what is dark matter? explain.
Answers
This universe have many mysterious things .
We are researching many things about it and we get only questions but not the real answer.
We were thinking till now that our universe contains only matters like electrons , protons , neutrons, stars , galaxies , planets , organisms etc, which we can see easily.
But it's not true
Actually the universe we can see is a small part of real universe.
You will be surprised to know that 96% part of our universe is made up of that matter which we can't even see .
Physicist thinks that 21% of our universe is made up of DARK MATTER , 74% of our universe is made up of DARK ENERGY and 4% of our universe is made up of NORMAL MATTER .
Let's talk about what is DARK MATTER AND DARK ENERGY
DARK ENERGY.
Till 1990s we only known to that our universe is expanding day by day .
Scientists were thinking that either the energy density of universe is too high that one day it will stop expanding and start contracting or it's energy density is too low that it will be expanding forever.
I think uh wanna know what is ENERGY DENSITY ?
Actually ENERGY DENSITY is the quantity of energy which a matter can store or a system can store.
But they thought that the gravitational force will slow down the speed of increasing universe because they were thinking that this universe is made up of normal matter and their gravitational force can slow down the speed of expanding universe.
But in 1998 Hubble telescope captured a picture of a supernova which gave an evidence that the speed of expanding universe in past comparing to present was slow that means the speed of expandation of universe is increasing day by day .
All scientists known to that fact that there is something which is leading this thing that is the increasing in the speed of expandation of universe but they were not sure about that
At last to solve this problem they imagined about an energy which is present in whole universe and gave a name DARK ENERGY.
DARK ENERGY is very mysterious.
It is present in whole universe also in our surrounding.
But we can neither calculate it nor test it but we can observe it's effect.
There are many thoughts about dark energy.
One of them is that dark energy can be the property of empty universe.
Albert Einstein was the first man who told that the empty spaces in universe exist .
Albert Einstein in his theory of gravity said about a cosmological constant and also said that empty universe have it's own energy.
DARK MATTER
In past few years we got that the gravitational force of normal matter or observable matter in this universe is not as much powerful to make a galaxy and other complex things . If it was so powerful then only stars were there in place of galaxies . That means there is something which makes galaxy but we can't see that
That's why we gave a name to that matter which is DARK MATTER .
But unfortunately we didn't get any proof about DARK MATTER till now by which we can know about it.
Till now we only know that it is present in the universe because it responds to gravity.
According to Einstein's theory of relativity, the body which have very high mass makes a curve in the space time and also bents the direction of light.
Dark matter are those empty matter present in whole universe.