Ah yes, this question is one that takes a little thought to understand. It's similar to the RE question, as to what it means when space bends: what direction does it bend in?
As far as easier ways to think of it goes, imagining a higher dimensional manifold is far from the worst way. That being said, there isn't inherently any need for it. Clearly space cannot 'move' by the conventional definition of the word: after all, objects move with respect to space. It's a way of thinking. It's a useful way to think of it, certainly, as it helps understand the process at hand, but to be rigorous, it isn't exactly true, as I think most people who read it would be aware. As you point out, the term movement doesn't mean much when applied to space.
Ultimately, all that happens is a variation in concentration. Technically that's not movement, but if you want to understand the variations, it's far easier to think of it in terms of a flow. More rigorously, it's just concentration or thickness that varies (I've used the analogy before that if spacetime under relativity is a blanket, under DET it's an elastic blanket) but, while what's said clearly still applies, it's much harder to visualize in that case.
I think I got it. I was also curious how would observe the concentration of space. Can evidence be demonstrated via experimental result? Or is it a theoretical result of a mathematical model like some quantum mechanical models?
I have read the evidence section and FAQ. I found experimental details regarding flow of Aether, friction of Aether, and existence of whirlpools, but I was not able to find anything regarding detecting or falsifying the hypothesis that Aether has low or high concentrations. There must be evidence or otherwise it would make more sense to me to just claim that Aether flows as a base assumption rather than try to explain why.
If you had read the evidence section, you would have seen that the only kind of evidence that exists, is evidence of consequences. All those observations you've referred to are evidence of the consequences of the model.
In the overview you give an example of higher concentration of water flowing to the lower when the divider is lifted. But that happens only if there is an external force present moving the water. In this case it’s gravity. Under no gravity conditions the two water levels will remain separate.
You also use this example to show how water sloshes back and forth. That is due to the fact that the water is in a container and has momentum. When flowing from one chamber to another it eventually reaches the other side of the container and bounces off. When we open a dam for example we see no water flowing back.
Also when heat for example flows from a hotter environment to colder we don’t see the colder one super heat and the hot one super cool and then go back and forth. They simply exchange energy until they are equal.
Therefore I see the assumptions you made about the movement of ether not following any existing laws.
When we observe the movement of heat, we can in fact observe a back-and-forth: that's just down to the flow of pressure. That's less intuitive however, so I didn't use it as an illustration. It's the same principle however: we only really observe heat when it affects matter. There have been no analogous situations for heat alone, however: heat requires a heat source, which prevents the high concentration notably decreasing.
If you want a better example than water, simply take free expansion of a gas which holds even without gravity. The liquid analogy helped to illustrate more in an intuitive sense, but it's clearly the case that all things go from high concentrations to low. Water simply helped us provide a better illustration, as the idea of a bubble of vacuum appearing in the middle of a gas is clearly absurd: while we can see in theory that a similar principle will hold, the divider experiment gives a far clearer picture. When we open a dam, the low concentration does not become a higher concentration as there is not enough water present. The container analogy is to make relevant how the flow of a concentration will alter the original concentration.
An analogy is only ever able to serve as an analogy. It provides a more intuitive understanding of the ideas: however, I'm sure if you consider the implications over the brute fact of the analogue, you'll see it makes sense.
We find higher concentrations going towards the lower intuitive because we see them often happening here on earth.
Gas has energy that overcomes the attraction between molecules. In water and solids molecules don’t have enough energy that’s why they stick together. It’s this additional energy in gases what causes them to spread. Do your ether strings have some pent up energy that cause them to move around?
Sorry but heat does not bounce back and forth. You can make a simple experiment. Take an icy glass of water and put it on your table with a thermometer. You will see the temperature staidly increase not jump higher than the room temp and then go down again.
When we open a dam the towns that sit below would definitely tell you that they experience a much higher concentration of water than usual. Also, taking gasses as an example, when you open a ballon we don’t see it reinflating after it goes empty.
There are some special cases where higher concentration dissolves into lower but it definitely doesn’t happen in general. If that were the case we would see the mountains (and us) spreading into thin air.
Gas bubbles in liquids are easy to observe and many of them are stable and don’t go anywhere. They are a bane of car mechanics who have to use tricks and a lot of energy to get them out of break or cooling fluids. By your account they should just wait a few seconds or minutes for the concentrations to equalize.
Since your analogies work only in very special case it needs to be shown that those special conditions exist in ether.
Once again, analogies are only going to be analogies. Liquids have surface tension, and if you break a damn/deflate a balloon there's no lower concentration left in the wake of the flow simply down to the sheer size of the low concentration it's flowing to. Focus on the principles, not the literal examples. Aether is not composed of strings, nor can it hold energy: both those notions are incoherent. It does not require energy to move, because it is not a mass.
A better example would be the inverse: air filling a vacuum for example. It doesn't just fill in and stop, there are wind currents that result. Your mountain example is barely worth mentioning. It's similar to liquids having surface tension. On your heating example, we're admittedly limited in this case by the same principle as the divider analogy. Generally things heat slowly, so there are no ripples. Further, they heat as a result of a heat source in the rapid cases: said source doesn't decrease in heat any noticeable amount, so now low concentration is formed for the heat to flow back to. If one object heats another (and in doing so has its own temperature lowered) it is pretty clear that the newly heated object will begin to hear the former. The only reason we don't observe this is down to the reasons previously given: the fact heat exists in an open system, and the fact the presence of a distinct source renders the situation fundamentally different to the ones we're describing.
I'd argue that the special conditions are in the exceptions you refer to. They universally require the presence of a force to prevent the natural behaviour. The same's true for every universal law: take thermodynamics, the laws of which hold only in a closed system. Laws hold only when something isn't preventing the usual behaviour. As there are no such special external forces governing aether (how could there be? To suppose there is would be an assumption that needs justifying), the law holds.
But it’s you who picked analogies that are not very analogous. Are you saying now that water was not a good example because it has surface tension and mass and is contained and flows because of the gravity? Maybe you should change your introduction then because with wrong analogies you’re going to confuse people.
"if you break a damn/deflate a balloon there's no lower concentration left in the wake” - why not? Why isn’t there a vacuum created in the balloon to which the air could flow back?
Are you saying that the air continuously flows into vacuum above the earth? Is there vacuum left behind to which the air flows back? I think gases also should be a bad analogy since they too have mass and friction, hence the currents you’re talking about. Gasses also tend to flow into much denser objects like water. That’s why life can still exist there because there is plenty of oxygen.
I think the closest analogy to what you’re describing would be heat and it definitely does not behave like you describe. Imagine a well insulated oven heated up to 99 deg c. If what you’re describing is true we would expect the water to boil over (and then what - go back to ice and boil again?). Could you tell me how you imagine this experiment to unfold?
In most cases that I described when you take away the external force nothing will happen. If you take away gravity different levels of liquids will not mix. If you take away the heat different levels of gases will not mix, even into vacuum.