How was it discovered?
How is it being recearched now?
Fritz Zwicky (1933)
Observed galaxy cluster that moved like its mass was 400 times bigger than it looked like.
Was convinced that something called Dark Matter, that didn't have visual, but had gravitational properties, can explain his observations.
The student who observed that galaxies are moving apart instead of coming together.
Then she helped to develop a prove based on completition of previous scientist's research.
In 2010 there was a failed telescope attempt.
Large Hadron Collider attempt also failed.
Russian - European spacecraft found indirect evidence of dark matter existed (found positrons in the space).
ISS found the same positrons, so it's more evidence.