# Cosmic microwave background and "white dielectric"

Arno Allan Penzias and Robert Woodrow Wilson were awarded (one half of) the 1978 Nobel prize in Physics, "for their discovery of cosmic microwave background radiation",

https://www.nobelprize.org/prizes/physics/1978/summary/

The story about their discovery is usually told with an anecdote about the pigeon droppings (allegedly described by Penzias as a "white dielectric") in their horn antenna, which was a cause of unwanted noise. I cannot find the origin of this story, presumably told by Penzias himself. Was this part of some interview or does it appear somewhere in a published (paper) form?

Wilson tells the story in his Nobel lecture of 1978:

Thus we seemed to be left with the antenna as the source of our extra noise. We calculated a contribution of $$0.9 \text{K}$$ from its resistive loss using standard waveguide theory. The most lossy part of the antenna was its small diameter throat, which was made of electroformed copper. We had measured similar waveguides in the lab and corrected the loss calculations for the imperfect surface conditions we had found in those waveguides. The remainder of the antenna was made of riveted aluminum sheets, and although we did not expect any trouble there, we had no way to evaluate the loss in the riveted joints. A pair of pigeons was roosting up in the small part of the horn where it enters the warm cab. They had covered the inside with a white material familiar to all city dwellers. We evicted the pigeons and cleaned up their mess, but obtained only a small reduction in antenna temperature.

• small addendum: more recent video, youtube.com/watch?v=2bnL_ztPo6s, Wilson mentions the "pigeon story" at 1:22 Oct 18 '20 at 19:43

With this help I found this old chat discussion from which I relocated the YouTube video Arno Penzias & Robert Wilson from BBC movie "Hawking" (2004) in which they recount the story, including both the dielectric euphemism and more literal (guttural) term.

Note that these are actors, this is historical fiction, so it's not a primary answer to your question, but let's assume the BBC at least tried to reflect some aspects of reality.

The reenactment is quite humorous in the telling and then quite compelling (closed captions available)

I still think that The Pigeons Were Innocent would be a great title for a film, but they'd probably use that for the working title and call it The His Was Still There upon release.