Albert Einstein Memorial Lecture: The Discovery of Cosmic Microwave Background Radiation and its Role in Cosmology

Robert Willson of the Harvard-Smithsonian Center for Astrophysics will discuss how he and Arno Penzias discovered radiation left over from the Big Bang. The talk is being presented as part of the Princeton Mercer Regional Chamber of Commerce’s Albert Einstein Memorial Lecture series.

Bell Labs built a giant antenna in Holmdel in 1960. It was part of a very early satellite transmission system called Echo. By collecting and amplifying weak radio signals bouncing off large metallic balloons high in the atmosphere, it could send signals across long distances. Within a few years, the Telstar satellite was launched. It had built-in transponders and made the Echo system obsolete.

Two Bell Labs employees at the time had their eyes on the antenna. Penzias, a German-born radio astronomer, joined Bell Labs in 1958. He had done his doctorate on using masers (microwave amplification by stimulated emission of radiation) to amplify and measure radio signals from the spaces between galaxies. He knew the Holmdel antenna would also make a great radio telescope and was dying to use it to continue his observations, but he pursued other research while the antenna was booked for commercial use. Another radio astronomer came to Bell Labs in 1962 with the same idea. Wilson also used masers to amplify weak signals in mapping radio signals from the Milky Way. The launch of Telstar in 1962 gave both researchers what they wanted: the Holmdel antenna was freed up for pure research.

When they began to use it as a telescope they found there was a background “noise” (like static in a radio). This annoyance was a uniform signal in the microwave range, seeming to come from all directions. Everyone assumed it came from the telescope itself, which was not unusual. It hadn’t interfered with the Echo system but Penzias and Wilson had to get rid of it to make the observations they planned. They checked everything to rule out the source of the excess radiation. They pointed the antenna right at New York City — it wasn’t urban interference. It wasn’t radiation from our galaxy or extraterrestrial radio sources. It wasn’t even the pigeons living in the big, horn-shaped antenna. Penzias and Wilson kicked them out and swept out all their droppings. The source remained the same through four seasons, so it couldn’t have come from the solar system or even from a 1962 above-ground nuclear test, because in a year that fallout would have shown a decrease. They had to conclude it was not the machine and it was not random noise causing the radiation.

Penzias and Wilson began looking for theoretical explanations. Around the same time, Robert Dicke at Princeton University had been pursuing theories about the big bang. He had elaborated on existing theory to suggest that if there had been a big bang, the residue of the explosion should by now take the form of low-level background radiation throughout the universe. Dicke was looking for evidence of this theory when Penzias and Wilson got in touch with his lab. He shared his theoretical work with them.

It is ironic, too, that many researchers — both theoretical and experimental — had stumbled on this phenomenon before, but either discounted it or never put it all together.

Penzias and Wilson received the Nobel Prize in physics in 1978.

Attendees will also get to celebrate Einstein’s birthday, Pi Day, with Einstein impersonator Bill Agress, who is full of facts about Einstein.

Pre-registration is required, and seating is limited and is on a first-come, first-seated basis. All visitors must be fully vaccinated against COVID-19 (at least two weeks have passed since receiving the second dose of a two-dose vaccine or the single dose of a one-dose vaccine) or be prepared to show proof of a negative COVID-19 test via PCR within 72 hours of the visit or Rapid Antigen test within 8 hours of the visit or wear a face covering at all times inside the building.