Which observational tool helped astronomers Arno Penzias and Robert Wilson discover the existence of the cosmic microwave background (CMB)? A.
optical telescope
B.
radio telescope
C.
a digital camera
D.
space telescope

Holmdel Horn Antenna

Answer. In 1964, while experimenting with the Holmdel Horn Antenna, which was used as a radio telescope, Penzias and Wilson accidentally discovered the microwave background radiation that exists universally. The Holmdel Horn Antenna was used to support the "Big Bang Theory" as opposed to the "Steady State Theory".

Idont really understand