I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree.
Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelming. It's still strong, but questions about the validity of standard candles should be taken seriously.
It is a fact in as real a sense as most anything is a fact when it comes to science. Arguing against the expansion of the universe without providing any evidence whatsoever to show it isn’t expanding is a waste of time. Questioning things is fine, when productive - you are not presenting any evidence to the contrary or even a hypothesis to explain even a portion of what expansion explains, shortly after showing that your understanding of the subject matter is not solid. Please do further research on these subjects before putting yourself in a position to mislead others.
To what end? If someone is mislead about the interpretation of astronomical observations on a cosmological scale there is absolutely no consequence. Your sensitivity to any suggestion that the most popular interpretation may be incorrect is, to be blunt, inappropriate.
It's not my burden to prove that expansion isn't well founded. It is consistent with the best data available, however it is, in the best possible light, still a post-hoc interpretation of that data. It requires significant assumptions that do not have any basis.
So lets unpack that. Given the assumption that the universe his homogeneous, what we observe isn't different from what would be observed from any other position in the universe. Given the assumption that the universe is isotropic, the universe should be the same no matter which direction we look. There is no evidence for either of these assumptions. Since we can only observe the portion of the universe that we are able to observe, we can only assume that our cosmological observations are (in the ways we are debating here) not a function of our position in the universe. This is no different from whom we may consider a less sophisticated observer on Earth who looks around and decides that the universe is full of breathable air. After all, the universe is homogeneous and isotropic, therefore it must be entirely full of air and no matter where you look you would see air. Obviously this is not consistent with our observations, but to someone without telescopes and a modern understanding of physics it would be the logical conclusion given the same assumptions you are making.
The point is that these assumptions are assumptions. We have no evidence for them, except that the best observations we can make do not currently contradict our most recent version of the conclusions we take from those assumptions when combined with the best data we have. The problem is that this is always true, even for the unsophisticated observer who just sees air everywhere they are able to look with their primitive technology.
If you can't see why it is not valid to make these assumptions at this point you should sit and think a bit.
>To what end? If someone is mislead about the interpretation of astronomical observations on a cosmological scale there is absolutely no consequence.
Except further propagating bad foundational knowledge.
>Your sensitivity to any suggestion that the most popular interpretation may be incorrect is, to be blunt, inappropriate.
I'm not sensitive to suggestions that have something backing them up. I am annoyed by people being overtly wrong, and quadrupling down on it. This whole thing is a distraction from the fact you completely misunderstood the study this entire discussion was spawned off of, and have yet to even acknowledge that.
Instead we're now on this bizarre discussion of isotropic vs anisotropic where you're making strange false analogies and making incorrect statements. Our understanding of cosmology is built on top of observations yes, but those observations are stacked up against experimentally verified data, and they pan out. Yes, we assume the universe is isotropic, and we've got such a large amount of data to support it that the human mind is incapable of grasping the enormity of it. There's also nothing inherent to an anisotropic universe that would rule out expansion - it's weird to suggest that is the case, and once again shows you have some fundamental gaps in your knowledge here. At any rate, the more we study the universe, the more the evidence continues to mount for us being in an isotropic one. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11...
>It's not my burden to prove that expansion isn't well founded.
I mean, fundamentally, it is. You're making a new assertion. If you were to say that gravity isn't real, at this point, the burden of proof is on you. When people asserted that the universe was expanding, the burden of proof was on them. And they succeeded in doing so. If you want to challenge that, you're going to have to provide some evidence or reasoning as to why it is, and it's going to need to be one that makes sense - claiming we're in an anisotropic universe is something that is not only almost certainly inaccurate, but also something that says nothing about whether or not the universe is expanding.
> Our understanding of cosmology is built on top of observations yes, but those observations are stacked up against experimentally verified data,
And a cave man who was curious would also do lots of observations. He would observe by the river, by the big tree, by the big rock, up at the top of the hill. No matter where he goes, he can breath. He can feel the air when he swooshes his hand through it. He keeps collecting data for 50 years, and everywhere that he can check he sees the same thing. Therefore, using the same level of proof you propose, he can conclude that there is air everywhere. Someone else might come along and say, well, he is assuming that the universe is the same everywhere, then checking where he is actually able to measure. The same is true for you, you can't make measurements of any kind beyond the CMB. We have no idea how large the universe is or how much of it we can observe. We can assume the stuff we can't see is just like the stuff we can see, but it's an assumption.
> There's also nothing inherent to an anisotropic universe that would rule out expansion
Sure there is. We might just be in a location where stars are diverging. There's no way to distinguish an area where the visible universe is diverging from one where the universe is expanding. Why do you think people are so excited about accelerating expansion? It would be evidence of expansion rather than divergent proper motion.
In fact, lets say there were some kind of massive explosion in space. If you took measurements from near the center of mass from the explosion after a long time, you would see the things that are far away red shifted more than things that are near by. Why? The things far away were the things which were ejected from the explosion with higher velocity than things that are nearby (that is why they are farther away now).
It's incredibly frustrating replying to you, because your arguments are fundamentally anti-science. Everything you're saying can basically be condensed down to "Well, we though we've known things before, and we think we know things now, but we can't EVER REALLY BE SURE, can we? It's all an assumption!"
Trying to compare our current understanding of the universe to that of a cave man is quite silly. We've nailed down quite a bit of the why and how of the structure of the universe, the laws of physics, etc. It's not perfect, there's parts we don't understand, and there's parts we may never be able to understand, but the scope is so much broader and understanding so much deeper that trying to act like it's meaningful to compare our understanding vs. that of a cave man is so disingenuous.
A cave man would have no idea why that would be the limit of his observations - no understanding of physical laws that would make it so. But we understand why there are limits to what we can see. We understand that there is a maximum speed for a massless particle in a void. We understand why we cannot examine objects under a certain size - because the energy requirements would literally create a black hole if put into the space needed to see. A cave man could not understand why there is not more out there for him to observe. We can.
>Sure there is. We might just be in a location where stars are diverging
You seem to be misunderstanding either the meaning of the word "inherent" or the phrase "rule out". An anisotropic universe can 100% be expanding. It can also not be expanding. But you were previously arguing that our (evidence backed) belief that the universe is isotropic being incorrect would immediately rule out expansion, when it simply isn't the case. It's also not particularly relevant, because all evidence points towards the universe being isotropic.
All the evidence points to everything being isotropic, so long as you can't see very far.
All the evidence the caveman could collect said the universe is isotropic. And full of air. All the evidence that you are able to collect can lead to incorrect conclusions.
Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelming. It's still strong, but questions about the validity of standard candles should be taken seriously.