CMB: How Was Matter Distributed Before Photon Decoupling?

[orricl]

According to the hot Big Bang model, about 380000 years after that violent explosion, the universe was transparent to radiation but before that moment photons were trapped in the soup of ionized plasma. And my question is how does the matter distribute in space before the photons decouple from the ionized plasma?

 

[Orodruin]

According to the hot Big Bang model, about 380000 years after that violent explosion,

There is a very common misconception here. The Big Bang was not an explosion in the common meaning of the word. Throughout the history of the Universe, matter and radiation have both been relatively evenly spread in it. This is not and have never been a problem for the Big Bang model.

 

[Chalnoth]

According to the hot Big Bang model, about 380000 years after that violent explosion, the universe was transparent to radiation but before that moment photons were trapped in the soup of ionized plasma. And my question is how does the matter distribute in space before the photons decouple from the ionized plasma?

Before decoupling, the matter was almost perfectly evenly-distributed. We can see the photons that resulted from that decoupling, and the temperature variance is approximately one part in 100,000. This roughly correlates to a density variance.

Those early density variations became the seeds of later galaxy clusters and galaxies, and by measuring the statistical distribution between later galaxies and the CMB we can show that the two match to a high degree of accuracy. This line of study is known as, "baryon acoustic oscillations".

 

[ChrisVer]

I want to clarify something:
Is "inflation" the reason of the density perturbations?

 

[Chalnoth]

I want to clarify something:
Is "inflation" the reason of the density perturbations?

Inflation does have the property that quantum fluctuations during inflation become small density variations in the early universe, variations that eventually grow to become galaxies, galaxy clusters, etc.

Those density variations are currently the primary piece of evidence we have for inflation, as their statistics are precisely what was predicted.

 

[rootone]

It's good to know that the evidence incriminates the suspect we thought it was.
That does not prove much though, other than humans seek patterns.

 

[phinds]

It's good to know that the evidence incriminates the suspect we thought it was.
That does not prove much though, other than humans seek patterns.

Huh ?

 

[ChrisVer]

Couldn't e.g. those perturbations happen due to chaotic/statistical events?

 

[Chalnoth]

Couldn't e.g. those perturbations happen due to chaotic/statistical events?

They are, but from a very particular random distribution (Gaussian, scale-invariant).