What is dark matter ? This is the first question that we ask ourselves when we hear this word (Dark matter).

Dark matter is around us . Its presence was to begin with proposed within 1920s and first taken genuinely within 1960s when space experts taken note something odd approximately how worlds were turning and what it implied for how much mass was interior them.

Dark matter

Dark matter is not at all like ordinary matter, it does not interact  with electromagnetic energy. it does not assimilate, reflect or emanate light, making it greatly difficult to spot.Analysts have been able to induce the presence of dull matter as it were from the gravitational impact it appears to have on unmistakable matter.

Methods  We Know black Matter Is There

1-Turning galaxies 
2-Gravitational lensing 
3-Colliding systems 

Spinning galaxies

A turning system works nearly the same way.Since the universe is turning, the stars in it tend to need to fly off their orbitals. The thing holding them together is the constraint of gravity from all the mass display within the world (gravity pulls things with mass together). The quicker the universe spins, the more mass you wish to hold all the stars in. On the other hand, knowing the mass of the system implies you'll foresee how quickly the system can turn،but there is a problem observed by the astronauts.
Dark matter

The problem is ( 
Estimations appeared that the systems were turning quicker than was anticipated by how many stars they contained.  In arranging to clarify the tall turn speed, stargazers were required to include a colossal sum of mass to the systems in their calculation so all the stars held together. But they couldn’t see where this mass was. This inconsistency can be settled on the off chance that you accepted there was a colossal sum of a few kind of overwhelming stuff that was undetectable, or “dark,” in each system.)

2- Gravitational lensing

Another imperative clue that persuaded researchers that dull matter was genuine was the perception that it can twist light . Typically called gravitational lensing.

3-Colliding galaxies

 The foremost persuading single piece of proof for dull matter came when we watched a monster galactic collision in space. Two clusters of universes slam into each other millions of a long time back in an epic occasion, as the two system clusters hammer into each other, the gas and tidies from the two clusters collided with marvelous comes about: enormous blasts, mammoth clouds of tidy getting tore separated, But space experts moreover taken note of something else. Near the collision location, they taken note two monster clusters of dim matter; of course, this dim matter was imperceptible, but they seemed to spot it in a roundabout way by measuring the mutilation the clusters were causing to the light from the galaxies behind them. So able to get it from this section that when the two clusters collided, most of the gas and tidy smashed together within the way you anticipate ordinary matter to do.  Let's ask a question ,what will happen when dull matter bumps into other dull matter? Nothing that we might identify with! The clusters of dim matter kept going and passing.

Dark matter

Finally these are the evidences that scientists put them to illustrate this mystery of dark matter .