mario wrote:Well, we may not be sure of course, but I thought that the belief today, as far as the CMBR is concerned, is that the entire Universe is just filled with almost uniform black body radiation and that there is no reason to believe that one part of the Universe is different from the other.
However, it is precisely the sort of data presented in today's APOD that has led cosmologists to look at the very real possibility that we don't fully understand all size scales of structure in the Universe. It is very difficult to observationally assess scales on the order of size of the observable universe. But data like this can hint at what we can't see directly.
Nobody can prove that, but this is the most logical and simple hypothesis, which is always the best choice.
Limiting our ideas to our easiest observations is not necessarily logical, and does not necessarily lead to the simplest hypothesis.
So my point is: if it was true (and if I understand it cannot be ruled out more than it can be proved), then an absolute reference system could be at least "defined" in a consistent way, and this would be a great change in our point of view.
Perhaps there is an absolute reference system for the Universe. But that certainly is not the CMB, because that is a local phenomenon, dependent upon the location of the observer. It is quite certain that the CMB I observe is different from the one you observe (although by an extremely small amount). It is certain that the CMB as observed from billions of light years away looks entirely different from the one we observe here. Whether it looks qualitatively the same is an unanswered question.
[quote="mario"]Well, we may not be sure of course, but I thought that the belief today, as far as the CMBR is concerned, is that the entire Universe is just filled with almost uniform black body radiation and that there is no reason to believe that one part of the Universe is different from the other.[/quote]
However, it is precisely the sort of data presented in today's APOD that has led cosmologists to look at the very real possibility that we don't fully understand all size scales of structure in the Universe. It is very difficult to observationally assess scales on the order of size of the observable universe. But data like this can hint at what we can't see directly.
[quote]Nobody can prove that, but this is the most logical and simple hypothesis, which is always the best choice.[/quote]
Limiting our ideas to our easiest observations is not necessarily logical, and does not necessarily lead to the simplest hypothesis.
[quote]So my point is: if it was true (and if I understand it cannot be ruled out more than it can be proved), then an absolute reference system could be at least "defined" in a consistent way, and this would be a great change in our point of view.[/quote]
Perhaps there is an absolute reference system for the Universe. But that certainly is not the CMB, because that is a local phenomenon, dependent upon the location of the observer. It is quite certain that the CMB I observe is different from the one you observe (although by an extremely small amount). It is certain that the CMB as observed from billions of light years away looks entirely different from the one we observe here. Whether it looks qualitatively the same is an unanswered question.