe something different with different observational consequences then you'll no doubt be describing a very creative and interesting universe, it just won't be our universe.