B Can we observe anything beyond the CMB 'wall'?

  • Thread starter Cerenkov
  • Start date
130
15
Hello.


The above article refers to the CMB "wall" in sections 2.4.2 and 2.4.2.1. It's my current understanding that this wall prevents observation of the very early universe; i.e, earlier than 380,000 years after the Big Bang. I also understand (I hope, correctly) that this is because photons from these earlier epochs are strongly scattered by the super-heated plasma. Thus the CMB is optically 'thick'. See section 2.1.1., Blackbody radiation.
Would it be possible for my understanding to be checked and confirmed/corrected, please? Thank you.

I also have two other questions relating to the CMB wall.
This article... http://inspirehep.net/record/827549/plots ...features the following diagram.

1567626673336.png


As you can see, the CMB is displayed as a kind of wall, albeit one that permits certain types of information to pass through it.
I read this diagram to mean that density fluctuations and gravitational waves can carry meaningful information to us about the inflationary epoch. Also, that primordial neutrinos can carry meaningful information to us about Big Bang Nucleosynthesis.

My questions are these.
1. Could my reading of this diagram please be checked and confirmed/corrected? Thank you.
2. Am I right to conclude that the CMB is optically 'thick' to all wavelengths of electromagnetic radiation?

Thank you for any help given.

Cerenkov.
 
285
127
Hello.


The above article refers to the CMB "wall" in sections 2.4.2 and 2.4.2.1. It's my current understanding that this wall prevents observation of the very early universe; i.e, earlier than 380,000 years after the Big Bang. I also understand (I hope, correctly) that this is because photons from these earlier epochs are strongly scattered by the super-heated plasma. Thus the CMB is optically 'thick'. See section 2.1.1., Blackbody radiation.
Would it be possible for my understanding to be checked and confirmed/corrected, please? Thank you.

I also have two other questions relating to the CMB wall.
This article... http://inspirehep.net/record/827549/plots ...features the following diagram.

View attachment 249161

As you can see, the CMB is displayed as a kind of wall, albeit one that permits certain types of information to pass through it.
I read this diagram to mean that density fluctuations and gravitational waves can carry meaningful information to us about the inflationary epoch. Also, that primordial neutrinos can carry meaningful information to us about Big Bang Nucleosynthesis.

My questions are these.
1. Could my reading of this diagram please be checked and confirmed/corrected? Thank you.
2. Am I right to conclude that the CMB is optically 'thick' to all wavelengths of electromagnetic radiation?

Thank you for any help given.

Cerenkov.
1. Your reading of diagram is correct
2. Shorter wavelengths of EM spectrum do bring information from earlier epoch, but difference in universe age in different EM bands is small - free electrons which scattered most of CMB light do scatter in broad spectrum, and their concentration fell pretty abruptly at recombination epoch
 
130
15
Many thanks for your reply, trurle.

Cerenkov.
 
33,387
9,107
2. Am I right to conclude that the CMB is optically 'thick' to all wavelengths of electromagnetic radiation?
Yes, matter was a plasma before. It is thin (essentially non-existent) for gravitational waves and neutrinos, however. They give direct access to the first few seconds.

Big Bang Observer
PTOLEMY
 
130
15
Thank you, mfb.

I had (sort of) figured out that all EM radiation was blocked by the CMB 'wall', but needed to check here at PF to make sure.

Those links are very interesting and I'll be looking further into them asap.

Thanks again.

Cerenkov.
 
1,509
613
From what I understand, what you said is correct. The CMB is a wall that we can not see behind using light. You are also correct that it's only an optical limit and particles like neutrinos should be able to give us information about the universe from before the CMB was created.
 

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