Dark Matter is an unknown matter which is not visible. The reason behind its invisibility is, it does not absorb, reflect or emit light. This makes it extremely hard to spot. Dark matter does not interact with the electromagnetic force thereby making it hard to spot.
Candidates would find this topic to be of importance while preparing for IAS Exam.
Why is Dark Matter Important?
Dark Matter is important because of its gravitational effects on many components of this universe. Its gravitational effects help in understanding the large scale structure of the entire universe, the rotation of galaxies, etc. The gravity of the dark matter is an important prerequisite for permitting the universe to hold on to the important elements that gave rise to life and habitable planets like earth. Without the presence of Dark Matter, the existence of life would not have been feasible.
What is the difference between Dark Energy and Dark Matter?
There is a difference between Dark Energy and Dark Matter. Ever since Big-Bang, the universe is expanding at an ever-increasing rate. The reason behind this continuous expansion of the universe is a force named Dark Energy. On the contrary, the role played by Dark Matter is to bind our universe together. Dark Matter is particles that cannot be seen through a telescope, but they can be located because of its gravitational effect on its surroundings and the X-ray it emits.
Are Black Holes Dark Matter?
Black holes could be considered as a dark matter for the reasons mentioned below:
- Almost collision-less.
- They are stable (if sufficiently massive)
- They have non-relativistic velocities.
- They formed very early in the history of the universe.
In March 2016, 3 groups of researchers proposed that Black Holes had a primordial origin. Results from 2 groups are consistent with the scenario that almost all dark matter is made of primordial black holes. 3rd group concluded that black holes contributed to only less than 1% of total dark matter.
The above details would help candidates preparing for UPSC 2020.