Doc Ewen: The Horn, HI, and Other Events in US Radio Astronomy

Slide 7: Detecting the Interstellar Hydrogen Line, 1951

Later in his 1948 paper, Shklovski says, "To sum up, one may say that with the resources of modern radio techniques it is fully possible to detect and measure the monochromatic radio emission of the galaxy." [Photo courtesy of Doc Ewen]
Slide 8