Penzias and Wilson weren’t even looking for the Cosmic Microwave Background (CMB) when they found it. The focus of their research was the detection of neutral hydrogen. It was just a happy coincidence that the Bell Labs antenna was perfect for sampling the microwave background radiation. The pair spent a good bit of time trying to figure out where the noise was coming from before realizing what it truly was. They chased off the birds (with a shotgun), checked all the wiring, and still the noise was present. But of course it was — it’s everywhere. They were hearing the heartbeat of the universe.
The pair quickly published their findings, and scientists around the world took note. The detection of the Cosmic Microwave Background has allowed us to study the universe in a way we had never been able to before, and offered the first tangible evidence of the big bang.
Other teams were actually looking for the CMB at the time, but were beaten by Penzias and Wilson. That must have stung a little, to be months away from one of the most important discoveries in physics only to have someone else stumble upon it. Penzias and Wilson were awarded the 1978 Nobel Prize in physics, but researchers who had previously theorized about the CMB were not recognized by the committee.
The Cosmic Microwave Background is basically what’s left over from the energy of the Big Bang. When the universe was young, it was permeated by extremely hot hydrogen plasma and was opaque to electromagnetic radiation. The Big Bang model holds that the universe expanded from that point and got cooler. The plasma cooled and formed molecules, and the electromagnetic radiation radiation (e.g. light) has been propagating through space ever since. The continued expansion of the universe has stretched the wavelength of this radiation from the visible into microwaves, and that’s where we get the CMB. This is a thermal measurement of the electromagnetic radiation of the universe, and can tell us a great deal about its evolution and structure.
In the 50 years since Penzias and Wilson discovered the CMB. It has been used by scientists to make many observations of the universe. We’ve made better estimations of the age of the universe, detected gigantic voids in space, and searched for the end of all things. A variety of probes have been deployed specifically to study the CMB over the years, most recently the ESA’s Planck spacecraft that operated from 2009 to 2013. With each new mission we learn more, and it all goes back to Penzias and Wilson chasing birds away from their radio telescope in 1965.
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