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)

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

1 million years have passed since the beginning of everything and now we are close to the things very interesting. Today we are going to talk about the first sound waves ever and how they helped in shaping and understanding the universe. 

The first sound waves have a fancy name - 

BARYON ACOUSTIC OSCILLATIONS

But don't freak out eh !

BARYON - The particles like neutrons , protons (1*)

ACOUSTIC- Dealing with sound 🔊

OSCILLATIONS- To and fro movement 🔔

Following the story till now , the universe is a hot 🌡️ place full of baryons , photons , electrons and dark matter . Electrons and protons formed a hot soup 🍵, plasma coupled with photons due to continuous scattering of photons by charged particles. 

The baryon photon plasma is opaque that means that there is no light in the universe till now 😲 .

The distribution of all the components was inhomogeneous ..a lil bit more here , a lil bit less there. 

How the inhomogeneity ?  They were considered to be the remenants of random quantum fluctuations of baby subatomic universe. 

The result of these fluctuations is two dominant agents coming into play - Gravity and Pressure

Each overdense region pulled matter towards it. 

Dark matter(2*) is not effected by light, and it was also far back the dominant as compared to the ordinary baryons so it flowed inwards towards density peak . Overdensity leads to Overpressure.

The photons coupled with baryons were also present there and they exerted enormous outward pressure and , the spherical sound waves were produced .

GREEN REGION- PHOTONS
RED REGIONS- BARYONS
BLUE REGION- DARK MATTER

The spherical shell travelled fast ⚡at half the speed of light . The shell expanded fast , so did the universe. The universe eventually became cooler, the photons were redshifted to lower energy. At  370,000 years the plasma hit a critical temp of 3000K  recombination( I don't know why  recombination cuz they combined for the first time )took place - protons , neutrons and electrons combined to form neutral atoms . Light wasn't able to able to interact very much now with the atoms formed from baryons. 

Gravity pulled the newly formed matter in and the photons were finally free to stream through the universe and there was 'light' for the very first time - now called Cosmic Microwave Background

 ( more about this in the next blog )

So finally , light and matter decoupled . Light was free to travel through cosmos but the distribution of baryon inhomogeneity was frozen at a distance 'r' from the centre of intial overdensity which is referred to as sound horizon. Its value is about 450,000 light-years. If this distance is rescaled to today, taking into account the expansion of universe, it's about 500 million light-years or 150 megaparsecs (1 pc = 3.26 light-years). The dark matter and the ordinary one flowed together to make the structures we see today.

And how can we see them now? 

Well we can see it imprinted in the form of galaxies. The shells of over and under densities all were  overlapping at the time of recombination. And the pattern looked like this - 

Detecting🕵️ it required the most detailed surveys of sky💻 and we entered the era of precision cosmology .

How we did that ? We made the map of universe , (with the help of galaxy redshift surveys). The resulting pattern shows the galaxies to be dominantly found in the central density peak regions and the regions where the sound horizons intersect i.e there were slight excess with separation of 150 megaparsecs from centre. All the galaxy surveys confirm this and we are getting more and more precise with every measurements .

SDSS-III DATA RELEASE

every pixel in this image represents entire galaxy

Baryon Acoustic Oscillations tell us a great deal about position🚩 of galaxies . They also hold the key to understanding the expansion of universe . It confirms that dark energy behaves the way as predicted by Einstein's cosmological constant. 

The first sound waves carry so much information and thrill with it !!

Neil deGrasse Tyson rightly said - "Not only we are in the universe , the universe is in us . I don't know of any deeper spiritual feeling than what that brings upon me "

Any questions , anything you wanna express or share ?

Drop it down in comments !

(1*) - To know more about baryons check my blogpost here  -WHAT THE HECK IS PARTICLE PHYSCIS

(2*) -To know more about dark matter check my blogpost here - DARK MATTER

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OUR JOURNEY : FROM NOTHING TO 1 MILLION YEARS (BIG BANG-3)

Asymmetric laws of physics made matter win over anti-matter(1*). Annihilation💥 stopped when thermal energy fell 🌡️ to rest mass energy of proton ; temperature being 10^13 K. The universe has expanded by a factor of 100 from the quark soup 🍲 era(3*). 

10^(-6) seconds after big bang

Hadron Epoch(2*):

Quarks combined to form hadrons and anti-hadrons. Somehow one of the hadrons managed to survive till the first second when this epoch ended. Theory predicts, about 1 neutron remained for every 7 protons. This ratio of 1:7 is still observable strengthening the theory.

About One second after big bang☄️

Neutrino Decoupling and Cosmic Neutrino Background(CNB) : 

Neutrinos which were till now in thermal equilibrium with protons , neutrons and electrons ceased interaction with other types of matter and influencing the dynamics of early universe.The🌡️ temperature of universe was about 10 billion kelvin.

Big Bang Cosmology also makes prediction about the neutrino environment called CNB. It says that about 1 sec after big bang the map of universe was imprinted with CNB. We haven't been able to detect it till now due to its extreme low energy📉

Primordial Black Holes :⚫

Due to high densities and inhomogeneities during the first second , some regions would have become sense enough to undergo gravitational collapse and form black holes. Current theories have many unanswered questions to this event.

First 10 seconds 

Lepton(2**) Epoch:

Similar to the hadron epoch , the leptons dominated📈 the mass of universe now. About 10 seconds after big bang , the leptons and anti-leptons annihilated each other leaving high energy photons.

Between 10 seconds and 370,000 years after the Big Bang

Photon(2***) Epoch : 

Photons now , interacting with charged particles , continued dominating the universe for a long time. 

Between 2 minutes and 20 minutes after big bang 

Nucleosythesis of light elements :

The temperature 🌡️ and pressure conditions are now right enough to allow nuclear fusion to occur giving rise to a few light elements beyond hydrogen.

About 25% of the protons with all the neutrons fuse to form deuterium and most of the deuterium quickly fuses to form helium-4. Other unstable elements were also formed.

The resulting matter is about 75% hydrogen nuclei, 25% helium nuclei, and 10−10 by mass of lithium-7.

                                     

47,000 years after Big Bang

                                       

Now the universe is matter dominated. The densities of ordinary matter and photons becomes equal to Jeans length - the length at which the structure formation by dominance of gravity can take place.

1 million years after Big Bang

Now the universe has sufficiently cooled down to form the first molecule - helium hydride. Much later on the timeline , atomic hydrogen and helium hydride reacted to form molecular hydrogen necessary for star⭐formation . The universe till now was opaque. If you could somehow travel back to that time, you will see nothing . The universe was blind !

 So, how we got from 0 visibility to pointing Hubble telescope in space ?

What do you think about this? Any ideas? let me know your guesses in the comments below.

We have now come too far , from the first microsecond to 1 million years. More interesting events ,   are yet to come. To all those who are reading this till last  ,  just take some time to appreciate the complex existence of our life structures.

(1*)- To know how matter won over anti-matter , check out my blogpost -

  BIG BANG(2)-ANTIMATTER        

(2*) (2**)  (2***)- 

Hadrons,leptons,photons are a part of particle physics. To know more check my blogpost -

WHAT THE HECK IS PARTICLE PHYSICS

(3*)-To know more check out my blogpost-

THE BEGINNING OF EVERYTHING - BIG BANG (1)

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