Robert Wilson was awarded half the 1978 Nobel Prize in physics with Arno Penzias "for their discovery of cosmic microwave background radiation.” The remaining half was won by Pyotr Kapits “for his basic inventions and discoveries in the area of low-temperature physics." Robert Wilson did his Ph.D. research in radio astronomy. From there he began working at Bell Labs with Arno Penzias. They used an antenna made from a 20 foot expanding waveguide (called a horn) and part of an off-axis parabolic reflector that focuses the electromagnetic signal it receives into a radiometer (a receiver tuned to a specific radio frequency). The antenna is designed to disregard the signal from the Earth and collect the signal received from the sky (originally it was made to receive signals from a satellite used by Bell Labs). The radiometer was calibrated using a transmitter less than one kilometer away, and incorporated a maser. Best of all, the scientists could recalibrate it to receive different frequencies, so that they could measure multiple frequencies from the sky very accurately. One of their first measurements Wilson and Penzias made of the cosmic background radiation that led them to the Nobel prize. By altering the antenna to 21 cm, they researched galactic and inter-galactic atomic hydrogen studies. Later, their research involved millimeter electromagnetic waves, which led to the discovery of different molecules in space. Observations of interstellar substances could be traced back to nuclear processes. Their measurements provided evidence supporting the Big Bang theory.