Penzias and Wilson

Discovery of cosmic microwave background radiation

Penzias and Wilson discovered a 3.5 K isotropic microwave background in 1964 using the Holmdel Horn Antenna at Bell Labs. They eliminated local interference — including pigeon droppings — and confirmed the signal originated outside the Milky Way. Its match to Dicke’s prediction prompted interpretation as the Big Bang’s remnant. But the work itself claimed only a persistent, unexplained antenna temperature — not cosmology.