What is this ''Dark Matter'' ?

There is something that exists in space. We cant see this but we are assuming it in there. This secret thing name is ''dark matter''. Scientists think its nearly %80 mass of the universe. We cant see this with the naked eye, why we think it should exist?

  Since 1920 scientists have hypothesized that the universe contains more matter than seen by the naked eye. Since this date, the idea of dark matter has grown although there wasn't any logical evidence.

 "Motions of the stars tell you how much matter there is," Pieter van Dokkum, a researcher at Yale University, said in a statement. "They don't care what form the matter is, they just tell you that it's there." Van Dokkum led a team that identified the galaxy Dragonfly 44, which is composed almost entirely of dark matter.

  Why are we think the black matter should exist?

  If scientists can't see dark matter, how do they know it exists?

  Scientists examined spiral galaxies in the 1970s and they expected to see the material in the center moving faster than on the outer edges. Instead, they found the stars in both locations traveled at the same velocity, indicating the galaxies contained more mass than could be seen. Studies of the gas within elliptical galaxies also indicated a need for more mass than found invisible objects. Clusters of galaxies would fly apart if the only mass they contained were visible to conventional astronomical measurements.

 Researches for Dark Matter

 Despite dark matter is not an ordinary matter, scientists made an experiment for this. 

The Alpha Magnetic Spectrometer (AMS),  tracked more than 100  billion cosmic ray hits in its detectors. AMS lead scientist Samuel Ting said ''We have measured excess of positrons [the antimatter counterpart to an electron], and this excess can come from dark matter. But at this moment, we still need more data to make sure it is from dark matter and not from some strange astrophysics sources,".

Also, The Large Underground Xenon dark-matter experiment (LUX) is working to find dark matter. It worked in a gold mine in South Dakota, have also been hunting for signs of WIMP and xenon interactions. But so far, the instrument hasn't revealed the dark matter.

 "Though a positive signal would have been welcome, nature was not so kind!" Cham Ghag, a physicist at University College London and collaborator on LUX, said in a statement. "Nonetheless, a null result is significant as it changes the landscape of the field by constraining models for what dark matter could be beyond anything that existed previously."

 All researches and experiments aren't just these. In the world researches for dark matter is continuing in many places. Dark matter is still mysterious and maybe it will be revealed one day.