Tag #Vera Rubin

What observational evidence definitively proves dark matter's existence, and what is its estimated proportion of the universe's matter?

Vera Rubin's 1977 observations of galactic rotation curves showed that stars' speeds remained constant far from galactic centers, contradicting Newtonian gravity's predictions unless unseen matter, estimated to be nine times the visible matter's mass, existed. This, along with gravitational lensing in galaxy clusters revealing only 20% luminous matter, and cosmic microwave background radiation analysis indicating over 80% dark matter, strongly supports its existence.