[oneshtein]

CMB is produced by atoms, right? We see darker/lighter regions in CMB, so we should see a transition somewhere. 300M years is very short period of time, unless everything cooled very very uniformly, which is not the case. Sometimes, somewhere there must be a galaxy past CMB.

[ben_w]

> 300M years is very short period of time, unless everything cooled very very uniformly, which is not the case

~300M years is the time between the Big Bang singularity and the CMB, but not really relevant. The entire universe was everywhere as hot as the surface of a star at the time of the CMB, so any evidence of galaxies forming before that is surprising.

The surprisingly high uniformity of the temperature of the CMB — isotropic to roughly one part in 100,000 — is one of the reasons the Big Bang model replaced one of the older competing hypotheses (continuous creation IIRC).

So it is in fact the case that everything cooled very very uniformly and I'm not sure why you think otherwise?

I'm also not clear what you're saying with

> so we should see a transition somewhere

Given the CMB is itself the transition that we see.

> Sometimes, somewhere there must be a galaxy past CMB.

I think here you're mixing up space and time.

It's reasonable (please permit my use of conventional language rather than 4-vectors) to assume that a galaxy exists on the other side in space of the CMB as we see it now, but that happens at a point in time after the recombination epoch began and space became transparent, and light from that event hasn't reached us yet; when it does, the apparent distance of the CMB will be large enough for the galaxy to appear on this side.

Are you familiar with light cones and the convention of one space axis and one time axis? It might help you visualise it if you draw what's going on.

[oneshtein]

https://en.wikipedia.org/wiki/GLASS-z12

GLASS-z12 is 33.2Bly away from us. It should be behind some of the CMB produced by BB, isn't?

> Given the CMB is itself the transition that we see.

In BB model, CMB emitted by hot plasma. Where it is, that plasma?

In steady universe model, CMB is light with z=1000, emitted by distant galaxies, in range of 4Tly. It explains high uniformity of temperature. It's like the temperature of a water stream from underground: it's uniform across a climate area because underground temperature averages seasonal temperature shifting.

[ben_w]

> It should be behind some of the CMB produced by BB, isn't?

A reasonable mistake, but no.

If you look at the info box on your link, you'll see there are two different distances:

≈33.2 billion ly (10.2 billion pc) (present proper distance)

≈13.6 billion ly (4.2 billion pc) (light-travel distance)

The latter is what we're talking about when we say the CMB is about 13-point-whatever billion years old.

The difference with the other number is that the universe got bigger in the meantime, and that's where we recon it is now.

> Where it is, that plasma

The plasma itself?

Everywhere. The whole universe, including here.

The bit we see?

An echo made of light emitted at the last moment in time that it stopped being plasma — the light from the plasma that was here is now as far away from us as the plasma that caused the light we can see.

[oneshtein]

These numbers means that nothing can travel at FTL speed except this galaxy. It travelled 20Bly in 13By at the speed of 1.5 c. Extraordinary claim requires extraordinary evidence. Where is the source of energy for this FTL galaxy? Why this galaxy is not ripped apart into ball of gluon plasma?

Echo requires something to reflect of. Moreover, echo will be an order(s) of magnitude weaker and will have a stamp of the reflective surface on it properties.

[ben_w]

> These numbers means that nothing can travel at FTL speed except this galaxy

Nothing including this galaxy can beat light locally.

Look up the balloon (or raisin bread) analogy.

> echo will be an order(s) of magnitude weaker and will have a stamp of the reflective surface on it properties.

It does. That's in the CMB.

[oneshtein]

> Look up the balloon (or raisin bread) analogy.

In bread analogy, sugar is the source of energy and CO2. In balloon analogy, new air is added to balloon (with lot of turbulence). What is added to our Universe, which causes the inflation? Where we can see it?

In case of Steady Universe model, light just changes it's properties over time, for example, because gravitational waves are stretching photons and photon beams. Gravitational waves are produced by massive objects, which are orbiting each other.

[DiogenesKynikos]

GLASS-z12 is way in front of the CMB.

You have to be careful with what you mean by "distance" at cosmic scales. Space is expanding with time, and there are several different definitions of "distance" that give very different results at cosmic scales.

The best "distance" measure here is simply redshift. GLASS-z12 is at redshift z=12, as the name suggests. The CMB is at redshift z=1100, so it's father away.

In fact, for very straightforward physical reasons, no light can reach us from beyond the CMB. The universe was opaque before the time of the CMB, because it was ionized and dense. Before the CMB time, photons could not travel very far at all before they hit an electron and were scattered.

[oneshtein]

Nobody pointed to a source of energy for this "expansion" of "space". Usually, coordinate system doesn't expand with time. An extraordinary claim requires extraordinary evidence.

Yes, CMB emitters are much further away, at a distance of about 4Tly, while BB claimed to be just 14By ago. Your claim, that CMB is produced by BB, requires a lot of stretching.

[DiogenesKynikos]

There's no point in arguing about this here. There's a very well defined, mathematical theory called General Relativity, which explains gravitational phenomena from Mercury's precession all the way to the expansion of the Universe.

If you take the time to learn General Relativity, and to learn how to apply it to cosmology, you will see that there are rigorous mathematical answers to the various questions you're raising.

I want to point out that this isn't esoteric stuff that only a few people understand. General Relativity and cosmology are part of a standard undergraduate physics curriculum. It only takes a few years of study, starting from Physics 101, to get to the point where you can derive the answers to all your questions from scratch.

[ben_w]

Doesn't even need that much — their questions so far are at my level, and I keep messing up the much simpler special relatively questions on brilliant.org

[oneshtein]

How GR explains claimed FTL speed of GLASS-z12? (20Bly travelled in 13By, 1.5c).

I'm listening with both ears.

[ben_w]

> Nobody pointed to a source of energy for this "expansion" of "space".

Several have been made, the suggestions have issues.

> Usually, coordinate system doesn't expand with time.

Define "usually". Do you have experience of other universes?

> An extraordinary claim requires extraordinary evidence.

Indeed, but this comment box is too small to do the evidence justice.

Edit: that's unhelpful in retrospect, so I suggest the Youtube channel "PBS Space Time". The videos build on each other, so start at the beginning and work through the back catalogue.

> Yes, CMB emitters are much further away, at a distance of about 4Tly,

I have no idea where you got this belief from.

[oneshtein]

> Define "usually". Do you have experience of other universes?

I have experience with coordinate systems. I can bend or expand space-time on my computer all day long, to simulate reality, but I cannot do that in the real world at all.

> Indeed, but this comment box is too small to do the evidence justice.

Looking for the paper or a blog post! However, I suspect that you will just stretch evidence until it will match your model.

> I have no idea where you got this belief from.

Just by looking in the window, I see that some object are close, other are far away, then even further away, and so on, up to 4Tly. Nothing extraordinary. No Big Bangs, no FTL speeds, no hidden sources of energy of epic size, just ordinary physics.

[ben_w]

> ~300M years is the time between the Big Bang singularity and the CMB, but not really relevant.

Nobody else has pointed out my mistake here, the time between them is ~380ky not ~300My. My bad.

[bigbillheck]

> a transition somewhere

A transition from what to what?

> which is not the case.

Why not?

> Sometimes, somewhere there must be a galaxy past CMB.

If there is we'd have to wait for the light from it to get to us, by which time the CMB will have receded further and it would then be in front of the CMB.

[oneshtein]

> A transition from what to what?

A transition from plasma to the cold mater in the form of galaxies we see.

> Why not?

As you see, there are big clusters everywhere. It means that some regions were cooler from the start, to form these cluster in so short period of time. It means that regions around them were hotter, thus they should emit light longer.

> If there is we'd have to wait for the light from it to get to us, by which time the CMB will have receded further and it would then be in front of the CMB.

300My is a short period of time. Why they cannot sometimes overlap?