Although not large by standards of the time, the horn reflector could be finely tuned, making it ideal for certain types of astronomy. AT&T's next-generation Telstar satellites were designed to take over the signal-amplification work that the horn reflector had been designed to perform, thus freeing the antenna for astronomy. Bell Labs supervisors were aware that the projects Penzias and Wilson proposed for the telescope -- searching for gasses in space and exploring the halo of the Milky Way -- might never contribute to the company's bottom line. But Bell Labs had a distinguished history of making pure scientific research into important, commercially valuable technology.
Hadn't Charles Hard Townes' fundamental work in the field of quantum electronics led to Bell Labs' invention of the laser, and the maser provided the foundation for Bell System oscillators and amplifiers? Hadn't William Shockley's Ph.D. research on sodium chloride contributed to the 1947 invention of the transistor, which allowed the Bell telephone system to spawn the information age?
In this tradition, it wasn't a startling leap for Bell Labs, with an idle, state-of-the-art radio telescope on its hands, to hire a pair of astrophysicists to study the cosmos.
But the scientists had a problem.
Penzias and Wilson needed an extremely quiet antenna to detect the microwave radio perturbations emanating from the far reaches of the galaxy. But, contrary to their expectations, the antenna produced a maddening buzz.
It would have been possible to do many of the observations they had planned by working around the buzz. But Penzias and Wilson chose to remove the static from their receiver. First, they cleaned droppings from a pair of pigeons who had made a home in the horn. Then, they set about getting rid of the birds themselves.
"There was a wonderful old-time hardware store nearby, and we bought this Have-a-Heart trap -- it's a standard way of catching critters in your backyard without killing them. So we got this trap, set it up, baited it with something that attracts pigeons, and sure enough, we trapped them," Wilson recalls. "We heard about somebody in Whippany -- that was the most distant place the company's in-house mail went -- so we mailed them to a pigeon fancier who worked for AT&T in Whippany. He looked at them, said they were junk pigeons, and he let them go. A day or so later they were back at Crawford Hill [one of 21 Bell Labs facilities]. So a technician who worked there at the time brought in his shotgun and got rid of them."
The buzz continued. The astronomers continued to tinker.
"There were joints in the horn reflector between the aluminum pieces, so we taped those over with aluminum tape whose adhesive was conductive, and we tested the tape's conductive properties in the lab," Wilson recalls. "We thought hard about it and tried to think of every possible source and went around squirreling them all out. We still believed in the laws of physics, and we knew that what was coming out had to come from somewhere."
They pointed the antenna toward New York City, with its myriad radiation sources; toward a high-altitude nuclear weapons test near Hawaii; and across the various potential weak radio sources in the Milky Way. None of these proved to be the radio wave source they were seeking. The maddening signal was exactly the same, no matter where they pointed the horn reflector. They flew a helicopter carrying a signal generator over the antenna, and it seemed to work perfectly -- except for the small, background buzz.
As Penzias and Wilson toiled to tune their antenna, Princeton physicists Robert Dicke and Jim Peebles were struggling to refine the Big Bang. According to that theory, the universe began in a massively hot explosion that has continued surging outward ever since. The resulting gas and dust eventually cooled, drifted together, and compacted under the force of gravity into stars and galaxies. This dynamic, rather than static, theory of cosmology was not as widely accepted then as it is today. A group of prominent British scientists had attracted a following to what was called the Steady State theory, which described an eternally unchanging universe.
If, Dicke and Peebles surmised, astronomers could detect the faint afterglow of that original explosion -- if they could perceive the remains of the universe's first light -- then they would have "seen," and thereby proven, the Big Bang theory. Such radiation would necessarily be faint; the universe had cooled dramatically since the explosion.
At the time of creation 15 billion years ago, the universe's temperature is estimated to have been around 100,000,000,000,000,000,000,000,000,000,273 degrees Celsius. Like a cup of boiling water dropped into a pond, this heat -- and the electromagnetic waves that naturally emerge from such a heated body -- have been dispersing into the cosmos ever since. Big Bang theorists at Princeton, other American theorists, and Soviet cosmologists had predicted that the universe had spread and cooled across the eons until it reached a temperature just slightly above a theoretical construct known as absolute zero -- that is, the temperature at which heat ceases to exists. (Absolute zero is -273.15 degrees on the Celsius temperature scale, or zero degrees on the Kelvin scale.)
Radiation from a heat source as faint as the remnants of the Big Bang would only be detectable somewhere in the microwave region, whose wavelengths range from one millimeter to a meter in length, and are invisible to the naked eye. So the Princeton scientists perched a small antenna atop a university building, and went about searching for the faint cosmic microwave background radiation that would confirm the Big Bang.