ORANGE IS THE NEW BLANK : CMB : THE MAP OF UNIVERSE-(BB-5)

Ever tried switching between channels in antenna tv ? You must have heard that static buzz and be like .. ah ! such a mess

Well , about 1 % of that buzz carries information about the whole of universe. We have built a cosmic map out of that !
I have introduced it a bit in the previous blog(*1) and now we will dig into it in bit detail.
Cosmic microwave background is a information about baby universe(3,80,000 years after Big Bang ) in the from of radiation filling entire space. It's the first light ever!

How did it happen ?

Just before recombination , the universe was a hot dense soup of baryon-photon plasma . Most of electrons were not free to travel very far due to constant interaction with ionised particles. There was no light !
Eventually the universe cooled down to a point where electrons can combine with hydrogen and helium nuclei to form neutral atoms-event known as 'recombination'.

 The light didn't interact with newly formed atoms very much and was free to stream through the whole universe.The photons released had the temperature / energy of 4000 Kelvin .

The early photons that streamed through the universe were orange in colour . Universe looked orange !🔶

Then how the the universe black now ?
Answer : Expansion

The expansion cooled down the universe , stretched the wavelength of photons to microwave region . As our eyes cannot see this radiation , it is dark or transparent to us. Orange is the new black

 The temperature of this radiation has dropped down to 2.7 Kelvin🌡

How did we measure the radiation ?

It was first predicted theoretically by Ralph Alpher and Robert Herman .

But , was an accident that sparked the research. In 1964.

 The Holmdel Horn Antenna was designed to be used for satellite communications by Bell Laboratories. But when Arno Penzias and Bob Wilson tried to calibrate the instrument, there was a noise that just couldn't go . No matter where and when they point the antenna there was a constant low level "hum" having an excess temperature of 4.2 Kelvin . All the tricks were tried to get rid of it but in the end it was discovered that this Buzz is due to CMB winning Penzias and Wilson Nobel prize in 1978.

The theoretical predictions about inhomogeneities and and the nature of CMB were all examined in great detail by satellites and telescopes and they all reproduced the big bang model of universe.

Features of CMB
Understanding the image - 

CMB is like the map of universe , this picture pretty much tells us every thing about the universe .
Before the time of recombination, in the very early Universe , small density inhomogeneities lead to baryons and dark matter flowing inwards into dense regions . (*2)The photons were coupled with baryons till then and they exterted outward pressure . This play between gravity and pressure produced the first sound waves oscillations in universe , the bouncing shell of matter flowing inwards and outwards till it was decoupled from light and froze where it is. These overlapped frozen shells of matter then collapse into galaxies as we see them today . Cosmic microwave background is the image of universe at time of recombination .

When Recombination hit, most were caught in the middle of in and out flow - like between maxima and minima of oscillations . But some oscillations were caught at maximum density - where matter flowed in the middle of fluctuation and some were at minimum density where matter is most spread out - called maximum rarefaction. These maximas and minimas define the most obvious points on the picture.
Now lets have the information in the form of graph to get a better sense .
This graph is called the power spectrum of cmb .

Each of these peaks tells us something unique. The peaks of this size had exactly had collapsed just once before recombination .Which means it's size is equal to speed of time (0.58c) × amount of time they had to collapse (3,80,000 years ) × expansion factor = half a million light years .When we go to actually measure the size of these spots by telescope , the measurements correspond to flat universe. Thus there will be no big rip , the universe will expand forever.

The first peak tells us about the total energy present in the universe.
The second peak tells us about the amount of Baryons present in the universe (roughly 5 % of total energy of universe ) and the other peaks give us the information about dark matter - the amount of dark matter compared to radiation .
Thus , we get to reproduce this pie chart from CMB

                                 

This static buzz has helped us in understanding the colour of early universe , the composition and temperature of universe , the geometry and the ultimate fate of universe. It is a strong support to big bang model and has helped us clearing our assumptions about the model of universe directing us to the ''till now the best model of our existence".
We get an insane amount of information from it !

Every portion of the sky tells a story , be curious to detect one !
Never stop questioning , curiosity has it's own reason for existing

(*1),(2*)-CHECK PREVIOUS BLOG HERE

  -STORY OF FIRST SOUND WAVES OF UNIVERSE-(BIG BANG-4)