Robert Wilson came to Lindau in 1982 together with his co-Nobel Laureate, Bell Labs colleague and astronomy research collaborator Arno Penzias. Their two talks did not explicitly touch upon their Nobel discovery, but reported from ongoing radio astronomy research concerning the interstellar medium, the space between the stars. Radio astronomy started up around 1950, but in the beginning the radio astronomers in general “saw” only a diffuse radiation of varying intensity. Then there was the important and promising discovery of a sharp line at 21 cm wavelength, emanating from hydrogen, the most abundant element in the Universe. With the invention of the maser amplifier by Charles Townes in 1954 (rewarded by a Nobel Prize in Physics ten years later), a very rapid development took place and from around 1960 characteristic radiation from a whole series of molecules was detected. Bell Labs were at the forefront in constructing amplifiers using the new technique and Robert Wilson in his lecture describes results from very precise observations of the molecule CO, carbon monoxide, in interstellar space. When this molecule rotates, it emits radio waves at around 2.6 mm wavelength, with small variations depending on what isotopes of C and O enters into the molecule. It turned out that “empty space” was not empty at all, but filled with molecular clouds of varying sizes and densities. Wilson describes how his measurements of three isotopes of CO laid the foundation of a new picture of, e.g., the Orion nebula. Behind the nebula he detected a giant molecular cloud, which made this well known and well studied nebula appear as only the tip of an iceberg! Anders Bárány