Dark matter and Energy

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Dark matter and Energy








Well we all know that our universe was born 14 billion years ago , after the big bang explosion...According to the great physicist stephen hawking universe have began from a singularity...And there were two main hypotheses about the beginning of our universe...  which were the big bang theory and the steady state theory..

I will explain about these both hypotheses in my upcoming articles....Now lets focus on our main topic....

What is dark matter ?


The observable universe has a radius around 47 billion light years...Due to the expansion of the universe this might get minimized in the next billion years...The average temperature of the universe was 2.7K ..Our universe was made of three major substances....And they were Visible matter , Dark matter and Dark energy....

Astronomers believe that 69% of the universe was about dark energy and 26% was dark matter....Only 5% represents what we observe in the universe as normal matters....Black holes , stellars , comets , planets etc... These all substances are categories of normal matters...


The theory of dark matter is not a hypotheses at all...Due to plenty of observations we can precisely predict about the exist of dark matter....Dark matter was different from ordinary matter which were made of atoms and their subatomic particles due to not interacting with electromagnetic radiation....Due to that reason its so difficult  to detect directly yet we can observe dark matter by their gravitational interference on visible matter and also large scale objects....


The existence of dark matter first proposed by swiss astronomer fritz zwicky in 1930s...Usually the matter density of the near center of a galaxy was much higher than its boundaries....Because of that gravitational affect was much higher in the center area than the boundaries.....According to newtonian physics if a object get close to a higher gravitational field its rotational speed get increased than the low  gravitational field objects....Due to less matter in a galaxy boundary its gravity assistance was way smaller than the center gravitational field....Due to that objects in the boundary should have a less rotation speed comparing to other...But fritz didn't discover that kind of variety of speeds of matter....



Due to this observation and further studies helped to find evidence about the existence of dark matter... scientist and astronomers still have no idea about the exact nature of dark matter due to its nature of not emit , absorb or reflect electromagnetic radiation and that's the reason its named as "dark matter"...

There were four main hypotheses that scientist made to explain the nature of dark matter.... 
  1. Massive compact halo objects(MaCHOS)
  2. Weakly interacting massive particles (WIMPS)
  3. Primordial black holes
  4. Extra dimensions...
   Now lets clarify about each hypotheses....MaCHOs hypotheses says that huge amount of matter was consist in a small volume and these huge matter was situated in a far distance in a galaxy....WIMPS hypotheses says about a huge matter that doesn't interact with other matter but can make gravity assistance towards other matter...The third hypotheses says that plenty of primordial black holes may contain in a galaxy and can act like dark matter...  And the final hypotheses says that these types of dark matter can be contain in extra dimensions which that we cannot observe...

Dark matter plays a huge in the formation and the evolution of a galaxy and the large scale structure of the universe....85.7% of the total matter in our universe was dark matter....Due to its mysterious nature scientist constrains to observe about these dark matter using astrophysics methodologies and quantum physics...

Now lets talk about dark energy......

What is dark energy ?



Edwin hubble discovered about the expansion of the universe in 1929....Dark energy plays a huge role behind this expansion of the universe..But after this observation scientist believed that this expansion speed might get less and lesser due to gravitational assistance which formed by matter....But lately scientist observed that the universe expansion speed was happening in a accelerating speed....


The orange , green and blue lines indicate the hypotheses that scientist believed about the universe expansion...But the red line indicate about the expansion of the universe.....

The existence of dark energy first suggested in the 1990s due to a supernova observation...Dark energy is a type of energy that exert negative pressure....Due to the expansion of the universe we should expect a dilution of dark energy likewise matter density and radiation....But now scientist have discoverd that the magnitude of dark energy stays constant or else get increased rather that getting minimized.....This specific behavior plays a huge role behind the expansion of the universe....



Their were several hypotheses behind how the universe gets end...and the hypotheses of big crunch was one of them....The big crunch theory suggest that expansion of the universe eventually reverse and the universe recollapse.....causing the cosmic scale factor to reach zero....Cosmological constant was built up by albert einstein to balance his equation about the theory of general relativity...His theories proved that the universe was expanding ...But he didn't want to believe that...Therefore he used this cosmological constant to get reduce of the theory of expansion of the universe...But now we can use that cosmological constant to explain about the expansion.....we can arise about the concept about dark energy using modifications of general relativity.....

Observation of dark energy was much harder than observation of dark matter....Dark energy 
Interference is primarily seen on cosmological scales...


( cosmic microwave background radiation  - CMBR    ) 

Scientist use various measurements to study about dark energy including CMBR , large scale galaxy surveys and the large scale of the structure of universe.....These observation may helpful to find out about dark matter and also about the expansion of the universe and its nature....


           ( Heat extension in the universe)


Understanding in Dark energy and dark matter is a significant frontier in cosmology , modern and fundamental physics ......And understanding about these two concepts may helpful to us for the observation of mysterious nature in our universe.....

                                        Thank you, 
                                  🖊️ Shehan Manoj
                ( undergraduate in physics )
                            Space Explorations 
 

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