Of course some wavelength region of the CMB will be absorbed in our line of sight, but who did and do this measurements observes in a region in which little or no absorptions are present.

Also the intergalactic media has so little density that the particle can't thermalize and usually you can't even define a temperature

Davide Vatteroni: "in a region in which little or no absorptions are present."

According to "tired-light" hypotheses redshift of light from distant galaxies is explained by accumulating energy loss due to repetitive collision with intergalactic particles.

"intergalactic media has so little density that the particle can't thermalize"

Thermalization just requires spatial dimensions to be large enough for intermolecular collisions to happen at significant rates.

If you had enough stuff in the way, it could limit the distance you can see. But there isn't that much stuff in the way, and if not for the expansion of the Universe (and the time it takes light to get from there to here) we could see far further than we actually can. The distance we can see is the distance at which the cumulative expansion of space (about 70 km/sec per megaparsec, or 3.26 million light years) adds up to the speed of light. At that distance, the space between us and whatever we might have otherwise been able to see is expanding at the speed of light, and since light cannot go faster than the local limit (the "speed of light" c, equal to about 300,000 km/sec), no light from that or further distances can reach us. Dividing the speed of light by the rate of expansion per megaparsec we get a distance limit of just under 4300 Mpc, or not quite 14 billion light years.

We don't actually get see quite that far, since any light coming from far away is slowed down by the expansion of the space between us and the object that emitted that light; and even if we could see that far, in its early days the Universe was so dense and hot that it was completely opaque, just like a star's surface, so we can't see the last half million of so light years of distance, anyway. However, ignoring just what the numbers are, none of this discussion has anything to do with anything blocking our view. There are things that block the view of more distant objects -- galaxies and such, and here and there, clouds of gas and dust -- but by and large, the limit of the distance we can see is not set by those things, because they cover very little of the sky. The limit is set by the age of the Universe, and even when the Universe is much older than now, by the rate of expansion of the space between here and "out there".

Courtney Seligman: "The limit is set by the age of the Universe, and even when the Universe is much older than now, by the rate of expansion of the space between here and "out there".

Your reasoning is obviously based on Big Bang theory which I'm unable to follow as I regard the BB concept itself as rather artificial and questionable.

Only the statement about the age is related to the Big Bang theory. That theory does set a limit to the visible distance based on its age; but no matter how old the Universe is (even if is infinitely old), the rate of expansion sets a completely separate upper limit. If the Universe is very young, the limit of sight is the age in light years. But if it has any age as large or larger than the limit set by the Universal Expansion, then the distance limit is based only on the rate of expansion per unit of distance (the current Hubble Constant), and even if the Universe were infinitely old, we still wouldn't be able to see much as far as 14 billion light years, because anything further away than that is being carried away from us faster than the speed of light in any given part of the intervening space, so its light could never reach us. In other words, any theory that fits the observed increase in recessional velocities for more and more distant objects will have a limiting distance that determines what can or cannot be observed, regardless of how old that theory posits the Universe to be, and regardless of how that theory explains the structure of the Universe. I do happen to believe in the Big Bang theory, but that has nothing to do with my original argument, save for the fact that when the Universe was much younger than now, its apparent size would have been even smaller than the limiting distance determined by its rate of expansion.

Courtney Seligman: "the limit set by the Universal Expansion"

Doesn't universal expansion follow from Big Bang theory?

The Big Bang theory does require Universal Expansion; but Universal Expansion does not require Big Bang theory. In fact, Hoyle's Steady State theory also incorporated Universal Expansion, but tried to explain away what Hoyle disparagingly said was "Just a Big Bang theory" (thereby unwittingly giving it its current name) by presuming that the Universe was infinitely old, and wasn't getting emptier as it expanded simply because new galaxies were being created out of nothing all the time. The discovery of the Cosmic Microwave Background destroyed acceptance of the Steady State theory (which was actually just as popular or more so than Gamow's renamed Big Bang theory at the time), but the point is that Universal Expansion is a product of direct observation, and does not require one theory or another to explain it. It is only when trying to explain the origin of the Universe that you have to consider the Big Bang as a possibility. And it does have to be considered as a possibility, but not because of the Universal Expansion; it has to be considered as a theory because far away galaxies and things associated with them, such as quasars, are very different from close galaxies, meaning that in the distant past the Universe was a very different place (e.g., early on there were no elements beside hydrogen and helium, whereas now as much as 6% of some galaxies is other atoms). So no, Universal Expansion does not follow from Big Bang theory, though it is a critical part of it; Universal Expansion is simply a reality that could have been explained in any number of ways, if evidence wasn't available to favor one particular theory.

We are duplicating universe, it means we are born, grow, get old and ultimately die. This the nature of everything inside of the universe, nothing can scape from it, even universe itself. Universe at this time is growing by its nature. If we believe this concept, then a big bang is not presenting universe as complete organized well structured, conscious, and it has a journey to follow. The building block of universe is panpsychist quantum mechanics elementary particle, with billions of galaxies, like an apple tree as it is growing creating more apple. It is not made of mechanical atom as unit of the universe, and it is not one galaxy universe as the big bang theory stating

https://www.academia.edu/38373675/Creation_of_a_Quantum_Mechanic_Universe_and_its_Rotation.doc

Courtney Seligman: "the observed increase in recessional velocities for more and more distant objects"

What is the real basis for "observational evidence" of those recessional velocities?

Javad Fardaei: "We are duplicating universe, it means we are born, grow, get old and ultimately die."

Such reasoning in fact favours the Big Bang idea but at the same time discards any idea of eternal life even though the latter is envisaged at least in christian theology.

I'm not a Christian, but I believe that eternal life refers to life after death in a realm that has nothing to do with the existence, origin or characteristics of the physical universe. In fact, the eternal realm presumably exists throughout all time, predating the origin of the Universe and if the Universe were to ever cease existing, continuing without end. (A theologian could probably provide a more comprehensive and cogent discussion.)

At any rate, although there used to be viable theories about our Universe being one of a series of Universes that formed, grew, disappeared and were replaced by others, all of them had flaws that did not agree with experimental observations of the properties of the Universe; so not many if any cosmologists believe in any such theories.

Finally, one result of theories about how our Universe came into being is the suggestion that new Universes can be created out of the empty space-time that is most of our Universe, and that when they are, they create their very own space-time, completely separate from all other such Universes, in which case there could be an infinite multiplicity of Universes lasting throughout eternity, even if the individual Universes do not (there are version of this multiverse theory in which communication or travel between different such Universes is possible, but that is basically science fiction, not science).

Courtney Seligman: "I believe that eternal life refers to life after death"

When life time of the universe is allowed to extend into future infinity why shouldn't that similarly apply towards the past. Limitation in time is apparently derived from our personal limited existence as has been stated before by Javad Fardaei. I'm unable at all to comment on multiverses theory.

Intergalactic media is the part of the Universe, consequently it is the result of the Universe as a whole object. Visible radius and cosmic background are also results of the Universe, as just the Universe is the cause of all its parts and phenomena. Because the Universe is a whole object, all its parts must correspond one another. The behavior of intergalactic medium reflects the structure of the Universe and its evolution.

Light travels the fastest in the universe, to which all else is therefore relative. As the fastest, light travels the shortest path, a geodesic in 3D, elliptically in 2D. Along the longitudinal axis, light travels relatively linearly or c=1, but must slow (slowed energy=matter) at h or the BB to enter electromagnetically (orthogonal c² or c-squared, c times c) its more parabolic (gravitational) transverse or minor axis, our physically visible universe, thereby gravitationally forming self-similar or fractal matter from quanta to helical DNA, planets, and galaxies with their respective entropies at their respective apexes before returning linearly (flatlining?) to c=1, a timeless vacuum or Black Hole, again and repeating eternally along this more self-similarly fractal Mobius path (cf. Grigory Perelman's Poincaré conjecture solution) of radii that follow the Ulam spiral or nonfactorable primes distribution.

Based on this geodesic light view, the universe therefore consists in BOTH c and c² as well as self-consists in both ABSOLUTE 0 TIME longitudinally and RELATIVE TIME transversely along a parabolic conic, our 'visible' universe. Derived from the fastest speed, light, generalized as speed=distance/time, time therefore=distance/speed. In a dimensionless point or Black Hole, distance is theoretically 0 as would then time also be 0, no longer relative, while the time constant speed of light remains as c=1.

First, background radiation should be called mid-ground radiation, because the universe is infinite so that the visible part of the universe can forever have room to expand into. It is the invisible part of the universe that has been offering the fuel to sustain the continuous burning of the visible part of the universe so that new heavenly objects can incessantly appear in every direction. The burning heavenly bodies send us the various kinds of radiation which constitutes the mid-ground radiation. It is called mid-ground, because behind it is the infinite and true background. Second, what is intergalactic media? Aether, the material that makes electromagnetic waves possible? If it is, it fills the universe in both parts, the visible part, which is expanding, and the invisible part, which is infinite. Therefore, the radius of the visible part of the universe cannot be determined by whatever media, but instead, determined by the power density per unit mass of the fuel that sustains the burning and also by the spatial density of the fuel. Such fuel is homogeneously spread all over in the universe in large scale, but also with irregularity everywhere.