Forty years ago, physicists Arno A. Penzias and Robert W. Wilson received the Nobel Prize in physics for discovering cosmic microwave background radiation, the most important proof of the Big Bang theory.
The story began in 1963, when Penzias and Wilson were using the antenna in Holmdel, New Jersey, to study the Milky Way. Early on, the two astrophysicists detected a uniform “parasitic noise” coming from all the regions of the sky. Thinking their equipment was malfunctioning, they checked every component of the antenna, going so far as to remove pigeon droppings that had found their way in. Despite their efforts, the “parasitic noise” remained.
It was then that Penzias and Wilson contacted their colleagues at Princeton University to get their opinion on this mysterious background noise. The astrophysicist John Peebles quickly remarked that our experimenters had detected the oldest picture of the Universe: cosmic microwave background radiation.
Where did cosmic background radiation come from?
The Big Bang happened 13.8 billion years ago, when the Universe, infinitely dense and hot, began to expand in a dizzying way.
In the Universe’s first moments, the density of matter was so great that the slightest photon of light was immediately reabsorbed. It is believed that the Universe at the time was opaque, because no photon from that period is observable. After 380,000 years, expansion had sufficiently dilated the Universe for photons to begin to move about freely, creating the cosmic microwave background radiation that can be observed today.
A discovery of importance
As early as the 1940s, theoreticians had predicted that it would be possible to observe that light in the microwave range. After a number of unsuccessful efforts, Penzias and Wilson would be the first to accomplish the feat of detecting cosmic microwave background radiation.
In July 1965 they published an article in the specialist publication Astrophysical Journal to announce their discovery. Peebles and his Princeton colleagues wrote a second article explaining the significance of that discovery.
As a consequence of the observation of cosmic microwave background radiation, the Big Bang theory, which was still highly controversial, came to be accepted by the astronomical community, and established itself as the best theory for explaining the birth and evolution of the Universe.