A question about uniformity and the CMB

[Astro Noodles]

So, we can see the CMB, and from it we can determine a number of things, including that the big bang happened and when it happened. For those of us who don't understand the maths or science, a visual representation has been produced.

When I look at the representation, the first thing that strikes me is it's lack of uniformity. To my mind, if the big bang happened from a singularity, and was obeying a single law or set of laws, surely the CMB would be uniform across the whole sky.

What does this mean? What am I missing? 

[vlaiv]

19 minutes ago, Astro Noodles said:

What does this mean? What am I missing? 

Two things

1. It is very very uniform although visual representation suggests it is not. It was deliberately done so to show variations in CMB - but picture itself does not show how tiny these variations are.

If you look at color scale - it tells you magnitude of variations and it is +/- 500µK, or +/-0.5mK or +/-0.0005K

Yes, that is 1/1000 of a single Kelvin

2. Although things were very uniform - in physics we don't have perfectly smooth things. Even vacuum is not empty / smooth - it is full of quantum fluctuations. It is the same thing here - CMB is image of quantum fluctuations at the time before inflation. When inflation happened those quantum fluctuations were frozen in moment and blown up in size to represent the grain we see (and other things contributed to this grain like baryon acoustic oscillations).

[saac]

Fluctuations in the void, virtual particles appearing and disappearing created irregularities at a quantum level effectively being mapped to the macro domain.  These irregularities in the void effectively provided nucleation sites around which matter would coalesce.  The universe, spacetime, is thought to be a mass of thread like filaments around which structure was built.  Take a look at the video posted elsewhere Everything and Nothing (Amazon Prime or BBC 4) by prof Jim Al Kahlili , very watchable. 

Jim 

image source https://www.space.com/37191-we-live-in-a-cosmic-void.html

Edited July 13, 2021 by saac

[Astro Noodles]

5 minutes ago, saac said:

Take a look at the video posted elsewhere Everything and Nothing (Amazon Prime or BBC 4) by prof Jim Al Kahlili , very watchable. 

Jim 

I've watched it.

I am still not clear on a number of things though.

[saac]

There is a section in the video - the 2nd part about Nothing - where Prof Al Kahili is explaining that the void (the true vacuum of space) isn't actually "nothing".  Randomly, so called virtual particles,will appear as he explains "borrowing energy" from the void. These particles only exist for the briefest of moments of time, almost instantly annihilating so returning the energy back to the void.  This results in quantum fluctuations in the void energy which in turn manifests as variations in density throughout space . These sites of varying density become the nucleation sites for baryonic matter to form and are impressed on space at the macro level.  Perhaps think of these fluctuations in energy as ripples in space around which dust settles. 

Jim 

[randomic]

The perhaps more astound non-uniformity is the lack of anti-matter we observe in the universe. All things being symmetric (which things tend to be in the standard model), there should be equal amounts of anti-matter and matter in the universe. The apparent dominance of matter in the universe (among other things) opens the question of what the mechanism for this symmetry breaking is.

Another important thing to note is that the CMB isn't as far back as things go, it manifested when the universe became transparent (before then matter was ionised and so light couldn't get very far before being absorbed).

[George Jones]

3 hours ago, saac said:

There is a section in the video - the 2nd part about Nothing - where Prof Al Kahili is explaining that the void (the true vacuum of space) isn't actually "nothing".  Randomly, so called virtual particles,will appear as he explains "borrowing energy" from the void. These particles only exist for the briefest of moments of time, almost instantly annihilating so returning the energy back to the void.  This results in quantum fluctuations in the void energy which in turn manifests as variations in density throughout space . These sites of varying density become the nucleation sites for baryonic matter to form and are impressed on space at the macro level.  Perhaps think of these fluctuations in energy as ripples in space around which dust settles. 

Jim 

 

The way I like to put it: when we look at galaxies through our telescopes, we are looking at quantum fluctuations blown up to galactic proportions by the expansion of the universe! Mind blowing!

[saac]

36 minutes ago, George Jones said:

 

The way I like to put it: when we look at galaxies through our telescopes, we are looking at quantum fluctuations blown up to galactic proportions by the expansion of the universe! Mind blowing!

I like that, it's like the Universe did an image stretch on itself    I think it's also reassuring in a way that detail/patterns in the smallest dimensions are reflected at the largest scale . It's like the Universe knows itself. 

Jim 

[ollypenrice]

You might find The Book of Nothing, by the late John Barrow, very helpful. It isn't devoted entirely to the non-emptiness of space since it also looks at the concept of zero, but it's characteristically well-written and enjoyable. It's high time I re-read it.

Olly