How did they see or determine that matter was dark?

Answer 1

The velocity at which stars in any galaxy revolve around the center is determinded by it radius and the "total mass" of that galaxy. In all the galaxies they found that the observed mass was just 10% of the "calculated mass" required to justify that speed.

Hence scientist predicted that each of those galaxies must have a lot more matter that that is "visible". Hence that missing matter was called "dark matter". By the way till now only neutrino has been mentioned as one possible "dark matter" candidate

Answer 2

They can't see it. They calculated that it was necessary to explain the rate of expansion of the universe. Problem is, it's still not enough. That's why they also postulated dark energy. Personally, I think they're 'barking up the wrong tree'. C. Miller determined that there really was an Aether back in the 1930's. But by then, everyone was running with Einstein's ideas, and he got left behind. I think that's funny, because Einstein was actually very interested in Miller's experiment.

But it is possible that dark energy and Aether are the same thing.

Answer 3

The more you study physics,the more the questions.I guess they saw or felt the effect of 'dark' matter and concluded that it was dark. For instance nobody,even with the most sophisticated equipment has ever seen an electron,but we see its effects in many aspects-electricity,light..etc so we conclude that electrons exist!!

Answer 4

if it doesnt emit light i guess it is dark, they can see where it should be cause they cant through it.