Dark Matter Spectrograph
1960s-1970s, Air and Space Museum
A peek at distant galaxies unlocked a cosmic mystery
In the early 1970s, astronomer Vera Rubin and colleagues at the Carnegie Institution for Science attached this instrument to several large telescopes to analyze distant spiral galaxies. What they found would change our understanding of the universe: The galaxies’ outer arms were rotating at velocities that should have made their stars fly away—but didn’t. The only explanation, Rubin decided, was that the galaxies contained far more mass than we could see. It was the strongest evidence yet for the existence of dark matter, now believed to make up 26.8 percent of all the stuff that exists.