What observational evidence supports the conclusion that most of the mass of the Milky Way is in the form of dark matter? Although dark matter emits no visible light, we have detected it with radio telescopes. The orbital speeds of stars and gas clouds far from the galactic center are surprisingly high, suggesting that these stars and gas clouds are feeling gravitational effects from unseen matter. There is no observational evidence; it is only a theoretical idea based on computer models indicating that the Milky Way could not have formed unless it had much more mass than it contains in stars and gas. They have directly seen dark matter with no guess work.