Strange

Well, obviously, we can only base our theories on what we can observe, i.e. the observable universe. However , the observable universe is not a black hole (I assume that is what BH stands for).

Well, the evidence shows that the density (and therefore temperature) used to be higher. And gravity has always been there.

Just to avoid confusion, the contents of that infinite space used to be more dense than now.

Indeed. If space is infinite, then it has always been infinite.

The big bang model says nothing about that.

The big bang model describes the expansion and cooling of the universe from an early hot, dense state. Current theories do not allow us to say what happened any earlier than that. It probably needs a theory of quantum gravity to say more.

It is not expanding into anything. The simplest model is that the universe is infinite, in which case there is nothing outside of it. And then it may be easier to think of the expansion as a decrease in density. (And note that "[metric] expansion of space" is a metaphor for the mathematics and can be misleading if taken too literally.)

I guess if space were a "substance" or aether existed, then that might be true. Depending on the nature of the substance. For example, meutrinos can pass through the balloon as if it weren't there - in fact they could pass through several light years of solid lead without noticing. While it is true that space has no physicality (it is not a substance with properties) that does not imply that measurements cannot change. If anything, I would have thought it was the other way round: if space were a substance, then it might have a fixed shape/size/density and so could not contract. The fact that "space" just means a set of coordinates for measuring relative positions between events (which is what it means in physics) then there is no reason why that coordinate system cannot change (and hence change the measurement of distances between things (or the measurements of the lengths of things).

So why would "emptiness" be blocked by the wall of a balloon.

That is a good attitude. Until you take it to the extreme of never accepting explanations or facts, because they disagree with your opinions. That is often a good idea. You may find out that the answer you "know" turns out to be incorrect. (Can you imagine that as a possibility?)

Remember, though, that there was no oxygen in the atmosphere the.

It is when your opinion is based on a very obvious misunderstanding and refusal to even try and understand. The present scientific theories are accepted because they work; i.e. they are consistent with the evidence. You can't show them to be wrong simply by misrepresenting them or misusing the mathematics of the theory. I am frequently shown to be wrong. I always thank the person (and give them a +1 vote). No one will every be able to prove you wrong because you refuse to listen and understand where your errors lie. Despite the fact they are trivially obvious. So it is hard to understand why anyone would cling to them so desperately. (Which is why you get accused of trolling; people find it hard to believe that anyone can be so impervious to simple explanations of a very simple error.)

It is the geometry or the measurements that remain the same when you inflate a balloon. It is the geometry or the measurements that change in length contraction. Length/geometry is not a substance but it can change, anyway. Why do you think it needs to be a substance? Measurements.

The quantum explanation is that photons are absorbed and re-emitted (and travel at c between the atoms). The classical explanation is that the speed of light changes because of the different permittivity and permeability. The classical explanation is because the waves change speed. The quantum explanation has nothing to do with the size of the photons but is rather more complex. I recommend Feynman's lectures on QED - available as a book or you can find videos online of him explaining it.

Or ... American English is descended from UK English. But they still speak English in the UK. And, of course, worth noting that humans did not evolve from monkeys. The apes (including humans) and monkeys evolved from a common ancestor.

Or the tachyonic anti-telephone: https://en.wikipedia.org/wiki/Tachyonic_antitelephone

There is zero evidence for that.

I wonder why ... People spent time trying to explain your errors (in this and your previous threads) but you are so arrogant, you refuse to listen. You still have time to study and learn some science, instead of making things up.

With a stake through the heart of it.

As that is never going to be happen, I am quite happy for you to post anywhere else but here.

Except you can't. You just think you can. The combination of ignorance and arrogance leads to self-delusion.

Good.

No. I am saying that you posted a lot of ignorant nonsense. You then resist any attempt to explain your errors and insist that you are right and more than a century of scientists, students and interested people are wrong. How arrogant. This is exactly the same behaviour you showed before. You should learn a little humility and consider the possibility that you might be wrong.

The experimental evidence contradicts you. The existing theory contradicts you. From this, logic dictates that you must be wrong.

No, I am saying that this is a science forum with rules. You agreed to abide by the rules when you joined. The rules override a dictionary definition of a section of the forum. Nonsense.