Rubin's calculations showed that galaxies must contain at least five to ten times as much dark matter as ordinary matter. Rubin's results were confirmed over subsequent decades, and became the first persuasive results supporting the theory of dark matter, initially proposed by Fritz Zwicky in the 1930s. This data was confirmed by radio astronomers, the discovery of the cosmic microwave background, and images of gravitational lensing. Her research also prompted a theory of non-Newtonian gravity on galactic scales, but this theory has not been widely accepted by astrophysicists.